what type of hydraulic pump is most efficient factory
Which pump you choose for your power unit affects the nature of your HPU builds. Pump choice usually depends on cost, complexity, and performance. There are three major types of pumps to select from: the gear pump, the piston pump, and the vane pump. Below, we’ll get into the specifics of each pump to help you make the best decision for your system.
Gear pumps are usually very economical but hold lower efficiency values. Their efficiency typically drops over time. However, they are quite durable. A pump’s job is to convert incoming mechanical energy into hydraulic energy. The more efficient the pump, the smaller the motor you can choose. Efficiency saves you the most money over time. Traditional spur gear pumps an average of about 80% efficiency, which puts you at a disadvantage over time.
Vane pumps fall between gear pumps and piston pumps when it comes to practicality. They’re more efficient than gear pumps but less efficient than piston pumps. Vane pumps are known for being very quiet, making them ideal for industrial applications. They’re also available with a myriad of control options, like pressure compensation, displacement control, and load sensing. However, Vane pumps usually can’t handle high-pressure circuits.
Piston pumps account for the premium end of the range. These pumps are capable of supporting very high pressure and have infinite methods of control, including pressure compensation, servo control, load sensing, horsepower control, and more. Piston pumps are also incredibly efficient, with many designs being capable of 95% efficiency. The biggest downside to choosing a piston pump is cost. The initial investment will be pricey, and service or repair can be costly as well.
If you’d like more information about choosing the best pump for your HPU design, contact GCC, Inc. today! Our team of experts is ready to help you find a pump that suits your needs.
In a condition-based maintenance environment, the decision to change out a hydraulic pump or motor is usually based on remaining bearing life or deteriorating efficiency, whichever occurs first.
Despite recent advances in predictive maintenance technologies, the maintenance professional’s ability to determine the remaining bearing life of a pump or motor, with a high degree of accuracy, remains elusive.
Deteriorating efficiency on the other hand is easy to detect, because it typically shows itself through increased cycle times. In other words, the machine slows down. When this occurs, quantification of the efficiency loss isn’t always necessary. If the machine slows to the point where its cycle time is unacceptably slow, the pump or motor is replaced. End of story.
In certain situations, however, it can be helpful, even necessary, to quantify the pump or motor’s actual efficiency and compare it to the component’s native efficiency. For this, an understanding of hydraulic pump and motor efficiency ratings is essential.
There are three categories of efficiency used to describe hydraulic pumps (and motors): volumetric efficiency, mechanical/hydraulic efficiency and overall efficiency.
Volumetric efficiency is determined by dividing the actual flow delivered by a pump at a given pressure by its theoretical flow. Theoreticalflow is calculated by multiplying the pump’s displacement per revolution by its driven speed. So if the pump has a displacement of 100 cc/rev and is being driven at 1000 RPM, its theoretical flow is 100 liters/minute.
Actualflow has to be measured using a flow meter. If when tested, the above pump had an actual flow of 90 liters/minute at 207 bar (3000 PSI), we can say the pump has a volumetric efficiency of 90% at 207 bar (90 / 100 x 100 = 90%).
Its volumetric efficiency used most in the field to determine the condition of a hydraulic pump - based on its increase in internal leakage through wear or damage. But without reference to theoretical flow, the actual flow measured by the flow meter would be meaningless.
A pump’s mechanical/hydraulic efficiency is determined by dividing thetheoretical torque required to drive it by the actual torque required to drive it. A mechanical/hydraulic efficiency of 100 percent would mean if the pump was delivering flow at zero pressure, no force or torque would be required to drive it. Intuitively, we know this is not possible, due to mechanical and fluid friction.
Table 1. The typical overall efficiencies of hydraulic pumps, as shown above, are simply the product of volumetric and mechanical/hydraulic efficiency.Source: Bosch Rexroth
Like theoretical flow, theoretical drive torque can be calculated. For the above pump, in SI units: 100 cc/rev x 207 bar / 20 x p = 329 Newton meters. But like actual flow, actual drive torque must be measured and this requires the use of a dynamometer. Not something we can - or need - to do in the field. For the purposes of this example though, assume the actual drive torque was 360 Nm. Mechanical efficiency would be 91% (329 / 360 x 100 = 91%).
Overall efficiency is simply the product of volumetric and mechanical/hydraulic efficiency. Continuing with the above example, the overall efficiency of the pump is 0.9 x 0.91 x 100 = 82%. Typical overall efficiencies for different types of hydraulic pumps are shown in the Table 1.
System designers use the pump manufacturers’ volumetric efficiency value to calculate the actual flow a pump of a given displacement, operating at a particular pressure, will deliver.
As already mentioned, volumetric efficiency is used in the field to assess the condition of a pump, based on the increase in internal leakage due to wear or damage.
When calculating volumetric efficiency based on actual flow testing, it’s important to be aware that the various leakage paths within the pump are usually constant. This means if pump flow is tested at less than full displacement (or maximum RPM) this will skew the calculated efficiency - unless leakage is treated as a constant and a necessary adjustment made.
For example, consider a variable displacement pump with a maximum flow rate of 100 liters/minute. If it was flow tested at full displacement and the measured flow rate was 90 liters/minute, the calculated volumetric efficiency would be 90 percent (90/100 x 100). But if the same pump was flow tested at the same pressure and oil temperature but at half displacement (50 L/min), the leakage losses would still be 10 liters/minute, and so the calculated volumetric efficiency would be 80 percent (40/50 x 100).
The second calculation is not actually wrong, but it requires qualification: this pump is 80 percent efficient at half displacement. Because the leakage losses of 10 liters/minute are nearly constant, the same pump tested under the same conditions will be 90 percent efficient at 100 percent displacement (100 L/min) - and 0 percent efficient at 10 percent displacement (10 L/min).
To help understand why pump leakage at a given pressure and temperature is virtually constant, think of the various leakage paths as fixed orifices. The rate of flow through an orifice is dependant on the diameter (and shape) of the orifice, the pressure drop across it and fluid viscosity. This means that if these variables remain constant, the rate of internal leakage remains constant, independent of the pump"s displacement or shaft speed.
