Hydraulic systems are in general members of the fluid power branch of power transmission. Hydraulic pumps are also members of the hydraulic power pack/hydraulic power unit family. Hydraulic units are encased mechanical systems that use liquids for hydraulics.
The hydraulic systems that hydraulic pumps support exist in a range of industries, among them agriculture, automotive manufacturing, defense contracting, excavation, and industrial manufacturing. Within these industries, machines and applications that rely on hydraulic pumps include airplane flaps, elevators, cranes, automotive lifts, shock absorbers, automotive brakes, garage jacks, off-highway equipment, log splitters, offshore equipment, hydraulic motors/hydraulic pump motors, and a wide range of other hydraulic equipment.
When designing hydraulic pumps, manufacturers have many options from which to choose in terms of material composition. Most commonly, they make the body of the pump–the gears, pistons, and hydraulic cylinders–from a durable metal material. This metal is one that that can hold up against the erosive and potentially corrosive properties of hydraulic fluids, as well as the wear that comes along with continual pumping. Metals like this include, among others, steel, stainless steel, and aluminum.
Considerations and Customization
Before designing a pump, manufacturers must answer a few questions.
First, what are operating specifications of their customer? They must make sure that the pump they design matches customer requirements in terms of capabilities. These capabilities include maximum fluid flow, minimum and maximum operating pressure, horsepower, and operating speeds. Also, based on application specifications, some suppliers may choose to include discharge sensors or another means of monitoring the wellbeing of their hydraulic system.
Next, what is the nature of the space in which the pump will work? Based on the answer to this question, manufacturers will design the pump with a specific weight, rod extension capability, diameter, length, and power source.
Manufacturers must also find out what type of substance does the customer plan on running through the pumps. If the application calls for it, manufacturers can recommend operators add other substances to them in order to decrease the corrosive nature of certain hydraulic fluids. Examples of such fluids include esters, butanol, pump oils, glycols, water, or corrosive inhibitors. These substances differ in operating temperature, flash point, and viscosity, so they must be chosen with care.
All hydraulic pumps are composed in the same basic way. First, they have a reservoir, which is the section of the pump that houses stationary fluid. Next, they use hydraulic hoses or tubes to transfer this fluid into the hydraulic cylinder, which is the main body of the hydraulic system. Inside the cylinder, or cylinders, are two hydraulic valves and one or more pistons or gear systems. One valve is located at each end; they are called the intake check/inlet valve and the discharge check/outlet valve, respectively.
How They Work
Hydraulic pumps operate under the principle of Pascal’s Law, which states the increase in pressure at one point of an enclosed liquid in equilibrium is equally transferred to all other points of said liquid.
To start, the check valve is closed, making it a normally closed (NC) valve. When the check is closed, fluid pressure builds. The piston forces the valves open and closes repeatedly at variable speeds, increasing pressure in the cylinder until it builds up enough to force the fluid through the discharge valve. In this way, the pump delivers sufficient force and energy to the attached equipment or machinery to move the target load.
When the fluid becomes pressurized enough, the piston withdraws long enough to allow the open check valve to create a vacuum that pulls in hydraulic fluid from the reservoir. From the reservoir, the pressurized fluid moves into the cylinder through the inlet. Inside the cylinder, the fluid picks up more force, which it carries over into the hydraulic system, where it is released through the outlet.
All hydraulic pumps can be categorized as either single action or double action.
Single action pumps can propel, pull, and lift unidirectionally only.
Double action pumps can move loads in more than one direction.
In addition, all hydraulic pumps are divided into two main groups: piston pumps and gear pumps.
Piston pumps create positive displacement and build pressure using pistons. Piston pumps may be further divided into radial piston pumps and axial piston pumps.
Radial pumps are mostly used to power relatively small flows and very high-pressure applications. They use pistons arranged around a floating center shaft or ring, which can be moved by a control lever, causing eccentricity and the potential for both inward and outward movement.
Axial pumps, on the other hand, only allow linear motion. Despite this, they are very popular, being easier and less expensive to produce, as well as more compact in design.
Gear pumps, or hydraulic gear pumps, create pressure not with pistons but with the interlocking of gear teeth. When teeth are meshed together, fluid has to travel around the outside of the gears, where pressure builds.
Gear pumps are also divided into two categories: external gear pumps and internal gear pumps.
External gear pumps facilitate flow by enlisting two identical gears that rotate against each other. As liquid flows in, it is trapped by the teeth and forced around them. It sits, stuck in the cavities between the teeth and the casing, until it is so pressurized by the meshing of the gears that it is forced to the outlet port.
Internal gear pumps, on the other hand, use bi-rotational gears. To begin the pressurizing process, gear pumps first pull in liquid via a suction port between the teeth of the exterior gear, called the rotor, and the teeth of the interior gear, called the idler. From here, liquid travels between the teeth, where they are divided within them. The teeth continue to rotate and mesh, both creating locked pockets of liquid and forming a seal between the suction port and the discharge port. Liquid is discharged and power is transported once the pump head is flooded. Internal gears are quite versatile, usable with a wide variety of fluids, not only including fuel oils and solvents, but also thick liquids like chocolate, asphalt, and adhesives.
