News

Orbit hydraulic motor: The ring gear is fixedly connected to the housing, and the oil entering from the port pushes the rotor to revolve around a center point. This slowly rotating rotor drives the output through a splined shaft into a hydraulic orbital motor. After the introduction of this initial orbitl motor, after decades of evolution, another concept of the motor began to form. This motor has a roller mounted in the built-in ring gear. The motor with roller provides high starting and running torque, and the roller reduces friction,which increases efficiency even at very low speeds and produce a stable output. By changing the direction of the input and output flow, the motor is quickly reversed and produces equivalent torque in both directions. Each series of motors has a variety of displacement options to meet a variety of speed and torque requirements. The hydraulic orbit motor is a small low-speed high-torque hydraulic motor with one-axis flow-setting insert and rotor pair. The advantages are as follows: 1. Small in size and light in weight, its outer dimensions are much smaller than other types of hydraulic motors of the same torque. 2. wide range of speed, stepless speed regulation, the lowest stable speed up to 15 rev / min, easy installation,low investment costs. 3. It can be used in series in the hydraulic system, or it can be used in parallel. 4.the rotation inertia is small, easy to start under load, both forward and reverse can be used, and there is no need to stop when commuting. hydraulic orbit motors are widely used in agricultural, fishing, light industry, lifting and transportation, mining, engineering machinery and other mechanical slewing mechanisms. Examples of foreign applications of orbital hydraulic motors: 1. Agricultural use: various combine harvesters, planters, rotary tillers, lawn mowers, sprayers, feed mixers, ground drilling machines. 2. Fishing: use the net machine. 3. Light industrial use: winder, textile machine, printing machine, business washing machine. 4. Construction industry: road roller, cement mixer, sweeping vehicle. Second, the structure and performance characteristics The orbital hydraulic motor is an integral part of the output shaft and the valve, and the gear-type stator and rotor sub-cycloid hydraulic motor. The specific structure is shown as below Main features: 1. Adopting end face distribution and axial flow distribution, the structure is simple and compact, and the flow matching precision is high; 2, using the insert stator and rotor pair, high mechanical efficiency, long life with high pressure operation; 3, the use of double-corner ball bearings, can withstand large radial and axial loads, low friction, high mechanical efficiency. 4. Advanced flow distribution mechanism design, featuring high flow matching precision and automatic wear compensation. 5, the motor can be used in series and parallel, when connected in series should be connected to the external drain. 6, using tapered roller bearing support design, with a large radial load capacity, so that the motor can directly drive the working mechanism. More than 7 types of flanges, output shafts, oil ports, etc. Third, the operation notes (1) Check all components of the hydraulic system correctly before operation, and add oil to the specified height through the filter. (2) Start the operation for 10 to 15 minutes without load, and perform exhausting, foam in the fuel tank, noise in the system, and stagnant motor cylinders to prove that there is air in the system. (3) After removing the air, fill up the fuel tank, and then gradually increase the load to the motor until the maximum load, observe whether there are abnormal phenomena, such as noise, oil rise and oil leakage. (4) Replace the oil by running for 50 hours, and replace it according to the maintenance rules. (5) If it is not a motor failure, please do not disassemble it easily. Fourth, disassembly and assembly When the hydraulic motor fails to be disassembled, please pay attention to the following: (1) Do not touch the joint surface when disassembling. If there is a bump, it needs to be trimmed before assembly. (2) Wash all parts with gasoline or kerosene before assembly. Do not use cotton yarn or rag to scrub the parts. Apply brush or silk cloth. Do not immerse the rubber ring in gasoline. After the motor is installed, add 50~100ml of hydraulic oil to the two ports before installing the machine, and rotate the output oil. If there is no abnormality, install the machine. (3) In order to ensure the correct rotation direction of the motor, attention should be paid to the positional relationship between the rotor and the output shaft. (4) The back cover bolts must be tightened diagonally, and the tightening torque is 4~5 kg force·meter.

