Magnitude of Pipeline Pig Trap Forces on Closure

Hi,

I am currently performing stress analysis of a pipeling facility containing a pig trap.

Client specifications require us to consider all safety scenarios when investigating facilities. As such a scenario may occur where the valve on the bypass line to the pig trap is closed too soon, be it from a false signal from the pig indicators or otherwise. This would mean that the pig will not slow down as it enters the pig receiver.

This is a 42" pipeline carrying a 5tonne pig at a operational speed of approximately 5m/s. If faulty the pig may travel up to 9m/s I'm told.

In previous facilities have taken a conservative route my assuming a simply Impulse type equation where the mass will come to rest in 0.1 seconds, this would result in a worst case force of 450kN. This has been fine previously as a lot of the force is transfered to directly to an underground anchor block upstream of buried induction bend. When applied to this facility model where no such mitigation is present, movement of the pig receiver on its sliding supports is too great resulting in very high nozzle loads on the kicker line nozzle.

Rather than redesigning the inlet to the facility, which may turn out to be a costly exercise, and may not be possible due to space, I was wondering what best practice is in design is when considering such scenarios, whether it is actually considered at all?

Are there any references around covering pig impacts into closure and methods of calculating the resulting force.

Cheers,

James