Commissioning LPG pipeline

[Iradah]

Hello all,

With reference to my earlier thread:

http://www.eng-tips.com/viewthread.cfm?qid=354614

as a result of the stuck pig in C4 pipeline, another pipeline is to be used for C4.
This line is currently used for fuel gas.
Can you please help me on how to commission C4 pipeline that has fuel gas.

 

[LittleInch]

How did you get on with the pig?

Commissioning should relatively simple - pressure the gas to the minimum pressure you need to maintain liquid state of the C4, put a pig in and then pump C4, maintaining the gas pressure at the receiving end until the pig arrives.

Might be a good idea to run a couple of clenaining pigs in the gas line before you do that....

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[Iradah]

Hi LittleInch,
Thanks for your continuous help.

The pig is still stuck, they have decided to force it to move by creating the pressure drop I discussed earlier. At the same time they will have the fuel gas line to be used in case of any need. We will see how this issue will end.

We already ran the cleaning pig, and the fuel gas line is clean. It is pressurized up to 400 psig currently.

We keep a pressure of 120 psig usually for Butane at the terminal end. So I was just thinking of depressurizing the fuel gas line to that pressure and then lunch the pig. Is this ok?
Also, what happens if I just depressurize the line to 120 psig and start pumping butane without sending a pig? Is this to do with the pipeline topography?

 

[LittleInch]

Ummm, I wouldn't stnad anywhere near the pipeline when they're trying that...

Yes, you can de=pressurise, but try to keep a reasonable margin. You need to use a pig otherwise you will create a two phase pipeline which will slug and surge and deliver gas with your butane for some time after the pig has arrived.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way