Flanged QOC ( Quick Opening Closure ) for Liquid pipeline Pig Receiver

[gasoperations]

Recently there was a malfunction in QOC of the receiver. The welded QOC was cut & and replaced with Std. Flange and Blind as a temporary measure.
Now we are planning to replace the QOC. Is it acceptable to have a QOC as Flanged instead of welded ( Almost all Launcher / Receiver that I have seen are with welded QOC ) This is due to cost only or some code / Operational requirement?
Any comments will be appreciated.

P.S
Is there any preference in terms of cost and / or functionality between Bayonet Type and Bandlock type QOC. Original QOC was Bayonet type with #300 Lb rating

 

[1503-44]

What size pipe? Usually it is not convenient to mess around with so many bolts on a flanged connection.
If the pig doesn't fly, you gotta open the bolts again.
Are you trying to find out how many times you can reuse bolts, nuts and gaskets?
and flanges do not have safety pressure locks.

Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[gasoperations]

1503-44
Exactly that is the reason to replace the temporary flange & blind with proper QOC. The temporary arrangement is implemented to continue the existing monthly pigging as QOC procurement may take some time. The line size is 20" and receiver is 24" x #300

 

[LittleInch]

Mr 44, I think he's going to replace the blind flange with a flanged QOC instead of cutting off the flange and rewelding it. Correct?

AFAIK there is no stipulation one way or the other, normally you wouldn't put a flanged connection here simply for cost and weight purposes.

Personally I like Band lock closures. So long as you don't paint them but keep them well greased, they are to me a more fail safe closure method.

Bayonet is probably the next best, but much better than the hub clamp type.

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

 

[akpipelineengr]

I've seen at least one operator put a flange set between the closure and the trap on new traps so that the closure could be more easily replaced in a situation like yours, as they can tend to corrode and fail faster than the trap. IMO the upfront cost of the flange set and added leak point on the trap aren't worth the minimal time saved down the road. But in your case, what you've proposed seems reasonable and isn't prohibited by the pipeline code (31.4/8, I presume).

 

[1503-44]

A lot of temporary launchers used for cleaning purposes during construction are flanged. And there are usually a number of flanges on launchers anyway, especially if they are 3rd party fabricated and skid mounted for setting on offshore platforms. I've used them for both on and offshore installations. Flanges offshore or for underground use should be protected with Flange bands with grease fittings.

Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[saplanti]

gasoperations,

Have you checked the material and the code requirement for the flange on the receiver¿ If your receiver is higher grade material you need to take off the std wt flange from the system as well. I hope this is not the case. Unfortunately some operators do not have this kind of material problem for the design pressure and temperature.

I agree with other recommendations above.

 

[gasoperations]

Thanks Everyone for their valuable input.
Saplant: the existing receiver is CS with #300Lb rating. So I believe as long as #300lb B16.5 flange is used, i hope there will be no violation of code.

 

[alchemon]

Need to think about how frequently you are using it. If this is once every seven years, yeah it is a pain, but it is every seven years. And yes the flange is a leak point. That may or may not be an issue depending on where it is and the like.

As long as the MAOP of the piping system is under the flange rating at your temperature, then yeah it is fine to use from an MAOP perspective.