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Pig Receiver/Launcher Non Operational State

Pig Receiver/Launcher Non Operational State

Pig Receiver/Launcher Non Operational State

(OP)
Hopefully posted within the correct forum to get the most. Iews, replies and experiences.

I am currently working on a new build on-shore gas processing facility. As part of the build, a large pipeline transporting mainly clean gas with some liquids (c5+)is being attached. It is expected that the pipeline will require to be pigged once a week to ensure liquid slugs are brought through.

Obviously as part of the design we have an appropriate pig receiverbeing installed and this is wheremy question is.

The pig receiver in question is an appropriate rated pressure vessel with a bandlock door seal. Due to the make upof the new facility it is actually located in the middle of the plant (slightly different from other facilites).

In your experiences, in what state would people normally leave the pig receiver? Isolated, Depressurised and inertered or isolated and left at pressure with hydrocarbons?

The current design (as I believe with most pig receivers) does not have a relief valve but is rated for the maximum pipeline pressure. However, a design has been made to fireproof the vessel.

Really appreciate any comments.

RE: Pig Receiver/Launcher Non Operational State

First off, no PSV on the receiver barrel is a major mistake. It doesn't take much leakage to end up with the barrel liquid full in the sun. I've seen it happen in 2-3 days. It doesn't take much of a PSV, but you need something for thermal protection.

Second, there really isn't a standard way to leave receivers, and if you assume one, an operator will figure out a reason to ignore you. I've had good luck with purging the barrel through the bypass line and leaving the barrel isolated at around 1 barg. That way you can check the pressure before starting the process to see if valves are leaking in (i.e., barrel at line pressure) or leaking out (i.e., barrel at atmospheric pressure). Going to the trouble of inerting it is simply a waste of resources, it does not add to safety in any tangible way. A lot of people are happy leaving the barrel vented, but I have a problem with that--if the bypass or barrel-isolation valves leak through then you don't really have any indication.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.

RE: Pig Receiver/Launcher Non Operational State

A receiver would probably be isolated (receiver barrel valve certainly closed), depressurised and quite possibly containing air, but you should assume that hydrocarbons (from a leaking barrel valve), or HC + N2, or HC + air are present and always drain, vent and purge before opening again, which you would most likely do anyway, if it is a receiver.

You're asking because it doesn't have a thermal relief, correct?

What would you be doing, if you knew that you could not fail? Ans. Gov lobbyist.

RE: Pig Receiver/Launcher Non Operational State

BTW yes, it should have thermal relief.

What would you be doing, if you knew that you could not fail? Ans. Gov lobbyist.

RE: Pig Receiver/Launcher Non Operational State

(OP)
Gents,

Thanks for the replies.

You are correct it does not have thermal relief as the designer has designed it like they would (i.e it is a pig receiver within a field) others they have designed. The problem it is in the middle of gas plant but it does have a tie in/blow down line to the flare system, manual only. I felt that an operational procedure, stating that it is depressurised and isolated would provide adequate safeguards in case of thermal relief. Thermal relief is only a problem in the event of a pool fire underneath it.

RE: Pig Receiver/Launcher Non Operational State

Not even close. A barrel that is liquid full will overpressure in a few minutes in the sun. Nothing to do with a fire case.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.

RE: Pig Receiver/Launcher Non Operational State

A procedure is NOT sufficient. The design codes REQUIRE PRESSURE RELIEF in the event of overpressure. A procedure will never be able to meet that requirement.

What would you be doing, if you knew that you could not fail? Ans. Gov lobbyist.

RE: Pig Receiver/Launcher Non Operational State

Quote (Shell DEP 31.40.10.13-Gen)


A thermal relief valve shall be installed where the shut-in pressure of trapped fluid could
exceed the design pressure as a result of thermal expansion of the static fluid. Thermal
relief valves are not normally required for gas or multiphase pipelines, but should be
considered for liquid pipeline systems. The relief valve capacity and setting shall comply
with the pipeline design code and DEP 80.45.10.11-Gen.
NOTE: Where operating procedures restrict isolation of the pig trap to the period of loading or retrieving pigs,
it may be possible to eliminate the thermal relief valve.

Steve Jones
Materials & Corrosion Engineer

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

RE: Pig Receiver/Launcher Non Operational State

That's just fine if it's a SHELL plant, but B31.8 itself doesn't recognize Shell DEPs.

Quote:


B31.8
845.2.1 Control and Limiting of Gas Pressure in Holders, Pipelines, and All Facilities That Might at Times be Bottle Tight.

Suitable types of protective devices to prevent overpresuring of such facilities include,
(a) spring-loaded relief valves of types meeting BPV Code, Section VIII
(b) pilot-loaded back-pressure regulators used as relief valves, so designed that failure of the pilot system or control lines will cause the regulator to open
(c) rupture disk of the type meeting the provisions of BPV Code, Section VIII, Divsion 1

If it ain't broke, don't fix it. If it's not safe ... make it that way.

