Startup Purge for new gas main

[pneveu]

We have been asked to perform a startup for a new natural gas line consisting of 2000' of 12" pipe and 1800' of 6" pipe. Are there purging requirements or standard procedures for this type of distribution system? The operating pressure will be 25psi. The system has already been pressure tested to 100psi to meet the owners specifications.

Would static electricity be a concern if there are ball joints in the line for expansion and contration since this pipe is located on a roof. (a really big roof)

 

[BigInch]

Yes of course you must purge the line.

Are the ball joints insulated?
If you want to ensure conductivity, bond across them.

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[MTPipeliner]

There is a manual that is published by the AGA (I think) that discussed purging times and pressures. I don't have a copy available right now, so I can't give you the number.

You may want to check it out.

 

[zdas04]

The AGA Purging Principles and Practices manual is the single worst document that the AGA (a fine organization, by the way) ever published. Following the recommendations of that book creates some very high-risk conditions.

As far back as statistics are avaiable, the Oil & Gas industry has had about one purge-related fatalaty per month somewhere in the world. Getting this wrong is pretty high risk, but the safety mavens have consistently ignored the potential. If you are interested, I have a document on my web page (follow the link below and go to "samples") that a group of us wrote a few years ago to provide guidance to people writing purge procedures. It is a bit long, but the topic is very large.

David Simpson, PE
MuleShoe Engineering

http://www.muleshoe-eng.com

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