variable displacement hydraulic pump animation factory

Piston design - Solid, hollow, or with piston rings. The design and weight of the pistons will have a major effect on pump efficiency. The Parker F11 design with its lightweight head and retained balls can reach significantly higher speeds than swashplate pumps with their longer, heavier pistons.

Some pumps and motors can run over-centre, which means they can provide flow or rotate their drive shaft in both directions. These are commonly used in closed circuit, mobile vehicle drives systems.

Bent axis designs tend to have much heavier duty shaft bearings than swashplate pumps. This is because they are more commonly used as motor drive units and have to take the wheel loads against their shaft. Swashplate pumps, on the other hand, tend to be driven through flexible couplings that will remove any side loads, so the internal bearing is sized just to take the internal loads from the dynamic and pressure loading forces.

Noise level can be an issue with piston pumps. The noise is generated by the discontinuities in the flow e.g. as the pistons move forward and backward they create a pulsating flow that passes into the complete hydraulic system and vibrates or radiates from other components further down the circuit. This flow discontinuity is further complicated by the supply port which connects and disconnects each piston as it rotates. The timing of the opening and closing can create other, higher frequency flow discontinuities. Often different timing plates are available for different operating conditions e.g. fixed speed or variable speed applications.

Case leakage line pressures are critical for controlling the pressure balance of the slipper against the suction pressure. Care should be taken with some pump controllers as the valves exhaust into the pump casing and can create dangerous pressure spikes. Make sure case drain lines are sufficiently sized. One possible solution may be to use a more compliant, clear plastic hose for the case leakage line which will have the effect of damping out these peaks before damage the slippers. Case leakage line temperatures are also a good way of monitoring the health of the pump as discussed in the vane pump section.

If you are in doubt about the most appropriate pump to use in your application then always talk to manufacture or distributor who should be able to offer the most appropriate pump range and advise the expected service life.

Designed for power and speed, the Oilgear PVV open-loop axial-piston hydraulic pumps can handle large, heavy-duty systems. Manufactured with advanced engineering and computer-optimized, the PVV pump range delivers up to 450 Bar / 560 horespower which equates to four times the horsepower at less than half the cost of other manufacturers pumps.

With it"s compact design available in several displacements, the PVV pumps offer a large selection of readily interchangeable controls. With improved response controls and reduced noise levels, its rugged cylinder design enhances performance.

The patented, pressure lubricated swashblock design offers high performance for high-cycling operations. It also contributes to the pump’s ability to run on low-viscosity fluids, including high water content, fire-resistant and other special fluids.

Zeus Hydratech fully supports the Oilgear PVV pump product line and is the only valid source for OEM parts. All Oilgear repairs are machined and tested per our original factory specifications.

A pressure compensator is a device built into some pumps for the purpose of automatically reducing (or stopping) pump flow if system pressure sensed on the pump outlet port, should rise above a pre-set desired maximum pressure (sometimes called the "firing" pressure). The compensator prevents the pump from being overloaded if an overload is placed on the hydraulic system.

A compensator is built into the pump at the factory and usually cannot be added in the field. Any pump built with variable displacement can be controlled with a compensator. These include several types of axial piston pumps and unbalanced (single lobe) vane pumps. Radial piston pumps can sometimes be built with variable displacement but do not lend themselves readily to this action. Most other positive displacement pumps including internal and external gear, balanced (double lobe) vane, gerotor, and screw types cannot be built with variable displacement.

Figure 1 is a schematic of a check valve axial piston pump, variable displacement, controlled with a pressure compensator. The pistons, usually 5, 7, or 9 in number, are stroking inside a piston block which is keyed to and is rotating with the shaft. The left ends of the pistons are attached through swivel joints, to piston shoes which bear against and slide around on the swash plate as the piston block rotates. The swash plate itself does not rotate; it is mounted on a pair of trunnions so it can swivel from neutral (vertical) position to a maximum tilt angle. The angle which the swash plate makes to the vertical causes the pistons to stroke, the length of stroke being proportional to the angle. Normally, at low system pressures, the swash plate remains at its maximum angle, held there by spring force, hydraulic pressure, or by the dynamics of pump construction, and pump flow remains at maximum. The compensator acts by hydraulic pressure obtained internally from the pump outlet port. When pump pressure rises high enough to over-come the adjustable spring behind the compensator piston, the "firing" pressure has been reached, and the compensator piston starts to pull the swash plate back toward neutral, reducing pump displacement and output flow. The spring in the compensator can be adjusted for the desired maximum or "firing" pressure.

