Standard for Pressure Gauge

[Kene1]

We have completed the Nitrogen preservation of a 10'' 16Km pipeline in a swamp location at a pressure of 0.6bar. I have requested for the installation of 0-2bar pressure gauge for the monitoring of pressure over a period of 3 years before the pipeline will be used. The contractor supplied a gauge of 0-10bar which was rejected. I know that there is a standard specifying the use of gauge with range of 1-1/2 to 3 times the desired pressure but can't say the code governing the practice. Can someone help me with the governing code or standard.

 

[weldstan]

That requirement is for the hydrostatic test, in general. It is up to the engineer/owner to provide gauge requirements for preservation.

 

[LittleInch]

The only "standard" I am aware of are company standards.

Good practice is that the max pressure of the fluid is no more than ~75% of the max pressure on the guage. Working range is anywhere up to that point.

I agree that approx. 5% of the range of a guage is too low.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[danw2]

Ashcroft's Pressure Gauge Installation Operation and Maintenance guide says,

1.1 Range – The range of the instrument should be approximately twice the maximum operating pressure. Too low a range may result in (a) low fatigue life of the elastic element due to high operating stress and (b) susceptibility to over- pressure set due to pressure transients that exceed the normal operating pressure. Too high a range may yield insufficient resolution for the application.

[URL unfurl="true"]http://www.ashcroft.com/installationandmaintenance_pdf/upload/manual-pressure-gauges-large.pdf[/url]

ASME B40.100-2005

4.3.1 Operating Pressure.
The pressure gauge selected should have a full-scale pressure such that the operating pressure occurs in the middle half (25% to 75%) of the scale. The full-scale pressure of the gauge selected should be approximately 2 times the intended operating pressure.

 

[donf]

Don't know if there's a code that governs, but...........

My wife's grandfather was a boiler engineer in a Canadian paper mill. He actually gave me a pressure gauge from the 1920's that still functioned, and is a work of art. I had always heard that one should specify the range to be two times the normal operating pressure, and I asked him for the reasoning for doing so.

He said that by doing so, an operator could quickly scan a bank of gauges (of different pressure ranges) some distance away, and if they all pointed to 12 o'clock, the system was happy.

Makes sense to me.

donf

 

[IRstuff]

The question isn't really complete without some understanding of what results from the readings, and what consequences are associated with the results. What change in pressure is expected to be detectable? Is it 10% or 50% or ...? Only then can you ascertain whether the accuracy of the proposed gauge is insufficient to do the job.

TTFN
faq731-376

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[BigInch]

I've always thought you can generally expect an accuracy of +/-1% of full gauge range.