Hydrostatic Testing of Gas Pipelines

Good morning ANDREI. In another life I worked for a gas distribution co. Thru the cobwebs of time, I remember for Design Pressure we used DP = (2St/D)FET, where S was the yield strength of the steel, t the wall thickness, D the OD, F a factor based on location, E a factor based on pipe construction, and T a derating factor for temperature. Assuming the location was away from sensitive public areas, F=1. Assuming the pipe was modern Electric Resistance Welded, E=1. And of course, temperature was not elevated, so T=1. This gives a DP of 9,057psi in your case. We always tested at 1.5 x MAOP (Maximum Allowable Operating Pressure), so TP would be 1.5 x your 4118psi, or 6177psi. Assuming constant weather parameters, we always tested for 24 hours, so the plot of pressure always came back to the same pressure, after decreasing for night temperatures. I am curious as to the value of T for your temperature of 110ºC (230ºF). Inasmuch as they want $350 to download ASME B31.3, I do not have access to this info.

Thanks flyinghigh for answer.

As per your information : "..Pressure we used DP = (2St/D)FET, where S was the yield strength of the steel, t the wall thickness, D the OD, F a factor based on location, E a factor based on pipe construction, and T a derating factor for temperature. Assuming the location was away from sensitive public areas, F=1. Assuming the pipe was modern Electric Resistance Welded, E=1. And of course, temperature was not elevated, so T=1."'

I saw the same formula for TESTED PRESSURE in API 5L is present - you can find, that for X60 Steel

--> P = (2St/D) (for Imperial System) or P = (2000St/D) (for SI).

And for my case (WT=0.5in, 6", X60, P= 4118psi) P=(2*0.75*60000*0.5)/6.626; P=6790psig (or standard limited = 3000psig).

So, which is the kind of this pressure in formula?

Good morning ANDREI. I wonder what the 0.75 is in your formula? Also, you are not considering temperature; why?

Hi,

in formula 0.75 - is a percentage for SMYS (in i.9.4.3 API 5L) for material X42-X60 and pipe Diameter 5"-8".

If you are testing a piping system that has been fabricated/installed - don't worry about the original piping specification, API 5L; you must test to the design/fabrication code whether it is ASME B31.3, B31.4, B31.8, or .........