Proplug's Welding Pigs are used to create a safe welding atmosphere inside a new pipe as it is being laid off the back of a vessel.
Two types are available, Mid-Line and End-Line. The Mid-Line Welding Pigs remain in the pipe after welding and are pigged out. The End-Line Pigs are retrieved immediately post-weld.
Typically the pipes are stainless steel or have a high chromium content, so the purge gas needs to be carefully controlled to allow the critical first weld pass to be carried out.
Welding Pigs act as a barrier against the bellows effect caused within the pipe from normal vessel motion.
The Welding Pig is inserted into the lower end of the pipe, centralised using the C-Plate assembly and the seal within the pipe is inflated.
When the top section of pipe is mated to the lower section, the second seal is inflated through the root gap between the pipes using a lance.
With the Welding Pig in position the purge atmosphere may be controlled by inserting purge lances into various points around the pig body as required to allow welding of the pipe ends.
If required, the Mid-Line Pigs may still be used where a post weld heat treatment is carried out and successfully pigged from the line.
Sizes of Welding Pigs range from 6" and upwards. Contact Proplug for more information or a specific solution to your project.