Understanding Pump Rotation: A Comprehensive Guide

rtexer
Aug 14
3 min read

Updated: Oct 31

Determining the rotation direction of your pump is crucial for its proper functioning. In this guide, I will break down the importance of pump rotation, how to identify it, and what to do if you're unsure about your pump's configuration.

Why is Pump Rotation Important?

For any piston pump, such as Rotary Power "C-range" or Rexroth A2/A7 pumps, the pump is designed to pull fluid in from one direction and push it out in another. When the pump rotation is reversed, it can lead to significant issues. The pump will attempt to pull fluid from upstream and push it backward into the supply line. This often results in the pump being starved of fluid.

When a pump is starved, the wear surfaces—such as pistons, control plates, and barrels—heat up significantly. This excessive heat can lead to premature pump failure. Understanding the correct rotation direction is essential to avoid these costly mistakes.

Rexroth A2VK Piston Operation — Piston Pump Operation

You can also view this video to understand the basic operation of a piston pump:

Clockwise vs. Anti-Clockwise

First, we need to establish standard nomenclature. When discussing pump rotation, the direction is always determined when looking at the pump shaft. The diagram below illustrates this concept clearly:

Two Scenarios for Pump Rotation

There are two primary scenarios to consider when determining pump rotation:

Scenario 1: You have a pump in operation and want to know its rotation direction.
Scenario 2: You are unsure what rotation direction your pump is set up for, often the case when setting up a new line or finding a pump on a shelf.

Scenario 1: My Pump is Currently Running. How Do I Determine Which Way It's Rotating?

To determine your current pump rotation, look at the electrical motor driving the pump from the back. There should be a fan shroud on the back of the motor. Observe the direction the fan is spinning to determine the rotation. You may need to stop the pump and watch the fan direction while the motor is decelerating.

Looking at the back of the motor is equivalent to looking directly at the pump shaft, as mentioned earlier.

Motor Rotation — From the back of the motor, fan rotation is the same as pump rotation

Scenario 2: How Do I Determine What Direction My Pump is Set Up For?

To determine how your pump is configured, examine the model code.

For Rexroth A2VK Pumps:

For Rexroth A7VK Pumps:

For Rotary Power C-Range Pumps:

What If I Don't Have the Pump Tag? (It's Damaged or Missing)

You can still determine the pump rotation. The ease of this depends on the manufacturer.

For Rotary Power Pumps, look for an arrow on the pump casing. If it points to "CW," you have a clockwise-oriented pump. If it points to "ACW," it is oriented anti-clockwise (or counter-clockwise).

Unfortunately, for Rexroth A2 or A7 pumps, you would need to disassemble the pump to determine its rotation direction.

In Summary

In most cases, pump rotation can be easily determined. Review the scenarios above if you're still unsure about your specific situation. If you need assistance, reach out to us at MHR, and we can guide you through the process!

Finally, MHR maintains stock of most Rotary Power and Rexroth pump models, ready to ship. We also rebuild Rexroth pumps back to like-new condition. Reach out to us if you need a new or spare pump!