Fuel Gas line recommissioning ? 2

[MechaSam]

Hi everyone,

This is my first thread and hope to get some useful information.
I am working on a fuel gas line which has been isolated 4 years ago and we look for the possibility to re use it.
As you may imagine, there may be integrity issues and we will have to do some wall thickness checks.
Can somebody tell me if we have to re-do a hydotest, do a leak test of if the thickness control can be considered as sufficient ?

Are there indications in the b31.3 or fitness for service ? Thank you

Regards

Sam

 

[MechaSam]

anyone ?

 

[zdas04]

I don't think you're going to find a hard and fast set of rules. This happens seldom enough that standards wouldn't have much coverage. When I'm confronted with a non-mainstream problem, I generally write a position paper describing the problem, any portions of codes that may be germane (even if not strictly applicable), and the approach I'm going to take. This paper becomes part of the project file and I've never had a subsequent auditor look at the position paper and say "that is wrong".

You have to remember that standards are NEVER a substitute for Engineering Judgement.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.

 

[TD2K]

Good suggestions David.

I'd look at the service (dry fuel gas, wet fuel gas, sour fuel gas, etc), how it was laid up (drained and blown dry, put under an N2 pad, just blinded off, etc), do some UT and perhaps drop a couple of spools if you have them at low points such as control valves to check for the internal condition. I'd then look at the UT results and see how much corrosion has occured relative to the amount of pipe needed to meet your design conditions and the original corrosion allowance.

If the line had been in service these past four years you wouldn't be looking at a full hydro again, you'd be depending on your NDE examinations by the inspectors. I'd be concentrating on seeing if there was something in the layup that could have resulted in high corrosion and therefore a hydrotest is a prudent precaution. Remember, if something goes wrong, those questions are going to be asked including why you didn't proceed with a hydrotest. Dead legs are a known location for corrosion problems.

 

[BigInch]

Unless this line was nearing the end of its design lifetime before it was laid up, a new hydrotest would normally be unnecessary, unless of course you found a very good reason to justify a new one.

"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek

 

[austsa]

Leak test may be necessary if there is a chance that a third party may have damaged your pipe and thought that it was an abandoned pipeline. Naturally, if your piping is all within your own plant, you don't need to consider this.

 

[MechaSam]

Thank you for your help everyone.

@David: That seems to be the optimal solution. I will gather the informations as suggested by TD2K and look for any portion of standards / Guidelines that may apply (even partially).
and, I like your signature :
"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.


@Simon: you are right, considering the current state of the line, hydrotest wouldn't be necessary, I believe. However, I would personally look to find a good reason not to do it rather than the opposite.

@austsa: well, as I wrote to Simon, you are right. I believe it's not necessary, however I prefer being sure and having my decision backed up. I will, as suggested by David, prepare a position paper and see if I can find something.

Thank you all for your help

 

[dcasto]

you are just in time to be a guinea pig on the new NFPA 56 for commissioning

http://www.nfpa.org/aboutthecodes/AboutTheCodes.asp?DocNum=56&cookie_test=1