Hydraulic machinery From Wikipedia, the free encyclopedia Jump to navigationJump to search This article is about power machinery. For civil engineering concerning water management, see Hydraulics. "Hydraulic equipment" redirects here. For exercise equipment using hydraulic cylinders for resistance, see Resistance training. A simple open center hydraulic circuit. An excavator; main hydraulics: Boom cylinders, swingdrive, cooler fan and trackdrive Fundamental features of using hydraulics compared to mechanics for force and torque increase/decrease in a transmission. Hydraulic machines use liquid fluid power to perform work. Heavy construction vehicles are a common example. In this type of machine, hydraulic fluid is pumped to various hydraulic motors and hydraulic cylinders throughout the machine and becomes pressurized according to the resistance present. The fluid is controlled directly or automatically by control valves and distributed through hoses, tubes, or pipes. Hydraulic systems, like pneumatic systems, are based on Pascal's law which states that any pressure applied to a fluid inside a closed system will transmit that pressure equally everywhere and in all directions. A hydraulic system uses an incompressible liquid as its fluid, rather than a compressible gas. The popularity of hydraulic machinery is due to the very large amount of power that can be transferred through small tubes and flexible hoses, and the high power density and wide array of actuators that can make use of this power, and the huge multiplication of forces that can be achieved by applying pressures over relatively large areas. One drawback, compared to machines using gears and shafts, is that any transmission of power results in some losses due to resistance of fluid flow through the piping. Contents 1History 2Force and torque multiplication 2.1Examples 2.1.1Two hydraulic cylinders interconnected 2.1.2Pump and motor 3Hydraulic circuits 3.1Open loop circuits 3.2Closed loop circuits 4Constant pressure and load-sensing systems 4.1Constant pressure systems 4.2Load-sensing systems 4.3Five basic types of load sensing systems 5Components 5.1Hydraulic pump 5.2Control valves 5.3Actuators 5.4Reservoir 5.5Accumulators 5.6Hydraulic fluid 5.7Filters 5.8Tubes, pipes and hoses 5.9Seals, fittings and connections 6See also 7References and notes 8External links History[edit] Joseph Bramah patented the hydraulic press in 1795.[1] While working at Bramah's shop, Henry Maudslay suggested a cup leather packing.[2][clarification needed] Because it produced superior results, the hydraulic press eventually displaced the steam hammer for metal forging.[3] To supply large scale power that was impractical for individual steam engines, central station hydraulic systems were developed. Hydraulic power was used to operate cranes and other machinery in British ports and elsewhere in Europe. The largest hydraulic system was in London. Hydraulic power was used extensively in Bessemer steel production. Hydraulic power was also used for elevators, to operate canal locks and rotating sections of bridges.[1][4] Some of these systems remained in use well into the twentieth century. Harry Franklin Vickers was called the "Father of Industrial Hydraulics" by ASME.[why?] Force and torque multiplication[edit] A fundamental feature of hydraulic systems is the ability to apply force or torque multiplication in an easy way, independent of the distance between the input and output, without the need for mechanical gears or levers, either by altering the effective areas in two connected cylinders or the effective displacement (cc/rev) between a pump and motor. In normal cases, hydraulic ratios are combined with a mechanical force or torque ratio for optimum machine designs such as boom movements and trackdrives for an excavator. Examples[edit] Two hydraulic cylinders interconnected[edit] Cylinder C1 is one inch in radius, and cylinder C2 is ten inches in radius. If the force exerted on C1 is 10 lbf, the force exerted by C2 is 1000 lbf because C2 is a hundred times larger in area (S = πr²) as C1. The downside to this is that you have to move C1 a hundred inches to move C2 one inch. The most common use for this is the classical hydraulic jack where a pumping cylinder with a small diameter is connected to the lifting cylinder with a large diameter. Pump and motor[edit] If a hydraulic rotary pump with the displacement 10 cc/rev is connected to a hydraulic rotary motor with 100 cc/rev, the shaft torque required to drive the pump is one tenth of the torque then available at the motor shaft, but the shaft speed (rev/min) for the motor is also only one tenth of the pump shaft speed. This combination is actually the same type of force multiplication as the cylinder example, just that the linear force in this case is a rotary force, defined as torque. Both these examples are usually referred to as a hydraulic transmission or hydrostatic transmission involving a certain hydraulic "gear ratio". Hydraulic circuits[edit] A hydraulic circuit is a system comprising an interconnected set of discrete components that transport liquid. The purpose of this system may be to control where fluid flows (as in a network of tubes of coolant in a thermodynamic system) or to control fluid pressure (as in hydraulic amplifiers). For example, hydraulic machinery uses hydraulic circuits (in which hydraulic fluid is pushed, under pressure, through hydraulic pumps, pipes, tubes, hoses, hydraulic motors, hydraulic cylinders, and so on) to move heavy loads. The approach of describing a fluid system in terms of discrete components is inspired by the success of electrical circuit theory. Just as electric circuit theory works when elements are discrete and linear, hydraulic circuit theory works best when the elements (passive component such as pipes or transmission lines or active components such as power packs or pumps) are discrete and linear. This usually means that hydraulic circuit analysis works best for long, thin tubes with discrete pumps, as found in chemical process flow systems or microscale devices.[5][6][7] The circuit comprises the following components: Active components Hydraulic power pack Transmission lines Hydraulic hoses Passive components Hydraulic cylinders For the hydraulic fluid to do work, it must flow to the actuator and/or motors, then return to a reservoir. The fluid is then filtered and re-pumped. The path taken by hydraulic fluid is called a hydraulic circuit of which there are several types. Open center circuits use pumps which supply a continuous flow. The flow is returned to tank through the control valve's open center; that is, when the control valve is centered, it provides an open return path to tank and the fluid is not pumped to a high pressure. Otherwise, if the control valve is actuated it routes fluid to and from an actuator and tank. The fluid's pressure will rise to meet any resistance, since the pump has a constant output. If the pressure rises too high, fluid returns to tank through a pressure relief valve. Multiple control valves may be stacked in series.[1] This type of circuit can use inexpensive, constant displacement pumps. Closed center circuits supply full pressure to the control valves, whether any valves are actuated or not. The pumps vary their flow rate, pumping very little hydraulic fluid until the operator actuates a valve. The valve's spool therefore doesn't need an open center return path to tank. Multiple valves can be connected in a parallel arrangement and system pressure is equal for all valves. Open loop and closed loop circuits Open loop circuits[edit] Open-loop: Pump-inlet and motor-return (via the directional valve) are connected to the hydraulic tank. The term loop applies to feedback; the more correct term is open versus closed "circuit". Open center circuits use pumps which supply a continuous flow. The flow is returned to the tank through the control valve's open center; that is, when the control valve is centered, it provides an open return path to the tank and the fluid is not pumped to a high pressure. Otherwise, if the control valve is actuated it routes fluid to and from an actuator and tank. The fluid's pressure will rise to meet any resistance, since the pump has a constant output. If the pressure rises too high, fluid returns to the tank through a pressure relief valve. Multiple control valves may be stacked in series. This type of circuit can use inexpensive, constant displacement pumps. Closed loop circuits[edit] Closed-loop: Motor-return is connected directly to the pump-inlet. To keep up pressure on the low pressure side, the circuits have a charge pump (a small gear pump) that supplies cooled and filtered oil to the low pressure side. Closed-loop circuits are generally used for hydrostatic transmissions in mobile applications. Advantages: No directional valve and better response, the circuit can work with higher pressure. The pump swivel angle covers both positive and negative flow direction. Disadvantages: The pump cannot be utilized for any other hydraulic function in an easy way and cooling can be a problem due to limited exchange of oil flow. High power closed loop systems generally must have a 'flush-valve' assembled in the circuit in order to exchange much more flow than the basic leakage flow from the pump and the motor, for increased cooling and filtering. The flush valve is normally integrated in the motor housing to get a cooling effect for the oil that is rotating in the motor housing itself. The losses in the motor housing from rotating effects and losses in the ball bearings can be considerable as motor speeds will reach 4000-5000 rev/min or even more at maximum vehicle speed. The leakage flow as well as the extra flush flow must be supplied by the charge pump. A large charge pump is thus very important if the transmission is designed for high pressures and high motor speeds. High oil temperature is usually a major problem when using hydrostatic transmissions at high vehicle speeds for longer periods, for instance when transporting the machine from one work place to the other. High oil temperatures for long periods will drastically reduce the lifetime of the transmission. To keep down the oil temperature, the system pressure during transport must be lowered, meaning that the minimum displacement for the motor must be limited to a reasonable value. Circuit pressure during transport around 200-250 bar is recommended. Closed loop systems in mobile equipment are generally used for the transmission as an alternative to mechanical and hydrodynamic (converter) transmissions. The advantage is a stepless gear ratio (continuously variable speed/torque) and a more flexible control of the gear ratio depending on the load and operating conditions. The hydrostatic transmission is generally limited to around 200 kW maximum power, as the total cost gets too high at higher power compared to a hydrodynamic transmission. Large wheel loaders for instance and heavy machines are therefore usually equipped with converter transmissions. Recent technical achievements for the converter transmissions have improved the efficiency and developments in the software have also improved the characteristics, for example selectable gear shifting programs during operation and more gear steps, giving them characteristics close to the hydrostatic transmission. Constant pressure and load-sensing systems[edit] Hydrostatic transmissions for earth moving machines, such as for track loaders, are often equipped with a separate 'inch pedal' that is used to temporarily increase the diesel engine rpm while reducing the vehicle speed in order to increase the available hydraulic power output for the working hydraulics at low speeds and increase the tractive effort. The function is similar to stalling a converter gearbox at high engine rpm. The inch function affects the preset characteristics for the 'hydrostatic' gear ratio versus diesel engine rpm. Constant pressure systems[edit] The closed center circuits exist in two basic configurations, normally related to the regulator for the variable pump that supplies the oil: Constant pressure systems (CP), standard. Pump pressure always equals the pressure setting for the pump regulator. This setting must cover the maximum required load pressure. Pump delivers flow according to required sum of flow to the consumers. The CP system generates large power losses if the machine works with large variations in load pressure and the average system pressure is much lower than the pressure setting for the pump regulator. CP is simple in design, and works like a pneumatic system. New hydraulic functions can easily be added and the system is quick in response. Constant pressure systems, unloaded. Same basic configuration as 'standard' CP system but the pump is unloaded to a low stand-by pressure when all valves are in neutral position. Not so fast response as standard CP but pump lifetime is prolonged. Load-sensing systems[edit] Load-sensing systems (LS) generate less power losses as the pump can reduce both flow and pressure to match the load requirements, but require more tuning than the CP system with respect to system stability. The LS system also requires additional logical valves and compensator valves in the directional valves, thus it is technically more complex and more expensive than the CP system. The LS system generates a constant power loss related to the regulating pressure drop for the pump regulator : {\displaystyle Powerloss=\Delta p_{LS}\cdot Q_{tot}} The average {\displaystyle \Delta p_{LS}} is around 2 MPa (290 psi). If the pump flow is high the extra loss can be considerable. The power loss also increases if the load pressures vary a lot. The cylinder areas, motor displacements and mechanical torque arms must be designed to match load pressure in order to bring down the power losses. Pump pressure always equals the maximum load pressure when several functions are run simultaneously and the power input to the pump equals the (max. load pressure + ΔpLS) x sum of flow. Five basic types of load sensing systems[edit] Load sensing without compensators in the directional valves. Hydraulically controlled LS pump. Load sensing with up-stream compensator for each connected directional valve. Hydraulically controlled LS pump. Load sensing with down-stream compensator for each connected directional valve. Hydraulically controlled LS pump. Load sensing with a combination of up-stream and down-stream compensators. Hydraulically controlled LS pump. Load sensing with synchronized, both electric controlled pump displacement and electric controlled valve flow area for faster response, increased stability and fewer system losses. This is a new type of LS-system, not yet fully developed. Technically the down-stream mounted compensator in a valve block can physically be mounted "up-stream", but work as a down-stream compensator. System type (3) gives the advantage that activated functions are synchronized independent of pump flow capacity. The flow relation between two or more activated functions remains independent of load pressures, even if the pump reaches the maximum swivel angle. This feature is important for machines that often run with the pump at maximum swivel angle and with several activated functions that must be synchronized in speed, such as with excavators. With the type (4) system, the functions with up-stream compensators have priority, for example the steering function for a wheel loader. The system type with down-stream compensators usually have a unique trademark depending on the manufacturer of the valves, for example "LSC" (Linde Hydraulics), "LUDV" (Bosch Rexroth Hydraulics) and "Flowsharing" (Parker Hydraulics) etc. No official standardized name for this type of system has been established but flowsharing is a common name for it. Components[edit] Hydraulic pump[edit] An exploded view of an external gear pump. Hydraulic pumps supply fluid to the components in the system. Pressure in the system develops in reaction to the load. Hence, a pump rated for 5,000 psi is capable of maintaining flow against a load of 5,000 psi. Pumps have a power density about ten times greater than an electric motor (by volume). They are powered by an electric motor or an engine, connected through gears, belts, or a flexible elastomeric coupling to reduce vibration. Common types of hydraulic pumps to hydraulic machinery applications are: Gear pump: cheap, durable (especially in g-rotor form), simple. Less efficient, because they are constant (fixed) displacement, and mainly suitable for pressures below 20 MPa (3000 psi). Vane pump: cheap and simple, reliable. Good for higher-flow low-pressure output. Axial piston pump: many designed with a variable displacement mechanism, to vary output flow for automatic control of pressure. There are various axial piston pump designs, including swashplate (sometimes referred to as a valveplate pump) and checkball (sometimes referred to as a wobble plate pump). The most common is the swashplate pump. A variable-angle swashplate causes the pistons to reciprocate a greater or lesser distance per rotation, allowing output flow rate and pressure to be varied (greater displacement angle causes higher flow rate, lower pressure, and vice versa). Radial piston pump: normally used for very high pressure at small flows. Piston pumps are more expensive than gear or vane pumps, but provide longer life operating at higher pressure, with difficult fluids and longer continuous duty cycles. Piston pumps make up one half of a hydrostatic transmission. Control valves[edit] Control valves on a scissor lift Directional control valves route the fluid to the desired actuator. They usually consist of a spool inside a cast iron or steel housing. The spool slides to different positions in the housing, and intersecting grooves and channels route the fluid based on the spool's position. The spool has a central (neutral) position maintained with springs; in this position the supply fluid is blocked, or returned to tank. Sliding the spool to one side routes the hydraulic fluid to an actuator and provides a return path from the actuator to tank. When the spool is moved to the opposite direction the supply and return paths are switched. When the spool is allowed to return to neutral (center) position the actuator fluid paths are blocked, locking it in position. Directional control valves are usually designed to be stackable, with one valve for each hydraulic cylinder, and one fluid input supplying all the valves in the stack. Tolerances are very tight in order to handle the high pressure and avoid leaking, spools typically have a clearance with the housing of less than a thousandth of an inch (25 µm). The valve block will be mounted to the machine's frame with a three point pattern to avoid distorting the valve block and jamming the valve's sensitive components. The spool position may be actuated by mechanical levers, hydraulic pilot pressure, or solenoids which push the spool left or right. A seal allows part of the spool to protrude outside the housing, where it is accessible to the actuator. The main valve block is usually a stack of off the shelf directional control valves chosen by flow capacity and performance. Some valves are designed to be proportional (flow rate proportional to valve position), while others may be simply on-off. The control valve is one of the most expensive and sensitive parts of a hydraulic circuit. Pressure relief valves are used in several places in hydraulic machinery; on the return circuit to maintain a small amount of pressure for brakes, pilot lines, etc... On hydraulic cylinders, to prevent overloading and hydraulic line/seal rupture. On the hydraulic reservoir, to maintain a small positive pressure which excludes moisture and contamination. Pressure regulators reduce the supply pressure of hydraulic fluids as needed for various circuits. Sequence valves control the sequence of hydraulic circuits; to ensure that one hydraulic cylinder is fully extended before another starts its stroke, for example. Hydraulic circuits can perform a sequence of operations automatically, such as trip-and-reclose three times, then lockout, of an oil-interrupting recloser.[8] Shuttle valves provide a logical or function. Check valves are one-way valves, allowing an accumulator to charge and maintain its pressure after the machine is turned off, for example. Pilot controlled check valves are one-way valve that can be opened (for both directions) by a foreign pressure signal. For instance if the load should not be held by the check valve anymore. Often the foreign pressure comes from the other pipe that is connected to the motor or cylinder. Counterbalance valves are in fact a special type of pilot controlled check valve. Whereas the check valve is open or closed, the counterbalance valve acts a bit like a pilot controlled flow control. Cartridge valves are in fact the inner part of a check valve; they are off the shelf components with a standardized envelope, making them easy to populate a proprietary valve block. They are available in many configurations; on/off, proportional, pressure relief, etc. They generally screw into a valve block and are electrically controlled to provide logic and automated functions. Hydraulic fuses are in-line safety devices designed to automatically seal off a hydraulic line if pressure becomes too low, or safely vent fluid if pressure becomes too high. Auxiliary valves in complex hydraulic systems may have auxiliary valve blocks to handle various duties unseen to the operator, such as accumulator charging, cooling fan operation, air conditioning power, etc. They are usually custom valves designed for the particular machine, and may consist of a metal block with ports and channels drilled. Cartridge valves are threaded into the ports and may be electrically controlled by switches or a microprocessor to route fluid power as needed. Actuators[edit] Hydraulic cylinder Hydraulic motor (a pump plumbed in reverse); hydraulic motors with axial configuration use swashplates for highly accurate control and also in 'no stop' continuous (360°) precision positioning mechanisms. These are frequently driven by several hydraulic pistons acting in sequence. Hydrostatic transmission Brakes Reservoir[edit] The hydraulic fluid reservoir holds excess hydraulic fluid to accommodate volume changes from: cylinder extension and contraction, temperature driven expansion and contraction, and leaks. The reservoir is also designed to aid in separation of air from the fluid and also work as a heat accumulator to cover losses in the system when peak power is used. Reservoirs can also help separate dirt and other particulate from the oil, as the particulate will generally settle to the bottom of the tank. Some designs include dynamic flow channels on the fluid's return path that allow for a smaller reservoir. Accumulators[edit] Accumulators are a common part of hydraulic machinery. Their function is to store energy by using pressurized gas. One type is a tube with a floating piston. On the one side of the piston there is a charge of pressurized gas, and on the other side is the fluid. Bladders are used in other designs. Reservoirs store a system's fluid. Examples of accumulator uses are backup power for steering or brakes, or to act as a shock absorber for the hydraulic circuit. Hydraulic fluid[edit] Also known as tractor fluid, hydraulic fluid is the life of the hydraulic circuit. It is usually petroleum oil with various additives. Some hydraulic machines require fire resistant fluids, depending on their applications. In some factories where food is prepared, either an edible oil or water is used as a working fluid for health and safety reasons. In addition to transferring energy, hydraulic fluid needs to lubricate components, suspend contaminants and metal filings for transport to the filter, and to function well to several hundred degrees Fahrenheit or Celsius. Filters[edit] Filters are an important part of hydraulic systems which removes the unwanted particles from fluid. Metal particles are continually produced by mechanical components and need to be removed along with other contaminants. Filters may be positioned in many locations. The filter may be located between the reservoir and the pump intake. Blockage of the filter will cause cavitation and possibly failure of the pump. Sometimes the filter is located between the pump and the control valves. This arrangement is more expensive, since the filter housing is pressurized, but eliminates cavitation problems and protects the control valve from pump failures. The third common filter location is just before the return line enters the reservoir. This location is relatively insensitive to blockage and does not require a pressurized housing, but contaminants that enter the reservoir from external sources are not filtered until passing through the system at least once. Filters are used from 7 micron to 15 micron depends upon the viscosity grade of hydraulic oil. Tubes, pipes and hoses[edit] Hydraulic tubes are seamless steel precision pipes, specially manufactured for hydraulics. The tubes have standard sizes for different pressure ranges, with standard diameters up to 100 mm. The tubes are supplied by manufacturers in lengths of 6 m, cleaned, oiled and plugged. The tubes are interconnected by different types of flanges (especially for the larger sizes and pressures), welding cones/nipples (with o-ring seal), several types of flare connection and by cut-rings. In larger sizes, hydraulic pipes are used. Direct joining of tubes by welding is not acceptable since the interior cannot be inspected. Hydraulic pipe is used in case standard hydraulic tubes are not available. Generally these are used for low pressure. They can be connected by threaded connections, but usually by welds. Because of the larger diameters the pipe can usually be inspected internally after welding. Black pipe is non-galvanized and suitable for welding. Hydraulic hose is graded by pressure, temperature, and fluid compatibility. Hoses are used when pipes or tubes can not be used, usually to provide flexibility for machine operation or maintenance. The hose is built up with rubber and steel layers. A rubber interior is surrounded by multiple layers of woven wire and rubber. The exterior is designed for abrasion resistance. The bend radius of hydraulic hose is carefully designed into the machine, since hose failures can be deadly, and violating the hose's minimum bend radius will cause failure. Hydraulic hoses generally have steel fittings swaged on the ends. The weakest part of the high pressure hose is the connection of the hose to the fitting. Another disadvantage of hoses is the shorter life of rubber which requires periodic replacement, usually at five to seven year intervals. Tubes and pipes for hydraulic n applications are internally oiled before the system is commissioned. Usually steel piping is painted outside. Where flare and other couplings are used, the paint is removed under the nut, and is a location where corrosion can begin. For this reason, in marine applications most piping is stainless steel. Seals, fittings and connections[edit] Main article: Seal (mechanical) Components of a hydraulic system [sources (e.g. pumps), controls (e.g. valves) and actuators (e.g. cylinders)] need connections that will contain and direct the hydraulic fluid without leaking or losing the pressure that makes them work. In some cases, the components can be made to bolt together with fluid paths built-in. In more cases, though, rigid tubing

