Pig impact at riser bends

During the pigging process of wet gas lines, large volumes of liquid may be swept out. If the line is operating at high pressures, the velocities and momentum of the pig and associated slug of liquid can be high, leading to large impact forces at the riser bends. This can lead to overstressing of the riser or fatigue failure.

Jee carried out a study to analyse the effects of the impact of pigs on these riser bends.   Our study included:

• Calculation of force-time histories for the pig and slug train passing around various bends in the riser
• FE analysis of the riser and its supports to determine the peak stresses and the likelihood of fatigue
• Specifying site measurements to be taken and instrumentation to be used
• Analysis of the obtained data

We provided a full set of recommendations to enable our client to continue operating with confidence in the integrity of the riser system.