The analog pressure gauge is one of the simplest, mostly used instruments, and the easiest to calibrate in pressure calibration. It has a simple setup where you can easily execute the calibration. But analog pressure gauge is also one of the instruments where errors are mostly encountered.
Most errors are either “out of tolerance” or the needle is not in the “zero settings”. The following are the commonly encountered problems with the analog pressure gauge:
1. pressure gauge needle stuck;
2. pressure gauge not zeroing;
3. the pressure reading is very far or out of calibration;
4. the worst, the pressure gauge not working at all
When this happens, do not immediately throw or discard the gauges. Luckily, there are still ways to adjust or repair pressure gauges.
In this post, I will share with you the following:
1. 5 ways on how to adjust a pressure gauge
2. The things to consider before making an adjustment or repair
3. how to identify the error in the pressure gauge and execute the adjustment.
4. How to verify a pressure gauge.
5. Some useful tools to use to perform adjustments
Pressure gauges have different applications and therefore have many construction designs.
I will present in this post the different setups for different models of gauges to be adjusted.
Below are some reasons why pressure gauges are getting out of whack (out of tolerance or not in the zero settings):
Changes in the altitude and temperature (due to changes in environmental factors).
Overstressed bourdon tube due to exposure to overpressure.
Overused or overexposed to the pressure cycle
Exposure to high temperatures and excessive vibrations
Wear in the mechanical parts.
Things to Consider Before Performing Pressure Gauge Adjustment or Repair
Pressure gauge errors can be identified during the execution of calibrations where we compare the readings of the pressure gauge against the reference standard or pressure calibrator.
Pressure gauge errors can be calculated using the formula:
ERROR = UUT Reading – Reference Standard Reading
If the identified error is not acceptable or too large based on verification, then an adjustment is necessary.
During the pressure gauge calibration process, we observed the below defects, chances are high that adjustment or repair is impossible.
A reading near its full-scale value is shifted to more than 10% (a span shift)
Pressure gauges that have a zero shifted to more than 25 % (a zero shift)
Gauges with signs of leakage and corrosion of its body.
Gauges with a needle showing an error due to excessive friction or wear on its movement (loose)
With damaged sockets and threads.
When the above signs are observed, there is a high chance that replacement is the only option.
The Process of Pressure Gauge Repair
Pressure gauge repair becomes necessary when a gauge no longer responds to adjustment or exhibits physical damage. Repairing a pressure gauge involves a series of steps to restore its functionality and accuracy. To repair it, you would typically follow these steps:
Isolate the Gauge: First, shut off the system and isolate the gauge from the pressure source. This prevents any further damage or injury during the repair process.
Disassemble the Gauge: Carefully disassemble the gauge, removing the damaged parts. In the case of a cracked glass face, you would remove the glass and any broken components.
Replace Damaged Parts: Obtain replacement parts, such as a new glass face, needle pointer, and gasket, if necessary. Ensure that the replacement parts are compatible with your gauge model.
Reassemble and Test: Reassemble the gauge with the new parts and ensure proper sealing. Then, verify the gauge’s accuracy using the appropriate reference standard and make any necessary adjustments.
Calibrate: Perform calibration on the gauge to ensure it provides accurate readings covering its full range.
By following these repair steps, you can extend the life of your pressure gauges and avoid the expense of replacing them. Regular maintenance and repair help keep your operations running smoothly while minimizing downtime and safety risks.