What Is Gear Pump? | How Does Gear Pump Work? January 18, 2022 by Jignesh Sabhadiya What Is Gear Pump? A gear pump uses the meshing of gears to pump fluid by positive displacement. They are one of the most common types of pumps for hydraulic fluid power applications. The gear pump was invented by Johannes Kepler around 1600. Gear pumps are also commonly used in chemical plants to pump highly viscous liquids. There are two main variations: external gear pumps, which use two external spur gears, and internal gear pumps, which use an external and internal spur gear. Gear pumps are positive displacement (or fixed displacement) pumps, which means they pump a constant amount of fluid with each revolution. Some gear pumps are designed to function as either a motor or a pump. MORE: What is Pump and Their Types? What Is External Gear Pump? An external gear pump consists of two identical, interlocking gears supported by separate shafts. Generally, one gear is driven by a motor and this drives the other gear (the idler). In some cases, both shafts may be driven by motors. The shafts are supported by bearings on each side of the casing. As the gears come out of mesh on the inlet side of the pump, they create an expanded volume. Liquid flows into the cavities and is trapped by the gear teeth as the gears continue to rotate against the pump casing. The trapped fluid is moved from the inlet, to the discharge, around the casing. As the teeth of the gears become interlocked on the discharge side of the pump, the volume is reduced and the fluid is forced out under pressure. No fluid is transferred back through the center, between the gears, because they are interlocked. Close tolerances between the gears and the casing allow the pump to develop suction at the inlet and prevent fluid from leaking back from the discharge side (although leakage is more likely with low viscosity liquids). External gear pump designs can utilize spur, helical, or herringbone gears. MORE: What is Spur Gear? What Is Internal Gear Pump? An internal gear pump operates on the same principle but the two interlocking gears are of different sizes with one rotating inside the other. The larger gear (the rotor) is an internal gear i.e., it has the teeth projecting on the inside. Within this is a smaller external gear (the idler – only the rotor is driven) mounted off-center. This is designed to interlock with the rotor such that the gear teeth engage at one point. A pinion and bushing attached to the pump casing hold the idler in position. A fixed crescent-shaped partition or spacer fills the void created by the off-center mounting position of the idler and acts as a seal between the inlet and outlet ports. As the gears come out of mesh on the inlet side of the pump, they create an expanded volume. Liquid flows into the cavities and is trapped by the gear teeth as the gears continue to rotate against the pump casing and partition. The trapped fluid is moved from the inlet, to the discharge, around the casing. As the teeth of the gears become interlocked on the discharge side of the pump, the volume is reduced and the fluid is forced out under pressure. Internal gear pump designs only use spur gears. How Does A Gear Pump Work? Gear pumps use the actions of rotating cogs or gears to transfer fluids. The rotating element develops a liquid seal with the pump casing and creates suction at the pump inlet. Fluid, drawn into the pump, is enclosed within the cavities of its rotating gears and transferred to the discharge. Gear pumps work by trapping fluid between the teeth of two or three rotating gears. Often, they are magnetically driven, which means they use less [wetted" materials for greater chemical compatibility. Gear pumps move a cavity that rotates rather than reciprocates. These pumps move many small cavities per revolution, so they do not pulse nearly as often as diaphragm pumps. The major disadvantage of gear pumps is that increasing the backpressure does decrease the flow rate. They work best when pumping against stable backpressure. Since gear pumps operate by carrying fluid between the teeth of two or three rotating gears, they are best suited for applications in which fluid shearing or particle contamination from gear wear is not a concern. These pumps operate well with high system pressure applications and are commonly used for hydraulic fluid power uses, for example in tractors and garbage trucks, and with heavier viscosity fluids, such as oil, that are not compressible. Gear pumps feature true positive displacement with every revolution delivering a precise volume. Since each pocket of fluid that passes through the chamber is small and so many pockets go through per unit of time, the flow rate is virtually pulseless. Why Choose Gear Pumps? They offer many advantages, mainly: Low Shear. Their design and operating speed are low meaning movement is low shear. Self-Priming. They are self-priming up to 6.5M. Reversible. Due to their design, they can operate in both directions, ensuring hoses can be emptied and allowing full recovery of any products. However, the relief valve will only operate in one direction. Efficient. Models are up to 85% efficient. Predictable. Flow is proportionate to speed ensuring repeatable and predictable flow rate. Non-Pulsating. The smooth rotary motion at low rpm means pulsations are not experienced as is more common with other positive displacement designs. Materials. Designs are in complete metal meaning units can be Atex rated (explosion proof), handle solvents as internals parts are not rubber as in other positive displacement pumps. They can also accommodate high temperatures of up to 350°C. Limited dry running. Units can run dry for a limited time providing the gears have been immersed in a lubricating liquid. Low NPSH. NPSH requirements are very low due to their slow operation. Internal gear pumps NPSH ranges from 0.5M to 4M based on water, with external designs generally being up to 3M. Application Of Gear Pumps Gear pumps are commonly used for pumping high viscosity fluids such as oil, paints, resins, or foodstuffs. They are preferred in any application where accurate dosing or high-pressure output is required. The output of a gear pump is not greatly affected by pressure so they also tend to be preferred in any situation where the supply is irregular. Petrochemicals: Pure or filled bitumen, pitch, diesel oil, crude oil, lube oil etc. Chemicals: Sodium silicate, acids, plastics, mixed chemicals, isocyanates etc. Paint and ink. Resins and adhesives. Pulp and paper: acid, soap, lye, black liquor, kaolin, lime, latex, sludge etc. Food: Chocolate, cacao butter, fillers, sugar, vegetable fats and oils, molasses, animal food etc. Advantages Of Gear Pump Easy to use and maintain. The gear pump is compact and consists of only two gears, the pump body and the front and rear covers. Therefore, compared with other pumps, the gear pump has a small weight, which is convenient for daily transportation and does not require much labor. It is also because of its light weight, the gear pump is more convenient to use, and it is more convenient when the work content is the same. At the same time, because of its simple structure and fewer components, it is more convenient to repair when problems are encountered. Low cost. Compared with the conventional pump, the gear pump is smaller in weight and easy to transport, which saves transportation costs to some extent. In addition, the gear pump is cheaper because of its simple structure and lower manufacturing cost. The maintenance procedure is simple in the future and the maintenance cost is low. Therefore, in general, gear pumps are more economical and can effectively save costs. High work efficiency. In fact, the fluid loss in the gear pump is small. Although some of the fluid is used to lubricate both sides of the bearing and gear, the pump body can never be fitted without clearance, resulting in a gear pump operating efficiency of 100%. However, the pump can still operate well and can achieve an efficiency of 93% to 98%. Insensitive to fluid viscosity and density. If the viscosity or density of the fluid changes, the gear pump will not be affected too much. If a strainer or a restrictor is placed on the side of the discharge port, the gear pump will push the fluid through them. If the filter is dirty or clogged, the gear pump will still maintain a constant flow until it reaches the mechanical limit of the weakest part of the unit. This also causes the gear pump to be insensitive to oil contamination and is more suitable for use in petrochemical industries. Disadvantages Of Gear Pump Not easy to repair after wear. Because the gear pump parts are poorly interchangeable, it is not easy to repair after wear. Although the gear pump repair process is simple, if the parts are worn, the entire gear pump is almost impossible to repair. Large noise. Because the gear pump has the characteristics of radial force imbalance and large flow artery, it generates very loud noise. If it is in an area where there is a decibel requirement for the surrounding environment, or if it is used in the middle of the night, the gear pump will affect the work or rest of others, causing inconvenience. The existence of unbalanced radial forces will also affect the service life of the bearings to a certain extent. Unadjusted displacement. The inter-tooth groove of the end cap and gear constitutes a number of fixed sealed working chambers, so the displacement of the gear pump is not adjustable and can only be used as a dosing pump. This is not possible if you want to increase the displacement of the pump.

Gear Pump Types and Its Working The gear pumps essential as well as most frequently used pumps. As the name suggests, these pumps are inbuilt with gears. The main function of these gears is to provide force energy to the water within the pumps. In simple terms, the function of this pump is to transfer the water from one location to another location with the help of gear instrument. If the system`s force remains similar then they`ll supply you the fixed flow speed. This article discusses an overview of Gear-Pumps. So let us discuss an overview of these pumps with types, working, advantages, disadvantages and their applications. What is a Gear Pump? The gear pump definition is, it is a PD (positive displacement) rotating pump which assists you to move water otherwise fluid with the help of inbuilt gears. This type of pump includes two or more gears that create vacuum force to drive the liquid within the pump. This pump can be built with different parts like shaft, rotors, and casing. Gear Pump These pumps have high-pressure and are available in tiny sizes to supply constant liquid flow & a pulseless as contrasted to other types of pumps such as diaphragm & peristaltic pumps. The main benefits of using these pumps are superior like it can drive high thickness fluids, easy to use, operate and also maintain. How does it Work? The gear pump working principle is, it uses the gears actions otherwise rotating actions to move liquids. The rotating part extends the seal of liquid by the pump case to create suction at the inlet of the pump. Liquid drawn into the pump can be included in the rotating gears cavities and moved to the expulsion. Types of Gear Pumps These pumps are classified into different types but some of the basic gear pump designs are classified into two types which include the following. External Gear Pump Internal Gear Pump 1). External Gear Pump An external gear-pump can be built with two gears namely interlocking and identical where interlocking gear is held up with separate shafts. In general, single gear can be driven with the help of a motor to drive the other gear. In a few cases, shafts can be driven by electrical motors, and these are held with bearings on every casing side. When the gears appear from the mesh on the pump`s inlet side, they make an extended quantity. Fluid supplies into the cavities as well as trapped with the teeth of gear because the gears continue for rotating next to the casing of the pump. The trapped liquid can be moved from the inlet side to the discharge side in the region of the casing. When the gears teeth become linked on the discharge surface of the gear-pump, then the amount can be decreased & the liquid is forced out beneath force. No liquid can be moved back throughout the center, among the gears, since they are linked. Close tolerances among the gears as well as the covering let the pump to expand suction on the inlet & stop liquid from leaking reverse from the expulsion side. The designs of these pumps can use helical, spur, otherwise herringbone gears. Features of External Gear Pump The features of this pump include the following These pumps are solid in size with a simple design These are sufficient to distribute high capacities because of their huge outlets. It manages the pressures like low, medium otherwise high The shaft support as well as close tolerance on both surfaces of gears. 2). Internal Gear Pump An internal gear pump works on a similar principle except the two linking gears sizes are different with one revolving within the other. The rotor is a larger gear and also an inner gear, and it has the teeth projecting inside. A minor external gear is mounted, and this is mainly designed for linking by the rotor so that the teeth of the gear connected at a single end. A bushing and pinion can be connected to the pump case that holds the idler within the location. A permanent semi-circular formed divider otherwise spacer seals the void shaped through the off-center mounting location of the idler & performs like a seal among the ports like inlet & outlet. When the gears appear from the mesh on the pump`s inlet side, they make an extended quantity. Fluid supplies into the cavities as well as trapped with the teeth of gear because the gears continue for rotating next to the casing of the pump. The trapped liquid can be moved from the inlet side to the discharge side in the region of the casing. When the gears teeth become linked on the discharge surface of the pump, then the amount can be decreased & the liquid is forced out beneath force. Inner gear pump plans only utilize spur gears. Features of Internal Gear Pumps The features of internal gear pumps include the following It can be run for a small phase. It has a huge and big footprint. The net positive suction head (NPSH) requirement is very low. Advantages and Disadvantages of Gear Pumps The advantages of these pumps include the following. Maintenance is simple It handles an extensive range of viscosities Output is controllable Easy to reconstruct Cavitations are less sensitive The disadvantages of these pumps include the following. The liquid should be free of abrasives Interlocking gears can also be loud Applications of Gear Pumps The gear pumps applications include the following. These pumps are usually used for driving high thickness fluids like oil, resins, paints, otherwise foodstuffs. These pumps are chosen where a high force o/p is necessary. These pipes are preferred in any condition wherever the supply is unequal. Because the pump output is not really influenced by force. Both the internal and external pumps are commonly used in different fuel, lube oils, solvents and alcohols The external pumps are used in chemical preservative, polymer metering, mixing and blending of chemical, agriculture, industrial, and mobile hydraulic applications. Thus, this is all about the gear pump, this pump can be used to move a liquid with frequently surrounded a permanent volume in linking cogs otherwise gears, moving it automatically to push a flat pulse-free flow relative to the rotating velocity of its gears. Here, is a question for you, what are the main features of a gear pump?