Overall efficiency is used to calculate the drive power required by a pump at a given flow and pressure. For example, using the overall efficiencies from the table above, let us calculate the required drive power for an external gear pump and a bent axis piston pump at a flow of 90 liters/minute at 207 bar:
As you’d expect, the more efficient pump requires less drive power for the same output flow and pressure. With a little more math, we can quickly calculate the heat load of each pump:
No surprise that a system with gear pumps and motors requires a bigger heat exchanger than an equivalent (all other things equal) system comprising piston pumps and motors.
Brendan Casey has more than 20 years experience in the maintenance, repair and overhaul of mobile and industrial equipment. For more information on reducing the operating cost and increasing the...
The hydraulic pumps found in virtually all mobile and industrial applications today use pistons, vanes, or gears to create the pumping action that produces flow. Each method features individual characteristics that differentiate it from the others and make it suitable for a particular range of applications.
Piston pumps can have the pistons arranged in a radial or axial fashion. Radial types tend to be specialized for applications requiring very high power, while axial piston pumps are available in a wide range of displacements and pressure capabilities that make them suitable for many mobile and industrial tasks.
Axial-piston pumps consist of a set of pistons that are fitted within a cylinder block and driven by an angled swash plate powered by the input shaft. As the swash plate rotates, the pistons reciprocate in their respective cylinder block bores to provide the pumping action. (Figure 1 above)
Axial-piston pumps are available with the input shaft and pistons arranged coaxially, or with the input shaft mounted at an angle to the piston bores. Bent axis pumps tend to be slightly more volumetrically efficient for technical reasons, but they also tend to be slightly larger for a given capacity and their shape can present packaging difficulties in some applications.
A unique characteristic of a piston-type pump is that the displacement can be changed simply by changing the angle of the swash plate. Any displacement between zero and maximum is easily achieved with relatively simple actuators to change the swash plate angle.
The most commonly encountered vane-type pump generates flow using a set of vanes, which are free to move radially within a slotted rotor that rotates in an elliptical chamber. A typical configuration uses an elliptical cam ring with the rotor spinning within in a cylindrical housing and a pair of side plates to form the pumping chambers. (Figure 2) The changing volume of the cavity between adjacent vanes creates the pumping action as the rotor rotates.
It is possible to vary the displacement of a vane-type pump, but this is not commonly done except for very specialized applications. The majority of the vane-type pumps used in industrial and mobile applications have a fixed displacement.
Vane pumps can be hydraulically balanced, which greatly enhances efficiency. Some designs place the rotating group in a cartridge, which makes them very easy to repair. The entire rotating group is easily removed and replaced by simply removing the back cover, pulling out the old rotating cartridge and replacing it with a new one.
The simplest gear-type pump uses a pair of mating gears rotating in an oval chamber to produce flow. As the gears rotate, the changing size of the chambers created by the meshing and unmeshing of the teeth provides the pumping action. (Figure 3)
Another design uses an external rotating ring with internal gear teeth that mesh with an internal gear as it rotates. As the inner gear rotates, the tooth engagement creates chambers of diminishing size between the inlet and outlet positions to create flow.
A more sophisticated variant of this principle is the gerotor pump, which has a non-concentric inner and outer rotor with different numbers of teeth. As the pair rotates, the changing volume of the space between the rotors creates the pumping action. Replacing the meshing teeth of the gerotor pump with low-friction rolling elements produces a geroter pump.
All gear-type pumps have a fixed displacement. These pumps are relatively inexpensive compared to piston and vane type pumps with similar displacements, but tend to wear out more quickly and are not generally economically repairable.
Piston-type pumps have a very good service life, provided contamination and heat are controlled. They also have the highest pressure ratings, and the significant advantage of variable displacement. This makes them the best choice for applications where high efficiency and high power density are important considerations. The ability to configure piston-type pumps with both pressure sensing and load sensing capabilities is an important advantage, particularly in mobile applications.
Vane-type pumps are widely used in constant flow/constant pressure industrial applications because they are quiet and easily repaired. They also have the unique attribute of allowing a “soft start” because vane-type pumps typically do not achieve full output at speeds below about 600 rpm. This characteristic can significantly reduce the starting current requirements of electric motors driving a vane-type pump which extends motor life.
Gear pumps are very common in constant flow/constant pressure applications on mobile equipment because of their low cost and dirt tolerance. They are also widely used as charge pumps to pressurize the inlets of piston and vane pumps because of their excellent inlet vacuum tolerance.
Sizing a pump is not really dependent on which technology is chosen. In all cases, it is best to start with the load and then work back through the system calculating losses at each point. Once the theoretical pressure and flow characteristics are calculated, the input horsepower requirement can be determined. A 20% safety factor is commonly used in determining the pump input horsepower requirement to account for efficiency losses in the pump.
Mobile applications that may encounter overrunning loads often require special valve plates that alter the stroke of a piston pump more quickly than standard units. Such proper valving reduces the internal forces in the pump allowing it to come out of stroke more quickly to respond to the load condition.
You should also be aware that many pump options often are not listed in manufacturer’s catalog literature. It is always a good policy to consult with the pump manufacturer or your local representative when sizing or selecting a pump for a specific application.
Today’s hydraulic pumps are sophisticated, precision products that will enhance the customer value of the equipment they power. Knowing the characteristics of each of the common pump technologies and selecting the units that deliver the best balance of cost versus performance in your application is the best way to maximize that value.
Piston pumps have the highest pressure capabilities of the three technologies, up to 7250 psi (500 bar) for those in common use, and as high at 10,000 psi (690 bar) for certain specialized units. Vane and gear pumps are commonly limited to pressures up to about 4000 psi (275 bar).
Hydraulic power density is directly related to operating pressure; the higher the pressure the greater the power density. Piston pumps offer the highest power density with vane and gear types following in that order.
Like power density, the conversion ratio of input power to output power is directly related to operating pressure. Piston pumps offer the highest conversion ratio, followed by vane and gear pumps in that order. The ability of piston and vane pumps to be hydraulically balanced is also a factor in their greater conversion efficiency.
No hydraulic component is immune to damage from dirt! But of the three pump technologies, the gear-type is the most dirt tolerant, followed by vane and piston pumps in that order.
