variable displacement hydraulic pump symbol brands

The base symbol for the hydraulic pump (Figure 1) is actually quite simple. It starts with the standard circle and a directional arrow pointing out one end from within that circle. The solid-filled triangle makes this a hydraulic pump while pneumatic pumps (and most pneumatic symbols) are outlines only. There exist no other options for this particular pump symbol, which can be accurately described as a fixed displacement, unidirectional hydraulic pump.

It’s rare to see a pump in any orientation but North when reading schematics, and they are often paired below to a line terminating into the reservoir symbol, which I show just once. If multiple components such as filters, ball valves, accessories or even other pumps are used, the tank line can be widened as needed. Other designers prefer to show every tank line terminate into the same small symbol, while others will place a tank symbol right at every component requiring it, just is done in electrics with the ground symbol.

Unfortunately, and except for rare circumstances, there are no symbology differences between the type of pumps available. The symbols for a gear pump, a vane pump, a piston pump or any other type of physical configuration does not carry with it any symbolic difference, nor does it matter as you’ll find out by the end of this.

The second pump is not much different from the first, with the exception of the second black directional triangle, which informs us this pump can expel fluid from what would otherwise be the suction port. This is the symbol for a bi-rotational pump, which is rare outside of advanced mobile machinery, especially in the fixed displacement version as shown. Although a series of check valves could allow both ports to become either the tank or pressure lines, depending upon the direction of rotation, this is still a rare concept.

The third symbol in Figure 1 illustrates the very simplified version of the variable displacement, pressure compensated, unidirectional hydraulic pump. It includes the variable arrow across the entire symbol, explaining that the pump displacement can be modified. To the left is a smaller arrow, and as you may have picked up on from earlier symbol articles, it tells us the pump displacement varies automatically with pressure compensation. As a fan of ISO 1219 symbology, I don’t find this symbol visually pleasing, concise as it is.

My favourite symbol to express the pressure compensated pump is the smaller of the two symbols in Figure 2. This is a slightly more detailed example of the symbol I depicted in Hydraulic Symbology 101, and I’ve added colour to help with the explanation. Don’t worry about the scary looking object to the right, we’ll get to that shortly.

For this particular symbol of the pressure compensated pump, the shaft sticks out to the right, which can be attached to the square of a combustion engine prime mover symbol or the circular symbol of an electric motor. The semicircular arrow shows us the shaft rotates clockwise, or to the right since rotation direction is always observed from the vantage point of the shaft end.

The variable arrow bisects the pump symbol and of course tells us the pump is adjustable displacement. The method of displacement control is defined by the compound symbol attached to the pump’s left. Under the long rectangle is a spring with a variability arrow, which represents the pressure compensator spring, itself semi-enclosed and attached to the bottom of the pump’s variable arrow. Opposite the spring is a triangular input for pilot pressure, and this juxtaposition is intentional.

The orange pilot signal is taken directly from the red system pressure line exiting the pump, with the dashed orange line confirming it is indeed pilot energy. The spring setting fights with pilot pressure to infinitely and smoothly adjust the flow rate to match downstream pressure drop equal to the compensator setting. For example, if the setting is 3,000 psi, any downstream combination of load and flow-related pressure below 3,000 psi will see the spring maintain full displacement of the swashplate, producing full pump flow.

Moving along to the scary looking thing on the right, we have here the detailed breakdown of the variable displacement, pressure compensated, load-sensing, unidirectional hydraulic pump. You’ve likely seen this symbol before because the manufacturers prefer to show this level of detail, especially to differentiate advanced controls options like remoted compensation or horsepower control. This “load-sensing pump” will make sense to you shortly. I’ll warn that it will take some time and effort to understand this symbol as you methodically work through the rest of this article.

Starting with the pump (a), it has the diagonal variability arrow bisecting the circle and is attached to the rod ends of two cylinders. Cylinder (b) is the bias piston meant to force the pump to full displacement whenever possible, a task made easier by spring pushing the piston forward. Some pumps make do with only a strong spring, but this example is balanced with pilot energy. Affixed on the right is a tiny object with a variable arrow, which can be adjusted to move left or right within the cylinder. Not all pumps have this additional component, which is the minimum volume stop, preventing the bias piston from retracting fully, which subsequently prevents fully standby of the pump.

