Pig Traps: Pig Launchers and Pig Receivers
Intended Purpose • to introduce or retrieve pigs, spheres or inspection tools; • to launch or receive so-called “dividers”. Pigging is used: • to batch or separate dissimilar products; • for displacement purposes; • for internal inspection.
Pig trap Components • • • Trap barrel Actuated valves Trap signallers Pressure control devices Bypass line
Typical Pig Launching Procedures
Typical Pig Receiving Procedures
Pigging Problems To Solve • The pigs fails to launch. • The pig is launched successfully but fails to arrive on time with no major changes in pipeline pressures or flows. • The pig is launched successfully but fails to arrive on time and there is an increase in pipeline pressure drop in pipeline flow.
Pigging Problems To Solve The pigs fails to launch. The possible causes are: 1. The pig is too small (wrong pig or undersized) and the flow cannot pick up the pig in the launcher barrel. 2. The pig is too large, wrong pig or oversized and it is jammed in the exit to the launcher. 3. The pig is too far back in the launcher.
Pigging Problems To Solve The pig is launched successfully but fails to arrive on time with no major changes in pipeline pressures or flows. The possible causes are: 1. The pig is too small (wrong size) and cannot climb the riser into the receiver. 2. The pig has disintegrated into its component parts. 3. The pig is hung on a bend and the cups have “flipped” forwards to allow full flow.
Pigging Problems To Solve The pig is launched successfully but fails to arrive on time and there is an increase in pipeline pressure drop in pipeline flow. The possible causes are: 1. The pig has hung up on a bend or ’T ’piece (pig is too long for bend radius). 2. The wrong size of pig was launched (too large in diameter). 3. The pipeline has been dented and the pig is stuck at the damaged section.
Pigging Problems To Solve The pigs “leap-frog” each other in the pipeline. The possible causes are: 1. The operator launched them 1, 3, 2 but did not realise (most common); 2. The front pig hangs up on an obstruction and is only cleared by the second pig rolling over it.