Positive inlet pressure is always preferred in hydraulic pump applications to avoid wear and premature failure. However, of the three technologies, gear-type pumps are the most vacuum tolerant handling vacuums up to 10 in.-Hg (254 mm-Hg). Vane-type pumps can handle inlet vacuum up to 6 in.-Hg (152.4 mm-Hg) and piston-type pumps up to 4 in.-Hg (101.6 mm-Hg).
It is worth noting that piston pumps can be significantly quieted by altering the metering notch geometry on the valve plate. Doing so, however, reduces their efficiency. There is no free lunch.
Gear pumps tend to the lightest for a given displacement, followed by vane and piston pumps in that order. Note also that all three types can be “ganged” by stacking multiple sections together. This is more commonly done with gear and vane pumps, but double piston pumps are also available.
Piston and gear pumps tend to offer the greatest range of fluid compatibilities. Note that is it often necessary to de-rate a pump when it is used with non-petroleum fluids.
Fluid compatibility depends on the type of seals, O-rings and materials used in the construction of a pump. It’s best to consult the manufacturer before using any alternative fluids.
The goal of a hydraulic pump is to move hydraulic fluid through a hydraulic system, acting much like the beating heart of the system. There are two things that all hydraulic pumps have in common: (1) they provide hydraulic flow to other components (e.g., rams, hydraulic motors, cylinder) within a hydraulic system, and (2) they produce flow which in turn generates pressure when there is a resistance to flow. In addition, most hydraulic pumps are motor-driven and include a pressure relief valve as a type of overpressure protection. The three most common types of hydraulic pumps currently in use are gear, piston, and vane pumps.
In a gear pump, hydraulic fluid is trapped between the body of the pump and the areas between the teeth of the pump’s two meshing gears. The driveshaft is used to power one gear while the other remains idle until it meshes with the driving gear. These pumps are what is known as fixed displacement or positive displacement because each rotation of the shaft displaces the same amount of hydraulic fluid at the same pressure. There are two basic types of gear pumps, external and internal, which will be discussed in a moment.
Gear pumps are compact, making them ideal for applications that involve limited space. They are also simple in design, making them easier to repair and maintain. Note that gear pumps usually exhibit the highest efficiency when running at their maximum speed. In general, external gear pumps can produce higher levels of pressure (up to 3,000 psi) and greater throughput than vane pumps.
External gear pumps are often found in close-coupled designs where the gear pump and the hydraulic motor share the same mounting and the same shaft. In an external gear pump, fluid flow occurs around the outside of a pair of meshed external spur gears. The hydraulic fluid moves between the housing of the pump and the gears to create the alternating suction and discharge needed for fluid flow.
External gear pumps can provide very high pressures (up to 3,000 psi), operate at high speeds (3,000 rpm), and run more quietly than internal gear pumps. When gear pumps are designed to handle even higher pressures and speeds, however, they will be very noisy and there may be special precautions that must be made.
External gear pumps are often used in powerlifting applications, as well as areas where electrical equipment would be either too bulky, inconvenient, or costly. External gear pumps can also be found on some agricultural and construction equipment to power their hydraulic systems.
In an internal gear pump, the meshing action of external and internal gears works with a crescent-shaped sector element to generate fluid flow. The outer gear has teeth pointing inwards and the inner gear has teeth pointing outward. As these gears rotate and come in and out of mesh, they create suction and discharge zones with the sector acting as a barrier between these zones. A gerotor is a special type of internal gear pump that eliminates the need for a sector element by using trochoidal gears to create suction and discharge zones.
Unlike external gear pumps, internal gear pumps are not meant for high-pressure applications; however, they do generate flow with very little pulsation present. They are not as widely used in hydraulics as external gear pumps; however, they are used with lube oils and fuel oils and work well for metering applications.
In a piston pump, reciprocating pistons are used to alternately generate suction and discharge. There are two different ways to categorize piston pumps: whether their piston is axially or radially mounted and whether their displacement is fixed or variable.
Piston pumps can handle higher pressures than gear or vane pumps even with comparable displacements, but they tend to be more expensive in terms of the initial cost. They are also more sensitive to contamination, but following strict hydraulic cleanliness guidelines and filtering any hydraulic fluid added to the system can address most contamination issues.
In an axial piston pump, sometimes called an inline axial pump, the pistons are aligned with the axis of the pump and arranged within a circular cylinder block. On one side of the cylinder block are the inlet and outlet ports, while an angled swashplate lies on the other side. As the cylinder block rotates, the pistons move in and out of the cylinder block, thus creating alternating suction and discharge of hydraulic fluid.
Axial piston pumps are ideal for high-pressure, high-volume applications and can often be found powering mission-critical hydraulic systems such as those of jet aircraft.
In a bent-axis piston pump (which many consider a subtype of the axial piston pump), the pump is made up of two sides that meet at an angle. On one side, the drive shaft turns the cylinder block that contains the pistons which match up to bores on the other side of the pump. As the cylinder block rotates, the distances between the pistons and the valving surface vary, thus achieving the necessary suction and discharge.
In a radial piston pump, the pistons lie perpendicular to the axis of the pump and are arranged radially like spokes on a wheel around an eccentrically placed cam. When the drive shaft rotates, the cam moves and pushes the spring-loaded pistons inward as it passes them. Each of these pistons has its own inlet and outlet ports that lead to a chamber. Within this chamber are valves that control the release and intake of hydraulic fluid.
In a fixed displacement pump, the amount of fluid discharged in each reciprocation is the same volume. However, in a variable displacement pump, a change to the angle of the adjustable swashplate can increase or reduce the volume of fluid discharged. This design allows you to vary system speed without having to change engine speed.
When the input shaft of a vane pump rotates, rigid vanes mounted on an eccentric rotor pick up hydraulic fluid and transport it to the outlet of the pump. The area between the vanes increases on the inlet side as hydraulic fluid is drawn inside the pump and decreases on the outlet side to expel the hydraulic fluid through the output port. Vane pumps can be either fixed or variable displacement, as discussed for piston pumps.
Vane pumps are used in utility vehicles (such as those with aerial ladders or buckets) but are not as common today, having been replaced by gear pumps. This does not mean, however, that they are not still in use. They are not designed to handle high pressures but they can generate a good vacuum and even run dry for short periods of time.