HYDRAULIC PUMPS R. Keith Mobley, in Fluid Power Dynamics, 2000 Gear Pumps A gear pump develops flow by carrying fluid between the teeth of two meshed gears. One gear is driven by the drive shaft and turns the other. The pumping chambers formed between the gear teeth are enclosed by the pump's housing and the side plates. A partial vacuum is created at the inlet as the gear teeth unmesh. Fluid flows in to fill the space and is carried around the outside of the gears. As the teeth mesh again at the outlet, the fluid is forced out. High pressure at the pump's outlet imposes an unbalanced load on the gears and their bearing support structure. Gear pumps are classified as either external or internal gear pumps. In external gear pumps, the teeth of both gears project outward from their centers (Figure 3-2). External gear pumps may use spur, herringbone, or helical gear sets to move the fluid. Sign in to download full-size image Figure 3-2. External gear rotary pump. View chapterPurchase book Gear Pumps John R. WagnerJr., ... Harold F. GilesJr., in Extrusion (Second Edition), 2014 Gear pumps provide consistent polymer flow, which results in more consistent product dimensions. Potential advantages associated with gear pumps include the following: • Higher product yield per pound of material from more consistent gauge control, allowing an overall reduction in the average product dimensions. • Increased extruder output attributed to reduced pressure flow backward into the extruder caused by high die pressure. Eqn (36.1) shows that extruder output decreases as pressure flow from high head pressure increases: (36.1)ExtruderOutput=DragFlow−PressureFlow • Potential increased regrind use by eliminating extruder surging from nonuniform regrind feed. • Start-up time reduction as the gear pump automatically adjusts the screw speed while providing the desired constant die pressure. • Energy reduction as the extruder operates at a lower backpressure or pressure flow. The lower pressure flow generates a higher throughput at a lower screw speed and less shear heat. Lower shear heating generates less heat that has to be removed through cooling. Gear pumps Gear pumps control the output of the screw to the die. Gear pumps use a set of rotating gears to control the melt pressure and output volume to the die within very tight tolerances (< 1%) with little or no pulsation of the melt flow. This isolates the die from any upstream fluctuation such as surging in the screw area due to material or machine variations. Gear pumps can be driven by AC or DC motors but accurate speed control is essential. • Tip – Check gear pumps regularly and monitor the pump for changes in power use as this can act as an early warning for many gear pump problems. • Tip – Herringbone geared gear pumps tend to have a lower pressure fluctuation than standard spur gears. Gear pumps can also be used to raise the melt pressure. This will lower the screw pressure, the melt temperature and potentially increase the output of the extruder. Getting the right motor and drive system is critical to energy-efficient extrusion. It is the basic and most important action. Summary of the AC and DC drive options DC motors For Against ■ Accurate, fast and direct torque control. ■ Good speed response. ■ Simple control systems. ■ High accuracy of speed and torque control. ■ Flat speed versus torque profile. ■ Low motor reliability. ■ High initial motor cost. ■ High maintenance costs. AC motors + VSD For Against ■ Small, light and robust. ■ Simple design. ■ Lower initial motor cost. ■ Lower maintenance cost. ■ Reduced operating cost. ■ Improves site power factor. ■ More complex control system. ■ High motor controller cost. ■ Variable torque versus speed profile.

What is hydraulic machinery? Hydraulic machinery are tools that use fluid power to perform work. Hydraulic tools are often heavy equipment that transmits high pressure hydraulic fluid throughout the various hydraulic motors and cylinders. This fluid is controlled automatically or directly by control valves, which are themselves distributed through hoses and tubes. Companies that use heavy equipment often choose hydraulic machinery because of the large amount of power that is able to transfer between the small tubes and hoses. Hydraulic tubes: Seamless steel precision pipes that are manufactured exclusively for hydraulic machinery. There are standardized sizes for these pipes, depending on the pressure ranges specified. Hydraulic tubes are manufactured in lengths of 6m, and are cleaned, oiled and plugged. These precision tubes are interconnected by various types of flanges, welding cones, flare connections and cut-rings; yet they are not joined due to the need for inspectors to view the interior of the tubes. Hydraulic pipes: In cases where standard hydraulic tubes are not available, hydraulic machinery that uses low pressure may include pipes. These hydraulic pipes are generally connected by welds, because their large diameter allows for internal inspection. Non-galvanized black pipe is suitable for welding. Most piping for marine applications is stainless steel, which resists corrosion. Hydraulic hose: These hoses are used when hydraulic pipes or tubes cannot be used, and are graded-or categorized-by pressure, temperature and fluid capacity. The design includes a rubber interior, which is surrounded by several layers of woven wire and rubber. The exterior is intended to resist abrasion, and the bend radius is carefully designed into the exact specifications of the machine (hose failures can cause the hydraulic machinery to malfunction, resulting in deadly situations). Steel fittings are swaged to the ends of the hoses. Hydraulic hoses tend to have a shorter lifespan than pipes or tubes, and generally need replacement every five to seven years. Hydraulic fluid Hydraulic tubes and pipes are internally oiled before the tools are even commissioned. Sometimes known as [tractor fluid", this lubricant is the lifeblood of the hydraulic machinery. The general composition of hydraulic fluid is petroleum oil with other additives, including some fire resistant fluids for particular applications. Hydraulic fluid functions to: Transfer energy Lubricate components Suspend Contaminants and filings for transportation to the filter Allow for hydraulic tool performance in extreme temperatures

Hydraulic Machines: Working, Principle, Applications & Examples Jasmine Grover Senior Content Specialist | Updated On - May 12, 2022 Hydraulic machines are the machines or tools that operate using fluid power. A great amount of electricity is transferred through hoses and little tubes in these machines. The fluid is passed throughout the machine to motors and hydraulic cylinders where it is pressurized before being sent to end effectors via control valves and tubes. The hydraulic system is similar to pneumatic systems as it is also based on Pascal's law which asserts that any pressure applied to a fluid inside a closed system would be transmitted equally everywhere in all directions. Instead of a compressible gas, a hydraulic system uses an incompressible liquid as its fluid. Read More: Mechanical Properties of Fluids Table of Content Applications Uses of Hydraulic Machines Hydraulic Machines : Sample Questions Key Terms: Hydraulic machines, pressure, energy, force, Pascal`s Law. Applications of Hydraulic Machines [Click Here for Sample Questions] Hydraulic Brakes: Breakers, also known as hydraulic brakes, are a braking mechanism arrangement in which appropriate brake fluid is utilized to transfer pressure from the control mechanism to the brake mechanism. Automobile hydraulic brakes function on the same principle. When we apply a small amount of effort to the pedal with our foot, the master piston moves inside the master cylinder and the pressure created is communicated through the brake oil which acts on a larger piston. A strong force is applied to the piston which is pushed down, expanding the brake shoes against the brake lining. We can observe that a modest force on the pedal results in a huge retarding force on the wheels in this way. The hydraulic brake system has the advantage that the pressure applied by pressing a pedal is distributed evenly among all cylinders which are normally coupled to the four wheels resulting in equal braking effort on all four wheels. Hydraulic Lift: Hydraulic Lift refers to an elevator powered by fluid pressure generated by a suitable fluid. It is commonly used in service shops and garages to raise automobiles. A hydraulic lift consists of two pistons that are separated by a liquid-filled gap. A piston with a tiny cross-section A1 is employed to exert a force, of say F1, on the liquid immediately. The pressure, given by P=F/A, is passed via liquid to the larger cylinder which is then connected to a larger piston with an area A2, resulting in an upward force given by PxA2. Read More:Units of Pressure F2 = P x A2= FA1FA1 x A2 Thus, we can state that the piston can hold a large force such as the weight of a car or truck that is parked on the platform. The platform can be moved up or down by altering the force at the A1 area. As a result, we can say that the applied force has been increased by a factor of A2/A1, where A2/A1 is the overall mechanical advantage of the device. Hydraulic Lift Hydraulic Jacks - Hydraulic jacks are more powerful than other tools as they can lift more weight. Hydraulic jacks are divided into two categories - floor jacks and bottle jacks. For storing and transporting hydraulic fluid, a hydraulic jack consists of a cylinder and pumping system. A hand-driven or mechanically powered pump is used to apply pressure to the fluid in the pumping system. The one-way valve directs the fluid toward the jack cylinder and prevents it from returning. Pascal's principle is used to guide the process. Read More: Bulk Modulus Hydraulic Jacks Hydraulic Shock Absorbers - This is a stress absorption and dampening device. The components of a shock absorber are a cylinder filled with hydraulic oil and a piston. The piston will rise and fall in response to the string's compression and expansion. Read More: conservation of energy Uses of Hydraulic Machines [Click Here for Sample Questions] Today, hydraulics is used in practically every industry to move machines and equipment to fulfill various tasks. Some examples are the usage of cranes in construction, tractors in agriculture, forklifts in manufacturing, and braking in transportation. Hydraulic machines use hydraulic fluid pressure to power movement or to provide a basic source of energy. Dump trucks, aluminium or plastic extruders, cranes, jackhammers, and hose crimpers are all examples of hydraulic machines. Metal stamping, injection molding, and hose crimping are other activities performed by hydraulic machinery. The spinning motors, such as the Ferris wheel, are a great source of enjoyment in amusement parks. They use hydraulics technology to power rides and subsequently offer a motion to them. The concept of Hydraulics is used in almost every vehicle on the road. Brake fluid is an essential component of a vehicle's braking system. The act of pressing one's foot on the brake pedal causes a rod and piston within the master cylinder to move, achieving the desired effect which is preferably slowing or halting the car. As we all know, lifting a really big motor vehicle for repair and maintenance would be quite difficult without a hydraulic system. The system helps lift any heavy load to the appropriate height by using hydraulic fluid. Read More: Stress and Strain Sample Questions Question: How do hydraulic machines work? (1 Mark) Question: What are some of the hydraulic systems' drawbacks? (1 mark) Question: Explain the benefits of hydraulic systems. (1 mark) Ques: What characterizes a hydraulic machine? (2 marks) Ques: Compressed air produces a force F1 on a tiny piston with a radius of 5.0 cm in a car lift. This pressure is transferred to a 15-cm-radius second piston. Calculate F1 if the mass of the car to be raised is 1350 kg. What is the level of stress required to complete this task? (g = 9.8 milliseconds-2) (2 marks)

The ultimate guide to hydraulic motors There are many different types of hydraulic motor. Most of them can be categorised as: axial piston motors, radial piston motors, hydraulic gear motors or hydraulic vane motors. Unlike a linear, force-moving cylinder, the hydraulic motor uses hydraulic pressure to rotate. A hydraulic motor is built very much like a pump. However, when operated, oil enters the hydraulic motor and turns the shaft. The amount of oil supplied by the hydraulic pump determines the speed of a hydraulic motor. Subsequently, the torque is dependent on the amount of pressure supplied. Learn about radial piston motors Radial piston motors are highly efficient and generally have a long life. Furthermore, they provide high torque at relatively low shaft speeds, as well as excellent low speed operation with high efficiency. The low output speed means that, in many cases, a gearbox is not necessary. Radial piston motors are often referred to as LSHT – Low Speed High Torque motors. We supply radial piston motors from brands worldwide, including Bosch Rexroth, Staffa (Kawasaki) and the Italgroup. Which applications are radial piston motors commonly found in? Radial piston motors are commonly fund in: excavators, cranes, ground drilling equipment, winch drives, concrete mixers, trawlers and plastic injection moulding machines. Which types of radial piston motors are there? Generally, there are two basic types of radial piston motors. These are explained further here. Crankshaft radial piston motor The Crankshaft radial piston motor has a single cam and pistons pushing inwards. Moreover, it has an extremely high starting torque and is available in single displacements from 40 cc /rev through to about 5400 cc/rev. In addition, the Crankshaft type radial piston motors can run at [creep" speeds. And, some can run seamlessly up to 1500 rpm with virtually constant output torque. To sum up, the Crankshaft radial piston motor is the most versatile hydraulic motor. Multilobe cam ring design This type is constructed with a cam ring, which has multiple lobes and piston rollers that push outwardly against the cam ring. In essence, this produces a very smooth output with high starting torque. However, they are often limited in the upper speed range. Moreover, these high power motors are particularly good on low speed applications. Other types of radial piston motors include: compact radial piston motors, dual displacement radial piston motors and fixed displacement radial piston motors. And in addition, we can also help you source: low speed high torque radial piston motors, two speed radial piston motors and variable displacement radial piston motors. How do hydraulic gear motors work? Gears are used to reduce the shaft output speed for applications that require a lower speed. This means that the gear motor`s operating pressure typically is very low, ranging between 100 and 150 bar. In addition, some of the more modern gear motors operate at, up to, 250 bar continuous pressure. However, the downside is that this motor can be rather noisy. To sum up, gear motors are generally lightweight and small units with relatively high pressures. In addition they are known for their low cost, variety of speeds, broad temperature range, simple design and large viscosity range. About hydraulic vane motors Hydraulic vane motors are used in both industrial and mobile applications. For example, screw-drive, injection moulding and agricultural machinery. These motors tend to have less internal leaking than a gear motor. And subsequently, they are better to use in applications requiring lower speeds. Hydraulic vane motors feature reduced noise level, low flow pulsation, high torque at low speeds and a simple design. Moreover they are easy to service and suitable for vertical installation. To function correctly, the rotor vanes must be pressed against the inside of the motor housing. This can be done through spiral or leaf springs. But rods are also suitable. A vane motor typically features a displacement volume between 9 cc/rev to 214 cc/rev and a maximum 230 bar pressure. The speeds range from 100 to 2,500 rpm. Maximum torque of up to 650 Nm. Learn more about axial piston motors Axial piston motors use a bent axis design or a swash plate principle. The fixed displacement type works as a hydraulic motor and can be used in open and closed circuits. In contrast to this, the variable displacement type operates like a hydraulic pump. In the bent axis design, pistons move to and fro within the cylinder block bores. This movement is converted into rotary movement via the piston ball joint at the driving flange. In the swash plate design, pistons move to and fro in the cylinder block. Subsequently it revolves and turns the drive shaft via the connected cotter pin. What are the main characteristics of a gerotor motor? Low speed, high torque (LSHT) hydraulic Gerotor motors feature a high starting torque and large range of speeds with a continuous output torque. In addition, the motor has a good power-to-weight ratio and a smooth operation, even at low speeds. The Gerotor motor`s design is furthermore very robust and built for harsh working conditions.

