7 replies to this topic

[gazepdapi1]

I just have a general question. I have noticed that on a gas system, the launcher typically has the kicker door near the pig trap door which make sense since you want pressure behind the pig to push it down the line. My question is, why is it that on a receiver this bypass line is closer to the end of the trap? I don't see why this kicker can't been near the door for both cases? Similar to what the attached shows.

 

Thanks for your help.

Attached Files

•  PIG LAUNCHER3.pdf   106.85KB   86 downloads

[gazepdapi1]

Anyone?

[mattbeddow]

the pig has to pass the t-point for the bypass line before you can remove it.
If the bypass line was right next to the door, the pig wouldnt be able to pass it so the line will become blocked and you would then have to open the door on a "live" system, resulting in the pig getting shot out when you open the door followed by all your product.
That is, if you can even get the door open.

[gazepdapi1]

the pig has to pass the t-point for the bypass line before you can remove it.
If the bypass line was right next to the door, the pig wouldnt be able to pass it so the line will become blocked and you would then have to open the door on a "live" system, resulting in the pig getting shot out when you open the door followed by all your product.
That is, if you can even get the door open.

But if the pig makes it to the bypass line, I just close the bypass line and the trap valve and I can still remove the pig? Or am I looking at this wrong? 

[neel_avi]

Dear Nertil1,

 

in case of a pig receiver, the gas flows from the main pipeline into the pig receiver and from the receiver into the main pipeline again via the bypass line in order to receive the pig.

 

When a pig enters a pig receiver and passes through the reducer and comes into the major barrel, the seal is lost and the gas is no longer that efficient to push it through. Rather pig drops down by gravity in the barrel. it might also have a chance to move forward because of the momentum. If the receiver bypass line was located nearer to the closure door of the pig receiver, there could be a possibility that the pig would move and block the bypass nozzle partially during the receiving operation which would disturb the flow significantly. Thats the reason why may be the bypass line is placed at minimum spacing from the start point of the reducer between the major and minor barrel. 

 

Further, in scenarios where gas can be received and transported in any direction in the pipeline bi-directional pig launcher/receivers are provided with both the bypass and the kicker line. 

 

Regards

Avijit

[neel_avi]

Another thing, if suppose for a receiver the bypass is nearer to the trap door, there may arise a chance for impact between the pig and the closure door during receiving. That may be another reason why the bypass is situated nearer the reducer between the major and minor barrel.

 

Regards

Avijit 

Edited by neel_avi, 14 June 2013 - 04:11 AM.

[mattbeddow]

Alspo, youre forgetting any material that the pig may pick up during a run. if the pig had to come to a stop right by the door it might never get there if there was something large it had picked up, like a sheep (true story)

[gazepdapi1]

ok now it makes sense. Thank you guys