minor barrel lenght - pig receiver/launcher

[Fario]

Hi guys,

I have a question that I have not been able to find an answer to in any handbook or paper.

Does exist any rason than lenght (of minor barrel) of pig receiver has between 100 to 200 inch more that pig launcher?

I had seen the "Pipeline Rules of Thumb Handbook 8th Edition 2014" Table 1 pag.36 and some datasheets of pig launcher/receiver with that huge difference.

Any operational rason or safety or mandatory?

Thanks for any advice or guide

DM

 

[LittleInch]

Yes there is.

Any trap acting as a receiver needs to have the minor barrel at least as long as any pig you plan to use.

The reason is that depending on the pig or the wear on the pig, when the first set of cups come through the reducer the pig can stop dead.

If the pig then extends through the pig trap isolating valve you can't close the valve to retrieve the pig. BIG PROBLEM.

The advent of intelligent pigs at 4+m long has made it worse as many of the intelligent pigs are "towed" through the line by only the driving cups on the front portion of the pig train. Then 3/4 at least of the pig is within the minor barrel. e.g. the red bits on the picture below are the driving cups. Once they break through the reducer on the end of the minor barrel the pig stops.

Launcher don't have the same issues as the pig is wholly within the major barrel before launch.

Personally I would just prefer nowadays to order a single trap which can do both. Makes it much easier.

Does that help you understand?

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

 

[Fario]

LittleInch, completely clear and thank you.

DM