variable displacement hydraulic pump symbol quotation

To enable engineers to communicate and understand the circuitry associated with hydraulic systems there is an International Standard for hydraulic symbols – ISO1219/1 2006

The symbols do not identify component size or their actual position on the machine however the symbols do provide vital information relating to the configurations and flow path connections.

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.

Hydraulics engineers regularly encounter these diagrams, but these symbols can be daunting to interpret if you have limited experience with schematics and the fluid power industry.

On this page, Carr Lane ROEMHELD provides a comprehensive table outlining the definitions of each symbol used in a hydraulic diagram. Engineers can use this page as a reference to determine common schematic symbols used in fluid power, hydraulics, pneumatics, diagrams and circuits.

In the world of manufacturing and industry, pumps play a crucial role in keeping operations running smoothly. There are different types of pumps available, and two common ones are hydraulic pumps and vacuum pumps. Since it is not always easy to choose the right equipment in front of a multitude of manufacturers, we have produced several buying guides with tips and recommendations to help you make the right purchasing decision.

A pump is a device used to move fluids, such as liquids or gases, from one place to another. It works by creating pressure that drives the fluid through a system of pipes or hoses. The type of pump used depends on the application and the fluid being moved.

There are different types of pumps available. Understanding what they do and how they work can help businesses make informed decisions about their operations.

A pump is a mechanical tool that converts motor energy into hydraulic energy in order to transport fluids. When selecting a pump, the first aspect to consider is the type of fluid being transported. It is essential to factor in the technical properties of the fluid since they determine the appropriate pump to use. To properly size the pump and determine its operating point, it is necessary to know various parameters of the system, such as flow rate, suction head, discharge head, and head losses. This guide provides an overview of the primary types of pumps and their typical applications.

For businesses operating in industries that require the use of heavy machinery, a hydraulic pump is an essential component in maintaining smooth and efficient operations.

A hydraulic pump is responsible for circulating hydraulic fluid like oil, at high pressure through pipes to activate hydraulic actuators, such as cylinders or motors. By utilizing this pressurized fluid, the hydraulic actuators are able to produce linear or rotary motion, generating the necessary force and power required for various applications.

Given the critical role of a hydraulic pump in a hydraulic circuit, selecting the appropriate pump is crucial to ensure optimal performance and longevity. A well-chosen pump can enhance the system’s efficiency, and reduce energy consumption and maintenance costs.

A vacuum pump is a device that extracts air or gas from a tank to create a partial or complete vacuum within a given system. This is achieved through the gradual reduction of pressure within the enclosed space, which allows air to be drawn into the pump. The pump then extracts the aspirated gaseous molecules from the system and releases them into the ambient air or another tank.

In various industrial sectors, such as laboratories, the medical industry, food packaging, and the chemical industry, a vacuum pump is a critical tool that enables efficient and effective operations.

There are several types of vacuum pumps available, including diaphragm pumps, rotary vane pumps, and scroll pumps. Each type has its own advantages and disadvantages, and the selection of the appropriate vacuum pump will depend on the specific requirements of the application.

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.

A radial piston pump is a form of hydraulic pump. The working pistons extend in a radial direction symmetrically around the drive shaft, in contrast to the axial piston pump.

When filling the workspace of the pumping pistons from "inside" (e.g., over a hollow shaft) it is called an inside impinged (but outside braced) radial piston pump (picture 1). If the workspace is filled from "outside" it"s called an outside impinged radial piston pump (but inside braced) (picture 2).

The outer ring for bracing of the pumping pistons is in eccentric position to the hollow shaft in the center. This eccentricity determines the stroke of the pumping piston.

The piston starts in the inner dead center (IDC) with suction process. After a rotation angle of 180° it is finished and the workspace of the piston is filled with the moved medium. The piston is now in the outer dead center (ODC). From this point on the piston displaces the previously sucked medium in the pressure channel of the pump.

A disadvantage is the bigger radial dimensions in comparison to the axial piston pump, but it could be compensated with the shorter construction in axial direction.

Due to the hydrostatically balanced parts it is possible to use the pump with various hydraulic fluids like mineral oil, biodegradable oil, HFA (oil in water), HFC (water-glycol), HFD (synthetic ester) or cutting emulsion. That implies the following main applications for a radial piston pump:

"Variable Stroke Radial Piston Pump", T.S. Patriot State Engineering Manual, Massachusetts Maritime Academy, 1996, pp. 234–241, retrieved 14 September 2022

Out of any topic under the patio-sized umbrella of fluid power, hydraulic symbology garners the most requests from those wishing to learn more about fluid power. Reading any schematic with more than three symbols can be daunting if your experience is limited. But it’s not impossible to learn. In fact, it only takes a basic level understanding of how symbols work and how they’re arranged in a diagram. One challenge – even if you’ve memorized every symbol in the library – is understanding why a particular symbol is used in a circuit; that part is hard to teach and just comes with experience.

The third most common line you will see is the simple dashed line. This is a dual function line, representing both pilot and drain lines. A pilot line in both representation and function uses hydraulic energy to signal or operate other valves. Learning to comprehend pilot lines is key to understanding advance hydraulic schematics. As a drain line, the dashed line simply represents any component with leakage fluid needing a path represented in the drawing.