RE: Pig Receiver/Launcher Non Operational State

Who said it was B31.8? There's more to the world than 31.8!

Steve Jones
Materials & Corrosion Engineer

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

RE: Pig Receiver/Launcher Non Operational State

Well that's just it isn't it. Nobody said anything about any specific code, Shell included (or actually not). Given the preponderence of codes and company standards in the world, most based on B31 series anyway in one way or another, even the Chinese code is a virtual copy, it is reasonable to mention their requirements. I've been working outside the USA for 20 years and I never have been able to escape ASME (even as much as I'd like to at times). What's the problem anyway? I never said he had to use them.

Now, since you brought up this Shell, let's talk about it.

Given the circumstances of this question, specifically directed towards pig launchers and receivers in slug clearing service run once per week, I would not follow the Shell DP, even if I worked for Shell. While I would agree that a relief valve might not be needed on a pipeline in gas or multiphase service, this case is not discussing the pipeline, it is a localized bottle-tight device that could easily be full of liquids. Furthermore it is not way out on the edge of a plant or on the pipeline somewhere, it is in the MIDDLE of the plant. If there is anywhere you would want to have a relief valve on any part, or component, of a gas or multiphase pipeline, especially on a LAUNCHER/REVEIVER, and even the DP allows for it, I will requote you, "not NORMALLY required", this is one of those cases where it needs to be given a whole lot of thought. IMO, the Shell DP does not give a safe practice in this circumstance. I would not follow it. The B31.8 code is far superior in the degree of safety provided and .... costs relatively nothing. They are handling the liquids in some manner at present anyway.

If it ain't broke, don't fix it. If it's not safe ... make it that way.

RE: Pig Receiver/Launcher Non Operational State

The Shell DEP simply provides a contextual response framework to the original statement

Quote (Brnmcgn)

The current design (as I believe with most pig receivers) does not have a relief valve

]Whether it is right or not will have to be determined by HAZID, HAZOP and other process safety activities.

Steve Jones
Materials & Corrosion Engineer

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

RE: Pig Receiver/Launcher Non Operational State

Codes and company specs ONLY describe a minimum level of performance. If an engineer has a reasonable expectation that the code provides inadequate protection for a given situation then he needs to go beyond the code or company spec for that particular situation. That is what Engineering Judgement is all about.

This may become moot anyway. I am starting to see regulations (starting with Norway, but others are following) that reject the idea that pigging facilities are "pipeline accessories" as defined in B31.8 et al and requiring them to be treated as pressure vessels. I don't agree with this trend, but I understand where it is coming from. If a receiver barrel is a pressure vessel then this whole discussion becomes moot because there is no way to say that thermal relief is not required under the BPVC.

I started noticing 4-5 years ago that the horrible pre-fabricated pigging facilities that you can purchase from folks such as the old Tube Turns (they have changed their name) now have code stamps and include pressure relief on the barrels. This is recent, but it is a response to some pretty dramatic failures.

What you do with the PSV exhaust is another issue. A thermal relief generally dumps a couple of tablespoons of liquid and reseats until next time. Piping that to a flare is a really bad idea. Mostly people don't pipe it at all, and just let it splash the pipeworks. I support that approach, but in the middle of a plant that would probably be seen as wrong. If I had to pipe it somewhere it would be into a sump or waste water collection system.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.

RE: Pig Receiver/Launcher Non Operational State

(OP)
Firstly a big thank you for taking the time for reply to my original query. Obviously some differing approaches and sound justification for both stances. I think I will be pushing our pig receiver/pipeline EPC to design with a thermal relief valve included. While the stream is gas/multi phase and not totally liquid, any HAZOP would push for a TRV due to the potential for an operator not getting the isolations right.

In terms of relief route, it will be fed through to our flare which has a liquid knock drum before the actual flare which will be suitable.

Thanks again

RE: Pig Receiver/Launcher Non Operational State

The problem with piping a thermal relief to flare is RUST. These stupid things spit a few ml of liquid that will wet down the piping and never get very far down the pipe. I don't like taking any PSV on predominantly water service to a flare stack (even with a knockout), but nothing says you can't do it.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.

RE: Pig Receiver/Launcher Non Operational State

you were really saying wonderful things and I was saying, "Great! I agree with THAT!!!", then you got to this one. "Mostly people don't pipe it at all, and just let it splash the pipeworks. I support that approach,", then I said ...

If it ain't broke, don't fix it. If it's not safe ... make it that way.

RE: Pig Receiver/Launcher Non Operational State

(OP)
Again thanks for the replies. Rust won't be a problem as it will be a mix of hydrocarbon liquids, MEG and corrosion (no free water) and our flare header and knock out drums are stainless steel. Our knock out drum also has a pumping system to reclaim liquids.

