Hydrotest Pressure Determination 1

[shafmech]

Hi,

we have a request for quotation (RFQ) for providing Bend pipes. Customer needs 6" 0.5 wall thickness 8D bends. Pipe specification is API 5L,GRADE-X60, PSL-2; WITHOUT MILL COATING. I need to calculate the Hydrotest pressure for this pipe and submit to the estimation dept for pricing. Since the job is still at bidding stage we don't have a PO, so the design pressure is not known. QC manager gave me the following reference to calculate the same...
"Each length of pipe shall be given a mill hydrostatic test at a pressure not less than the pressure necessary to obtain a hoop stress equal to 95% of the specified minimum yield strength of the material. as per API 5L 44th Edition and SAMSS-035 "

I am a fabrication shop floor engineer with limited design knowledge. Could anyone guide me with some explanation/reference material on how to arrive at a test pressure without a known design pressure?

Thanks in advance

 

[zdas04]

If you're going to 95% of SMYS then you only need to consider hoop stress. For that use Barlow's Formula.

S(test)=P(test)*OD(pipe)/2/t(actual)

Then you can divide the answer by SMYS (which would be 60,000 psi under B31.8, not sure about other codes). When I do that I get 8600 psig for a 95% test, but you'll want to do the calcs yourself.

David

 

[ilzafcukena]

hi shafmech,

based on your description above, may i know the unit of wall thickness are u refer to?....

i agree with zdas04...that's the right equation to calculate the maximum allowable hoop stress for hydrotest. but, if u have the design pressure, u need to calculate the hydrotest pressure based on the applied code. for example, B31.8, it is 1.25xMAOP(DP) for the whole system hydrotest or 1.4xMAOP(DP) for zone 2 offshore pipeline.

correct me if i'm wrong..

thanks.

ilzafcukena

 

[shafmech]

Hi ilzafcukena

The wall thickness is in inches (0.5"),
As I mentioned in my earlier post, the disgn pressure is not known since the job is stil at bidding stage.
It will be available once we get the job and receive the PO (purchase order). Now the Test pressure is required for estimation/pricing purpose only.
The formulae you mentioned will be applied when we have a known design pressure.
I then used Table 26 of API 5L 44th Edition in which Standard Test pressure is given for a Pipe of specific size and wall thickness.
I got 2970 Psi as my test pressure.

thank you.

Shafmech

 

[BigInch]

ilzaf, its a mill hydrotest, not the pipeline hydrotest, so zdas is right.

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