Under working conditions, on a moderate system overload, the compensator piston reduces the swash plate angle just enough to prevent the system pressure from exceeding the "firing" pressure adjusted on the compensator. On severe overloads the compensator may swing the swash plate back to neutral (vertical) to reduce pump flow to zero.

Maximum Displacement Stops. Some pumps are available with internal stops to limit the tilt angle of the swash plate. These stops limit the maximum flow and limit the HP consumption of the pump. They may be fixed stops, factory installed and inaccessible from the outside, or they may be externally adjustable with a wrench.

Manual Control Lever. Some pressure compensated pumps, especially hydrostatic transmission pumps, are provided with an external control lever to enable the operator to vary the swash plate angle (and flow) from zero to maximum. On these pumps the pressure compensator is arranged to override the manual lever and to automatically reduce the swash plate angle if a system overload should occur even though the operator control lever is still shifted to maximum displacement position.

Basically the pressure compensator is designed to unload the pump when system pressure reaches the maximum design pressure. When the pump is unloaded in this way, there is little HP consumed and little heat generated even though pressure remains at the maximum level, because there is no flow from the pump.

Variable displacement pumps are usually more expensive than fixed displacement types, but are especially useful in systems where several branch circuits are to be supplied from one pump, and where full pressure may be required simultaneously in more than one branch, and where the pump must be unloaded when none of the branches is ill operation. If individual 4-way valves are used in each branch, each valve must have a closed center spool. The inlet ports on all 4-way valves must be connected in parallel across the pump line. However, if all branch circuits are operated from a bank valve of the parallel type, a pressure compensated variable displacement pump may not be necessary; a fixed displacement pump, gear, vane, or piston, may serve equally well because the bank valve will unload the pump when all valve handles are placed in neutral, but when two or more handles are simultaneously shifted, their branch circuits will automatically be placed in a parallel connection.

As in all hydraulic systems, more pump oil will flow to the branch with the lightest load. Bank valve handles can be modulated to equalize the flow to each branch. When individual 4-way valves are used in each branch, flow control valves may be installed in the branch circuits and adjusted to give the flow desired in each branch.

Figure 2 shows a multiple branch circuit in which a variable displacement pump is used to advantage. Individual 4-way valves, solenoid operated, are used for each branch, and they have closed center porting. Please refer to Design Data Sheet 54 for possible drift problems on a pressure manifold system. A pressure relief valve is usually required even with a pressure compensated pump due to the time interval required for the swash plate to reduce its tilt angle when a sudden overload occurs. The relief valve will help absorb part of the pressure spike generated during this brief interval. It should be adjusted to crack at about 500 PSI higher than the pressure adjustment of the compensator piston spring to prevent oil discharge across it during normal operation.

All hydrostatic transmission systems use a variable displacement pump with pressure compensator, and often combine the compensator with other controls such as the horsepower input limiter, load sensing, flow sensing, or constant flow control.

Pumps are mechanical devices used to create fluid flow. There are many different kinds of pumps, from a basic hand pump to vacuum pumps. Many pumps are identified by what they do, for example, boiler feed pumps, pressure washer pumps, and windshield washer pumps, and the intended application is a useful attribute for narrowing down pumps meant for specific applications. This article looks at a particular type of piston pump, the radial piston pump.

Piston pumps are durable and relatively simple devices. A basic piston pump is made up of a piston, a chamber, and two valves. The pump operates by driving the piston down into the chamber, thereby compressing the media inside. In a hydraulic pump, this is some sort of fluid, often water or oil. Once the pressure of the fluid exceeds that of the outlet valve spring, the compressed media goes through the open outlet valve. When the piston is drawn back up, it opens the inlet valve and closes the outlet valve, thereby utilizing suction to draw in new media for compression.

Although somewhat expensive, piston pumps are among the most efficient types of pumps. They have an excellent pressure rating (as high as 10,000 psi), but their design makes them susceptible to contaminants. They provide an excellent solution for many high-pressure hydraulic oil pumping applications. Hydraulic Pumps are any of a class of positive displacement machines used in fluid power applications to provide hydraulic flow to fluid-powered devices such as cylinders, rams, motors, and other devices.

A radial piston pump is a type of hydraulic piston pump. The working pistons extend in a radial direction symmetrically around the shaft, marking the main difference beween them and another piston pump, the axial piston pump, which has axially rotating pistons.

Radial piston pumps arrange a series of pistons radially in a cylindrical block around a rotor hub. The block consists of a pintle, a cylinder barrel with pistons, and a rotor. The pintle directs the fluid in and out of the cylinder. The rotor, mounted eccentrically in the pump housing, forces the pistons in and out of cylinders as it rotates, which cause hydraulic fluid to be sucked into the cylinder cavity and then be discharged from it. Inlets and outlets for the pump are located in a valve in a central hub. Each piston is connected to inlet port when it starts extending while it is connected to the outlet port when start retracting.