RE: Pig Receiver/Launcher Non Operational State

I've always been more of a cowboy than you could tolerate BigInch, I understand that. In the middle of an undeveloped field in New Mexico 20 miles from the nearest house, letting a thermal relief vent locally (i.e., splash the pipeworks) is not (in my opinion) unreasonable.

In a plant (even on the edge) I'll pipe it to a sump of some sort, but putting a stream that will be exclusively water into a flare header is a problem for me.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.

RE: Pig Receiver/Launcher Non Operational State

zdas, I really just don't know where you come with those things. I think, hey he's kidding, right. Right?? Fortunately Brnmcgn's engineers are mostly on top of the situation, granted they missed the PSV, but the STAINLESS flare was a good move... water keeps the flare cooler, so they say. Venting to atmosphere, even in New Mexico, contributes to global warming for all of us. It's hot enough here as it is thanks. Also might be one more reason you got so many forest fires around U this year. smile

If it ain't broke, don't fix it. If it's not safe ... make it that way.

RE: Pig Receiver/Launcher Non Operational State

Releasing a few mL of water is a contribution to climate change??? On that note I'll bow out.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.

RE: Pig Receiver/Launcher Non Operational State

That button didn't work.
OK. I was envisioning much more than a few ml "splashing the pipeworks". You painted a much bigger picture.

If it ain't broke, don't fix it. If it's not safe ... make it that way.

RE: Pig Receiver/Launcher Non Operational State

Thermal relief is always a tiny fluid volume that if you don't relieve is a major pressure problem.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.

RE: Pig Receiver/Launcher Non Operational State

you do not need a relief valve, you can use a tubing check valve around the block valve that isolates the receiver.

The pig receiver doesn't have to be an ASME vessel, it can be made of pipe and fittings designed to a piping code, most people use B31.8.

RE: Pig Receiver/Launcher Non Operational State

dcasto,
I've done the check valve thing and it mostly worked, but the Nanny Society has ripped all of them out because: (1) you can't open a vessel that is only protected by a check valve; and (2) the check on a bypass would have to have a locked-open block valve behind it to protect personnel from (1) above which requires an MOC to remove the lock for every pig run (I'm serious, and the MOC takes 6-9 months to process every time the state changes, weekly for a weekly pig run). I expect the MOC disaster to resolve itself over the next few years, but I don't think that it will never again be easy to shift a lock.

There are states and countries that have overruled ASME B31.8 and mandated that launchers and receivers be code vessels. I expect that nonsense to become more widespread with time.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.

RE: Pig Receiver/Launcher Non Operational State

Quote (Biginch)

I would not follow the Shell DP, even if I worked for Shell
enough reason why you would never work for shell pirate ah just kidding but ppl who work for Shell seems to think of the DEP's as if they were handed down to Moses at a certain occation envolving a burning bush etc.

Best regards

Morten

RE: Pig Receiver/Launcher Non Operational State

Company men.
Since that DP apparently allows for deviations as I suggested, it turns out that I could follow that one.

If it ain't broke, don't fix it. If it's not safe ... make it that way.

RE: Pig Receiver/Launcher Non Operational State

zdas, I understand your pain. We had pig traps that we owned and operated inside chemical plants where we delivered the feedstock to them. The chem plants wanted to force us to do similar things. One time they drew a line in the sand and would not let us use such things or allow us to maintain our pielines. They changed their tune when I hit the shutdown valve via the scada system 100 miles away and shutdown their plant.

We had signage that had operating proceedures much like ones at loading racks. Tell me, how would that plant load out say condensate, LPG, would it require an MOC to open and close the valve? How about a prover? Or proving a dp meter.

you can only dumb down the workforce so much....

Good Luck

RE: Pig Receiver/Launcher Non Operational State

If only they would dumb down the workforce. The field guys I work with are as smart as field guys ever were (actually pretty smart), but the Nanny Society trying to eliminate ALL risk through (administrative) processes won't allow them to think. I keep telling companies that field operators in Oil & Gas make over $25/hour. You pay that kind of money for people to think, not to mechanically follow scripts. If you want script followers you can get them for $10/hour. The field guys are so frustrated with crap like an absolute prohibition against unlocking a LO valve without an MOC. Not many of them are so frustrated (yet) to leave a $30/hour job for a sweaty $15/hour job somewhere else, but some are getting close.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.

RE: Pig Receiver/Launcher Non Operational State

I got rid of the stainless steel carseals and went to plastic. During the quarterly LDARS inspection, the gas sniffer verifies the carseal status on those few valves as documentation of no tampering.

If someone needs a carseal open, thats in the work permit for the job.

I remeber the days of serial munbered car seals and keeping the broken ones as proof, proof of what I don't know.

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