Pigging is an integral part of the maintenance regime for pipelines. Pipelines are pigged for several reasons. If water is present in the line, it must be removed periodically in order to minimize corrosion. Water will accumulate at low points in the pipeline and as a result will be corrosion hot spots.  In addition to corrosion prevention, a proper pigging regiment can help keep the process facility operating at the specified design parameters.  By regular pigging pipelines, blockages in the pipeline can be removed and thus reduce pressure drops in the pipeline.  Additionally, periodic pigging can also impact the sizing of the slug catcher allowing for a more optimized design. 

Pig Trap System

BARREL
The barrel is the section of the pig trap, from the pig trap valve up to and including the end closure which is required to launch and receive pigs.
It consists of three parts:

• Major barrel: An enlarged section of the barrel used for loading or retrieving pigs
• Reducer: A between major and minor barrel
• Minor barrel: A section of the barrel between the pig trap valve and the reducer.

The major barrel is equipped with a quick open closure end.  This allows for more efficient loading and unloading of the pigs. 

Kicker Line
A kicker line is required to connect the major barrel with the bypass line to enable diversion of the fluid through the barrel to launch or receive a pig. For a launcher the kicker line is connected to the major barrel as close as possible to the end closure and for a receiver as close as possible to the reducer.

Bypass Line
A bypass line is connected the pipeline with related facilities.

Balance line
A balance line is provided on launchers to enable filling and pressurizing of the barrel on both sides of the pig at the same time. This is to prevent a pig which is ready to be launched from moving either forwards and thereby hitting and possibly damaging the pig trap valve)or backwards and losing the seal in the reducer. To ensure this, the balance line, branching off from the kicker line, shall be connected to the minor barrel as close as possible to the pig trap valve.

In addition to the above system, pig traps are often supplied with Jib Cranes and Pig Trays to facilitate operators loading and unloading the pigs from the system.  SPEC has a variety of Pig Trap systems on offer ranging from simple, standalone launcher and receiver all the way to fully automated skid mounted packages.  Contact SPEC for your requirements.