Pig Trap Launcher: Kicker line size

[LupusLupis]

Good morning people, this is the 1st time I write here and hope to find help.

I am going to design a pig lancher for spheres and pig tool 32", this is a 2 kicker lines trap, client suggest to use both nozzle 12" for pig and spheres, one collegue suggest to use 6" to move the pig tool and 12" for spheres (for an economical matter), I fear that 6" is not enought to move a 2000Kg pig tool.

What do you think about this matter, any suggestion?

 

[zdas04]

The area that the force needs to work over is pretty big, so the dP required to just be in equilibrium (assuming starting friction is negligible) is around 40 kPa. Since starting friction is not negligible, call it 80 kPa or around 12 psid for the heavy pig.

The procedure I use for launching pigs is (1) load pig ensuring that it is seated in the throat of the launcher; (2) purge air from barrel; (3) Open kicker line; (4) open barrel isolation valve; (4) throttle the side valve toward shut until the pig leaves (it rarely has to go fully shut before the pig leaves). Step 4 puts the full flow behind the pig while the downstream processes pull the gas they need from pipeline storage--dP rapidly increases. A 2-inch kicker line will eventually launch your 32" pig, but you'll starve the downstream processes for a while.

Over the years, I've developed several rules of thumb for sizing a kicker line that have worked well (it would take more space than I want to use here to lay them out), and those rules would suggest that a 10" kicker is the best trade off between cost and efficiency. Using two different sized kicker lines is a waste of time, money, and effort.

David