An alternative design places inlets and outlets around the perimeter of the pump housing. Radial piston pumps can be purchased as fixed- or variable-displacement models. In the variable-displacement version, the eccentricity of the rotor in the pump housing is altered to decrease or increase the stroke of the pistons.

They have many advantages, such as high efficiency, high-pressure capability up to 1,000 bar or 14000 psi, low flow and pressure ripple, low noise level, very high load at the lowest speed, and high reliability. A disadvantage is that they are bigger than axial pumps, because of the bigger radial dimensions, and so cannot always be used in applications with space constraints.

The hydrostatically balanced parts of radial piston pumps make it possible to use them with various hydraulic fluids such as mineral oil, biodegradable oil, HFC (water-glycol), HFD (synthetic ester), HFA (oil in water), and cutting emulsion. Radial pumps are used for machine tools, such as the displacement of cutting emulsion, and as a supply for hydraulic equipment like cylinders. They are also used in high-pressure units (HPU) for overload protection, and for test rigs.

The automotive sector uses them for automatic transmission and hydraulic suspension control in upper-class cars. Radial piston pumps are also used in plastic- and powder injection molding and wind energy.

This guide provides a basic understanding of radial piston pumps. To find out more about other types of pumps, read our guide here. For more information on related products, consult our other product guides or visit the Thomas Supplier Discovery Platform to locate potential sources or view details on specific products.

Variable Displacement Pumps Market was valued at $3,322 million in 2016, and is projected to reach $4,478 million in 2023, growing at a CAGR of 4.4%. The substantial growth in automotive and manufacturing sector fosters the demand for variable displacement pumps. Variable displacement pump is a type of hydraulic pump that makes positive displacement. Variable displacement pumps are energy-efficient as compared to fixed displacement pumps as the pumps doesn"t require manual control and can control the amount of flow via valves that control speed of hydraulic actuators. Growth in construction industry is the major driver for the incremented demand for variable displacement pumps, which are used to have better control over large machine activities. Rising population and rapid urbanization would further contribute to the blooming construction industry, thus, the market for variable displacement pumps would also grow.

The global variable displacement pump market is segmented based on type, application, end-user and geography. Based on type, the market is categorized into vane pump and piston pump. Piston pumps would dominate the market throughout the analysis period owing to its wide volumetric & pressure efficiency range. Market by application comprises hydraulic and IC engine. Hydraulic pumps accounts for maximum market share due to increasing usage of hydraulic pumps in the manufacturing industry. The end-user segment include construction, agriculture, mining, automotive, material handling, oil & gas, water & waste water management, and others.

Variable displacement piston pumps market share is expected to grow at a considerable growth rate during the forecast period. It is a type of positive displacement pump in which number of pistons are arranged in a certain manner. It could be used as a stand-alone pump, an automotive air conditioning compressor, or a hydraulic motor.

Variable displacement pumps market for construction and water & waste water management industries is expected to grow at the significant growth rate during the forecast period. Water & waste water management is one of the crucial task of a city or a town, for which high-pressure, high torque, and highly efficient motors and pumps are required. Increase in innovations, high demands for high-performance, and efficient high-pressure pumps are expected to offer numerous growth opportunities for market expansion. Furthermore, the demand for hydropower energy and tidal energy is expected to drive the market growth. Increase in need for planned cities and towns and rise in standards of living in the developing countries are expected to fuel the market growth in this sector.

The Asia-Pacific variable displacement pumps market is expected to show significant growth in the near future, owing to development in infrastructure, availability of multiple manufacturing facilities, increase in population, significant growth in GDP in the developing countries, and increase in construction activities.

Technological advancements, increase in process automation, growth of oil & gas industry, and design upgradation of pumps & motors are expected to drive the market growth. Deep water and ultra-deep water reserves in Asia-Pacific are expected to contribute toward oil & gas production, and is expected to increase the sales of hydraulic pumps.

The key players profiled in this report are Bosch Rexroth AG, Parker Hannifin Corp., Danfoss A/S, Eaton Corporation, The Oilgear Company, Kawasaki Heavy Industries, Ltd., Yuken Kogyo Co., Hawe Hydraulics, Casappa SPA and Ranger Caradoc Hydraulics Ltd.

The study provides an in-depth analysis of the global variable displacement pumps market and current & future trends to elucidate the imminent investment pockets.