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31.3 and 31.4 test

31.3 and 31.4 test

31.3 and 31.4 test

(OP)
Hello all,

we have a 4500 meter 48" pipe line. 3000 meter of it is designed in accordance with asme B31.3 and 1500 meter of it is designed in accordance with asme B31.4. the line is continuous line.

31.3 states test pressure of 1.5 X Desgin pressure.
31.4 states test pressure of 1.25 X Desgin pressure.

Which criteria should be used.

Or is there another way of soving this problem.

thanks in advance.

RE: 31.3 and 31.4 test

prensllus,

Test pressure, whether 1.5X or 1.25X, could be viewed as a minimum test pressure.  You are allowed to test to a higher pressure, but should check to not exceed 90% of yield stress (SMYS, not allowable stress SA) for pipe wall and other components subjected to test pressure.  The corrosion allowance in the wall thickness could be included in the available wall thickness for check of not exceeding the yield stress in pipe wall during testing.   

The large 48" diameter of your pipe probably does not have much extra wall thickness for over-pressure.  If the same pipe wall thickness has been used for both the B31.3 and B31.4 sections of pipeline, then I would suggest testing entire pipeline to the 1.5X design pressure of B31.3 code.

RE: 31.3 and 31.4 test

(OP)
thanks apc2kp

RE: 31.3 and 31.4 test

As apc2kp noted, test pressures are a minimum, you can test higher.

I do not know of a reason to limit test pressure to 90% SMYS.  apc2kp, if you have a reference, I'd appreciate knowing what it is.  I personally have tested to 110% in unusual circumstances involving extreme elevation changes.

NOTE! You might not be able to test at 1.5 X through both segments if there is a significant elevation change.  Since your line is so short, its not likely you have a problem, unless you're going up a 3000 meter riser to the topsides of an offshore platform.  Hey, its a possibility, right?  

Therefore, before I give any tips, I would want to see a list of,

Distance from start, Code, Design Pressure, Elevation, Pipe Mfg Spec, Pipe Grade, Pipe Wall Thickness.

Include any valves, fittings, flanges and their ratings too.



http://virtualpipeline.spaces.msn.com

RE: 31.3 and 31.4 test

To BigInch,

Both the B31.1 and B31.3 piping codes use full yield as the limit for the 'not to exceed' stress value.  I realize that the 90% of yield stress is a company standard procedure to limit test pressures. It might include a 10% pressure build up factor for the safety relief valve on test pump.

Testing to 110% of yield stress certainly does not guarantee any failure.  Most materials are produced such that the minimum strength required will always be achieved, to avoid reject scrap. The situation is apporoaching the use of Probabilistic Design methods to take into consideration average material properties plus variations.  Perhaps in the past many materials were produced with strengths testing out at 10-20% more than the required minimum values.  Maybe more modern manufacturing processes (Six Sigma, etc.) may have allowed materials to be produced consistently to a 3-5% extra strength over the required minimum strength.  Is it still be possible to test to 110% of SMYS? Most likely yes.

If one had to push the limits of a pressure test, then I suppose that 1) corrosion allowance would be backed out of the deduction from wall thickness, 2) the measured actual wall thickness could be used for calculation instead of nominal wall minus mill tolerance, 3) actual yield strength from MTR could b used instead of SMYS of code book, 4) the weld efficiency factor would be considered.  

RE: 31.3 and 31.4 test

There is a very very long 31 inch diameter pipeline in the US.  Guess how it got to be 31".  Hint:  It started out as a 30.

         Going the Big Inch!
http://virtualpipeline.spaces.msn.com

RE: 31.3 and 31.4 test

BigInch-

So did the contractor issue a change order for the 6% incrase in flow area / capacity achieved with the 31" pipe? tongue

jt

RE: 31.3 and 31.4 test

He tried lightsaber   But he had already laserØ it up when it was 30"Ø , so I put the thumbsdown on the extra rods.  Then he reading and tried to bluegreedy for the increased flow area, but I curse told him it was actually a worm hole and that it should be smarty classified as a negative area, so I put a -1 x to it, gave it to banghead and wound up getting a pretty good rebate on the elephant.   

         Going the Big Inch!
http://virtualpipeline.spaces.msn.com

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