The dual or multi diameter pig should not be confused with a pig that can traverse changes in wall thickness of any given size; a true dual or multi diameter pig can traverse a full size step change of 18” to 20”, which is a difference of 2”, or from 24” to 30”, which is a size change of 6”.
Dual or multi diameter pipeline pigs designed to traverse different pipe sizes need to be designed in a specific way and generally with experience. In order to achieve the necessary flexibility a combination of options need to be carefully considered.
By using specially designed discs of different sizes or petalled designs a degree of flexibility can be achieved; often specially designed cups, or a combination of discs and cups need to be considered. In addition to cup/disc alternatives it is occasionally necessary to consider a mechanical support wheel system or a flap system could be an option.
All or a combination may be needed to enable a pig to traverse a line section that has a combination of two sizes of internal diameter [I/D] due to a size change and rather than a simple wall thickness change.
Additional design considerations include the number and distance of constrictions to be travelled. It is important to remember that to design a pig of this type ALL information with regard to the pipeline has to be known and taken into consideration at conceptual design stage to ensure the pig will safely travers the pipeline section.
Depending upon the complexity of design, it may be prudent to conduct full-scale proof testing, and iNPIPE PRODUCTS™ has significant experience developed over the last 35 years in this field and also has a purpose designed test facility located adjacent to the engineering and manufacturing on the new 6 acre site.
Benefits of Dual or Multi Diameter Pigs
- Stable and centralised operation
- High performance sealing
- Can travel in either direction within the pipeline
- Polylast AAA abrasive resistant systems mean that these pigs can withstand up to 1,000km distances
- Can be designed to accommodate multi diameter pipelines
- Successful design for removing light deposits from the pipe wall
- High strength neodymium magnetic cleaning for removal of ferrous debris
- Radial and spring mounted brush options
- Spring mounted plough blades for wax or scale removal
- Pipeline gauging and data logging options
- Articulated dual module bi-di options to traverse all pipeline features
- Check valve design options
- Spring mounted support wheels
- Magnetic, acoustic, electro-magnetic and radioactive source tracking options