There are other key aspects to choosing the right hydraulic pump that goes beyond deciding what type is best adapted to your application. These pump characteristics include the following:
Selecting a pump can be very challenging, but a good place to start is looking at the type of pump that you need. Vane pumps have been largely replaced by compact, durable gear pumps, with external gear pumps working best for high pressure and operating speeds while internal gear pumps are able to generate flow with very little pulsation. However, vane pumps are still good for creating an effective vacuum and can run even when dry for short periods of time. Piston pumps in general are more powerful but, at the same time, more susceptible to contamination.
Whether the pump is needed for the rugged world of mining, the sterile world of food and beverage processing, or the mission-critical aerospace industry, MAC Hydraulics can assist you with selecting, installing, maintaining, and repairing the right pump to meet the needs of your hydraulic system. In the event of a breakdown, our highly skilled technicians can troubleshoot and repair your pump — no matter who the manufacturer happens to be. We also offer on-site services that include common repairs, preventative maintenance, lubrication, cleaning, pressure testing, and setting.
There are three primary types of hydraulic pumps. These are the main ones that you’ll see in any given hydraulic system. First you have a gear pump, a vane pump and the piston pump. We’re going to start with the gear pump.
With a basic gear pump, it is the kind of pump you’ll see on any given mobile machine. You can see it off of a PTO, you can see it on a log splitter. Typically, a log splitter would have a two-stage pump, but that will be left out of this discussion.
It’s pretty basic. Some have a steel housing, some smaller pumps (lower pressure) can have aluminum housing and steel ends. Your prime mover, whether it be electric, motor or a gas engine will rotate the shaft, which is your primary inlet shaft.
Inside the pump, spur gears mesh together; as you rotate the inlet shaft, it has no choice but to rotate the secondary set of gears that are below it. Fluid is sucked in, and as we know sucked in means being pushed from the atmosphere by increasing displacement inside the cavity. What happens is the fluid gets trapped between the spur gears and the walls of the housing. It gets carried around the outside, so it happens in two locations, both sides. It gets carried around the outside and then hits the pressure side of the pump where it gets fed into your system.
Here are the advantages and disadvantages of a gear pump: One advantage is they’re inexpensive, so a gear pump, you can get some down and dirty ones anywhere from maybe 50 to $100, anywhere up to a few hundred on the upper end. Those are ones that would have actual roller bearings and large displacement, all steel construction. Even then, $300 is pretty inexpensive for any hydraulic pump.
They are also contamination-resistant. What that means is part of our examination can be trapped or passed through a gear pump without doing a whole lot of damage. Even if you were to have a high contamination system, the amount of damage that can be done to it isn’t significant enough that it would stop pumping. Even a worn pump, gear pump, is able to pump whereas some other pump designs, as they wear or as they are damaged by contamination they pretty much become useless, so in that sense gear pumps are pretty contamination-resistant.
They’re also capable of high speed. This is kind of a requirement, because a lot of prime movers in the mobile industry are either gas engines—you might have a small engine such as a little 10 horse Honda or something like that that is running 3,600 rpm. Often, you will have a gear pump able to run up to 4,000 rpm in that case. The rotation can be easily changed.
Gear pumps are reliable. In that sense, I mean that because they’re contamination resistant, they can go for a long time. You might see Grandpa’s log splitter has been running in the backyard for 30 years or so. That’s because it’s hard to destroy a gear pump.
They do eventually go. Sometimes it’s from catastrophic failure, but when it’s wear related failure, it can take years and years. Another advantage is they can be stacked together. You could have two, three or four gear pumps that are all stacked in tandem with one input shaft.
This has some advantages of creative use of displacement or it just allows you to save some space, so rather than having two different sources and two different prime movers, you can stack two pumps together, two, three, four and have different parts of a circuit be fed from different pumps. The disadvantage of gear pumps is they are inefficient. Even a brand new gear pump—and not talking about crescent pumps or internal gear pumps—is inefficient.
Right off the factory floor, you’re lucky to get 80% efficiency. Efficiency in a pump is the amount of fluid by volume that is being pumped compared to theoretical volume. If you were to do the math and figure out the theoretical volume of a pump and it’s supposed to give you 10 gallons per minute. Even with a brand new gear pump, you’re lucky to be 80% efficient. As they wear, even though they can still be reliable and they can still run and give you some flow and pressure, that can drop to 40%, 50%, 60% or around that range.
If you’re trying to create a hydraulic system that is taking best user input power, a gear pump isn’t always your best choice. It’s not your first choice anyway. It’s your most economical choice. They can also be noisy, another disadvantage. By noisy, I don’t necessarily mean that they have the highest volume in decibels. Sometimes they do, but it all depends on the application. Sometimes, they can have a really annoying noise, the frequency and harmonics of a gear pump can be pretty annoying sometimes. You can spot the sound of a noisy gear pump a mile away.
As I mentioned, they quickly become less efficient with wear and higher pressure. Because of the nature of the clearances and the way a gear pump is designed, as you increase pressure too high in one of these pumps more is just lost to leakage. The same thing as the pumps wear.
Now we’re going to talk about vane pumps. You might notice on a lot of pumps that the suction port is larger. That’s to reduce restriction and reduce vacuum and reduce gravitation. With this particular pump design, the suction and pressure ports can be rotated. This allows you to have ideal suction and pressure configurations. For example, if you wanted to have this pump mounted below a reservoir, you’d have a large suction plumbing coming straight down into it, but it wouldn’t make any sense for the pressure to be going straight up into the reservoir as well.
On a variable displacement pump, whether it’s vane or whatever, there’s essentially a relief valve that controls the control piston. The internals of a variable displacement vane pump, you can see the example where I have this blue cam ring. Within it you have the rotating group that has the vanes and the input shaft. This particular design, what we have here with the compensators, what they do is they control the pressure that is added to this little control piston.
This one right here is, sorry. This one here would be the, yes, the bias piston. What’s happening is that it’s always … Sorry, the control piston. I was right the first time. This one right here is always trying to push on the cam ring to make it go full displacement. As it tries to go full displacement and you restrict it downstream, pressure will rise and cause this cam ring to spin in a neutral circle.
If you imagine that if you were to move the cam ring over this way as pressure increases, that there would be no increase and decreasing of displacement. It would just kind of spin in a circle and idle and nothing would really happen. The higher you set your compensator, the more it’s trying to force full displacement and the more downstream pressure has to rise before you reduce flow.