Introduction to Gate Drives Ryszard Daniel, Tim Paulus, in Lock Gates and Other Closures in Hydraulic Projects, 2019 11.3.7 Hydraulic Motors Hydraulic motors convert fluid pressure into rotary motion. Pressurized fluid from the hydraulic pump turns the motor output shaft by pushing on the gears, pistons, or vanes of the hydraulic motor. Hydraulic motors can be used for direct drive applications, where sufficient torque capacity is available, or through gear reductions. Most hydraulic motors must operate under reversible rotation and braking conditions. Hydraulic motors often are required to operate at relatively low speed and high pressure and can experience wide variations in temperature and speed in normal operation. Hydraulic motors can provide extremely high torques. In gate drive applications, hydraulic motors are often combined with mechanical drives (Figs. 3.151b and 11.23) in particular pinion gears. The schematic representation in Fig. 11.23 shows the hydraulic motor driving the pinion gear for the LPV 149 sector gate in New Orleans. This is the case for many sector gates in the United States and multiple rolling gate applications in Europe. In rolling gate applications, hydraulic motors often are the driving force for a mechanical winch (Fig. 11.8). Hydraulic motors can also be the input for a gearbox as shown in the photo in Fig. 11.24. This is the system used at the Bremerhaven Fishery port lock chamber for driving the rolling gates. Sign in to download full-size image Fig. 11.24. Hydraulic motor driving a gearbox for Bremerhaven rolling gate, Germany. There are three types of hydraulic motors: gear, piston, and vane. Gear motors are compact and provide continuous service at rated power levels with moderate efficiency. They have a high tolerance for contamination of the hydraulic oil which is a consideration for applications in dirty environments. External gear motors consist of a pair of matched gears enclosed in one housing. Both gears have the same tooth form and are driven by the pressurized fluid. One gear is connected to an output shaft and the other to an idler. Pressurized fluid enters the housing at a point where the gears mesh. It forces the gears to rotate, and follows the path of least resistance around the periphery of the housing. The fluid exits at low pressure at the opposite side of the motor. Close tolerances between the gears and the housing help to control fluid leakage and increase volumetric efficiency. There are several variations of the gear motor, including the gerotor, differential gear motor, and roller-gerotor. All of these variations produce higher torque with less friction loss. All hydraulic piston motors are available in fixed and variable volume versions. The most common type of hydraulic motor available is the axial piston type. Axial piston hydraulic motors have high volumetric efficiency. This allows steady speed under variable torque or fluid viscosity conditions. Axial piston hydraulic motors are also among the most adaptable to variable loading conditions. They are available in two basic design types including swash plate and bent axis. The swash plate design is the most commonly available but the bent axis design is the most reliable and generally more expensive. Radial piston hydraulic motors have a cylinder barrel attached to a driven shaft and can usually produce more torque than axial piston hydraulic motors. They do have a limited speed range, however, and are more sensitive to hydraulic fluid contamination. The barrel contains a number of pistons that reciprocate in a radial bore. The outer piston ends bear against a thrust ring and pressurized fluid flows through a pintle in the center of the cylinder barrel to drive the pistons outward. The pistons push against the thrust ring and the reaction forces rotate the barrel. Motor displacement is varied by shifting the slide block laterally to change the piston stroke. When the centerlines of the cylinder barrel and housing coincide, there is no fluid flow and therefore the cylinder barrel stops. Moving the slide past center reverses direction of motor rotation. Radial piston motors are extremely efficient and rated for relatively high torque. In many USACE sector gate drives radial piston hydraulic motors are used. The hydraulic motor shown in Fig. 11.23 is a radial piston type and provides a torque of 260 Nm/bar. The rated speed is 50 rev/min. The hydraulic motor drives a pinion gear which in turn drives a rack gear on the sector gate. Vane motors are compact, simple in design, reliable, and have good overall efficiency at rated conditions. They have limited low-speed capability, however. Vane motors use springs or fluid pressure to extend the vanes. Vane motors have a slotted rotor mounted on a drive shaft that is driven by the rotor. Vanes, closely fitted into the rotor slots, move radially to seal against the cam ring. The ring has two major and two minor radial sections joined by transitional sections or ramps. Vane motors generally use a two or four-port configuration. Four-port motors generate twice the torque at approximately half the speed of two-port motors. The high starting torque efficiency of vane-type motors makes them adaptable to hoist winch drives allowing the motor to start under high load. Vane motors provide good operating efficiencies, but not as high as those of piston motors. The service life of a vane motor typically is shorter than that of a piston motor.

Things to Check if your Hydraulic System Isn`t Working Save Time and Money by Gathering All the Information Possible on your Down Equipment It can be challenging to own hydraulic equipment sometimes, especially when your company relies on them very much to keep business rolling. When your system stops working as it should, we would encourage you to do some evaluating of your machinery before you have an experienced mechanic come in for repairs. Please note – hiring an experienced mechanic is always going to be a smart decision when it comes to your equipment, but try to get the most information possible so that your mechanic can evaluate the machinery and equipment in the best and most efficient way. Saving you time and money! Gather Information on The Issue First thing is first when it comes to your Hydraulic System. If things are not running smoothly like normal, do your best to gather the most amount of information possible to explain the issue. This requires you to pay attention closely, we would even encourage you to take notes if you are able! Is your equipment operation slow or is your machine completely un-functioning? Is there a lot of noise or vibrations happening? Do your best to gather the most amount of information on what exactly is happening with your equipment as you try and use it. It might be that your equipment isn`t functioning at all and that you really aren`t able to gather too much information. The next step is going to be trying to put together some finer details about the overall issues. For example, if you are experiencing a large increase in vibration or noise when you are operating your equipment – when is it happening? Is it only when you are in a certain gear? Or is it 100% of the time. When did the issues start, and when was the last time you had your equipment or machine maintenanced? All of these details are good things to help you begin the troubleshooting process as you think about the various issues that could be happening within your hydraulic systems. Rule Out Common Issues The next step would be to rule out any common issues or problems that might be preventing your hydraulic systems from working to the best of their ability. These problems could be anything from overheating hydraulic fluid, to improper hydraulic fluid levels, to even a hydraulic leak or dirty/clogged filters. These common problems can be the cause of a lot of hydraulic system drama in your company, so take the time to check them out first if you are able. Now let`s take a look at some other issues that might be the root of your hydraulic system issues. Other Possible Issues Too Thick or Too Cold of Hydraulic Fluid Having too thick or too cold of hydraulic fluid can cause various issues within your systems including slow operation and unpredictable operations. Another culprit could be air in your system. These things can really take a toll on your system if not addressed properly. So be sure to let your mechanic know if you suspect any of these problems with your hydraulic system. Insufficient Oil, Incorrect Fluid, or Contamination A common issue that seems to arise is with an excessive amount of noise or vibration with your equipment or machine. This could be a result of an insufficient amount of oil or even contamination. Be sure to check that your machine has enough oil and that the oil is not showing signs of air within the fluid. It`s possible that there are other issues causing noise and vibrations such as internal issues with bearings or couplings that might not be secured properly. Fluid Leak A fluid leak although maybe minor initially can cause big problems for your machinery if not addressed. Leaking fluid can also lead to many other issues with contamination and damaging parts. A fluid leak is likely due to worn out seals, damaged lines, or bad connections – so be sure to take a look at each of them before deciding how to move forward.

When a hydraulic system stops working as intended, whether it is due to a major leak or a failing pump, it can bring productivity to a grinding halt (both literally and figuratively). The process of tracking down the source of the problem involves troubleshooting, which takes considerable skill, experience, and common sense. However, there are some valid guidelines and good hints to help with the process. Preparing for Troubleshooting The first step in effective troubleshooting is making sure you understand what the problem is - and this can involve asking quite a few questions. If someone says, for example, [The pump is vibrating really bad" then you need to delve a bit deeper with questions, such as: How long has this been going on or when did it start? What was going on when you first noticed it? (e.g., system startup or shut down, heavy load, drastic temperature change) Have there been any recent changes to the system, such as maintenance, modifications to the settings, or repairs? When was maintenance last performed? Once you have gathered all the facts that you can, it`s time to pull the hydraulic schematics for reference - do not attempt troubleshooting without this! The schematics provide valuable information about flow and pressure in the system. Common Problems There are certain problems commonly prevent hydraulic systems from working properly, such as an inoperative system or overheating hydraulic fluid. What follows are some troubleshooting tips for typical issues that arise in hydraulic systems. System Inoperative If the hydraulic system is inoperative, there are several things that can be checked. Verify the hydraulic fluid levels and keep in mind that leaks can lead to significant loss of hydraulic fluid. Take a look at the hydraulic filters, because if they are dirty or clogged badly enough, it can seriously impact performance. Check for restrictions in the hydraulic lines; restrictions often take the form of a collapsed or clogged line. Make sure there are no air leaks in the pump suction line. Also inspect the pump itself; if it is worn, dirty, or out of alignment, it will affect system performance. The pump drive can be a source of issues if it the belts or couplings are slipping or broken. It may be time to replace some components; as they begin to wear, it can lead to internal leakage. It is also a good idea to make sure that the unit is operating within its maximum load limits. Slow Operation When a hydraulic system begins working more slowly than normal, one of the causes can be hydraulic fluid that is too thick, which may be due to cold temperatures or the use of an inappropriate hydraulic fluid. Air trapped in the system can be a problem, as well as restrictions in the line, due to dirty hydraulic filters. Another potential issue is badly worn hydraulic components such as pumps, motors, cylinders, and valves. Erratic Operation If the system is operating in an erratic, unpredictable manner, the most common causes are air trapped in the system, hydraulic fluid that is too cold (which means the equipment needs an opportunity to warm up before use), and damaged internal components such as bearings and gears. Excessive Noise or Vibration Another common issue with hydraulic systems is excessive/abnormal noise or vibration. If it is the pump that is noisy, then check that the oil level is sufficient, the correct type of fluid is being used, and that the oil is not foamy. If the oil is foamy, that points to air in the fluid which can lead to cavitation and expensive damage. It is also wise to verify that the inlet screen and suction line are not plugged. For both pumps and hydraulic motors, there can also be internal issues, namely worn or misaligned bearings. And do not forget to make sure that the couplings are secure and tight. Keep in mind that pipes and pipe clamps can vibrate if they are not secured properly. Overheating Hydraulic Fluid Excessive heat is never a good sign in a hydraulic system and often leads to a system working at sub-optimal levels. One of the purposes of hydraulic fluid is to dissipate generated heat, but the system should not be generating enough heat to cause the fluid to reach high temperatures. There can be a host of causes behind hot hydraulic fluid, starting with contaminated hydraulic fluid or fluid levels that are too low. There may be oil passing through the relief valve for too long at a time; in this case, the control valve should be set to neutral when it is not in use. Worn out components within the system can also lead to excessive temperatures due to internal leakage. If there are restrictions in the line or dirty filters, hot hydraulic fluid will result. If hydraulic fluid viscosity is too low, it can lead to overheating as well. Finally, there may be a need to make sure that the oil cooler is functioning correctly and that the key components are clean enough for heat to radiate away from them. Low Viscosity We have discussed low viscosity as a symptom, but it also qualifies as its own problem. When trying to determine why the fluid is not as viscous as it should be, the three things that need to be checked are damage to the oil (often from extreme temperatures or aging), use of the wrong type of hydraulic oil, or the presence of water in the hydraulic fluid. In all three cases, the system will need to be flushed and the oil replaced. Leaks Even a small leak over time can lead to enough fluid loss to impact performance, and if fluid can make its way out of the system then damaging contaminants can make their way in. Most leaks are the result of worn out seals, damaged hydraulic lines, or bad connections. Looking for the source of a leak can be challenging and dangerous. Never try to locate a leak using your hand when the system is running because the high pressure hydraulic fluid can puncture your skin and get trapped beneath, leading to what is known as an injection injury. A quick and safe way to detect leaks is to use cardboard or plywood instead of your hand. If the leak is coming from a motor or pump, then the likely cause is a worn-out seal or gasket that needs replacement. No Fluid Flow Having no flow within the hydraulic system is a serious issue that can have several different sources. The first step is to determine exactly where the fluid flow stops, such as failure of the pump to receive fluid at the inlet (usually the result of a clogged line or dirty strainers) or a failure for fluid to exit the outlet, which could be due to a pump motor that needs replacing, a sheared coupling between the pump and drive, or a pump/drive failure. It would also be a good idea to make sure the pump rotation is set correctly and the directional valves are in the correct position. The most expensive problem would be a damaged pump that needs to be replaced or repaired. Conclusion The first step in troubleshooting is to gather as much information about the problem as possible and then pull the hydraulic schematics for the system. From there, you basically follow a process of elimination until the root of the problem is uncovered. Something else to keep in mind with regard to troubleshooting, however, is that once you have tracked down the source of a problem, it may lead you to yet another problem that will need some troubleshooting. Getting your hydraulic system back in working order can be a time consuming process. For example, you may uncover that the cause of overheating hydraulic fluid is low viscosity - but why is the fluid insufficiently viscous? The troubleshooting process is not over until that issue is uncovered. Take, as another example, the case of a pump whose internal components have worn out and affected overall system performance - why did the components prematurely wear? It may be a cause of misalignment, insufficient lubrication, or contaminated fluid. A good hydraulics technician will not just track down and address the problem, but will keep troubleshooting to make sure that the problem does not happen again.

