Similar to other measurement devices, pressure gauges need to be calibrated routinely. With routine calibration intervals, pressure gauge accuracy can be assured. In order to ensure pressure gauge calibration process runs smoothly, it is important to consider multiple factors.
Below, we have broken down 20 essential factors to help you better understand what is necessary to consider for pressure gauge calibration.
1. Accuracy Classes
2. Pressure Media
4. Height Difference
5. Leak test of piping
6. Adiabatic Effect
9. Pressure Generation
12. Number of calibration points
13. Direction of calibration points
16. Adjustment & Correction
17. Calibration Certificate
18. Environmental Conditions
19. Metrological Traceability
20. Uncertainty of Calibration (TUR/TAR)
In this blog series, we will walk you through each of the 20 essential factors and how they effect pressure gauge calibration.
One notable factor to consider when calibration a pressure gauge is accuracy classes. Accuracy classes among pressure gauges may differ due to the number of accuracy classes available. When calibrating a pressure gauge, it’s important to determine your gauge’s specified class. Most often, accuracy class specification is the “% of range,” which means that if the accuracy class is 1% and the scale range is likely zero to 100 psi, the accuracy is ± 1 psi. Knowing the accuracy class of the gauge you will be calibrating is very important because it will naturally specify the acceptable accuracy level and effect other pressure gauge calibration procedures
The most common pressure media when calibrating a pressure gauge is either a gas or liquid. Most often gas is regular air and liquid is water or oil. During pressure gauge calibration, the pressure media depends on the media that is being used during the process and is connected to the gauge. Pressure media also heavily depends on pressure range.
It’s important to take pressure media type into account when calibrating a pressure gauge. Media that could cause problems when a pressure gauge is installed back to process should not be used during pressure gauge calibration. This is because it could be harmful to the calibration equipment due to contaminates, such as dirt. Dirt could be present inside the gauge, which in turn, could harm calibration equipment.
Before pressure gauge calibration, it’s important to expect the height of the calibration equipment and the gauge that is being calibrated. This is because height difference can cause error due to the hydrostatic pressure of the pressure media. If it is not possible to set the calibration equipment and the pressure gauge to the same height, then the effect of height difference should be calculated and noted during calibration.
Leak testing is extremely important to perform prior to pressure gauge calibration. If leaks are present in the piping during calibration, unpredictable errors are likely to occur. A simple leak test technique is to pressurize the system and let the pressure stabilize. Notably, during this test, pressure should be monitored to ensure that it does not drop too much.