During hydrostatic testing of piping (B31.3 or API 1104) what is the criteria for pressure gage selection…?
Eg. design pressure is 10bar , so test pressure is 1.5 times design pressure so 15bar…which one of the pressure gage should be used…? (a 25bar gage or 40bar or 60bar)
My experience is that analog pressure gages should be used at approximately mid-scale. They tend to get non-linear at either end of scale. ASME B&PV Code stipulates analog gage range be 1.5 to 4 times test pressure which puts the test pressure between 25% and 67% of gage range.
Digital gages are entirely different. Digital gages should be used closer to their upper limit. Manufacturer certs for digital gages always state accuracy as % of full scale reading. Again using ASME B&PV Code as standard, acuracy of digital gage must be 1% of reading. If your gage is certed at .25% accuracy (standard gage), you need to be above 25% of full scale to achieve 1% of reading accuracy.
Above is a snippet.