Pigging – Soft Pigs/Abrasive Pigs/Ice Pigging
Pigging as a cleaning technique can have two functions. First where other cleaning methods have been utilised, a close fit pig may be passed through a pipe to make a final cleaning run to ensure that all possible debris has been removed. These would tend to be soft pigs made from flexible materials, plastics or sponges. Secondly, where a limited amount of cleaning is required some pigs are designed with abrasive, rough outer surfaces that in themselves may offer sufficient cleaning for the pipe.
Pigs are normally pushed through pipelines using either compressed air or water pressure, between two access points or may be operated via a winch cable. The technique of Ice Pigging is also possible whereby a flow of water is passed through the pipe which has a high degree of solid ice as a component. The ice particles act like a form of gravel and abrade the pipe wall to remove scale and detritus and stir sediments into the flow. It does not however need collecting and separating from the waste created as it melts to become part of the final water flow. Detritus is disposed of according to current regulations.