Fundamentals of hydraulic pumps

Hydraulic systems are one of the cornerstones of all industrial plant machinery. In fact, hydraulic systems are present in many important bits of technology throughout the modern world, from car braking systems to manufacturing lines. Anyone involved in the construction industry will be aware of how important hydraulic systems are to the everyday running of their business. But, even if you work with hydraulic equipment and machinery every day, you may still not know exactly how these systems work and which components make it all possible.

While this isn’t necessarily a fundamental requirement to get your job done, a basic knowledge of hydraulic systems and how they work can go a long way towards running your business that little bit more smoothly. An inevitable part of working with any type of machinery is breakdowns and repairs, so it’s important to understand what could go wrong with your hydraulic machinery and how to deal with hydraulic pump repairs. Below we’ll run through the basics of hydraulic systems, in particular hydraulic pumps, and explain why having a proper framework in place for hydraulic pump repairs is so important.

Key components

The two key components in hydraulic systems are hydraulic pumps and hydraulic motors. While hydraulic pumps turn kinetic/rotational energy into flow/pressure within the hydraulic system, hydraulic motors take the flow/pressure within the hydraulic system and turn it back into kinetic energy to drive the machinery’s moving tools and parts. As the components at the input side of hydraulic systems, we will focus on explaining hydraulic pumps in this blog post.

Hydraulic systems are useful for heavy machinery because they can transmit very high levels of power/force. Additionally, because they use hydraulic fluid, which travels through hydraulic lines, they can be shaped to fit systems with many different moving parts and complex structures.

Hydraulic systems need something to transfer kinetic energy into the hydraulic fluid. This job falls to hydraulic pumps, which are driven by a hydraulic pump motor. There are a number of different types of hydraulic pumps, which move/force the hydraulic fluid through the system, on to the hydraulic motors at the other end.

Classifications of hydraulic pumps

There are two main classifications of hydraulic pumps – positive-displacement pumps and non-positive-displacement pumps. Positive displacement pumps do not allow any slippage around the pumping element. This effectively means that hydraulic fluid cannot move past the pump itself unless the pump is turning. Additionally, positive displacement pumps displace the same amount of fluid during every turn of the pump.

The other main classification of hydraulic pump, non-positive-displacement pumps, do allow slippage in the hydraulic fluid. This means that if the pressure within the system rises to a certain point, the hydraulic element will still turn, but not be able to force any more hydraulic fluid through the system. Non-positive displacement hydraulic pumps produce continuous flow, which makes them useful in a number of specific applications.

Common types of hydraulic pumps

The most common type of hydraulic pump is the rotary hydraulic pump. These pumps push hydraulic fluid through the hydraulic system using a rotary element. There are a number of different mechanisms used to achieve this, most commonly gears which pull hydraulic fluid from the inlet, through the housing with their teeth as they turn, and then force it out of the outlet. An example of this mechanism is shown in Figure 1. below.

Figure 1. Spur gear pump.                  Figure 2. Gerotor and crescent internal gear pumps.

Another type of pump which relies on gears to push hydraulic fluid through a hydraulic system is a gerotor gear pump, a type of internal gear pump shown in Figure 2. above. This type of hydraulic pump makes use of a gerotor element which moves against an eccentrically set internal gear. The hydraulic fluid is pulled though the gap between these two gears as they turn against each other.

Vane pumps are another type of rotary hydraulic pump, but they do not rely on gears to pump hydraulic fluid. Instead they make use of an eccentrically-housed rotor which has a number of spring-loaded (some have other mechanisms) vanes protruding from the centre. As the rotor spins, the vanes are pushed outwards so that they maintain constant contact with the inside of the housing. Because the rotor is eccentrically mounted, hydraulic fluid is moved from the input to the output by the vanes, as seen in Figure 3.

Figure 3. Basic (unbalanced) vane pump.

Piston pumps are a different type of hydraulic pump, which rely on the action of small pistons to push hydraulic fluid through the hydraulic system. Similar to the way in which a rotary vane pump makes use of an eccentric mounting to move hydraulic fluid, an axial piston pump relies on eccentricity to move pistons mounted on a rotating swashplate, as seen in Figure 4.

Figure 4. Axial piston pump.

As you can see from the various diagrams above, hydraulic pumps can be pretty complicated. As a result, a broken pump or hydraulic pump motor can be a tricky fix. This means it is very important to have professional assistance for hydraulic pump repairs. That’s where we come in. At CJ Plant Maintenance, we have extensive experience providing plant maintenance services for all sorts of plant machinery, all year round. If one of your hydraulic systems breaks down or isn’t performing how it should be, you need quick repairs to keep your it up and running and to stop your business losing money.

If you would like to know more about the support we offer, or what we can do for your company, please get in touch today.