When a hydraulic system stops working as intended, whether it is due to a major leak or a failing pump, it can bring productivity to a grinding halt (both literally and figuratively). The process of tracking down the source of the problem involves troubleshooting, which takes considerable skill, experience, and common sense. However, there are some valid guidelines and good hints to help with the process. Preparing for Troubleshooting The first step in effective troubleshooting is making sure you understand what the problem is - and this can involve asking quite a few questions. If someone says, for example, [The pump is vibrating really bad" then you need to delve a bit deeper with questions, such as: How long has this been going on or when did it start? What was going on when you first noticed it? (e.g., system startup or shut down, heavy load, drastic temperature change) Have there been any recent changes to the system, such as maintenance, modifications to the settings, or repairs? When was maintenance last performed? Once you have gathered all the facts that you can, it`s time to pull the hydraulic schematics for reference - do not attempt troubleshooting without this! The schematics provide valuable information about flow and pressure in the system. Common Problems There are certain problems commonly prevent hydraulic systems from working properly, such as an inoperative system or overheating hydraulic fluid. What follows are some troubleshooting tips for typical issues that arise in hydraulic systems. System Inoperative If the hydraulic system is inoperative, there are several things that can be checked. Verify the hydraulic fluid levels and keep in mind that leaks can lead to significant loss of hydraulic fluid. Take a look at the hydraulic filters, because if they are dirty or clogged badly enough, it can seriously impact performance. Check for restrictions in the hydraulic lines; restrictions often take the form of a collapsed or clogged line. Make sure there are no air leaks in the pump suction line. Also inspect the pump itself; if it is worn, dirty, or out of alignment, it will affect system performance. The pump drive can be a source of issues if it the belts or couplings are slipping or broken. It may be time to replace some components; as they begin to wear, it can lead to internal leakage. It is also a good idea to make sure that the unit is operating within its maximum load limits. Slow Operation When a hydraulic system begins working more slowly than normal, one of the causes can be hydraulic fluid that is too thick, which may be due to cold temperatures or the use of an inappropriate hydraulic fluid. Air trapped in the system can be a problem, as well as restrictions in the line, due to dirty hydraulic filters. Another potential issue is badly worn hydraulic components such as pumps, motors, cylinders, and valves. Erratic Operation If the system is operating in an erratic, unpredictable manner, the most common causes are air trapped in the system, hydraulic fluid that is too cold (which means the equipment needs an opportunity to warm up before use), and damaged internal components such as bearings and gears. Excessive Noise or Vibration Another common issue with hydraulic systems is excessive/abnormal noise or vibration. If it is the pump that is noisy, then check that the oil level is sufficient, the correct type of fluid is being used, and that the oil is not foamy. If the oil is foamy, that points to air in the fluid which can lead to cavitation and expensive damage. It is also wise to verify that the inlet screen and suction line are not plugged. For both pumps and hydraulic motors, there can also be internal issues, namely worn or misaligned bearings. And do not forget to make sure that the couplings are secure and tight. Keep in mind that pipes and pipe clamps can vibrate if they are not secured properly. Overheating Hydraulic Fluid Excessive heat is never a good sign in a hydraulic system and often leads to a system working at sub-optimal levels. One of the purposes of hydraulic fluid is to dissipate generated heat, but the system should not be generating enough heat to cause the fluid to reach high temperatures. There can be a host of causes behind hot hydraulic fluid, starting with contaminated hydraulic fluid or fluid levels that are too low. There may be oil passing through the relief valve for too long at a time; in this case, the control valve should be set to neutral when it is not in use. Worn out components within the system can also lead to excessive temperatures due to internal leakage. If there are restrictions in the line or dirty filters, hot hydraulic fluid will result. If hydraulic fluid viscosity is too low, it can lead to overheating as well. Finally, there may be a need to make sure that the oil cooler is functioning correctly and that the key components are clean enough for heat to radiate away from them. Low Viscosity We have discussed low viscosity as a symptom, but it also qualifies as its own problem. When trying to determine why the fluid is not as viscous as it should be, the three things that need to be checked are damage to the oil (often from extreme temperatures or aging), use of the wrong type of hydraulic oil, or the presence of water in the hydraulic fluid. In all three cases, the system will need to be flushed and the oil replaced. Leaks Even a small leak over time can lead to enough fluid loss to impact performance, and if fluid can make its way out of the system then damaging contaminants can make their way in. Most leaks are the result of worn out seals, damaged hydraulic lines, or bad connections. Looking for the source of a leak can be challenging and dangerous. Never try to locate a leak using your hand when the system is running because the high pressure hydraulic fluid can puncture your skin and get trapped beneath, leading to what is known as an injection injury. A quick and safe way to detect leaks is to use cardboard or plywood instead of your hand. If the leak is coming from a motor or pump, then the likely cause is a worn-out seal or gasket that needs replacement. No Fluid Flow Having no flow within the hydraulic system is a serious issue that can have several different sources. The first step is to determine exactly where the fluid flow stops, such as failure of the pump to receive fluid at the inlet (usually the result of a clogged line or dirty strainers) or a failure for fluid to exit the outlet, which could be due to a pump motor that needs replacing, a sheared coupling between the pump and drive, or a pump/drive failure. It would also be a good idea to make sure the pump rotation is set correctly and the directional valves are in the correct position. The most expensive problem would be a damaged pump that needs to be replaced or repaired. Conclusion The first step in troubleshooting is to gather as much information about the problem as possible and then pull the hydraulic schematics for the system. From there, you basically follow a process of elimination until the root of the problem is uncovered. Something else to keep in mind with regard to troubleshooting, however, is that once you have tracked down the source of a problem, it may lead you to yet another problem that will need some troubleshooting. Getting your hydraulic system back in working order can be a time consuming process. For example, you may uncover that the cause of overheating hydraulic fluid is low viscosity - but why is the fluid insufficiently viscous? The troubleshooting process is not over until that issue is uncovered. Take, as another example, the case of a pump whose internal components have worn out and affected overall system performance - why did the components prematurely wear? It may be a cause of misalignment, insufficient lubrication, or contaminated fluid. A good hydraulics technician will not just track down and address the problem, but will keep troubleshooting to make sure that the problem does not happen again.

Maintenance of Hydraulic Systems Ricky Smith Lack of maintenance of hydraulic systems is the leading cause of component and system failure yet most maintenance personnel don't understand proper maintenance techniques of a hydraulic system. The basic foundation to perform proper maintenance on a hydraulic system has two areas of concern. The first area is Preventive Maintenance which is key to the success of any maintenance program whether in hydraulics or any equipment which we need reliability. The second area is corrective maintenance, which in many cases can cause additional hydraulic component failure when it is not performed to standard. Preventive Maintenance Preventive Maintenance of a hydraulic system is very basic and simple and if followed properly can eliminate most hydraulic component failure. Preventive Maintenance is a discipline and must be followed as such in order to obtain results. We must view a PM program as a performance oriented and not activity oriented. Many organizations have good PM procedures but do not require maintenance personnel to follow them or hold them accountable for the proper execution of these procedures. In order to develop a preventive maintenance program for your system you must follow these steps: 1st: Identify the system operating condition. a. Does the system operate 24 hours a day, 7 days a week? b. Does the system operate at maximum flow and pressure 70% or better during operation? c. Is the system located in a dirty or hot environment? 2nd: What requirements does the Equipment Manufacturer state for Preventive Maintenance on the hydraulic system? 3rd: What requirements and operating parameters does the component manufacturer state concerning the hydraulic fluid ISO particulate? 4th: What requirements and operating parameters does the filter company state concerning their filters ability to meet this requirement? 5th: What equipment history is available to verify the above procedures for the hydraulic system? As in all Preventive Maintenance Programs we must write procedures required for each PM Task. Steps or procedures must be written for each task and they must be accurate and understandable by all maintenance personnel from entry level to master. Preventive Maintenance procedures must be a part of the PM Job Plan which includes: Tools or special equipment required performing the task. Parts or material required performing the procedure with store room number. Safety precautions for this procedure. Environmental concerns or potential hazards. A list of Preventive Maintenance Task for a Hydraulic System could be: 1. Change the (could be the return or pressure filter) hydraulic filter. 2. Obtain a hydraulic fluid sample. 3. Filter hydraulic fluid. 4. Check hydraulic actuators. 5. Clean the inside of a hydraulic reservoir. 6. Clean the outside of a hydraulic reservoir. 7. Check and record hydraulic pressures. 8. Check and record pump flow. 9. Check hydraulic hoses, tubing and fittings. 10. Check and record voltage reading to proportional or servo valves. 11. Check and record vacuum on the suction side of the pump. 12. Check and record amperage on the main pump motor. 13. Check machine cycle time and record. Preventive Maintenance is the core support that a hydraulic system must have in order to maximize component and life and reduce system failure. Preventive Maintenance procedures that are properly written and followed properly will allow equipment to operate to its full potential and life cycle. Preventive Maintenance allows a maintenance department to control a hydraulic system rather than the system controlling the maintenance department. We must control a hydraulic system by telling it when we will perform maintenance on it and how much money we will spend on the maintenance for the system. Most companies allow the hydraulic system to control the maintenance on them, at a much higher cost. In order to validate your preventive maintenance procedures you must have a good understanding and knowledge of "Best Maintenance Practices" for hydraulic systems. We will convey these practices to you. Hydraulic Knowledge People say knowledge is power. Well this is also true in hydraulic maintenance. Many maintenance organizations do not know what their maintenance personnel should know. I believe in an industrial maintenance organization that we should divide the hydraulic skill necessary into two groups. One is the hydraulic troubleshooter, they must be your experts in maintenance and this should be as a rule of thumb 10% or less of your maintenance workforce. The other 90% + would be your general hydraulic maintenance personnel. They are the personnel that provide the preventive maintenance expertise. The percentages I gave you are based on a company developing a true Preventive / Proactive maintenance approach to their hydraulic systems. Let's talk about what the hydraulic troubleshooter knowledge and skills. Hydraulic Troubleshooter: Knowledge - • Mechanical Principles / force, work, rate, simple machines. • Math / basic math, complex math equations. • Hydraulic Components / application and function of all hydraulic system components. • Hydraulic Schematic Symbols / understanding all symbols and their relationship to a hydraulic system. • Calculate flow, pressure, and speed. • Calculate the system filtration necessary to achieve the system's proper ISO particulate code. Skill - • Trace a hydraulic circuit to 100% proficiency. • Set the pressure on a pressure compensated pump. • Tune the voltage on an amplifier card. • Null a servo valve. • Troubleshoot a hydraulic system and utilize "Root Cause Failure Analysis". • Replace any system component to manufacturer's specification. • Develop a PM Program for a hydraulic system. • Flush a hydraulic system after a major component failure. General Hydraulic: Knowledge - • Filters / function, application, installation techniques • Reservoirs / function, application • Basic hydraulic system operation • Cleaning of hydraulic systems • Hydraulic lubrication principles • Proper PM techniques for hydraulics Skills - • Change a hydraulic filter and other system components. • Clean a hydraulic reservoir. • Perform PM on a hydraulic system. • Change a strainer on a hydraulic pump. • Add filtered fluid to a hydraulic system. • Identify potential problems on a hydraulic system. • Change a hydraulic hose, fitting or tubing. Measuring Success In any program we must track success in order to have support from management and maintenance personnel. We must also understand that any action will have a reaction, negative or possible. We know successful maintenance programs will provide success but we must have a checks and balances system to ensure we are on track. In order to measure success of a hydraulic maintenance program we must have a way of tracking success but first we need to establish a benchmark. A benchmark is method by which we will establish certain key measurement tools that will tell you the current status of your hydraulic system and then tell you if you are succeeding in your maintenance program. Before you begin the implementation of your new hydraulic maintenance program it would be helpful to identify and track the following information. 1. Track all downtime (in minutes) on the hydraulic system with these questions answered. / Tracked daily / • What component failed? • Cause of failure? • Was the problem resolved? • Could this failure have been prevented? 2. Track all cost associated with the downtime. / tracked daily / • Parts and material cost? • Labor cost? • Production downtime cost? • Any other cost you may know that can be associate with a hydraulic system failure. 3. Track hydraulic system fluid analysis. Track the following from the results. / take samples once a month / • Copper content • Silicon content • H2O • Iron content • ISO particulate count • Fluid condition (Viscosity, additives, and oxidation). When the tracking process begins you need to trend the information that can be trended. This allows management the ability to identify trends that can lead to positive or negative consequences. Fluid analysis proved the need for better filtration. The addition of a 3-micron absolute return line filter to supplement the "kidney loop" filter solved the problem. Many organizations do no know where to find the method for tracking and trending the information you need accurately. A good Computerized Maintenance Management System can track and trend most of this information for you. Recommended Maintenance Modifications Modifications to an existing hydraulic system need to be accomplished professionally. A modification to a hydraulic system in order to improve the maintenance efficiency is important to a company's goal of maximum equipment reliability and reduced maintenance cost. 1st: Filtration pump with accessories: Objective: The objective of this pump and modification is to reduce contamination that is introduced into an existing hydraulic system through the addition of new fluid and the device used to add oil to the system. Additional Information: Hydraulic fluid from the distributor is usually not filtered to the requirements of an operating hydraulic system. Typically this oil is strained to a mesh rating and not a micron rating. How clean is clean? Typically hydraulic fluid must be filtered to 10 microns absolute or less for most hydraulic system, 25 microns is the size of a white blood cell, and 40 microns is the lower limit of visibility with the unaided eye. Many maintenance organizations add hydraulic fluid to a system through a contaminated funnel and may even used a bucket that has had other types of fluids and lubricants in them previously, without cleaning them. Recommended equipment and parts: • Portable Filter Pump with a filter rating of 3 microns absolute. • Quick disconnects that meet or exceeds the flow rating of the Portable Filter Pump. • A ¾" pipe long enough to reach the bottom of a hydraulic container your fluids are delivered in from the distributor. • A 2" reducer bushing to ¾"npt to fit into the 55 gallon drum, if you receive your fluid by the drum. Otherwise, mount the filter buggy to the double wall "tote" tank supports, if you receive larger quantities. • Reservoir vent screens should be replaced with 3/10 micron filters, an openings around piping entering the reservoir sealed. Show a double wall tote tank of about 300 gallons mounted on a frame for fork truck handling, with the pump mounted on the frame work. Also show pumping from a drum mounted on a frame for fork truck handling, sitting in a catch pan, for secondary containment, with the filter buggy attached. Regulations require that you have secondary containment, so make everything "leak" into the pan. 2nd. Modify the Hydraulic Reservoir Objective: The objective is to eliminate the introduction of contamination through oil being added to the system or contaminates being added through the air intake of the reservoir. A valve needs to be installed for oil sampling. Additional Information: The air breather strainer should be replaced with a 10-micron filter if the hydraulic reservoir cycles. A quick disconnect should be installed on the bottom of the hydraulic unit and at the ¾ level point on the reservoir with valves to isolate the quick disconnects in case of failure. This allows the oil to added from a filter pump as previously discussed and would allow for external filtering of the hydraulic reservoir oil if needed. Install a petcock valve on the front of the reservoir that will be used for consistent oil sampling. Equipment and parts needed: • Quick disconnects that meet or exceeds the flow rating of the Portable Filter Pump. • Two gate valves with pipe nipples. • One 10 micron filter breather. WARNING: Do not weld on a hydraulic a reservoir to install the quick disconnects or air filter. As in any proactive maintenance organization you must perform Root Cause Failure Analysis in order to eliminate future component failures. Most maintenance problems or failures will repeat themselves without someone identifying what caused the failure and proactively eliminate it. A preferred method is to inspect and analyze all component failures. Identify the following: • Component Name and model number. • Location of component at the time of failure. • Sequence or activity the system was operating at when the failure occurred. • What caused the failure? • How will the failure be prevented from happening again? Failures are not caused by an unknown factor like "bad luck" or "it just happened" or "the manufacturer made a bad part". We have found most failures can be analyzed and prevention taken to prevent their reoccurrence. Establishing teams to review each failure can pay off in major ways. To summarize, maintenance of a hydraulic system is the first line of defense to prevent component failure and thus improve equipment reliability. As spoken about earlier, discipline is the key to the success of any proactive maintenance program.

