Introduction to Varipig

Varipig was designed and patented as a direct result of the pipeline pig functional requirements for the Statoil Åsgard pipeline RFO commissioning project in 1998. FTL Technology (FTL), founded in 1973, is a company of Mechanical Engineers with the philosophy of providing solutions to solve customers problems based on sound mechanical engineering principles.

Customer problems are reduced to a set of functional requirements and through attention to detail monitored via an ISO 9001:2001 Quality Management system a solution to the particular problem is reached.
In the instance of Varipig it was resolved early on in the design procedure that a new and revolutionary approach had to be adopted if the functional requirements were to be met whilst at the same time upholding the philosophy of FTL.

By applying basic hydraulic cylinder design principals FTL decided that contrary to previous designs the support function of the pig should be completely separate from the sealing and drive function. Due to the expected high rate of wear that the sealing discs would have to withstand it was decided to take the hitherto unprecedented step for a commissioning pig to mount the whole unit on a self supporting and self centering suspension system.

A new and revolutionary approach had to be adopted if the functional requirements were to be met

The majority of previously designed commissioning pigs adhered to previous design concepts in that all functions of the pig could be met with a relatively simple low cost design. The Åsgard multi diameter gas transporter line however was totally different.
The pipeline length would be 710 km at 42” diameter and the last 500 metres would reduce to 28” diameter. Drive disc and support disc wear would be a critical consideration.

By carefully designing the suspension the potential to overload the wheel assemblies was avoided when passing from the larger to the smaller diameter pipeline sections. Furthermore, a slow rotary motion would be imparted to the whole pig train to even out the wear on the discs. The following describes our findings based on extensive running experience.