Pressure Gauge Selected

[180994]

Dear Expert,

I have some inquiry regarding the pressure gauge selected.
Based on ASME VIII 2015 Edition UG-102 the calibrated gauge selected is mandatory.
And for gauge selected range shall not less than 1.5 times and not more than 4 times the pressure.
Did the selected range is mandatory or not?

 

[danw2]

If you are using a mechanical pointer/dial indicating pressure gauge, then, yes, the stated test gauge range is the required range. Those ranges put the test pressure in about the middle third of the gauge range.

Example:
Max pressure = 10bar
Minimum gauge range = 0 - 16 bar (there is no 15 bar range)
Acceptable gauge range = 0 - 25 bar

 

[FIG Journey]

Then you get those processes where the design pressure is 7800 kPa-g but the operating pressure is 700 kPa-g. You wouldn't install a gauge with a range of 0 to 10000 kPa-g to meet the design pressure as the gauge would be reading in the lower end of the first third (Not very accurate). In this case a gauge snubber is sometimes utilized to allow for a lower range gauge to be installed to meet the readings within the middle third. Any pressures that exceed above and beyond the range of this gauge will be "snubbed out" (blocked) so no over ranges damage the device.