Testing Pressure Gauges: Verification and Functional Test Methods

Brian Craig

May 28, 2021

Pressure gauges are the industrial equipment used for measuring pressure fluctuations. Generally, they are installed on the fluid transmission lines in industrial supply systems, fluid-operated equipment, etc. Pressure plays a crucial role in industrial process control. Hence the pressure gauges are of great significance. However, the performance of these gauges should be precise and accurate, otherwise, sudden pressure buildup, pressure drop, etc can cause damage to the industrial systems. This is why testing the pressure gauges before an application is essential. These gauges are often tested, calibrated, and validated before and during the application. The testing plays the most significant role in ensuring the performance and verification of these devices. There are multiple ways of testing gauges. Out of which functional testing and verification testing are mandatory and are performed by the manufacturers or users of these gauges. This post discusses the processes of verification and functional tests for these gauges.

A Brief Discussion on Pressure Gauges

Pressure gauges are devices that can sense the fluctuation in pressure. These devices feature sensing elements like diaphragms, bourbon tubes, springs, etc. These sensing elements react to pressure changes. There are different types of gauges depending on the type of sensing element used and the type of displays it possesses. Generally, analog and digital gauges are used in various industries.

No matter what type of gauge it is, the need for testing remains of great importance. Let us discuss the significance of testing gauges.

Significance of Testing Pressure Gauges

Gauges are tested for various aspects such as accuracy, performance parameters, efficiency, etc. Based on the testing results, the activities such as calibration, maintenance, troubleshooting can be performed. If the pressure gauges are not tested, there will be errors in assembly, installation, and operation. Slight errors in installation or assembly of the gauge may result in leakages, high-pressure buildup, sudden pressure drop, etc. This may eventually result in the bursting of fluid lines, which may cause potential damage to the operator. Thus, to prevent the chances of accidents, it is essential to test the gauges. Verification testing and functional testing are two methods adopted in the industries. Let us discuss both.

Verification Testing

Verification testing is one of the steps involved in the calibration of gauges. In this step, the performance parameters of the working gauge are compared to master gauges’ parameters. This ensures that the gauge is operating to the best of its capabilities.

Pre-requisites
Master Gauge/ Calibrator
Disintegration Toolkit (For priming)
Valves (For Isolation of Gauge)
Procedure

The following steps are involved in verification testing.

Disintegrate the gauge from the industrial system or isolate it using valves.
If the system consists of any liquid fluid then release the air or gas trapped in the gauge or fluid transmission line. This may require priming the entire system.
Connect the working gauge to the reference gauge i.e.; the calibrator or master gauge. Run the system and measure the readings on both the gauges.
Compare both the readings.
If the readings are the same, the gauges can be concluded verified. If not, then the error calculation should be done in order to move ahead with the calibration process.

Notes:

The master gauge is the device tried and tested for the best efficiency of the gauges. It is used as a reference for the calibration process, therefore, known as a calibrator.
Before measuring the pressure readings on the working gauge and calibrator, let the system settle for a while. This reduces fluctuation in the reading.

Functional Testing

A functional test is performed to check for consistency in the operational capabilities of the gauges.

Pre-requisites
Dead-weight testers
Test Gauge/ Reference Gauge
Procedure

The listed steps are involved in a functional test of pressure gauges.

Cross-check the measuring range of the gauge from the manufacturer’s datasheets.
Connect the gauge and reference gauge in the same pressurized industrial setup.
Decide 5 point ranges such as 0%, 25%, 50%, 75%, and 100% on the measuring pressure range of the working equipment.
Begin with 0% pressure and raise the pressure slowly up to 100%.
Take readings on each point from both the gauges.
Compare the readings at all 5 points.
Reverse the process and drop the pressure from 100% to 0%.
Record readings during the reversed cycle.
Compare the readings of pressure rising and dropping cycles. Compare the readings with the reference gauge’s readings.

How to Test a Vacuum Pressure Gauge?

Testing a vacuum pressure gauge involves creating a vacuum environment and comparing its readings with a known standard, typically a calibrated digital vacuum gauge.

Steps:

Use a vacuum pump to reduce pressure in a sealed chamber.
Connect both the vacuum pressure gauge tester and reference gauge.
Compare readings at various vacuum levels.
Ensure consistent output during rising and falling pressure sequences.

This is essential in sectors like pharmaceuticals, semiconductor manufacturing, or food processing.

Since testing is a crucial part of calibration and maintenance, it should be performed by experts to avoid errors. That is why you should source gauge testing and calibration services from experts like The Transmitter Shop. The company offers high-quality gauges, transmitters, etc along with reliable testing, maintenance, and calibration services.

Frequently Asked Questions (FAQ):

Can I use a pressure gauge as a vacuum gauge?

No, standard pressure gauges aren’t suited for vacuum readings. Use a compound gauge or a dedicated vacuum pressure gauge for accurate and safe vacuum measurement.

How do you test a vacuum gauge?

Connect the gauge to a vacuum source and compare readings with a calibrated reference gauge. This ensures it accurately tracks vacuum levels, especially in sensitive processes.

How do you test a pressure gauge?

Use a reference gauge to compare readings through verification or functional testing. This confirms the gauge’s accuracy and reliability under operating conditions.

What are the standards for pressure gauge testing?

Testing follows standards like ASME B40.100 and ISO/IEC 17025, ensuring safety, precision, and regulatory compliance across industries like oil & gas and pharmaceuticals.