If you’re familiar with cylinder symbols, you’ll see that (c) also looks like a single acting cylinder with a stroke adjustor at the cap side. This is the control piston, which will always be a larger bore diameter than the bias piston. The control piston’s stroke adjustment is called the maximum volume stop and is used to modify the maximum displacement of the pump, convenient when you need a displacement between the two sizes available for the chosen pump. The two “cylinders” are attached by their rods to each other, and as one extends the other must retract and vice versa, and I’ll explain shortly why and how their battle develops.

Because all load sensing pumps must be pressure compensated, I’ll start with (d), which is the pressure compensator. Although it looks different, it is essentially a relief valve governing the control piston (c). It’s shown in its neutral condition, where it bleeds the chamber of the control piston (c) through orifice (e), orifice (f), and also through the other compensator (g) where it can choose any flow path directly to tank. Regardless of its flow path, pilot energy inside the control piston (c) is zero, so it loses the battle with the bias piston (b) and the pump is on full displacement pump at its highest rate.

The load sense compensator (g) looks much the same as the pressure compensator (d) and is similar in function except where it takes pilot energy and what it does with it afterward. As with the pressure compensator symbol (d), it is a 3-way, 2-position valve that is spring-offset with adjustable pressure settings for both. Each is supplemented with the parallel lines above and below both positional envelopes, and these lines tell us the valve is infinitely variable between the two positions.

The variable orifice at (j) could be any flow control, lever valve or proportional valve used to adjust flow (which creates backpressure when reduced) in the red system pressure line starting at the pump. You can see the node just after the pump outlet that combines system pressure with pilot lines supplying the bias piston and both compensators. Let’s first take the load sense compensator (g) out of the picture and describe the pressure compensator (d) and what occurs during operation.

When the pump fires up, and assuming all downstream directional valves are closed, the spring inside the bias piston (b) fully strokes the pump to max displacement. This immediately creates pressure in the work and pilot lines as fluid fills the plumbing with no exit strategy, and this rise in pressure at the pilot line at (d) forces the pressure compensator to shift to the right. The second pilot line attached to the top of compensator (d) allows pilot energy to enter through line (i) where it fills the control piston (c) rapidly. Because the control piston is larger bore than the bias piston, it wins the fight and moves the pump’s variable arrow to reduce displacement until the only flow is what is required to overcome leakage. The pump is on “standby.”

Now when a downstream directional valve is opened, a flow path is created that drops system pressure to below the setting of the (d) compensator, and it immediately succumbs to spring pressure and snaps back to near its neutral setting, opening the drain lines once again to tank. The orifices (e) and (f) dampen the motion of the compensator, preventing rapid oscillations, but the orifice also prevents pressure spikes into the pump’s case. They also ensure that pressure doesn’t decay from the control piston (c) when system pressure degrades rapidly for fractions of a second. Flow from the pump will be balanced by the opposing bias and control pistons to match downstream pressure drop at exactly the pressure compensator setting.

Finally, we look at the operation of the load sense compensator (g) shown on top. It also receives a pilot signal directly from the pump outlet, but you’ll see that it also gets a competing signal from the work line after the metering orifice. The pressure signal at (g) compares the combined effort of the spring value and the load-sense pilot signal just before (h). The setting of the pressure compensator (d) is much higher than the setting of the load sense compensator (g), which is set to create reasonable pressure drop across (j). If the (d) compensator is set to 3,000 psi, it’ll only see this pressure on standby or max load pressure, while the (g) compensator might be set to 300 psi, where it measures pressure drop across (j) valve.

Typically a load sense circuit will have multiple orifices in a load sense network all feeding back a pilot signal to the load sense compensator (g), where it picks the highest pressure signal and meters the pump’s flow to match that pressure differential and provides just enough flow to satisfy the desired flow rate at the desired work pressure plus the pressure of the load sense compensator’s spring value. For example, if load pressure is 1,000 psi, the pump will hold pressure at 1,300 psi, providing the extra 300 psi just to create flow across the metering valve (j).

This symbol shows you that no matter the initial feeling of complexity, breaking down any schematic thoughtfully reveals its purpose of design. I fell in love with hydraulics when I learned about the load sensing concept. That just using columns of fluid pressure to create an efficient supply and demand scenario to satisfy many downstream actuators with essentially the exact flow and pressure they need for the job, and little more, I found exhilarating.

