Requirement of Balance line connection for Pig receivers

[vinothsvk]

Hi All,

This is first time I am handling Pig Traps systems. As i understood that the Balance line is branch connection taken from Kicker line and connected on minor barrel of the Pig launchers as close as possible to Pig trap valves. Normally this balance line connection used for filling and pressurizing the barrel at bot side of Pig at the same time. So that the pig will not move when waiting to be launched. This balance line connection is only applicable for Pig launchers.

Please confirm, can we provide this balance line connection to Pig receivers? Also, let us know the Mandatory of this balance line for pig receivers?

 

[LittleInch]

vino,

A sketch would help but usually a balance line is attached further down the pig trap, not the kicker line.

In my opinion this is a vital piece of piping for both launcher and receiver, but you don't find it specified anywhere unfortunately.

There are a number of injuries and deaths each year when taking pigs out as the gas trapped behind the pig, which can be stuck in the trap due to debris or just stuck, is suddenly released and the pig flies out the trap like an artillery shell.

So my view is that it is MORE important in a receiver than a launcher to balance out and depressurise both sides of a pig at the same time.
Shown as balance line below. When venting the two white valves MUST be open before you start venting. If I design one I normally make the balance line tie into its own nozzle.
When launching a pig you need to close the balance line otherwise all the gas just bypasses the pig....

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

 

[georgeverghese]

From, memory, balance lines are installed for both launcher and receiver barrels.

 

[Krausen]

I've worked for some of the majors that required balance lines on all new pig trap designs. This was 5-7 years ago in midstream (pipeline). Not all the majors required this in their standards though at the time, but they should in my opinion. I've never seen balance lines branch off kicker lines like what's shown above. They always had dedicated branches to main pipe/pig barrel, 2" size typically. This question may be better posted in the Pipelines/Piping forum.

 

[LittleInch]

I agree as noted above - but this was just the best diagram I could find easily.

Too many people think a pig trap is a PV when it's really part of the pipeline....

They also still sometimes have a slope marked on them - I've been deleting that for years now so hopefully when they use the last one they built it won't perpetuate.

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