If we get slightly more advanced than your basic line, we have three other common shapes used in hydraulic schematics. These are the circle, square and diamond. Ninety nine percent of hydraulic symbols use one of these three as a foundation. Pumps and motors of every kind are drawn using a circle, as are measuring instruments. Valves of every kind use the basic square as a start. Some are simply one square, such as pressure valves, but others use three joined squares, such as with a three-position valve. Diamonds are used to represent fluid conditioning devices, like filters and heat exchangers.

Let’s assume the relief valve is set to 2,000 psi. You’ll have noticed the dashed line coming from the bottom of the symbol, rounding the corner and is attached to the left side. This dashed line indicates the valve is directly operated by the pressure at its inlet port, and that pilot fluid can affect the valve by pushing the arrow to the right. The actual valve has no arrow, of course, but as is the nature of hydraulic symbols, just represents a visual model of what occurs. As pressure in the pilot line approaches 2,000 psi, the arrow is pushed until the valve reaches the centre, allowing fluid to pass, which in turn reduces pressure until upstream is 2,000 psi.

The pressure reducing valve is the only normally open pressure valve in hydraulics. As you can see, it’s very similar to the relief valve, save two changes in the symbol. Firstly, the arrow shows it flows in its neutral position, whereas the relief valve is blocked. Secondly, it gets its pilot signal from downstream of the valve. When downstream pressure rises above the spring setting value, the valve closes, preventing incoming pressure from reaching the downstream path, which allows pressure to decay back to below the pressure setting.

The basics of hydraulic symbology are quite easy, but I’ve only scratched the surface. There are many specialized symbols representing things like electronics, accumulators, various cylinders and ball valves, which I don’t have the room to show. Furthermore, each symbol I’ve shown represents a small portion of the modifications possible to each; there is probably a hundred or more ways to represent a hydraulic pump with a schematic symbol.

Finally, the way in which hydraulic symbols are combined to create a complete schematic representing an actual machine is endless. I recommend you spend time reading hydraulic schematics to interpret the symbols, whenever you have time. Not only will you discover unique symbols, but you’ll come across unique ways to use old symbols and components in a hydraulic circuit.

For a simplified symbol use only the circle with a triangle showing the discharge port, suction port, and the crossing arrow at an angle. Don"t include the compensator piston or spring at the ends of the arrow. There is no need to show the motor shaft unless you also show the motor, and no need to show case drain unless the case drain has flow instrumentation.

That said, I prefer to show the full pump controls on a hydraulic diagram as it provides useful information about the compensator controls to the hydraulic technician.

The Metaris MA10V(S)O open loop piston pump has proven itself in many applications. Rear and side ported, through drive auxiliary pump mounting flanges and a large selection of flow and pressure controls makes this pump a strong, versatile alternative in both industrial and mobile applications. The 31 Series is available in 6 displacements.

The Metaris MA10V(S)O open loop piston pump has proven itself in many applications. Rear and side ported, through drive auxiliary pump mounting flanges and a large selection of flow and pressure controls makes this pump a strong, versatile alternative in both industrial and mobile applications. The 52 Series is available in 2 displacements.

Engineered around heavy duty construction and the durability of the cradle bearing design, we have our MPVH line of piston pumps. This series of pumps are ideally suited for the mobile market and are available in four displacements. Furthermore, our line of MPVH series pumps replace the obsolete PVE series.

Our MHPVB in-line variable displacement piston pumps have excellent operating features and are capable of operating with many types of hydraulic fluid. These units are durable and offer a long service life, which makes them suitable for the industrial market. Available in six displacements to meet the demands of many applications.

Our 20 series aftermarket replacement pumps and motors are engineered for quality, durability and versatility. Components used are designed for high efficiency. The PV type/series of units are available in 8 different frame sizes.

Our 20 series aftermarket replacement pumps and motors are engineered for quality, durability and versatility. Components used are designed for high efficiency. The MF type/series of units are available in 8 different frame sizes.

Metaris MT Series high pressure single vane pumps are perfect interchange replacements for Denison® T6 and T7 series vane units. Our units are available in a variety of different displacements with multiple shaft and porting options.

Metaris MM Series high pressure vane motors are perfect interchange replacements for Denison® M4 series vane motor units. Our motor units are available in a variety of different displacements with multiple torque, shaft, porting and port connection options.

Genuine Metaris MV & MVQ series are intra-vane design pumps for both industrial and mobile markets. These units are fit, form and function replacements for Vickers® V & VQ series components.

Metaris offers a large selection of balanced rotor vane pumps. With a variety of displacements, mounting flanges and input shafts, this pump has grown to be a mainstay in both mobile and industrial applications. Optional flow control and priority flow end covers are also available.

Hi Guys, Hydraulic pumps are of various types, axial flow variable displacement piston pump are used in heavy hydraulic construction equipments. Tracked exca...

2. The hydraulic circuits that use relief valves that are set to a ‘full flow’ setting and the hydraulic circuits that are set to a cracking pressure setting and how to set the relief valve for each

17. What are the 4 most important hydraulic applications that must use a ‘float’ center directional control valve and not use a ‘closed’ center directional control valve

19. How do pressure compensated pumps actually control system pressure20. How to set any pressure compensated pump and its spike pressure relief + many, many more good and usable ideas