The displacement of a pump is defined by the volume of fluid that the gears, vanes or pistons will pump in one rotation. If a pump has a capacity of 30 cm3, it should treat 30 ml of fluid in one rotation.

In axial piston variable pumps, the flow is proportional to the drive speed and the displacement. The flow can be steplessly changed by adjusting the swivel angle. Axial piston variable ...

... axial piston pump type V60N is designed for open circuits in mobile hydraulics and operate according to the swash plate principle. They are available with the option of a thru-shaft for operating additional ...

Variable displacement axial piston pumps operate according to the bent axis principle. They adjust the geometric output volume from maximum to zero. As a result they vary the flow rate ...

... piston pump type V30D is designed for open circuits in industrial hydraulics and operate according to the swash plate principle. They are available with the option of a thru-shaft for operating additional ...

... circuit axial piston pumps are used as hydrostatic transmission components in self-propelled machines and for rotary drives in both fixed and mobile equipment of all kinds.

Axial piston twin flow pump. With a very high performance in all job conditions. Due to its twin flow configuration this pump allows a great variety of solutions in different job applications.

Air hydraulic pump, double pneumatic motor, double effect, foot operated with lock-up function, lever distributor valve (4/3), 10L tank, oil flow 8.5 / 0.26 l / min

... customer system options for mechanical, hydraulic and electric input solutions are available. Further special regulating features like torque control and pressure cut-off are also available. The reliable ...

... needs of truck hydraulics, the TXV variable displacement pumps with LS (Load Sensing) control allow flow regulation to suit the application requirements. The pump ...

... rev. displacements, these pumps are designed to operate in both directions of rotation (clockwise or counter-clockwise). Only one reference regardless of direction of rotation. The TXV indexable pumps ...

... PVG is a variable-displacement axial-piston pump designed to take on your most demanding applications. It offers high-pressure, superior performance in a compact design ...

Variable displacement pumps in closed loop; 3 basic design units and 8 max. displacement sizes of 14, 18, 21, 28, 35, 46, 56, 64 cc/rev; various control options; max. ...

Parker P2/P3 High Pressure Axial Piston Pumps are variable displacement, swashplate piston pumps designed for operation in open circuit, mobile hydraulic ...

... Series pump offers variable displacement axial piston pumps for open-circuit applications. Featuring a compact footprint and continuous operating pressure ...

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.

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 (200-540cc/rev), 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 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.

Piston pumps are typically much more complicated and are often available in wither fixed or, commonly, variable displacement configurations and with pressure compensation. These are big words that mean that piston pumps can usually adapt to the system pressure, providing maximum efficiency and flexibility. They are often used in “closed center” systems where the pump displacement varies to meet the needs of the work being done. Piston pumps use a “swashplate” to move the pistons and the angle of the swashplate & bore of the pistons determines the displacement. Pressure compensation regulates outputs in response to variations in the system. Piston pumps are typically the most efficient type of hydraulic pumps.

In an axial-piston pump, the pistons and cylinder rotate around the center, longitudinal axis. The pistons and shoes move in and out of the cylinder because they are sliding upon a stationary, variable angle, swashblock.

Pumps do not make pressure, pumps make flow and the restriction of the flow is where the pressure is created.After the unit is deadheaded, start by bringing the relief and compensator up together. You should be able to tell by the sound when the pump is on stroke and when it is compensated.

Back the compensator out (CCW) until you hear the pump come on stroke (it gets loud) and then turn the adjustment back in (CW) until pump compensation is achieved and the pump is quiet again.

Tighten the lock nut on the relief and compensator to assure they will not change after setup. If you are in a noisy environment and can’t hear the pump come on stroke or the relief valve open, you can set the pump compensator and relief valve by watching the amp draw on one leg of the electrical service. You can tell by the amp draw on the motor when the relief cracks or when the pump compensates.

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We provide Hydraulic pumps and can be styles such as gear, vane, and piston pumps. Applications can be fixed or variable displacement pumps. With so many styles and brands, it’s important to speak with an expert who can get you the hydraulic pump you need at an affordable price. We offer a wide variety of hydraulic pumps to support your applications and carry trusted brands including:

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