calculation of hydro static test pressure for pipeline of API 5L grade B of 600mm dia

[ali513704]

i am working with client on a project of pipeline for water 20 km long. our design engineer designed the pipeline according to API 5L grade b 600 mm pipe using carbon steel of minimum yield strength of 30000 psi. i m confused as design engineer has approved 218 psi as hydro static test however my point of view is that it should be tested at 600 psi so i need help in this as what should be the test pressure

 

[LittleInch]

Pipe strength is only one item to consider.

You need to know or tell us the design pressure or MOP, design code, highest point versus lowest point, pipe wall thickness etc to calculate the minimum and maximum test pressure.

Providing that you don't exceed the rating of connected equipment or exceed the yield strength of the pipe at the lowest point you can test to a higher pressure if you want, but most people just aim for the minimum base don design pressure / MOP.

BTW, Grade B is normally SMYS of 35,000 psi



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[ali513704]

dear littleinch
our pipe line carries water pumped by turbine pumps ,standards adopted are AWWA standards, thickness of pipe wall is 6.4 mm dia of pipe is 600mm, our specification shows test pressure as 1.5 times the maximum working pressure know problem is in my opinion maximum working pressure can only be calculated from yield strength,dia,and thickness of wall which comes out 600 psi
there is no any other fitting is connected to pipe
pipes are welded adopting but joint with four laps according to API 1104 standards

 

[LittleInch]

Well I suppose that's one way of doing it, but if you don't know the MOP or design pressure of your system then you don't really now if the pipe is thick enough? Testing to the maximum the pipe can withstand might over pressurise something else if its design pressure is much lower.

I don't know what design factor AWWA use, but yes, pipe of this size, wt and grade is good for approx. 35barg design pressure.

just ask the designer for his calcualtions and where he gets his design pressure / MOP from and see if you agree.

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

 

[ali513704]

my design engineer insist that pumps we are going to install produce 10 bars pressure hence test pressure should be 15 bars.
my opinion is that pipe of 24 Dia, 6.4 mm wall thickness, of steel with SMYS of 30000 psi should have working pressure of 26 bars and should be tested on 39 bars

 

[LittleInch]

In this case you are both right. The MOP comes from the pressure source in a worst case (no flow) situation. If the pressure source cannot under an circumstances produce more than 10 barg, then your MINIMUM pressure test level is 15 bar. To test higher risks damage to some other component in the system not rated for anything higher than 10 bar (a valve maybe?)

Depending on your design calculation and design factor then yes, your pipe can take 26 barg or higher as an MOP and therefore if you test it to that pressure x 1.5, then you could uprate your system in the future without necessarily doing another test.

I don't know which of you has the contract power to force the other do one thing rather than another, but you probably need to find the AWWA design code and point out that the calculated test pressure is the minimum. If you are the client then you can insist on higher pressure providing all parts of the system can cope and you don't have a large elevation difference along your pipe. Minimum test pressure should apply a the highest point - make sure whatever test pressure you choose doesn't exceed yield strength and the lowest point.

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