Pressure compensation is a way of trying to achieve the most amount of flow with any given pressure. The pump is always trying to put out a particular pressure. The more you resist that it will just reduce flow. There are advantages to this such as controlling flow, but also maintaining [inaudible 20:23] flow control or through a valve. It’s also more efficient as well. Rather than just always giving you full flow and full pressure, this will just give you the pressure you want and cut back flow to compensate for a higher pressure.
The advantages and disadvantages of a vane pump is they are quiet. They’re very quiet actually so in most industrial applications where high pressure and speed aren’t really necessary you will see a vane pump. Especially ones where there are humans around to be annoyed or not annoyed by a pump, these are a good choice.
They are relatively contamination resistant. Luckily they can be easily repaired, so should contamination become a problem in them, they can be fixed quite easily. They are relatively inexpensive, especially the fixed vane pump. As you go through the costing of a pump, you have your cheap gear pumps and you can have an inexpensive fixed vane pump which would kind of come in at the high end of a gear pump and then go up in price from there.
Variable displacement, vane pumps can be a little bit pricier but they don’t tend to reach into the cost of a piston pump until you get some really fancy ones. Like I mentioned earlier, they’re also easily repairable. Some of the disadvantages of a vane pump are low speed, so they don’t go terribly fast. One of the reasons is that as you spin a vane pump fast the vanes, because of centrifugal force, kind of get pushed out too deep into the cam ring. They can wear more quickly.
Anyway, vane pumps can also get very expensive. Some of the top brands they have some pretty fancy designs. They can be really complex to set up and run, but still, like I said, not as expensive as most piston pumps. Also one of the disadvantages that they have low pressure capacity. Like I said, because of the nature of the vanes and how they get pushed into the cam ring, it’s often difficult to get a lot of pressure out of these. Not more than two or 3,000 psi.
Now we’re onto piston pumps. Piston pumps is a familiar closed-loop type pump. Three types of piston pumps. Here’s the axial piston pump, the bent axis piston pump and the radial piston pump. All three of these are nice designs and fairly common, each to the piston pump family. The axial piston pump, so that is a design where the piston, so if you look inside the pump, we’ll open it up here in a second, what they do is they move back and forth on the same axis as the input shaft.
They will spin around in a circle going back and forth about the axis of a pump easily explaining why it’s called the axial piston pump. These can be had in fixed displacements, just like in a gear pump or a vane pump. This particular one is a pressure compensated load-sensing pump. What we have here is we have instead of a bias piston, this one actually has a bias spring. What the spring here is doing, it has a lot of force. What it’s trying to do is always push this swash plate, this is this plate right here that can rotate on an angle to either increase or decrease displacement of the pistons.
You can imagine if this angle is relatively flat that as these pistons travel back and forth they wouldn’t go in and out at all or very much. The volume would be reduced. If this was a severe angle, so if it was angled across this way, you can imagine that the pistons would travel a far distance. They would go in and out very far, so it would increase and decrease displacement at a higher volume.
The bias piston tries to do its best to always have full displacement and how displacement decreases is with the control piston right here. Similar to the one that was in the vane pumps. This one here is controlled by the relief valve in the compensator up here. Whatever pressure you have this set to is the pressure that this thing wants to push backwards on the swash plate to try to get it to go to a zero angle. When it’s at zero angle it would be essentially on what’s called standby pressure, meaning it’s not pumping at all.
It’s trying to create a little bit of pressure but has nowhere to go so it just kind of idles. As pressure increases, so if you were to increase or decrease the pressure on this compensator here, it increases or decreases the force which this control piston pushes on the swash plate. At a lower pressure you can imagine that if you increase system pressure, it’s really easy to shut off flow coming from this pump. If you raise the pressure on this compensator to resist this pump and then subsequently have it go on standby.
I’m not going to talk about the load-sensing function of a pump. It’s a conversation that takes a lot of explanation. I’m sure some of you may be confused by the idea of pressure compensation to begin with. We have the bent axis piston pump. This one is pretty straight forward of why it’s called bent axis. You can see that the input shaft comes in a one five and the rotating group and the ports will be on an angle to the input shaft.
We’ll go back and explain this one. The reason you would have a bent axis like this is in the case of a motor, what it allows you to have something be driven and inside the input shaft side there’s a really large bearing that supports it. If you were to have this pulley-driven, so if you imagine that the forces on a pulley were being driven from below, the angle that is on the bent axis really resists those side note forces that are put onto a shaft.
If you were to have a pump that required for some reason because of space or design to be run by say a chain or a pulley, a bent axis piston pump is the way to go. One of the other advantages of these regardless of, because of the bearing and then the way it’s supported, is that they’re good for really high pressure and also good for very high speeds. These things can rotate very quickly and they can also withstand very high pressures.
Hydraulic pumps, this is the radial piston pump. I always compare it to an airplane engine. What you have inside of a radial piston pump is a shaft with a cam. You can imagine as this camshaft rotates, so because it’s off-center as it rotates, what it does as it pushes on these pistons, which are each inside one of these cylinders, and as it goes in a circle radial to the shaft each of these pistons moves in and out.
Depending on the length, that dictates the displacement and therefore the flow. One of the advantages of these pistons is that this case they’re spring bias but they’re easily changeable. You can imagine you take off this particular, this valve cover right here and you could easily replace the entire piston assembly.
Advantages to the piston pumps, regardless of configuration they’re available in high to very high pressure capacity. You’re hard to find a piston pump rated for anything less than 4,000 psi, but some applications such as some radial piston pumps are good for up to 10,000 psi and in some cases even more. Some designs are good for higher PM. This would be the axial piston pump or the bent axis piston pump.
Because of the wobbly nature of a radial piston pump with the camshaft and with the distance of the pistons moving about the outside of the pump, they’re not as high speed rated. Good for high pressure and very efficient, but not good for high speed. Most piston pumps are very efficient, so whereas a gear pump might be 80% efficient, a vane pump could be 85% efficient. Most piston pumps are 90% efficient or more. There are some designs of radial piston pump because of their actual soft seal technology or other things that are good for 95% efficiency or higher. This means that if you have 10 gallons a minute of theoretical displacement from your pump, they could be putting up upwards of 9.5 gallons a minute of actual output flow.
