What Are 3 Types of Hydraulic Pumps
There are typically 3 types of hydraulic pumps constructions found in the mobile hydraulic applications. These three pumps include gear, piston, and vane. However, we don’t want you to forget about the clutch pumps, dump pumps, and pumps to refuse vehicles such as the dry valve pumps and Muncie power products Live Pak. For the sake of this blog post we are going to answer the question: What are the Main 3 Types of Hydraulic Pumps.
The hydraulic pump is one of the components of the hydraulic system that takes the mechanical energy and converts it into fluid energy in the form of oil flow. The mechanical energy is taken from the prime mover, which a turning force, such as the power take-off or directly from the engine.
There are two designs for a hydraulic pump. Either a uni-rotational or bi-rotational design. The uni-rotational is designed to operate in one direction of the shaft rotation. In contrast, the bi-rotational pump is designed to operate in either direction.
Type of Hydraulic Pump #1: Gear Pump
The most common design for a truck-mounted hydraulic system is the gear pump. This design tends to have fewer moving parts, is easier to service, more tolerant of contamination than other designs, and relatively inexpensive. Gear pumps are fixed displacement, also called positive displacement pumps. Meaning the same volume of flow is produced in each rotation of the pump’s shaft. The gear pumps are rated in terms of their maximum pressure rating, cubic inch displacement, and their maximum input speed limitation.
Gear pumps are mostly used in open-center hydraulic systems. The gear pump will trap oil in the areas between the teeth of the pump’s two gears and in the body of the pump. Then it will transport it around the circumference of the gear cavity and then force it through the outlet port as the gears mesh. Behind the wear plates, a small amount of pressurized oil will push the plates tightly against the gear ends to improve the pump’s efficiency.
Gear Pump Recap
- Most common used design
- Fewer parts, easier to service, can tolerate more contaminates, relatively inexpensive
- Fixed, positive, displacement pumps
- Rated in terms of maximum pressure, cubic inch displacement, max input speed limitation
- Used in open center hydraulic systems
Type of Hydraulic Pump #2: Piston Pump
Piston pumps are often used when high operating pressures are required. Piston pumps traditionally will withstand higher pressure gear pumps with comparable displacements. However, there is a lower resistance to contaminants, increased complexity, and a higher initial cost. Piston pumps are often used with truck-mounted cranes but can also be found in other applications like snow and ice control where it’s desirable to vary system flow without compromising engine speed.
The piston pump contains a cylinder block with pistons that move in and out within the pump. The movement of the pistons draws from the oil supply port and then forces it through the outlet. The angle of the swash plate, which the slippery end of the piston rides against, will determine the length of the piston’s stroke. With the swash plat being stationary, the cylinder block (encompassing the pistons) will rotate with the pump’s input shaft. The pump displacement is then determined by the total volume of the pump’s cylinders. You can choose either a fixed or variable displacement design for the piston.
Piston Pump Recap
- Can withstand higher pressures
- Higher initial cost, increased complexity, and lower resistance to contaminants
- More moving parts, stricter filtration requirements, and closer tolerances
- Truck-mounted cranes or when desirable to vary system flow without compromising engine speed
- Fixed and variable displacement options are available
Type of Hydraulic Pump #3: Vane Pump
Vane pumps were commonly used on utility vehicles such as aerial buckets and ladders. Today, the vane pump is not as commonly found in those mobile hydraulic systems. The gear pumps have become more widely accepted and available.
Within a vane pump, as the input shaft rotates it causes the oil to pick up between the vanes of the pump which then will be transported to the pump’s outlet side. Similar to how gear pumps work, there is one set of vanes, rather than a pair of gears, on a rotating cartridge in the pump housing. When the area between the vanes decreases on the outlet side and increases on the inlet of the side pump, the oil is then drawn in through the supply port and expelled through the outlet as the vane cartridge rotates due to the change in the area.
Vane Pump Recap
- Was used in utility vehicles, but is not as common today since gear pumps are more widely accepted and available