pig launcher 5

[hkjoe]

we build a tank farm (API 650)with on- and off shore pipeline with pig launcher / receiver. Code for CH-transportation systems is 31.4 and it is written that 31.4 cannot be used for pressure vessels (chapter I, 400.1.2b. My understanding is a pig launcher is a pressure vessel (manufacturing acc. to ASME VIII-I but what about the design and materials (ASME VIII / II)? I want avoid of mixing up standards. Our pig launcher(shell) is made of X42.
Thanks

 

[zdas04]

Why do you think that a pig launcher is an ASME Code vessel? I've built dozens and every one has met the definition of a "pipeline accessory" in B31.8 (Gas transmission).

David

 

[hkjoe]

Hi David,
thanks for clarification. In our client's spec is written "manufactured acc to ASME VIII, that's I wasn't sure about the applic. standards. Indeed in 31.4 chapter V and VI (construction, assembly, welding / testing), so why ASME VIII? Thanks

 

[GregLamberson]

hkjoe

Typically pig launchers are designed to B31.8 or 31.4. You need to look at where the spec break is, again, typically it is at the side valve going into the facility. That will determine where the "plant" piping spec will take over.

In any case I have never seen a pig trap designed to ASME VIII.

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

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

 

[dcasto]

We had some ASME coded pig launchers which were a pain to maintain seperately from the B31.8 lines. They had to have their own PSV's because we didn't use PSV's on the pipeline. Those PSV's had to be test twice per year because the line was DOT jurisdictional.

Stay with B31.8.

 

[c1defence]

Greg,
Frequently the pipeline code covers the pig traps, but the traps are designed to ASME vessel code.
Cheers,
Shiv

 

[zdas04]

c1defence,
Where and in what industry? In Oil & Gas, and pretty much around the world every operation I've looked at has called them pipeline accessories. I've only seen PSV's on about 3 launchers, and never seen a code stamp on one.

David

 

[MortenA]

zdas04

Re PSV's what about PSV for fie protection? I have mostly seen pig launcers/traps on off-shore platforms and here they tend to include PSV (and deluge). Yes they will be part of the pipelien but you could put a PSV on it anyway couldnt you?

Best regards

Morten

 

[MortenA]

For reference: The North sea - danish section.

Best regards

Morten

 

[SJones]

It's probably because owners specify that the end closures have to comply with ASME VIII and it just gets extended (erroneously) to cover the whole trap.

Steve Jones
Materials & Corrosion Engineer

http://www.pdo.co.om/pdoweb/

 

[MortenA]

But Steve

On a platform the pig trap may very well be in a fire zone. Just because its allowed by code not to - wouldnt it still be a good idear to install a PSV for fire protection?

Best egards

Morten

 

[zdas04]

Morten,
That is an operational decision on gas pipelines. I specify (in operting proceedures) that idle launchers and receivers are always in connection with the pipeline (by keeping the kicker/bypass open). I used to specify that they be isolated and a vent left open until I had a vent line freeze (small leak-through in the barrel-isolation valve, candle-wax freeze in the vent pipe followed by a pressurized barrel that we thought was vented, really scary), now I call for the barrel to be left pressurized and ask people to pay attention to how long it takes to blowdown.

I think that I would put a thermal relief on a pig trap in a liquids line because of the pesky 100psi/degreeF pressure response to temperature. But I just don't do much with liquids lines.

David

 

[MortenA]

But couldnt you scenari be that there is a fire - and somebody by mistake left the isolation valve closed?

Best regards

Morten

 

[SJones]

Morten,

PRVs absolutely agree with you - put them on when deemed necessary. I was theorising about why ASME VIII gets applied to pig traps in response to David's posts and your two posts beat me to it!

Steve Jones
Materials & Corrosion Engineer

http://www.pdo.co.om/pdoweb/

 

[zdas04]

The way I design traps, if the kicker/bypass is open then the trap can't become liquid full. If you do the Thermal Expansion calcs on a trap that is half full of liquid and half full of gas, you'll find that the metal will flow from the temperature in a pooliing-liquid fire before pressure will increase enough to overpressure the trap. That would not be true on a liquid-full trap. The important scenario is to make certain that there is no credible way for the trap to become liquid-full.

If you can come up with a credible scenario that results in a trap being isolated liquid full then you have to have a PSV (probably sized for thermal)

David

 

[dcasto]

Our traps had ASME code stamps on them. These were in the US, BUT, the design standards were a combination or US, British, and Belgium companies.

The contractual settlement between the 3 owners were that the most stringent design standards, as put together by the general contractor, would be used. We ended up with quite a pipeline. We had 48 volt controls, no threaded fittings, flanged thermalwells, In station piping had ESDV every 25,000 pounds.

 

[SJones]

Just a little update - DNV OS-F101 calls pig traps 'pressure vessels' and requires them to be designed in accordance with ASME VIII or PD5500

Steve Jones
Materials & Corrosion Engineer

http://www.pdo.co.om/pdoweb/

 

[zdas04]

Steve,
It's interesting that Det Norske Veritas has changed the the status of two of the pipeliner's sacred cows--pig traps and slug catchers for submarine pipelines (

http://exchange.dnv.com/OGPI/OffshorePubs/ViewArea/OS-F101.pdf).

I've never known if DNV standards had the force of law anywhere or if their standards were more around ISO certifications. Do you know?

David

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 harder I work, the luckier I seem

 

[MortenA]

As far as I know OS-F101 is used in the north sea by many companies- but if its a law I don't know.

My company Ramboll designs a lot of pipelines in the Danish and Norwegian sector of the north sea and as far as I know they follow OS-F101.

Maybe that's why I have only seen traps with PSV's?

Best regards

Morten

 

[c1defence]

Steve Jones is correct.
I checked what we designed a few years ago for onshore pipelines.
The data sheet says: Scraper Design Code, (To be suitable for Scraper and Intelligent Tooling.): ASME B31.8 with a design factor of 0.6 for all aspects of the launcher/ receiver design except quick opening closure which shall be to ASME VIII, Div 1,
The spec states: The code ASME B31.8 / B31.4 for an ASME Class 600 / 900 pressure rating shall be used for all aspects of the VENDOR’S design of the launchers / receivers except for the quick opening
end closure which shall be designed to ASME Section VIII,
Division I.
For offshore an operator states: The end closure shall conform to the general requirements of ASME VIII, Division 1, Section.
Typical sizes for the major barrel (limited to common
standard ISO 3183-1 pipe sizes)
A thermal relief valve shall be installed where shut-in pressure of trapped fluid could exceed the design pressure as a result of thermal expansion of the static fluid.