Case Study 2 – Pig Design, Verification Trials and Supply
Pigtek were awarded a contract to design and supply a pig that would successfully traverse a 20in. pipeline with several challenging features, that included a 20in./24in. dual diameter tee section, 3D 180 degree bends and an asymmetrical wye piece. These were the parameters set by our client for Pigtek to deliver an efficient cleaning pig for an offshore FPSO loading system that also included a flexible riser with stainless steel lining.
Careful consideration had to be given to the design of the pig, as it had to be long enough to maintain a seal through the maximum crotch length of the wye piece, yet short enough to negotiate the tight bends. The compatibility of any brushes used for cleaning was also a factor, as incorrect material could cause damage, contamination and corrosion to the stainless steel lining in the flexible riser. Pigtek worked on the design of a Dual Module Brush/Magnetic Cleaning Pig.
Our initial studies identified that it would be possible to produce a pig compatible with the pipeline features. However, as the pipeline was subsea, it was critical to thoroughly test the performance of our proposed pig to minimise any risk of the pig becoming stuck.
Pigtek engineered the production and assembly of a full scale trials rig at our Chesterfield site in the centre of the UK. The rig also incorporated the actual wye piece that would later be installed into the operational pipeline system. The series of trials that were performed tested the pig through each separate pipeline feature before the final test, which incorporated all features in the sequence of the operational pipeline system.
Out of interest, a “standard” pig was run though the full test rig, but failed to negotiate the wye piece and lost complete drive due to excessive product by-pass. However, as a result of the trials performed by Pigtek, the risk of this occurring in the live operating pipeline was identified and eliminated. A tried and tested pig, fully compatible with the pipeline system was supplied ready for operational use.