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Check valve located into piggable portion of a pipeline 2

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mectub

mectub

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Mar 4, 2009
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ASME B31.4 state as mainline pipelines: all in-line pipeline pipes, fittings, bends, elbows, check valves, and block valves between scraper traps.

So it is a good practice to install a check valve (swing check valve)in a pipeline when pigging is required?

thanks to all
 
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No. But there is always some one that will come up with a reason. For example, if you do not want a back flow up a leg of the pipeline, you could install one.
 
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I think mectub was talking about whether it's good practice to install a swing check valve in the line to be pigged. I've not seen any used (lines didn't need them), but understand that you can procure swing check calves that can be pigged.

Cheers,
John
 
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For us, check valves in the mainline is not something we do. Reverse flow is controlled by components in compressor stations and meter stations, relieving the need for mainline check valves.

Beware of mainline check vavles and the use of some pigs, as some check valve cavities are so large, that a pig will not "bridge" through it very well, and may get stuck, or let bypass around the pig and stop.
 
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Me too, but for another reason. I've built lines where I was absolutely sure of the flow direction, and equally as certain that it would never change. I was young and naive then. If the gas marketing group finds an alternative transporter that requires a tap in the system upstream of the check then someone has to remember that it is there (not trivial) and when you shut down for the tie in you'll have to remember to remove it or you'll be shutting down again.

This was a Gathering example, but I can recall when a line built to take gas from the San Juan Basin to Texas was repurposed to take Permian gas to California. Check valves would have increased the cost of that repurposing significantly.

This is the same reason that the pig launchers I design look exactly like the pig receivers I design. I can't find any reason that they have to be different, and making them the same has saved my bacon a few times (Marketing's "creativity" caused flow in a line to reverse and my launchers became receivers and vice versa).


David Simpson, PE
MuleShoe Engineering
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

"It is always a poor idea to ask your Bridge Club for medical advice or a collection of geek engineers for legal advice"
 
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my case is ralated with an oilduct it cross a river and B31.4 recommends to use block valve up and downstream the river border to minimize oil to spill and it could be a gate or a check valve, the thing is using check valve could cause the pig to stuck, some one has use one.
 
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If you're in the US, DOT part 195, section 195.260 (e) states the following:

[A valve must be installed]On each side of a water crossing that is more than 100 feet (30 meters) wide from high-water mark to high-water mark unless the Administrator finds in a particular case that valves are not justified.

I don't interpret this as allowing a check valve, nor would I suggest that. A full port ball valve would be my suggestion here.
 
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Swing Checks are very commonly used in OIL and PRODUCT pipelines, especially on an uphill leg after a river crossing. Nobody really cares if gas backflows into a river, as far as having a pollution problem is concerned, so they are not often used in transmission gas pipelines, hence the answers above. DOT T49, P195 allows their use, as does B31.4 They are often specified because they are more economical than a full port ball valve and require no special (or remotely controlled) closing mechanism. They come with an external "hold open" lever for added insurance when pigging.

This is one of the better manufacturers and personally I wouldn't think of using any other,



"The top of the organisation doesn't listen sufficiently to what the bottom is saying." Tony Hayward X-CEO BP
"Being GREEN isn't easy." Kermit[frog]
 
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Thought I'd add that I've always used them in offshore gas pipelines, at the bottom of risers on platform export pipelines and at the tie-ins into other downstream pipelines; those places where you can't allow any backflow and don't necessarily want to complicate things by adding remote closing control to a ball valve.

"The top of the organisation doesn't listen sufficiently to what the bottom is saying." Tony Hayward X-CEO BP
"Being GREEN isn't easy." Kermit[frog]
 
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I would add that check valves are common in oil pipelines at pump stations to allow direct flow to bypass the pumps and a pig to pass through. You definitely need to make sure that the check valve is thru-conduit and fully piggable however. If the proper type of check valve is used (and is installed correctly too - don't underestimate that), it is rare that a pig will get stuck in it, (but it can happen). Tom Wheatley is a common brand of pipeline check valves.
 
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I always use check valves in oil pipelines (B31.4), after crossing rivers, swamps, or other sensitive areas, because is cheaper to have only one remote controlled valve before the crossing area, and the check at the other side that will respond automatically if something happens upstream. Read the attached article, that is a classical example and could clarify some concepts.

Be sure that your check valve is full piggable only.
 
 http://files.engineering.com/getfile.aspx?folder=26ccfedb-395c-4d57-a750-feaa11513788&file=lostpig.pdf
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