I should also mention that when it comes to efficiency it is the flow that is sacrificed as a result of efficiency and not pressure. Pressure can be created as long as there’s enough molecules to stuff downstream to overcome your resistance. Volume, so flow is what is sacrificed. I should also note that inefficiency, anything not used to create actual work is wasted as heat so if you have a 10 horsepower system and you have a gear pump that is 80% efficient, you would have 2 horsepower, that’s 20% of the energy being wasted as pure heat or as in my example with a radial piston pump being 95% efficient, you would have only .5 a horsepower being wasted as heat and any application requiring an efficient, economical and green pump, can’t go wrong with a piston pump.
Also advantage of the piston pumps is that there are myriad configurations of compensation, so load-sensing, they’re torque-limiting, horsepower-limiting. There are so many advanced controls that you can get for a piston pump. The sky’s the limit.
Disadvantages are they are expensive. It can cost a lot of money. You’re lucky to have any piston pump cost less than say $1,200 and that would be even for a small one. There are some economical lines. Some people make some cheaper piston pumps that are not as high pressure rated or not as efficient, but pumps can easily go up to five, six, $10,000 or more for some pump designs.
They are contamination sensitive, so this means that for the tighter tolerances that allow them to be efficient particle sizes can’t be so big as to be stuck between piston and wall clearances to be moving across the swash plate clearances. All the areas in a pump with a tighter tolerance are more sensitive to contamination and as well because they are higher pressure, this means they can be forced through these clearances with more energy.
Whereas a lower pressure system, even if it was with a gear pump, I’m sorry, with a piston pump, you could go with a poor filtration, but when it comes to high pressure very sensitive to contamination and you should be using only the best filtration systems for high pressure piston pumps. As well, piston pumps are most expensive to repair. The rotating groups and components that are involved with them can be 40, 50, 60% of the cost of an entire new pump especially when it comes to the cost of rebuilding them and testing them after they’re done as well.
We talked about gear pumps. Once again, they are inexpensive, contamination resistant, capable of high speed. The rotation is easily changed. They’re reliable. Lost of gear pumps that are 20, 30, 40 years old that are still on machinery today. They can be stacked together in tandem so multiple pumps all for one system or one prime mover.
However, they can be inefficient, noisy and quickly become less efficient with wear and high pressure. The vane pumps, they are quiet ones of the bunch, relatively contamination resistant. They are fixed displacement pumps, can be inexpensive, they’re easily repairable in most cases. This particular example we’re looking at right here is one of the ones that is not inexpensive to repair.
Yeah, they can be tricky to set up. Anyway, this is an exception. One of the disadvantages are vane pumps are capable of only low speed. You can’t spin them too fast. Usually 1,200 to 1,800 rpm is the max. Variable piston pumps can get expensive. The one we’re looking at now is, although you can get some other brands that are less. Low pressure capacity. Typically, 2,000 or 3,000 psi is the upper range for a vane pump.
Then piston pumps, this new here being an axial piston pump, variable displacement. They are good for high to very high pressure capacity. Some of them are good for high speed, especially the axial designs and the bent axis designs. They are extremely efficient and myriad configurations of compensation are available, but they can be expensive and they are contamination sensitive. Use only the best filters, kidney loops, pressure filters on these systems. They’re also the most expensive to repair.
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Hydraulic pumps are mechanisms in hydraulic systems that move hydraulic fluid from point to point initiating the production of hydraulic power. Hydraulic pumps are sometimes incorrectly referred to as “hydrolic” pumps.
They are an important device overall in the hydraulics field, a special kind of power transmission which controls the energy which moving fluids transmit while under pressure and change into mechanical energy. Other kinds of pumps utilized to transmit hydraulic fluids could also be referred to as hydraulic pumps. There is a wide range of contexts in which hydraulic systems are applied, hence they are very important in many commercial, industrial, and consumer utilities.
“Power transmission” alludes to the complete procedure of technologically changing energy into a beneficial form for practical applications. Mechanical power, electrical power, and fluid power are the three major branches that make up the power transmission field. Fluid power covers the usage of moving gas and moving fluids for the transmission of power. Hydraulics are then considered as a sub category of fluid power that focuses on fluid use in opposition to gas use. The other fluid power field is known as pneumatics and it’s focused on the storage and release of energy with compressed gas.
"Pascal"s Law" applies to confined liquids. Thus, in order for liquids to act hydraulically, they must be contained within a system. A hydraulic power pack or hydraulic power unit is a confined mechanical system that utilizes liquid hydraulically. Despite the fact that specific operating systems vary, all hydraulic power units share the same basic components. A reservoir, valves, a piping/tubing system, a pump, and actuators are examples of these components. Similarly, despite their versatility and adaptability, these mechanisms work together in related operating processes at the heart of all hydraulic power packs.
The hydraulic reservoir"s function is to hold a volume of liquid, transfer heat from the system, permit solid pollutants to settle, and aid in releasing moisture and air from the liquid.
Mechanical energy is changed to hydraulic energy by the hydraulic pump. This is accomplished through the movement of liquid, which serves as the transmission medium. All hydraulic pumps operate on the same basic principle of dispensing fluid volume against a resistive load or pressure.
Hydraulic valves are utilized to start, stop, and direct liquid flow in a system. Hydraulic valves are made of spools or poppets and can be actuated hydraulically, pneumatically, manually, electrically, or mechanically.
The end result of Pascal"s law is hydraulic actuators. This is the point at which hydraulic energy is transformed back to mechanical energy. This can be accomplished by using a hydraulic cylinder to transform hydraulic energy into linear movement and work or a hydraulic motor to transform hydraulic energy into rotational motion and work. Hydraulic motors and hydraulic cylinders, like hydraulic pumps, have various subtypes, each meant for specific design use.
The essence of hydraulics can be found in a fundamental physical fact: fluids are incompressible. (As a result, fluids more closely resemble solids than compressible gasses) The incompressible essence of fluid allows it to transfer force and speed very efficiently. This fact is summed up by a variant of "Pascal"s Principle," which states that virtually all pressure enforced on any part of a fluid is transferred to every other part of the fluid. This scientific principle states, in other words, that pressure applied to a fluid transmits equally in all directions.
