Pig trap
Pig trap
(OP)
Hello,
I am looking for information about the stresses of the pipe assocaited with a pig trap. I would also like to know how to calculate these stresses and the standards or code in which they are based on.
Thanks
I am looking for information about the stresses of the pipe assocaited with a pig trap. I would also like to know how to calculate these stresses and the standards or code in which they are based on.
Thanks





RE: Pig trap
Which code? This depends on where the interface is defined between the pipeline to the trap and the downstream piping. If the trap is considered to be part of the pipeline, then it can be designed to ASME B31.4, ASME B31.8, or similar pipeline code. If part of the plant being fed by the pipeline, it can be designed to ASME B31.3 or similar pressure piping code. After all, the trap is basically bits of pipe welded together. You can also treat the trap as a pressure vessel and design to ASME VIII or similar PV code.
RE: Pig trap
I am working with the B31.8. Could you tell me where I can find the information.
Thanks.
RE: Pig trap
Hoop stress=PD/(2t) for each section of the trap - see para 805.233 .
Secondary stress due to beam action and support loads are usually insignificant - just need to check that attached piping is not arranged to exert large reaction forces back into the trap.
Maximum pressure rating can be determined from para 841.11 - stress then will be equal to specified minimum yield strength multiplied by joint, design, and derating factors (but see para 841.111 for limitations). Required wall thickness in each part can also be derived from this formula (and watching para 841.113).
RE: Pig trap
RE: Pig trap
RE: Pig trap
RE: Pig trap
Yes, the closure is usually designed to ASME VIII and the weld end tapered bored to match the pig barrel.
You can design the trap to ASME VIII but you end up with a thicker wall thickness plus other more restrictive issues in Section VIII and hence more expensive.
You can use either code but common practice is to use the pipeline code for design of the launcher/receiver.
RE: Pig trap