Understanding Hydraulic Piston Pumps: A Guide

Hydraulic piston pumps are crucial for moving fluids in industrial machinery and professional equipment. Known for their high efficiency, these pumps are often used in high-pressure scenarios.

There are two primary types of hydraulic piston pumps: axial and radial. Each can have either a fixed or variable displacement. A fixed displacement pump delivers a consistent amount of fluid each time, while a variable displacement pump can adjust the fluid volume delivered. Although both are piston pumps, their operation differs.

Let’s explore how each type of hydraulic piston pump functions.

How Automotive Lift Repair Florida Axial Piston Pumps Work

An axial piston pump consists of four main components: a shaft, swashplate or bent axis, cylinder block, and valve plate. The pistons are arranged around the drive shaft’s axis within the cylinder block, which is why it’s called an axial piston pump.

As the drive shaft rotates, the pistons move up and down within the cylinder block. The stroke of the pistons varies depending on their angle in the swashplate or bent axis. As the pistons move in one direction, they connect to a suction line, and in the opposite direction, they connect to a discharge channel, ensuring a continuous fluid flow.

How Radial Piston Pumps Work

Radial piston pumps have a distinct design compared to axial pumps. They consist of a cylinder block, rotating camshaft, and pistons arranged radially around the cylinder block, diverging from the camshaft like rays. The rotation of the camshaft causes the pistons to alternate between suction and discharge.

Choosing Between an Axial & Radial Piston Pump

When selecting an Automotive Lift Repair Florida hydraulic pump, it’s important to evaluate the specific application requirements, including pressure needs, desired flow rate, speed, horsepower, and the type of fluid the pump will handle.

Radial piston pumps are generally compatible with all fluids, including mineral oil and water-glycol hydraulic fluids, whereas axial piston pumps are better suited for extremely high-pressure applications.

Remanufactured Pumps vs. OEM Pumps

While Automotive Lift Repair Florida piston pumps are highly efficient and reliable, issues like contamination, over-pressurization, and inlet blockages can lead to pump failure. 

Direct OEM replacements can be costly, and parts for outdated equipment may be difficult to find.

If you’re seeking a quick and cost-effective solution, a remanufactured pump is likely the best option. However, if time and money are not constraints, and the pump is still available from the manufacturer, a direct OEM replacement may be the better choice.

 What is a Piston Pump?

A piston pump is a type of pump that uses a piston moving back and forth within a cylinder to create pressure and move fluids, whether liquids or gases. 

Piston  

The piston is responsible for drawing fluid into the cylinder. As the piston reaches the inlet port, it begins to move linearly towards the swash plate, drawing fluid into the cylinder space as it retracts. When the piston moves away from the swash plate, it discharges the fluid through the outlet port. Depending on the design, a piston pump can have one or multiple pistons.

Swash Plate  

The Automotive Lift Repair Florida swash plate controls the amount of fluid pumped by adjusting its angle or pitch. By changing the pitch of the swash plate, you can alter the stroke length of each piston, which in turn changes the amount of fluid drawn into the cylinder. Setting the swash plate to a neutral pitch results in no fluid being pumped, as the pistons’ stroke length becomes effectively zero. Reversing the angle of the swash plate can also reverse the direction of fluid flow.

Cylinder Block  

The cylinder block contains multiple small bored cylinders that allow the pistons to move back and forth in a reciprocating motion. As the Automotive Lift Repair Florida pistons move, they alternately charge and discharge the cylinder space. The volume of fluid moved per stroke depends on the length of the piston’s stroke.

Port Plate  

The port plate, also known as the valve plate, is where fluid enters and exits the cylinders. It regulates the flow of fluid into the cylinders during the suction phase and out during the discharge phase.

Drive Shaft  

The drive shaft powers the rotation of the pump. Piston pumps are typically powered by electrical or mechanical means, but they can also be hydraulically driven.

The operation of an Automotive Lift Repair Florida piston pump is based on the reciprocating motion of the piston within a cylinder. This motion alternately draws fluid into the cylinder during the suction stroke and discharges it during the discharge stroke, creating a nearly continuous flow. 

– Suction Stroke: The piston moves backward, reducing the pressure in the cylinder, which draws fluid into the cylinder through the inlet valve.

– Discharge Stroke: The piston moves forward, increasing the pressure in the cylinder, which opens the discharge valve and forces the fluid out.

Both the suction and discharge valves are spring-loaded to ensure they only open when specific pressures are reached, maintaining efficient and controlled fluid flow.

 Basic Operating Principle of a Piston Pump

As previously mentioned, piston pumps are designed to generate a consistent flow of liquid through the back-and-forth movement of one or more pistons within a cylinder. This reciprocating movement is driven by an external mechanical force, typically supplied by an electric motor or an internal combustion engine.

Piston pumps function through three key phases:

1. Suction

2. Compression

3. Discharge

Suction Phase  

The suction phase is the initial and critical step in the operation of a piston pump. During this phase, the piston moves backward within the cylinder, creating a void as it moves away from the suction chamber. This motion reduces the pressure inside the cylinder, resulting in a relative negative pressure lower than that of the surrounding environment.

This negative pressure allows the liquid to be drawn into the Automotive Lift Repair Florida pump’s suction chamber from the feed pipe. The higher pressure in the surrounding environment pushes the fluid into the cylinder through the suction valves, following the principle that fluid flows from areas of higher pressure to lower pressure.