Furthermore, the force transferred through a fluid has the ability to multiply as it moves. In a slightly more abstract sense, because fluids are incompressible, pressurized fluids should keep a consistent pressure just as they move. Pressure is defined mathematically as a force acting per particular area unit (P = F/A). A simplified version of this equation shows that force is the product of area and pressure (F = P x A). Thus, by varying the size or area of various parts inside a hydraulic system, the force acting inside the pump can be adjusted accordingly (to either greater or lesser). The need for pressure to remain constant is what causes force and area to mirror each other (on the basis of either shrinking or growing). A hydraulic system with a piston five times larger than a second piston can demonstrate this force-area relationship. When a force (e.g., 50lbs) is exerted on the smaller piston, it is multiplied by five (e.g., 250 lbs) and transmitted to the larger piston via the hydraulic system.
Hydraulics is built on fluids’ chemical properties and the physical relationship between pressure, area, and force. Overall, hydraulic applications allow human operators to generate and exert immense mechanical force with little to no physical effort. Within hydraulic systems, both oil and water are used to transmit power. The use of oil, on the other hand, is far more common, owing in part to its extremely incompressible nature.
Pressure relief valves prevent excess pressure by regulating the actuators’ output and redirecting liquid back to the reservoir when necessary. Directional control valves are used to change the size and direction of hydraulic fluid flow.
While hydraulic power transmission is remarkably useful in a wide range of professional applications, relying solely on one type of power transmission is generally unwise. On the contrary, the most efficient strategy is to combine a wide range of power transmissions (pneumatic, hydraulic, mechanical, and electrical). As a result, hydraulic systems must be carefully embedded into an overall power transmission strategy for the specific commercial application. It is necessary to invest in locating trustworthy and skilled hydraulic manufacturers/suppliers who can aid in the development and implementation of an overall hydraulic strategy.
The intended use of a hydraulic pump must be considered when selecting a specific type. This is significant because some pumps may only perform one function, whereas others allow for greater flexibility.
The pump"s material composition must also be considered in the application context. The cylinders, pistons, and gears are frequently made of long-lasting materials like aluminum, stainless steel, or steel that can withstand the continuous wear of repeated pumping. The materials must be able to withstand not only the process but also the hydraulic fluids. Composite fluids frequently contain oils, polyalkylene glycols, esters, butanol, and corrosion inhibitors (though water is used in some instances). The operating temperature, flash point, and viscosity of these fluids differ.
In addition to material, manufacturers must compare hydraulic pump operating specifications to make sure that intended utilization does not exceed pump abilities. The many variables in hydraulic pump functionality include maximum operating pressure, continuous operating pressure, horsepower, operating speed, power source, pump weight, and maximum fluid flow. Standard measurements like length, rod extension, and diameter should be compared as well. Because hydraulic pumps are used in lifts, cranes, motors, and other heavy machinery, they must meet strict operating specifications.
It is critical to recall that the overall power generated by any hydraulic drive system is influenced by various inefficiencies that must be considered in order to get the most out of the system. The presence of air bubbles within a hydraulic drive, for example, is known for changing the direction of the energy flow inside the system (since energy is wasted on the way to the actuators on bubble compression). Using a hydraulic drive system requires identifying shortfalls and selecting the best parts to mitigate their effects. A hydraulic pump is the "generator" side of a hydraulic system that initiates the hydraulic procedure (as opposed to the "actuator" side that completes the hydraulic procedure). Regardless of disparities, all hydraulic pumps are responsible for displacing liquid volume and transporting it to the actuator(s) from the reservoir via the tubing system. Some form of internal combustion system typically powers pumps.
While the operation of hydraulic pumps is normally the same, these mechanisms can be split into basic categories. There are two types of hydraulic pumps to consider: gear pumps and piston pumps. Radial and axial piston pumps are types of piston pumps. Axial pumps produce linear motion, whereas radial pumps can produce rotary motion. The gear pump category is further subdivided into external gear pumps and internal gear pumps.
Each type of hydraulic pump, regardless of piston or gear, is either double-action or single-action. Single-action pumps can only pull, push, or lift in one direction, while double-action pumps can pull, push, or lift in multiple directions.
Vane pumps are positive displacement pumps that maintain a constant flow rate under varying pressures. It is a pump that self-primes. It is referred to as a "vane pump" because the effect of the vane pressurizes the liquid.
This pump has a variable number of vanes mounted onto a rotor that rotates within the cavity. These vanes may be variable in length and tensioned to maintain contact with the wall while the pump draws power. The pump also features a pressure relief valve, which prevents pressure rise inside the pump from damaging it.
Internal gear pumps and external gear pumps are the two main types of hydraulic gear pumps. Pumps with external gears have two spur gears, the spurs of which are all externally arranged. Internal gear pumps also feature two spur gears, and the spurs of both gears are internally arranged, with one gear spinning around inside the other.
Both types of gear pumps deliver a consistent amount of liquid with each spinning of the gears. Hydraulic gear pumps are popular due to their versatility, effectiveness, and fairly simple design. Furthermore, because they are obtainable in a variety of configurations, they can be used in a wide range of consumer, industrial, and commercial product contexts.
Hydraulic ram pumps are cyclic machines that use water power, also referred to as hydropower, to transport water to a higher level than its original source. This hydraulic pump type is powered solely by the momentum of moving or falling water.
Ram pumps are a common type of hydraulic pump, especially among other types of hydraulic water pumps. Hydraulic ram pumps are utilized to move the water in the waste management, agricultural, sewage, plumbing, manufacturing, and engineering industries, though only about ten percent of the water utilized to run the pump gets to the planned end point.
Despite this disadvantage, using hydropower instead of an external energy source to power this kind of pump makes it a prominent choice in developing countries where the availability of the fuel and electricity required to energize motorized pumps is limited. The use of hydropower also reduces energy consumption for industrial factories and plants significantly. Having only two moving parts is another advantage of the hydraulic ram, making installation fairly simple in areas with free falling or flowing water. The water amount and the rate at which it falls have an important effect on the pump"s success. It is critical to keep this in mind when choosing a location for a pump and a water source. Length, size, diameter, minimum and maximum flow rates, and speed of operation are all important factors to consider.
Hydraulic water pumps are machines that move water from one location to another. Because water pumps are used in so many different applications, there are numerous hydraulic water pump variations.
Water pumps are useful in a variety of situations. Hydraulic pumps can be used to direct water where it is needed in industry, where water is often an ingredient in an industrial process or product. Water pumps are essential in supplying water to people in homes, particularly in rural residences that are not linked to a large sewage circuit. Water pumps are required in commercial settings to transport water to the upper floors of high rise buildings. Hydraulic water pumps in all of these situations could be powered by fuel, electricity, or even by hand, as is the situation with hydraulic hand pumps.
Water pumps in developed economies are typically automated and powered by electricity. Alternative pumping tools are frequently used in developing economies where dependable and cost effective sources of electricity and fuel are scarce. Hydraulic ram pumps, for example, can deliver water to remote locations without the use of electricity or fuel. These pumps rely solely on a moving stream of water’s force and a properly configured number of valves, tubes, and compression chambers.
Electric hydraulic pumps are hydraulic liquid transmission machines that use electricity to operate. They are frequently used to transfer hydraulic liquid from a reservoir to an actuator, like a hydraulic cylinder. These actuation mechanisms are an essential component of a wide range of hydraulic machinery.
There are several different types of hydraulic pumps, but the defining feature of each type is the use of pressurized fluids to accomplish a job. The natural characteristics of water, for example, are harnessed in the particular instance of hydraulic water pumps to transport water from one location to another. Hydraulic gear pumps and hydraulic piston pumps work in the same way to help actuate the motion of a piston in a mechanical system.
Despite the fact that there are numerous varieties of each of these pump mechanisms, all of them are powered by electricity. In such instances, an electric current flows through the motor, which turns impellers or other devices inside the pump system to create pressure differences; these differential pressure levels enable fluids to flow through the pump. Pump systems of this type can be utilized to direct hydraulic liquid to industrial machines such as commercial equipment like elevators or excavators.
Hydraulic hand pumps are fluid transmission machines that utilize the mechanical force generated by a manually operated actuator. A manually operated actuator could be a lever, a toggle, a handle, or any of a variety of other parts. Hydraulic hand pumps are utilized for hydraulic fluid distribution, water pumping, and various other applications.
Hydraulic hand pumps may be utilized for a variety of tasks, including hydraulic liquid direction to circuits in helicopters and other aircraft, instrument calibration, and piston actuation in hydraulic cylinders. Hydraulic hand pumps of this type use manual power to put hydraulic fluids under pressure. They can be utilized to test the pressure in a variety of devices such as hoses, pipes, valves, sprinklers, and heat exchangers systems. Hand pumps are extraordinarily simple to use.
Each hydraulic hand pump has a lever or other actuation handle linked to the pump that, when pulled and pushed, causes the hydraulic liquid in the pump"s system to be depressurized or pressurized. This action, in the instance of a hydraulic machine, provides power to the devices to which the pump is attached. The actuation of a water pump causes the liquid to be pulled from its source and transferred to another location. Hydraulic hand pumps will remain relevant as long as hydraulics are used in the commerce industry, owing to their simplicity and easy usage.
12V hydraulic pumps are hydraulic power devices that operate on 12 volts DC supplied by a battery or motor. These are specially designed processes that, like all hydraulic pumps, are applied in commercial, industrial, and consumer places to convert kinetic energy into beneficial mechanical energy through pressurized viscous liquids. This converted energy is put to use in a variety of industries.
Hydraulic pumps are commonly used to pull, push, and lift heavy loads in motorized and vehicle machines. Hydraulic water pumps may also be powered by 12V batteries and are used to move water out of or into the desired location. These electric hydraulic pumps are common since they run on small batteries, allowing for ease of portability. Such portability is sometimes required in waste removal systems and vehiclies. In addition to portable and compact models, options include variable amp hour productions, rechargeable battery pumps, and variable weights.
While non rechargeable alkaline 12V hydraulic pumps are used, rechargeable ones are much more common because they enable a continuous flow. More considerations include minimum discharge flow, maximum discharge pressure, discharge size, and inlet size. As 12V batteries are able to pump up to 150 feet from the ground, it is imperative to choose the right pump for a given use.
Air hydraulic pumps are hydraulic power devices that use compressed air to stimulate a pump mechanism, generating useful energy from a pressurized liquid. These devices are also known as pneumatic hydraulic pumps and are applied in a variety of industries to assist in the lifting of heavy loads and transportation of materials with minimal initial force.
Air pumps, like all hydraulic pumps, begin with the same components. The hydraulic liquids, which are typically oil or water-based composites, require the use of a reservoir. The fluid is moved from the storage tank to the hydraulic cylinder via hoses or tubes connected to this reservoir. The hydraulic cylinder houses a piston system and two valves. A hydraulic fluid intake valve allows hydraulic liquid to enter and then traps it by closing. The discharge valve is the point at which the high pressure fluid stream is released. Air hydraulic pumps have a linked air cylinder in addition to the hydraulic cylinder enclosing one end of the piston.
The protruding end of the piston is acted upon by a compressed air compressor or air in the cylinder. When the air cylinder is empty, a spring system in the hydraulic cylinder pushes the piston out. This makes a vacuum, which sucks fluid from the reservoir into the hydraulic cylinder. When the air compressor is under pressure, it engages the piston and pushes it deeper into the hydraulic cylinder and compresses the liquids. This pumping action is repeated until the hydraulic cylinder pressure is high enough to forcibly push fluid out through the discharge check valve. In some instances, this is connected to a nozzle and hoses, with the important part being the pressurized stream. Other uses apply the energy of this stream to pull, lift, and push heavy loads.
Hydraulic piston pumps transfer hydraulic liquids through a cylinder using plunger-like equipment to successfully raise the pressure for a machine, enabling it to pull, lift, and push heavy loads. This type of hydraulic pump is the power source for heavy-duty machines like excavators, backhoes, loaders, diggers, and cranes. Piston pumps are used in a variety of industries, including automotive, aeronautics, power generation, military, marine, and manufacturing, to mention a few.
Hydraulic piston pumps are common due to their capability to enhance energy usage productivity. A hydraulic hand pump energized by a hand or foot pedal can conver