The hydraulic pump is an important component of the hydraulic system that converts mechanical energy into fluid energy. There are different types of hydraulic pumps to consider, depending on the application. There are three main types of pumps that are found in most hydraulic applications.
The gear hydraulic pump is the most common design found in truck-mounted hydraulic systems. This pump is relatively inexpensive, has few moving parts, is easier to service, and is more tolerant of contamination. These pumps are fixed displacement, which means the same volume of flow is produced with every rotation. These pumps are rated in terms of the maximum input speed limitation, maximum pressure rating, and cubic inch displacements. These pumps will typically be used in open center hydraulic systems, and they will trap oil in the areas between the teeth of the pump and force it out through the outlet port.
A piston pump is typically used when high operating pressure is needed because these pumps withstand higher pressures than gear pumps. There is a higher cost associated with these pumps and they are more complicated with lower resistance to contamination. These pumps are typically found on truck-mounted cranes but can be found in other applications as well, such as ice and snow control. These pumps work by a cylinder block that contains pistons that move in and out. The movement of the pistons draws oil from the supply port then forces it through the outlet. There are both fixed and variable designs. With a fixed displacement pump, the swashplate isn’t adjustable. With a variable displacement pump, the hydraulic flow requirements vary based on the different conditions. The swashplate isn’t fixed and the angle can be adjusted by a pressure signal using a compensator. There are also different variable displacement pumps and these can be pressure compensated, flow compensated, or both pressure and flow compensated.
Vane pumps were commonly used on utility vehicles but now the gear pump is more commonly used and available. A vane pump works with the input shaft rotating. As it does this, it causes oil to be picked up between vanes on the pump and then transported to the pump’s outlet side. It’s similar to how gear pumps work but instead there is a set of vanes instead of a pair of gears.
There are some other types of hydraulic pumps that fall into these categories. Clutch pumps are small displacement gear pumps equipped with a belt-driven clutch that is similar to one found on a car’s air conditioner compressor. Common applications for clutch pumps include aerial bucket trucks, hay spikes, and wreckers. Clutch pumps aren’t used when pump output flows are in excess of 15 GPM. Dump pumps are the most recognizable. These pumps are mostly used in dumping applications. They are designed for this one application and are not suitable for other common applications. What makes this pump different is that it has a built-in pressure relief assembly.