Detecting and Managing Hydraulic System Leakage Kevan Slater, Schematic Approach It is unfortunate that many leaks identified in hydraulic systems are left to drip away the profits of a company. And it is not just the cost of the hydraulic oil itself-profits are also lost to unnecessary energy consumption, reduced equipment performance, decreased reliability, increased housekeeping costs, increased maintenance costs, damage to hydraulic systems and components and many more costs. Leaks often go unnoticed because there are no visual indications to alert operators or technicians of the problem until system performance has been severely affected. The components with these leaks are typically repaired in an unplanned, fire-fighting mode of breakdown maintenance. If the problem had been caught earlier, it likely could have been fixed during planned downtime, resulting in lower associated costs and less impact on productivity. Identifying and controlling hydraulic system leakage is something that every company with hydraulic assets should be interested in. Hydraulic systems can leak both internally and externally, causing different issues and requiring different solutions. These problems can be tackled in a variety of ways from making simple lubricant changes to integrating advanced tools that help your teams detect and manage hydraulic leaks. But the key to any approach is faster, earlier detection and fast response. Let`s look at a few ways to accomplish this. How to Start Detecting External Hydraulic Leaks Faster There are many ways to help yourself and maintenance and operator teams to identify problem leaks more quickly, saving time, money, and headaches. The faster a leak is identified and reported, the more time you have to respond before it causes problems like loss of performance or long-term damage to your hydraulic equipment. Use a Hydraulic Oil with a Distinctive Color Consider using a hydraulic oil that has a distinctive color vs your other lubricants and fluids. This can help both skilled and entry-level staff to identify when a leak is hydraulic in nature and prioritize reporting the problem quickly and appropriately. Train Staff on Spotting and Reporting External Leaks Can your operators, technicians, and maintenance staff all quickly identify a hydraulic leak vs another fluid leak in your equipment? If not, you`re likely not catching important hydraulic leaks as quickly as you could. If the hydraulic oil is a different color, it`s easy to instruct staff to immediately report [green fluid leaks" (or whatever color your hydraulic fluid may be) to the proper person as soon as they are spotted. More Ways to Improve Leak Detection These simple steps are a great place to start improving your hydraulic leak detection and management with very little associated cost or effort, but they can be supplemented with other approaches as well. Taking an in-depth look at record keeping and surveillance based on monitoring leakage within hydraulic systems is a good way to understand trends over time By matching this data with a robust plan for performing repairs and/or modifications aimed at the root causes of the leaks, significant progress can be made. Internal Planned Hydraulic Leaks Not all leaks hydraulic leaks are very visible, or even necessarily bad. The vast majority of hydraulic systems in operation today have leaks-leaks that are planned. They are designed with a specific function in mind and. in many cases, are documented by the original equipment manufacturer (OEM) as the amount of acceptable leakage under normal operating conditions. Such internal planned leakage typically occurs through small orifices or pathways that allow a fluid from a higher pressurized zone of a system to travel into a lower pressurized zone to lubricate, clean and cool a specific component or area. These planned internal leaks do not allow the fluid to exit the hydraulic circuit, so there is no visual indication of its presence. The most common cause of unplanned, excessive internal leakage is wear of component surfaces during normal operation. Leakage can also result from poor system design, incorrect component selection, poor quality control tolerances during the manufacturing of a component or incorrect overhaul of rebuilt components. First Warning Signs of Excessive Internal Hydraulic Leaks The first symptoms of excessive internal hydraulic leakage are decreased system performance or reliability and increased operating temperatures, The major power loss hydraulic systems usually experience is the result of internal leakage on pumps and motors. This leakage is the result of excessive clearances within the pumping mechanisms of the pumps and motors resulting in reduced volumetric efficiency. Slippage-a common term used to describe the volumetric loss of a pump/motor-is typically identified when the input energy remains the same or higher, but less work is being performed in the hydraulic circuit. In hydraulic cylinders, cylinder rod drift or creep and the cylinder`s inability to hold the designed load would be identified by increased leakage. The excessive leakage is the result of the fluid bypassing a piston seal either through a worn seal or a worn cylinder barrel (Figure 1). In spool valves, excessive internal clearances between the spool and the valve body decrease control and stability of the hydraulic circuits and their functions. Profit-robbing energy loss is the result of energized fluid that is allowed to escape back to the reservoir through a spool valve that has an out-of-specification clearance problem. Relief valves or other spring offset valves with a weak spring or a jammed open condition will have the same effect of fluid energy loss by allowing the pressurized fluid to bypass the working circuit. Low fluid viscosity or excessive heat (reducing the effective viscosity of a fluid) will also increase leakage rates. This form of internal leakage reduces system performance and decreases fluid film strength, which will also result in premature wear of the equipment surfaces and the fluid`s properties.Eventually, all of these conditions will affect hydraulic system performance, and ultimately company profits. Detection of unplanned internal leakage in most cases would rely on specific tools to examine the location and quantity of the leak. How to Detect Internal Hydraulic Leakage Performance issues or the inability of a circuit to perform its designed function typically triggers craftsmen to install flow meters in various locations (such as case drains on pumps) to detect excessive leakage resulting from unacceptable clearances in mating surfaces. Many companies install flow meters on the case drains of pumps and motors to determine when to overhaul these components before performance is severely affected. In critical automated positioning systems, both the control valves and the hydraulic cylinders could require periodic bench testing to ensure an acceptable leakage rate is maintained. At this point, all components that fall outside the acceptable standards would require an overhaul ensuring that OEM minimum standards are achieved. OEMs recommend an optimum operating viscosity required by their equipment to perform within the design parameters. In many cases, selecting a fluid and maintaining an operating temperature which achieves the OEM recommended viscosity become the responsibility of the end user. Temperature measurement at the critical components ensures equipment is operating within that optimum range. Use of the Viscosity-Temperature Standard Charts (ASTM D341) assists in determining these variables (Figure 2). Noncontact infrared thermometers are useful for nonobtrusive measurement of operating temperatures of equipment. An abnormal temperature increase at a relief valve could indicate that the valve is in a bypassing condition. This bypass condition will generate heat locally in the component; in many cases, the anomaly would have gone undetected by monitoring the system reservoir temperature because of system coolers or dissipation of heat throughout the system. Using Ultrasonic Tools for Hydraulic Leak Detection Ultrasonic detection has proven to be another effective method of determining high pressure or high velocity leaks in various locations of valve and cylinder leakage. This method enables the localization of the internal leakage; but similar to temperature reading, the results are not quantifiable into the amount of leakage. The only quantifiable method is to measure the flow or quantity of fluid loss in a given time frame using a flow meter or other related test equipment. Figure 4. External Leakage - Difficult to Locate the Source. External leakage is the most recognizable type of leakage. Even the untrained eye can easily spot a broken hose spewing oil like a Texas geyser. These types of leaks will typically be repaired quickly, because the equipment, production line or process will quickly come to a halt if the problem is ignored. The constant drip or drop is not always repaired because system performance and production are usually not affected. The location and/or quantity of the leaked fluid is in many cases like [Waldo" - hard to find - and the repair not really worth the effort (Figure 4). Many companies spend tens of thousands of dollars a year replacing top-up fluids, not really understanding the financial impact of a drip. Reports show that the replacement cost of a fluid can cost five times more than the cost of the new fluid. Two areas that are not represented in the fluid replacement costs and should be to renew the interest in repairing leaks are: 1. Safety Issues 2. Environmental Issues Both of these areas have personal and financial implications when leaks are allowed to exist without competent maintenance practices to eliminate them. Detection and quantification of the fluid consumption is the first step in external leak control. Up-to-date reservoir management records must be maintained to determine when, by whom and how much fluid was required to top-up a reservoir. These records should be used along with visual inspections to determine the location and the leak rate of any detected anomalies. SAE J1176 Leak Classification Tables is a method used to quantify leaks once they have been located (Figure 5). Quantification of the leakage rate and location will allow for the opportunity to prioritize the repairs. In many cases, the source and quantity of the leaks cannot be determined, as they are difficult to see. The best practice recommends occasionally cleaning an area and fully wiping down equipment to examine the leaks. Using Black Light Sensitive Dyes to Help Detect Hydraulic Leaks When leaks are too small or too numerous to see clearly, you can take the color dye a step further by adding dyes sensitive to black light.. This liquid dye is formulated to be compatible with the existing hydraulic fluid and machine surfaces. The dye is mixed into the reservoir after which the mixture will emit a bright green/yellow glow when struck by the rays of a black light (Figure 6). This method of visual detection helps determine whether the fluid being viewed is from an active leak from the system in question (Figure 7). Figure 6. Fluorescent Dye Leak Detection Figure 7. Visual Enhancement Dyes The changing workplace, the environment and the need for equipment reliability require a concerted effort to monitor and maintain all unplanned leaks. While you can take simple steps now that may offersignificant savings, many companies have found success by creating entire Any leakage control programs that begin with the original equipment design and are maintained throughout the lifecycle of the equipment. This sort of investment helps to preserve system viability and system integrity long term. With the right training, lubricants, and equipment in place, you will be able to quantify, characterize, analyze all types of leaks. This collected information can give maintenance professionals an opportunity to perform leakage control activities by planning ahead and being proactive about their maintenance and reliability goals., If you are able to properly manage hydraulic system leakage, you will be able to achieve reduced energy consumption, reduced waste, increased uptime, improved equipment reliability and ultimately increased company profits.

