Equipment conservation

[PI055]

Can anyone tell me where I can find procedure for conservation of pig launcher/receiver or a drain vessel on a pipeline which shall be not in use for some longer period ?

 

[LittleInch]

PI055,

A detailed procedure only you can create.

In general for a pig trap you would want to drain it of any liquid / vent off any gas, then purge at low pressure from one end to the other, then pressure to a nominal pressure - say 5 bar, with dry Nitrogen.

A drain vessel is not as easy. If to be left for a long time then you could remove as much liquid as possible, then you need to get into the tank to get the last dregs out, dry it and then maybe spray the inside with some sort of thin oil or wax?

Or fill it with inhibited water to the top and then pump it all out when you want to use it. Most drain tanks are atmospheric so you can't shut it off and pressurise them.

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

 

[PI055]

LittleInch thank you for answer. When you speaking about pig trap purging and nitrogen pressurizing, in this case the whole pipeline from pig shall be put out of use and conserved for some time. Does that mean that whole pipeline should be purged and then I isolate receiver and pressurize it with nitrogen ?

 

[LittleInch]

That's a different question....

There are lots of variable you need to consider which we don't know.

Such as
What is in the pipeline? Gas, liquid, any water?
Do you need to empty the pipeline?
If so for how long?
How long / big is the pipeline?

So yes nitrogen purging and a hold pressure of a nominal 5 bar will preserve it quite well and allow you to monitor the pipeline for any leaks or damage resulting in a loss of containment. But be sure to mark that the pipeline is under Nitrogen pressure as if someone decides to vent it they can have asphyxiation risks.

Inhibited water is often used as well for liquid lines as it prevents any flotation and is cheap.

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

 

[KevinNZ]

Does anyone else have problem mothballing a vessel or pipeline with a positive N[sub]2[/sub] pressure? Seems to me if the vessel is under pressure it is still an operating pressure vessel and all the local regulations apply for 3rd party inspection, certification etc.

Now if vessel was under a small constant flow of N[sub][/sub]2 and no way of being pressured (e.g remove drain valves and fit waterfilled loop seals). It is not an operating vessel and the above does not apply.

 

[PI055]

Pipeline connecting two pig launchers intended for conservation for a next 3-5 years is 36" size and it is used for a crude oil. I guess it should be cleaned first in some way ? Drain vessel is apart of this line as I understood from PID's

 

[RandomAxe]

So is it in service now? If so you'd probably want to flush it with meg water mix or similar to remove hydrocarbons and then leave it filled with treated water (corrosion inhibtor, oxygen scavanger etc) as noted above. You may want a specific cleanliness (i.e. oil in water ppm) which would require sampling during flushing till it reaches desired cleanliness. The PLR's could be purged with nitrogen but depending on the length of pipeline it would be pretty expensive to purge a 36" oil line when you could use inhibited water.

 

[LittleInch]

Yes it needs cleaning.

Usually pushed by water and then flushed or a set of pigs to follow the first before finally filling with inhibited water is my best suggestion.

You can clear it and then fill with Nitrogen, but then it still remains "live" as it's under pressure, but it could be quite expensive in terms of the amount of Nitrogen

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

 

[PI055]

Thank you for replies, now I have a better picture what to do