Pressure test for differential pressure level gauge
Thread Content
The differential pressure level gauge was recently given preventive maintenance, and a pressure testing device was used to check whether there had been any decline in the performance of the gauge (the capillary). In the past, our company would conduct separate pressure tests on the high-pressure and low-pressure sides across the entire range. The results of this test showed that the high-pressure side maintained good linearity, while some readings from the low-pressure side exceeded the standards. However, the pressure fluctuations on the low-pressure side were minimal, so they had little impact on actual measurements. We’re unsure whether it’s necessary to replace the level gauge (it has been in use for 7 years). Do anyone have better methods for testing differential pressure level gauges?
Then let me ask this? How do you conduct pressure testing on diaphragm-type differential pressure level gauges?
From the title, I thought “pressure testing” referred to hydrostatic testing or leak testing; but it seems that the content is about transmitter calibration. There are regulations for calibrating transmitters, namely JJG 882 \"Regulations for the Calibration of Pressure Transmitters\", which specify the methods and requirements. The original poster might want to take a look at it. Generally, for liquid level measurement applications that allow for certain fluctuations in level, the acceptable range is quite wide; thus, high accuracy from the level gauge is not required. As long as the error is not too large, there is no need to replace it.
I didn’t understand it either; at first I thought it was a pressure test before starting work
The original poster doesn’t need to worry so much. Double-flange designs with static pressure calibration are only carried out during the final testing phase of products, even by large instrument manufacturers; some instrument manufacturers that do not engage in research and development do not even have this testing procedure. For the range testing of double-flange types, it is sufficient to apply a test signal to the positive-pressure diaphragm box; for the negative-pressure diaphragm box, it is only necessary to check that the diaphragm is intact. For the range testing of double flanges, a static pressure should be applied to both sides, and then the pressure on the positive-pressure side should be changed to check the range. Repeat several times, with different static pressures each time; if the range and linearity remain unchanged, it is considered acceptable. I’m not sure how it’s determined that the linear performance on the negative pressure side is poor, as you mentioned. Linearity refers to the performance of the entire table; I haven’t heard of any terminology related to just one side of it. It is recommended that the poster post the entire diagram showing how to connect the experimental equipment along with the experimental steps.
Senior, I happened to catch you – I have a question for you. You mentioned before that the accuracy of double-flange level gauges is lower than that of single-flange level gauges. Why is that?