GAS PIPELINES (PIG VALVES INSTEAD PIG LAUNCHERS AND RECEIVERS)

[hianbotech]

Right now, We are designing a Natural Gas Gathering Pipelines from different oil produced clusters. In the actual design we are considering use pig traps in the main trunklines, but we are thinking to use pig valves for some branches (economical reasons). However we have not had experience with these kind of Valves, only vendors references.

The question is knowing the experience with this kind of pig valves in similar services, instead using pig traps (launch and receiving). These valves are safety?. How is the recommended instalation?. There are some pressure restriction for using?.

This kind of specialty item permits a double block & bleed valve that can send or receive pigs, all in one only piece.

You can see the detail in this Weg page:

http://www.girardind.com/valves.htm

The conditions of the Gas Pipelines will be: 58-100 psig and 67 - 131°F. The fluid will be Natural Gas. the pipe sizes are between 4 and 10 inches.

An aditionally question regards Gas Pipelines is if there are some criterias to determine when is necessary to have a pigging clean system. I know that its depends of topography, diameter, length of pipelines, gas flows, gas composition and quantity of condensates, etc. But I do not have the guidelines for this issue.

I will apreciate your help on these issues.

Best Regards,

Hianbo

 

[Montemayor]

hianbo:

I have no doubt that the proposed "Pig" valve will work as described. What no one can predict is the odds of it failing to function when in normal service or, worse still, when it is in the open position - ready for pig insertion.

The jeopardy lies not only on the possibility of the turning mechanism(s) binding (or freezing up), but in the possibility of the ball's elastomer seat failing to seal. Sooner or later, all ball valve seats have to be maintained - that's why they are always designed to be removed. If you have no ability to block-bleed-and-bypass, what do you do? You shut down the pipeline and install block-bleed-and-bypass. I believe the SAFETY issue is the outstanding point in this application. in order to insert the pig, you must subject a human to the scenario where there is only an elastomer, soft ball valve seat between him and full, natural gas line pressure. I wouldn't do it without a fail-safe device or procedure to circumvent that scenario.

 

[hianbotech]

Thanks Montemayor for your soon answer.

We are considering in our design add block valves and bypass to these pig valves. However the big issue is the experience in this aplication. I have never seen this pig valves installed. We are familiarized with pig traps application.

Regards, Hianbo

 

[pmover]

my preference is to utilize proven equipment and system designs, i.e. pig traps/receivers. valve failure and safety aspects are certainly design considerations. however, new techniques and equipment should also be explored - interesting concept (the Argus valve). that being stated, perhaps there are section(s) of gathering pipeline in which the Argus valve can be utilized such that in the event of a failure, the failure has minimal impact on gathering pipeline system, equipment, and personnel. perhaps you can obtain reference(s) from mfg and investigate. somethings to ponder . . .

good luck!
-pmover