Various other types of hydraulic pumps include rotary vane pumps, centrifugal pumps, electric hydraulic pumps, hydraulic clutch pumps, hydraulic plunger pumps, hydraulic water pumps, hydraulic ram pumps, portable 12V hydraulic pumps, hydraulic hand pumps, and air hydraulic pumps.
Rotary vane pumps are fairly high efficiency pumps, though they are not considered high pressure pumps. Vane pumps, which are a type of positive-displacement pump, apply constant but adjustable pressure.
Centrifugal pumps use hydrodynamic energy to move fluids. They feature a rotating axis, an impeller, and a casing or diffuser. Most often, operators use them for applications such as petroleum pumping, sewage, petrochemical pumping, and water turbine functioning.
Electric hydraulic pumps are hydraulic pumps powered by an electric motor. Usually, the hydraulic pump and motor work by turning mechanisms like impellers in order to create pressure differentials, which in turn generate fluid movement. Nearly any type of hydraulic pump can be run with electricity. Most often, operators use them with industrial machinery.
Hydraulic clutch pumps help users engage and disengage vehicle clutch systems. They do so by applying the right pressure for coupling or decoupling shafts in the clutch system. Coupled shafts allow drivers to accelerate, while decoupled shafts allow drivers to decelerate or shift gears.
Hydraulic plunger pumps use plunger mechanisms in place of pistons and their hydraulic actuator.
Hydraulic ram pumps are a type of hydraulic pump designed to harness hydropower, or the power of water, to elevate it. Featuring only two moving hydraulic parts, hydraulic ram pumps require only the momentum of water to work. Operators use hydraulic ram pumps to move water in industries like manufacturing, waste management and sewage, engineering, plumbing, and agriculture. While hydraulic ram pumps return only about 10% of the water they receive, they are widely used in developing countries because they do not require fuel or electricity.
Hydraulic water pumps are any hydraulic pumps used to transfer water. Usually, hydraulic water pumps only require a little bit of energy in the beginning, as the movement and weight of water generate a large amount of usable pressure.
Portable 12V hydraulic pumps are a battery-operated hydraulic pump type. Operators can use in them emergency applications.
Hydraulic hand pumps are hydraulic pumps that only work after you manually pressurize their hydraulic fluid contents.
Air hydraulic pumps are hydraulic pumps powered by air compressors. In essence, these energy efficient pumps work by converting air pressure into hydraulic pressure.
Hydraulic pumps are useful for many reasons. First, they are simple. Simple machines are always an advantage because they are less likely to break and easier to repair if they do. Second, because fluid is easy to compress and so quick to create pressure force, hydraulic pumps are very efficient. Next, hydraulic pumps are compact, which means they are easy to fit into small and oddly shaped spaces. This is especially true in comparison to mechanical pumps and electrical pumps, which manufacturers cannot design so compactly. Speaking of design, another asset of hydraulic pumps is their customizability. Manufacturers can modify them easily. Likewise, hydraulic pumps are very versatile, not only because they are customizable, but also because they can work in places where other types of pump systems can’t, such as in the ocean. Furthermore, hydraulic pumps can produce far more power than similarly sized electrical pumps. Finally, these very durable hydraulic components are much less likely to explode than some other types of components.
To make sure that your hydraulic pumps stay useful for a long time, you need to treat them with care. Care includes checking them on a regular basis for problems like insufficient fluid pressure, leaks, and wear and tear. You can use diagnostic technology like discharge sensors to help you with detect failures and measure discharge pressure. Checking vibration signals alone is often not enough.
To keep yourself and your workers safe, you need to always take the proper precautions when operating or performing maintenance and repairs on your hydraulic pumps. For example, you should never make direct contact with hydraulic fluid. For one, the fluid made be corrosive and dangerous to your skin. For two, even if the pump isn’t active at that moment, the fluid can still be pressurized and may potentially harm you if something goes wrong. For more tips on hydraulic pump care and operation, talk to both your supplier and OSHA (Occupational Safety and Health Administration).
Pumps that meet operating standards are the foundation of safe and effective operations, no matter the application. Find out what operating standards your hydraulic pumps should meet by talking to your industry leaders.
Things to Consider
The highest quality hydraulic pumps come from the highest quality hydraulic pump manufacturers. Finding the highest quality hydraulic pump manufacturers can be hard, which is why we have we listed out some of our favorites on this page. All of those whom we have listed come highly recommended with years of experience. Find their information nestled in between these information paragraphs.
Before checking out any of these suppliers, we recommend you take some time to jot down your specifications. That way, you will have an easier time figuring out which ones have potential for you and which ones do not. Plus, when you are ready to talk to a supplier, your list will help you steer the conversation. Do not forget to include in your list the nitty-gritty details like your timeline, your budget and your delivery preferences.
Once you have put together you list, get to browsing. Pick out three or four hydraulic pump supply companies to which you’d like to speak, then reach out to each of them. After you’ve spoken with representatives from each company, decide which one will best serve you, and get started on your project. Good luck!
Hydraulic Pump Informational Video