Types of Hydraulic Pump Constructions in Mobile Applications

In mobile hydraulic applications, three primary types of hydraulic pump constructions are commonly used: gear pumps, piston pumps, and vane pumps. Additionally, there are specialized pumps such as clutch pumps, dump pumps, and pumps for refuse vehicles like dry valve pumps and Muncie Power Products’ Live Pak™.

The hydraulic pump is the component that converts mechanical energy into fluid energy in the form of oil flow. This mechanical energy is derived from a prime mover (a turning force) like the power take-off or directly from the truck engine.

Car Lift Repair Tampa Florida Hydraulic pumps can be either uni-rotational or bi-rotational. A uni-rotational pump operates in one direction of shaft rotation, whereas a bi-rotational pump can operate in either direction.

Gear Pumps

The most common type of pump used in truck-mounted Car Lift Repair Tampa Florida hydraulic systems is the gear pump. Gear pumps are known for their simplicity, ease of service, contamination tolerance, and affordability. These fixed displacement pumps, also known as positive displacement pumps, produce the same volume of flow with each shaft rotation.Gear pumps are typically used in open center hydraulic systems. They function by trapping oil between the teeth of the pump’s two gears and the pump body, transporting it around the gear cavity, and forcing it through the outlet port as the gears mesh. Pressurized oil behind the thrust plates improves pump efficiency by tightly sealing the gear ends.

**Quick Look:**

– Most common design

– Fewer moving parts, easy to service, more tolerant of contaminants, relatively inexpensive

– Fixed displacement

– Rated by max pressure, cubic inch displacement, max input speed

– Used in open center systems

– Oil transported around gear cavity, forced through outlet port

– Thrust plates enhance efficiency

Piston Pumps

Car Lift Repair Tampa Florida Piston pumps are preferred for high-pressure applications and can handle higher pressures than gear pumps of similar displacement. Despite their higher initial cost and complexity, they are vital for applications like truck-mounted cranes and snow and ice control, where variable flow is necessary without varying engine speed.

Car Lift Repair Tampa Florida Piston pumps consist of a cylinder block with pistons that move in and out, drawing oil from the supply port and forcing it through the outlet. The swash plate angle determines the pistons’ stroke length. Piston pumps come in fixed and variable displacement designs.

**Quick Look:**

– Withstand higher pressures

– Higher initial cost, lower contamination resistance, increased complexity

– Used in applications requiring variable flow

– Fixed and variable displacement designs

– Pistons in cylinder block move to draw and expel oil

– Swash plate angle controls piston stroke length

Fixed and Variable Displacement Piston Pumps

**Fixed Displacement:** The swash plate is non-adjustable, providing a proportional output flow to the input shaft speed, similar to gear pumps. Used in open center systems.

**Variable Displacement:** Used in applications where flow requirements vary based on operating conditions, such as snow and ice control. The adjustable swash plate angle, controlled by a pressure signal from the directional valve, varies the pump displacement. Variable displacement pumps are used in closed center systems and can be flow compensated, pressure compensated, or both.

**Flow Compensated:** Maintains a constant pressure margin by adjusting the swash plate angle.

**Pressure Compensated:** Maintains specified flow regardless of system pressure changes.

**Flow and Pressure Compensated:** Known as load-sensing systems, common in snow and ice control vehicles.

Vane Pumps

Once common in utility vehicles, vane pumps are now less prevalent, replaced by gear pumps. Vane pumps work similarly to gear pumps but use a set of vanes instead of gears. As the input shaft rotates, oil is picked up between the vanes and transported to the outlet as the area between the vanes changes.

**Quick Look:**

– Used on utility vehicles, but less common now

– Input shaft rotation moves oil between vanes

– Oil drawn through supply port, expelled through outlet

Clutch Pumps

Car Lift Repair Tampa Florida Clutch pumps are small displacement gear pumps with a belt-driven electromagnetic clutch, engaged by a switch in the truck cab. They are used where a transmission power take-off aperture is not available. Common in aerial bucket trucks, wreckers, and hay spikes, clutch pumps are limited to 15 GPM applications due to potential belt slippage.

**Quick Look:**

– Small displacement

– Belt driven

– Used in aerial bucket trucks, wreckers, hay spikes

– Limited to 15 GPM

Dump Pumps

Car Lift Repair Tampa Florida Dump pumps, recognizable for their use in dump trucks, are designed specifically for dumping applications. They feature a built-in pressure relief assembly and a three-position, three-way directional control valve. Not suitable for continuous-duty applications, dump pumps are often direct mounted to the power take-off and must be supported by a bracket to prevent damage.

**Quick Look:**

– Specifically designed for dump trucks

– Includes pressure relief and directional control valve

– Not for continuous-duty

– Two- and three-line installations available

Refuse Pumps

Pumps for refuse equipment, like dry valve and Car Lift Repair Tampa Florida pumps, conserve fuel when not in use but provide full flow when needed. They incorporate special valving to enhance efficiency.

**Dry Valve Pumps:** Large displacement, front crankshaft-driven pumps with a plunger-type valve that restricts flow when off and allows full flow when on. They require a functioning bleed valve to prevent cavitation and maintain lubrication.

**Quick Look:**

– Large displacement, front crankshaft-driven

– Plunger-type valve for flow control

– Requires bleed valve for lubrication

– Special wear plates and shaft seals

By understanding the various types of hydraulic pumps and their applications, you can select the appropriate pump for your specific needs, ensuring efficient and reliable hydraulic system performance.

In mobile hydraulic applications, three primary types of hydraulic pump constructions are commonly used: gear pumps, piston pumps, and vane pumps. However, it’s important not to overlook specialized pumps like clutch pumps, dump pumps, and those for refuse vehicles, such as dry valve pumps and Car Lift Repair Tampa Florida. In this blog post, we will focus on the three main types of hydraulic pumps.

This mechanical energy comes from the prime mover, a turning force such as the power take-off or directly from the engine.

Hydraulic pumps come in two designs: uni-rotational and bi-rotational. A uni-rotational pump is designed to operate in one direction of shaft rotation, while a bi-rotational pump can operate in either direction.