Pig Launching and Receiving 1

[Khansahib]

A 6” oil transport pipeline is being laid from point A, which is 18 km from the flow station. In the way, two pipelines from two different set of wells joins the transport line at point B and point C. The point B is 4 Km and point C is 13 Km from Point A. At point C the line dia is increased to 8” due to increase flow rate, making the last 5 Km pipeline to 8”. The wells are in remote area.

In order to pig the transport Pipeline I intend to install two-pig launcher and a pig receiver. One 6” pig launcher at Point A and one 8” pig launcher at point C. In order to receive these two different size pigs I intend to install an 8” pig receiver at flow station, 5 Km down stream from point C.

The questions are:
Can this idea work?
Can the 6” pig float through the last 8” leg of the pipeline?
What precaution required?

 

[Unotec]

If you post a diagram it might help understanding more, but I think your idea is not too bad

<<A good friend will bail you out of jail, but a true friend
will be sitting beside you saying ” Damn that was fun!” - Unknown>>

 

[djack77494]

I don't agree that this idea will work. I think you need a second pig receiver near point C, sized for removing the 6" pigs. Right downstream of it and the line size change is where to locate the 8" pig launcher.

 

[dcasto]

I've done this on gas lines, no problem.

 

[SJones]

What type of pigs are envisaged and what is the purpose of the pigging? Have you considered a multi-diameter pig if you are only cleaning and swabbing so that only the one pair of traps is required?

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[Khansahib]

unotec: I have attached a file that will give some idea.

dcasto: If it is working for a gas line then it should work on well fluid line having two phase flow. Thanks for encouragement.

djack77494: Why you say it is not going to work?

SJones: Since it is a well Fluid pipeline therefore mostly the pigs will be scrapper and sometime intelligent pigs to check the wall thickness.

Also would like to know if Y connections are available in the market. I would like to put a Y connection at Point B to facilitate pigging from point A as well as from Point D.

I was also thinking if there is an 8" pig shell standing by at point C in which 6" pig slips in and take ride to flow station

 

[GregLamberson]

Khansahib

Do you want to pig the D - B section? If so, don't know if you've considered portable pig traps - might want to look at that and reduce some 6" traps. If you don't need to pig D - B, then what you have should work.

Otherwise, if you want the whole system piggable by a smart and cleaning pigs - what I see is 6" traps at A and C. 6" traps at D and B. You would have 8" traps at C to FS.

Greg Lamberson, BS, MBA
Consultant - Upstream Energy
Website:

http://www.oil-gas-consulting.com

 

[maddocks]

Although dcasto has done this, there are some risks that the 6" pig will not move in the 8" line due to high slippage and fluid bypass. I wouldn't take the chance and would install a receiver/sender station at the transition point. Getting a pig stuck is a really ugly problem.....

 

[zdas04]

maddocks,
Dual diameter pigs don't work that way. A 6-8 launcher typically will have a 10-inch barrel with a 6-inch straight section. You stuff an 8-inch foam pig into the 6-inch section (it takes some force, but will go). Then at the transition to 8-inch the pig relaxes to the line size. They have been installed all over the world with many successes.

Dual diameter launchers work OK for many things. I just heard about a line with an 18-20 dual diameter launcher being smart pigged. Before a couple of years ago this was not an option in any size. I'm not sure what sizes they can accommodate today. My advice is still, if you think you will ever want to smart pig the line, design long launchers and receivers and put a receiver on the 6-inch line.

There was mention above about running a 6-inch pig and dropping it into the 8-inch line to be pushed home by the 8-inch pig. I've done this, and it has never worked as well as I'd hoped. The big pig will tend to run up on the small pig and the two can get irretrievably wedged in the line. My problem was with "turbo pigs" which are made of plastic and have vanes like the old mandrel pigs. If the big pig can ride up high enough to interlock the vanes, the pigs are never moving again without a cutting torch.

Another problem with dumping the small pig in the large line is that it is a tough build. If you just use a non-barred tee you have to use pigs that are either shorter than 8-inches or very flexible (like a foam pig). A turbo pig or a mandrel pig won't make the corner. A not-barred tee also has the ability for the 8-inch pig to try to go walkabout up the 6-inch line in certain field maintenance scenarios.

I have a picture of a dual-line piggable drip that has worked to allow multiple launchers to share a receiver (one system has 5 launchers and one receiver, been working fine for 15 years) on my web page under samples (it is in the "Rules of Thumb for Gathering System Equipment" file). They work, but they're expensive and while I have built a couple with different diameter lines (using a reducing lateral), I haven't had much luck with the actual pigging in that mode. The photo above the Gathering System Samples heading is a dual-line piggable drip. It works well, the two streams interfere with each other and drop out a lot of liquid in a gas gathering system.

David Simpson, PE
MuleShoe Engineering

http://www.muleshoe-eng.com

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

The main difference beteen humans and apes is that we have cooler tools

 

[maddocks]

Hey, this is good info!! Thanks for the tips...

 

[Khansahib]

David Thanks for the detailed explaination. Incase any question I will revert back to forum......Thanks for everone else who have participated and shared the knowledge.

 

[Unotec]

Just got back from the field and a warning that probably you already considered, but my mechanical dude did not. Make sure every valve/connection etc IS PIGGABLE!! In a 4" line we had multiple valves that were not full port. It got pretty interesting! Now I know how every PSV in the line works!

<<A good friend will bail you out of jail, but a true friend
will be sitting beside you saying ” Damn that was fun!” - Unknown>>

 

[MJCronin]

Gentlemen.....

Consider:

Title: The Pigging Handbook
ISBN 10: 0-9717945-3-7
Author: Jim Cordell, Hershel Vanzant
Publication Date: 1/1/2003
Pages: 282
Binding: Paperback
Price: $125.00 Single copy

http://www.gulfpub.com/default.asp?page=14&productID=4309&VS=

-MJC

 

[Khansahib]

unotec: I have considered the full port ball valves and things look fine. Thanks everyone for taking part in useful discussion.

MJCronin: Thanks for highlighting the book.

 

[zdas04]

MJCronin,
Have you used that book? Is it really useful for field applications?

I thumbed through it at Gulf's booth at the ASME World Congress a couple of years ago and couldn't find any of the things I was looking for in the index. I didn't study it, but my quick look at the table of contents and index wasn't very promising. If you are recommending it I'll take another look.

David

 

[Khansahib]

Gentlemen,
I am in the process of designing a pig launcher and a pig receiver, both are 8”x6”. The major and minor barrel are of API 5 L X65, ASME B31.8. I am proposing 4” Flange-O-Let for kicker and 2” flange-O-Lets for other nozzles instead of individual items, weldolets, nipples and flanges and weld them together.

The compatible flange metallurgy for API 5L normally is A 694 F65 whereas the fittings are A694 WPHY65. I am little confuse as to which metallurgy should I propose for flange-O-Let considering the Flange-O-Let is a combination of Flange and fitting (Butt well weldolet). Your expert opinion shall be appreciated.

 

[zdas04]

Khansahib,
You really should start a new thread with a new question. Many folks who could help you have already written this thread off as having deteriorated into "me too" posts like all threads eventually do.

David