Pig bypass

[productiondude]

I need a formula to help me disign the proper bypass on a pig i know how much gas,oil and water go into the line, what happens is when i send the pig the plant gets hit hard and we usually cause a upset is there any way to design this so this does not happen and i do not have to shut in production to accomdate sending the pig, also need to know for waxy lines so i dont get a build up in front of pig.I know to much bypass will cause pig stalling. Many thanks for any input.

 

[1969grad]

Don't know if I fully understand your question but if you are talking about a station bypass to let the pig go through then the bypass is generally the same line size as the pipeline.

I think the point you may be missing is that a pig must have a differential pressure across it to push it down the line which may be your real problem. If the line contains wax then the differential pressure may be even higher than normal. Hence, the pressure bump of the pig going through may be causing operating problems in the facility.

This a general answer but perhaps if you provided some more details then the forum could be more helpful. Be sure to describe what type of pig you are using.

 

[productiondude]

i guess what im trying to say is i want bypass of flow on my pig so it will hold wax in suspension as it moves down the line such as a 1 inch bypass port in the pig, im not sure how to size the bypass ports as i dont want the pig stalling in the line.I thought there might be a formula to use depending on pig size and product flow. Also trying to control the slug of fluids the pig brings into the plant.

 

[pmover]

simple answer, design a slug catching system capable of handling the quantity of fluids. it might be necessary to have multiple "drip legs" for catching the fluids. this should take care of plant upsets (high liquid levels in inlet drums).

installing a bypass, as you described, will not serve any purpose.

installing pig signals in piping system for monitoring pig location would help.

 

[JohnGP]

productiondude, I must agree with pmover. Much better to put your design effort into improving the liquid handling system in the plant and so reduce impact of pigging run. More frequent pigging could also reduce size of slugs.

Integral bypass with pig is not likely to achieve your goal - ports would block, particularly with waxy lines - back to square one, and if it did work, then you are basically leaving liquids in the line which kind of defeats the purpose.