Reciprocating Pump

Understanding the Working Principle of a Reciprocating Pump

Reciprocating pumps operate on the principle of positive displacement, meaning they displace a fixed amount of fluid with each stroke, regardless of the discharge pressure. The fluid is taken in through the inlet side of this positive displacement pump, captured inside the cavity as it expands, and discharged when the cavity decreases.

Reciprocating pumps are designed to pump in low-flow, high-head applications because they provide a constant flow at a fixed speed despite changes in differential pressure.

These pumps are often used to transport water but are also suited to applications that pump viscous and corrosive fluids.

The Working Principle of a Reciprocating Pump

A reciprocating pump converts mechanical energy into fluid flow through a piston or plunger’s reciprocating (back and forth) motion. To understand the working principle of a reciprocating pump, you need to first understand each step of the working process of this type of positive displacement pump:


The action of the reciprocating pump begins with the suction. As the piston or plunger moves away from the cylinder head, it creates an area of low pressure (or a vacuum) inside the cylinder. The suction valve, ordinarily a one-way valve, draws fluid inside the cylinder (both releasing the inlet valve and shutting the outlet valve in a suction effect).


Once the suction stroke is complete and the motion is reversed (the piston moves towards the cylinder head), known as the compression stroke, the fluid trapped inside the cylinder is compressed, which increases the pressure.


The pressure inside the chamber causes the inlet valve to close (when it exceeds the pressure in the discharge line or system), and the discharge valve opens to force the pressurised fluid into the discharge line or system.


After the discharge, the piston or plunger moves back into its original position, closing the discharge valve and preventing backflow. At the same time, the suction valve reopens, allowing fluid to enter the cylinder for the subsequent suction.

The piston or plunger’s reciprocating, or back-and-forth motion, allows this process to occur. A reciprocating pump’s suction, compression, discharge and intake/refilling occur quickly, much like a simple bicycle pump compresses air. It generates a pulsating flow of fluid, where each stroke contributes to the total volume of fluid transferred. Of course, the size of the cylinder in a piston pump and the size of the plunger in a plunger pump also contribute to the volume of fluid that can be pumped.

In conclusion, understanding the working principle of a reciprocating pump is essential for appreciating its reliability and versatility. Operating on the principle of positive displacement, these pumps offer consistent flow even in high-pressure, low-flow applications. The reciprocating motion of the piston or plunger, coupled with precise control adjustments (including adjusting stroke length, stroke speed or valve timing), ensures various industries choose reciprocating pumps, from oil and gas to chemical processing, water treatment, and metering applications. With their ability to pump varied fluids and maintain flow stability, reciprocating pumps are a valuable asset in many facilities.

To learn more about the working principles of reciprocating pumps and what type of reciprocating pump you need, contact our team of experts at 1-800-367-4180 (toll-free) for more information. We are your industrial pump supplier in Canada, and we’re here to help you choose, install, maintain, and monitor a variety of equipment. And to answer questions about things you’ve previously tried gone wrong. Contact us now!