How Does a Hydraulic Motor Work? The primary source of power in a hydraulic system is fluid pressure. But in order for this type of hydraulic energy to be converted into useful mechanical energy, you need a hydraulic motor. What happens is the hydraulic pump pushes fluid through the motor, and this fluid moves the gears, vanes or pistons of the hydraulic motor. This movement of the parts inside the motor generates power which can be used to activate other parts of the system. The two most important defining qualities of a hydraulic motor are torque and speed. These two qualities are related. Torque is a function of the volume of fluid a motor can displace and the pressure drop across the motor, and speed is a function of input flow and displacement. Increasing torque will reduce flow and therefore reduce speed, unless you compensate with increased flow. Types of Hydraulic Motors The main types of hydraulic motors are as follows: Low-end orbital motors: reliable for low-pressure, low-speed applications; inefficient at higher pressures and speeds. Gear motors: simple, inexpensive, and good for medium-speed applications; can be noisy. Vane motors: provide good efficiency for large displacement applications; can be pricey. Radial piston motors: very efficient and have very large capacities; can be expensive. Bent-axis piston motors: ideal for applications requiring a lot of power in a compact package. Buying Hydraulic Motors When it comes to buying hydraulic motors, you have a lot of options-not just in the products you choose but where you opt to purchase them. At Bernell Hydraulics, we are proud to offer an extensive selection of quality hydraulic motors from top brand names like Parker. For example, we carry the famous Parker Torqmotor, known as one of the most reliable motors on the market. But we believe that it is our high level of customer service that sets us apart and makes Bernell Hydraulics such a good place to buy hydraulic motors. We will be happy to discuss your needs with you to help you find the right product for your equipment. We can even provide onsite troubleshooting services if needed. We offer onsite hydraulic motor installation within our local service area too. Please call 909-899-1751 to learn more.

What is Gear Motor | Working , Diagram , Advantages ,Range Written by Sachin Thorat in Hydraulic and Pneumatic System Table of Contents What is Gear Motor | Working , Diagram , Advantages ,Range Advantages of Gear Motors Disadvantages of Gear Motors What is Gear Motor | Working , Diagram , Advantages ,Range A gear motor develops torque due to hydraulic pressure acting against the area of one tooth. There are two teeth trying to move the rotor in the proper direction, while one net tooth at the center mesh tries to move it in the opposite direction. In the design of a gear motor, one of the gears is keyed to an output shaft, while the other is simply an idler gear. Pressurized oil is sent to the inlet port of the motor. Pressure is then applied to the gear teeth, causing the gears and output shaft to rotate. The pressure builds until enough torque is generated to rotate the output shaft against the load. The side load on the motor bearing is quite high, because all the hydraulic pressure is on one side. This limits the bearing life of the motor. Schematic diagram of gear motor is shown in Fig. Read also : What is Hydraulic Motor or Rotary Actuator | Types , Application gear motor diagram Most of the gear motors are bidirectional. Reversing the direction of flow can reverse the direction of rotation.As in the case of gear pumps, volumetric displacement is fixed. Due to the high pressure at the inlet and low pressure at the outlet, a large side load on the shaft and bearings is produced. Gear motors are normally limited to 150 bar operating pressures and 2500 RPM operating speed. They are available with a maximum flow capacity of 600 LPM. The gear motors are simple in construction and have good dirt tolerance, but their efficiencies are lower than those of vane or piston pumps and they leak more than the piston units. Generally,they are not used as servo motors.Hydraulic motors can also be of internal gear design. These types can operate at higher pressures and speeds and also have greater displacements than external gear motors. Advantages of Gear Motors The gear motors are simple ill design, and very cheap in cost. Disadvantages of Gear Motors Gear motors are subjected to relatively high internal leakage. Therefore, they are not suitable for high torque, low speed applications. The high pressure at the inlet, coupled with the low pressure at the outlet, generates very high bearing loads. Ranges The gear motors are available for peak operating pressures upto about 125 bars, with rated capacities upto 10 Lps, and maximum speeds of about 3000 rpm.

What is Gear Motor | Working , Diagram , Advantages ,Range Written by Sachin Thorat in Hydraulic and Pneumatic System Table of Contents What is Gear Motor | Working , Diagram , Advantages ,Range Advantages of Gear Motors Disadvantages of Gear Motors What is Gear Motor | Working , Diagram , Advantages ,Range A gear motor develops torque due to hydraulic pressure acting against the area of one tooth. There are two teeth trying to move the rotor in the proper direction, while one net tooth at the center mesh tries to move it in the opposite direction. In the design of a gear motor, one of the gears is keyed to an output shaft, while the other is simply an idler gear. Pressurized oil is sent to the inlet port of the motor. Pressure is then applied to the gear teeth, causing the gears and output shaft to rotate. The pressure builds until enough torque is generated to rotate the output shaft against the load. The side load on the motor bearing is quite high, because all the hydraulic pressure is on one side. This limits the bearing life of the motor. Schematic diagram of gear motor is shown in Fig. Read also : What is Hydraulic Motor or Rotary Actuator | Types , Application gear motor diagram Most of the gear motors are bidirectional. Reversing the direction of flow can reverse the direction of rotation.As in the case of gear pumps, volumetric displacement is fixed. Due to the high pressure at the inlet and low pressure at the outlet, a large side load on the shaft and bearings is produced. Gear motors are normally limited to 150 bar operating pressures and 2500 RPM operating speed. They are available with a maximum flow capacity of 600 LPM. The gear motors are simple in construction and have good dirt tolerance, but their efficiencies are lower than those of vane or piston pumps and they leak more than the piston units. Generally,they are not used as servo motors.Hydraulic motors can also be of internal gear design. These types can operate at higher pressures and speeds and also have greater displacements than external gear motors. Advantages of Gear Motors The gear motors are simple ill design, and very cheap in cost. Disadvantages of Gear Motors Gear motors are subjected to relatively high internal leakage. Therefore, they are not suitable for high torque, low speed applications. The high pressure at the inlet, coupled with the low pressure at the outlet, generates very high bearing loads. Ranges The gear motors are available for peak operating pressures upto about 125 bars, with rated capacities upto 10 Lps, and maximum speeds of about 3000 rpm.

What are the main characteristics of a gerotor motor? Low speed, high torque (LSHT) hydraulic Gerotor motors feature a high starting torque ; and large range of speeds with a continuous output torque. In addition, the motor has a good power-to-weight ratio and a smooth operation, even at low speeds. The Gerotor motor`s design is furthermore very robust and built for harsh working conditions.

How do hydraulic gear motors work? Gears are used to reduce the shaft output speed for applications that require a lower speed. This means that the gear motor`s operating pressure typically is very low, ranging between 100 and 150 bar. In addition, some of the more modern gear motors operate at, up to, 250 bar continuous pressure. However, the downside is that this motor can be rather noisy. To sum up, gear motors are generally lightweight and small units with relatively high pressures. In addition they are known for their low cost, variety of speeds, broad temperature range, simple design and large viscosity range.

Hydraulic Fan Drive Systems By Tom Eystad Introduction In the internal combustion engine, much of the energy is lost to inefficiencies such as heat. Only about 30% of the input energy is actually converted to mechanical power. For large vehicles, engine cooling systems require a significant amount of horsepower and greatly increase the noise level of the machine. With Tier 4 engines, the cooling requirements have increased and the demand for more efficient systems has multiplied. There is a greater push for quieter operation and greater machine efficiency than ever before. Conventional fan drive systems overcool under most conditions in order to insure adequate cooling during the more demanding high heat operation condition. With this system, much of the power used to drive the fan is wasted. The temperature-activated, electronically-controlled, hydrostatic fan drive system can offer finer control and reduce the fan speed during times of low cooling demand. Therefore, the fan drive system can use less power. The power saved can be used to increase fuel efficiency and the overall operating efficiency of the machine. Variable and Alternating Hydraulic Fan Drives lternating, or on/off fan drive systems use a relief valve with a control that is either on, or off. It is the simplest and lowest cost option. The pump volume and relief setting determine the maximum fan speed. When engine temperature reaches a preset level, a signal is provided to turn the fan on by closing the vented system. When engine temperature drops below a certain level, the signal is removed to allow the system to vent and the fan is allowed to either stop or run at a low RPM. When the fan is on, it is at maximum speed and noise level. Variable fan speed control using a proportional relief valve is the most cost-effective solution, providing very high operating efficiency. The fan speed is varied as a function of the pressure set by the proportional relief valve. Maximum fan speed is attained when the proportional pressure control valve is at its highest setting. The relief valve will "failsafe" to high pressure so that losing the electrical signal causes the fan to operate at maximum speed for maximum engine cooling if electrical power is lost. Variable fan speed using a variable displacement pump is the most efficient and offers the quietest operation, however the initial cost of this type of system is relatively high, and therefore its use is limited. In this system the pump drives the fan but also provides other functions. When the other functions require a higher pressure than the fan, a reducing valve can be used to limit pressure to the fan. A proportional flow control is used instead of a pressure relief valve. The pump could include a load-sense control which would require a sensing line downstream of the flow control. In applications where the pump is completely dedicated to the fan drive, the pressure and flow control valves would typically be an integral part of the bolt-on pump control. Advantages of Hydraulic Variable-Speed Fan Drive Precise Control of Coolant Temperature - The curve below shows a typical result for fan speed vs. coolant temperature. The difference between the switch-on curve and the switch-off curve (hysteresis) is very small, approximately 1°C. This permits precise control of the coolant temperature with minimal temperature fluctuations, even when there are extreme changes in the engine load. Reduced Engine Wear - Allowing engine coolant to get too hot breaks down engine oil properties and reduces lubrication. Cylinder and bearing wear can be reduced considerably when the operating temperature is reached quickly and maintained. High Flexibility - The vehicle designer is allowed to optimize the arrangement of the engine and cooling system components. A considerable advantage can be achieved here in regards to noise insulation of the engine. Speed Modulation - Provides constant regulation from minimum to maximum fan speeds over a temperature range of approximately 10°C. This prevents abrupt speed changes which can lead to heavy loads on drive parts and high noise levels. The bandwidth of 10°C permits average cooling output without unnecessary switching between minimum and maximum fan speeds. Maximum Speed Limitation - The proportional pressure control valve also acts to limit maximum fan speed to control power consumption and noise level of the impeller. Energy Savings - Under normal cooling requirements, the fan will operate at about 50% to 80% of maximum RPM and can go as low as 10% to 20% in cold weather climates. This results in power savings and a drop in fuel consumption. The curve above shows a typical power requirement curve for a hydrostatic fan with proportional control. When the fan is running between 50% and 80% of maximum speed, the input horsepower is reduced to approximately 40% to 80% of maximum. In cold weather climates this could be as low as 15% to 20% of the maximum horsepower. The input horsepower is the sum of the fan horsepower plus the mechanical and hydraulic losses of the system. Electronic Control Systems and Components Hydrostatic fan drive systems can utilize electronic controls ranging from simple single-sensor circuits to complicated multi-sensor circuits with fan speed feedback. The type of electronics used in a given application is determined by the level of accuracy and control required. In a simple two-speed control there is a temperature sensor or switch and a proportional relief valve. In this system the fan will run at maximum speed when cooling demand is high, and at an intermediate speed when cooling demand is lower. The electronic control is set to wait until a signal is generated by the temperature sensor or switch before starting the fan. This allows the engine to come up to temperature before the fan starts operating. The electronic control has a built-in ramp function which will bring the fan speed up to maximum at a controlled rate of acceleration. This reduces the startup shock loading on the fan drive components. When the coolant temperature decreases below the set point, the fan RPM is reduced to the intermediate speed. The fan will then cycle between the two speeds with a ramped acceleration from intermediate to maximum speed. The proportional systems illustrated are more sophisticated, offering more precise control of fan speed. These systems can employ a separate fan module or use a signal from the engine control module (ECM). These systems can provide precise engine temperature control. Fan speed is constantly modulating over approximately 10°C with a hysteresis of about 1°C. Applications The major factors to consider when applying fan drive systems are: • Fan specifications • Pump/motor sizing • Proportional valve selection • Electronic control requirements The fan specifications will typically establish airflow at a given RPM which will result in a horsepower and torque requirement. From this specification, the pump/motor can be selected. This determines flow and pressure requirements which will determine the proportional relief valve to be used. The electronics can then be selected and programmed based on the system requirements for the inputs and final control parameters. Conclusion For the machine designer, the hydrostatic fan drive offers flexibility of installation along with reduced noise and high efficiency. The reliability of the fan drive system is improved because the components operate at a lower duty cycle with less shock loading.