After completing pipeline construction works the usually debris (welding rods, mud etc…) have to be removed out of the pipeline system in order to ensure a successful gauging and flooding pig run. Therefore a temporary low pressure launcher header and a low pressure receiver header has to be installed or welded to the pipeline ends. Those headers are equipped with back doors which will allow inserting and removing unlimited number of pigs. This is necessary to ensure a continuous operation. Usually there are two different kinds of cleaning pigs: brush and magnet equipped bi-directional pigs.
Immediately prior to launching, and upon receipt, each pig will be visually inspected and full details noted on a checklist, which will be submitted for approval to the client. Each pig has to be uniquely identified and marked for direction of travel. The cleaning pigs will be propelled by compressed air and the runs will be repeated until the debris removed from the pipeline are reduced considerably and accepted by the client. Therefore all debris recovered off the pigs, from the pigs or within the pig traps shall be monitored, measured and recorded. The debris removed from the pipeline shall be safely disposed at the location approved by the client and local authorities.