Industrial Automation and Motion Control Blog | The Knotts Company

This post is brought to you by Proportion Air.

A Little Background on Back Pressure

Pump manufacturers test their products to verify achieving the required flow at the pressures stated in specification documentation. Back pressure similar levels that are encountered by the pump in the system must be simulated for the test.

The Situation

One vehicle fuel pump manufacturer approached Proportion-Air with to build a fuel pump test stand that could be used to test all sizes of their pumps. There was a wide range of pressures and flows that would need to be simulated. 

The Solution

Proportion-Air offered a dual loop controlled back pressure regulator that satisfied their requirements and would be compatible with the test fluid, which was Stoddard solvent. A closed loop proportional control QB2/regulator/DSTY solution was provided. Then the assembly was installed in their new test fixture.

The Test

The back pressure regulator was plumbed downstream of the fuel pump during testing. The pump under test was turned on. At the same time, a command signal scaled to the back pressure for control went to the QB2.

The QB2 pressurized the dome of the back pressure regulator to the pressure level required. The back pressure regulator remained closed until pump pressure exceeded dome pressure on the regulator. Excess Stoddard solvent was vented through the outlet port of the back pressure regulator and was measured by an electronic liquid flow meter. The signal from the flow meter was taken back to the customer’s Programmable Logic Controller (PLC) to display and record flow.

The Results

Because the QB2 is a closed loop (the DSTY external pressure transducer was plumbed between the pump output and the back pressure regulator input), working pressure of the pump can be monitored at all times through pin 5 of the QB2’s main electrical connector.

The flow signal from the electronic flow transducer and the pressure signal from the DSTY were the necessary signals the customer needed to print a flow-to- pressure chart for each pump.

A Summary of Benefits for the Customer:

• One test fixture for all pumps replaced multiple test fixtures.
• The PLC-controlled electronic pressure regulator assembly eliminated the need for an operator to manually adjust a regulator for test set ups.
• The monitor signal of the QB2 assembly and the signal output of the electronic flow transducer allowed them to generate a flow-to-pressure chart with real data, and this eliminated the possibility of human recording error.

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