Frictional pressure loss of a pipeline pig 1

[Vikesh]

I need to calculate the time taken for a pig to accelerate from an initial to a final velocity in a pipeline. (The reason this value is of importance is because it determines the level trip settings of an upstream vessel.) I know how to calculate this value using the mass and size of the pig and the pressure driving force available, but how do I include the frictioal loss component?

 

[Cockroach]

Frictional losses simply act to restrict axial displacement, that is, to decrease velocity of the pig (mass) through the bore of the pipeline. Then model it as so.

Frictional loss equals a scalar coefficient times normal load, a negative vector relative to flow. This scalar coefficient is initally static friction factor until just after initiation of motion, then the kinetic friction factor can be used.

I would treat it no different than a block sliding down an incline plane under the influence of friction. This would give you a beginning point to model your equations for a mathematically equivalent pipeline system. After that, you can tinker with the differential equation(s) to your hearts content in order to gain accuracy.

Sounds like a nice problem, enjoy the moment!

Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada