The bore map of each platform was investigated and from this the most appropriate design of pig for these lines was considered. The presence of a wye piece meant that all pigs had to be articulated. Prior to delivery of the pigs, it was highlighted that there was the possibility of a further restriction in the line. Unfortunately the customer, contractor nor the final client could confirm or deny the presence and /or location of this possible restriction therefore the pigs had to be redesigned at short notice to ensure safe pigging through the line.
As the dimensions could not be confirmed, the pigs were made with multiple bore capability, rather than the dual diameter initially expected. The change in diameter was in the order of 20% variation from the maximum diameter known to the smallest diameter possible. Each pig was designed with petalled and segmented discs to ensure sufficient sealing in the larger diameters of the launchers and to allow the pig’s discs to drop down into the void between the discs in the restricted areas.
All pigs were delivered at short notice and all successfully received onto final platform having passed through the a small diameter section on one of the platform risers, inferred from increased pigging pressure.