Effect of Sudden Pressure on Piping System 2

[bonzci]

Dear all,
Just want to discuss. Is there any effect of sudden pressure on Piping system?
We did hydrotest for piping yesterday. Based on procedure, hydrotest shall be done in several stages. 25%, 50%, 75%, finally 100% MAWP. But unfortunately, we had problem with the system and it was difficult to manage the pressure. Eventually, hydrotest was done from 0% and suddenly pressed up to 100%. We are worried if this testing will give bad effect for the future. Need info plz. Thank you.

 

[LittleInch]

Sudden increase in pressure are usually followed by sudden movement of the pipework up or horizontally and can literally jump off supports. Otherwise I can't think of any particular general issues but as with any sudden event, you could get shock loading where the pressure spike could be higher than the steady state pressure. This could give rise to possible yield of a vulnerable component or fitting, but does depend on how sudden this pressure rise was - 0.1 sec, 1 second, 10 seconds, 1 minute??

The pressure rise as stated is usually just that you can find and correct leaks before they become a torrent or high pressure jet, but also allows the pipework to "shakedown" and adjust to internal pressure for the first time in its life.

That's my thoughts...

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[bonzci]

Dear @LittleInch,

Thank you for your opinion.
So that condition will be vulnerable to the pipe?
Do you think that this phenomenon is just happened like water hammer?
And, could you tell me, is there any standard or code that regulate how much pressure increment rate allowed?

Thank you very much for your kind assistance

 

[MJCronin]

I agree with LittleInch....

There are recommended guidlelines for a gradual increase in pressure ....

I would perform a detailed walk-down/evaluation of the system and document the evaluation. Evaluate and measure any gross deformation of the system.

MJCronin
Sr. Process Engineer

 

[LittleInch]

It might be vulnerable, it might not.
Other than mechanical damage caused by a sudden movement, yes, the issue is basically surge or shock loading. However you haven't answered the question of how fast this test pressure was applied.

You shouldn't exceed the test pressure.

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[bonzci]

Yes @MJCronin, I also think that there is recommended practice regarding this pressure increasing rate.
I have reviewed ASME also. But From ASME, its just noted that "The pressure shall be applied by raising gradually to hydrotest pressure specified". They are not mentioned about how much exactly the pressure rate are.

@LittleInch, I have reviewed the chart and the pressure was applied from 0-100% of MAWP within 1-2 minutes.
Yes it shouldn't but I dont know exactly how much the allowable rate is.

 

[LittleInch]

Over that sort of time period I cannot see any particular issues.
Not good practice, but the pressure rise thing is not a technically defined item so you won't find in a design code a time period.
Therefore there is no such thing as an "allowable rate" specified in a design code (AFAIK), only recommendations and guidance as to good practice.
This should be in the construction spec or testing spec issued by the design company.

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Also: If you get a response it's polite to respond to it.

 

[bonzci]

Hmmm. Okaaay noted LittleInch.
I hope following the best practice is okay as long as there's no probs for our piping system.
Thank you very much for your kindly advice guys.

 

[GD2]

What do you mean "difficult to manage thr pressure"? Are the pressure controlling and pressure releiving devices not working?


Ganga D. Deka, P. Eng
Canada

 

[786392]

Dear bonzci,
Are we 100% sure through master pressure guage& pressure checked and/or recorded at different points of "the piping segment under pressure test" as regards sudden pressure shoot up from 0 to 100%?
Was this a pressurizing with high pressure rotary or positive displacement piston etc.type pumps?
If all this is true and a confirmed high pressure 'sudden surge' took place like a water hammer that the whole "segment in question" needs to be thoroughly checked for deformities, dislocations or any other superficial/visible damage needing repairs/reinforcement prior to be in service

Best Regards
Qalander(Chem)

 

[racookpe1978]

I am trying to find out why you believe that the sudden pressure surge/application did not greatly exceed 100% of rated pressure. If it were "only" a surge to 100% - that could be a problem, as others above have said. But why are you sure it did not go well past 100%? Did a relief valve trip at 100% ? (It - the special relief valve installed for the hydrostatic test- should have been set above the hydrostatic pressure - NOT the piping system operating pressure, not the hydrostatic pressure of the one-time system hydrostatic test.)

 

[LittleInch]

Bonzci,

You keep mentioning "MAWP". This is more commonly used in pressure vessels and flange rating, but pipe systems usually use the terms MOP or MAOP.

In either case, neither of these are the hydrostatic test pressure which is considerably above the MAWP.

What is actually going on here?

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