WHEELED PIGS
A unique pig design using wheeled support arms to replace the conventional guide disc setup
With the increasing need for pigs to pass through multi-diameter pipelines there has been significant development of new pig types. Where traditional multi-diameter pipelines have stepped between 50-60mm, now diameter changes up to 150-250mm can be considered. Propipe has been providing a unique pig design, which uses wheeled support arms to replace the conventional guide disc arrangement.
This pig has proven to provide 100% reliability and also a dewatering ability that is second to none. Wheeled support pigs use a series of wheel mounted arms to carry the pig. These are mounted to a central suspension system, allowing the suspension arms to move as a collective unit and providing constant, non-rotational operation.
This action ensures that the pig does not drop its centreline below the pipeline centreline, which in turn means that the sealing discs are always centrally held within the pipeline.
Conventional pipeline pigs use rigid polyurethane guide disc to support the weight of the pig guide it through the pipeline, but these guide discs can suffer from compression set or slow recovery (when used for large diameter changes), which can mean a loss of seal. Sealing discs that are held centrally within the pipeline provide maximum sealing ability, which ensures maximum dewatering ability. In many cases, piggability trials and offshore operations have confirmed that a wheeled pig can be run with a small number of seals, but provides extremely high dewatering performance. The low running Dp needed also helps to ensure that the pig is allowed to perform at its optimum without any speed-affected loss in performance. This improved performance also allows the pig design to be used for cleaning and gauging operations as well as production maintenance operations. Pigs can carry brush modules, bypass jetting units and both standard or SMART gauge systems. Wheeled-support pigs have been designed, tested and field proven for the following diameter changes and Propipe continues to develop for larger step changes.
