As Helium (He) processing is boosted in reaction to the world’s cry for a solution to the helium shortage, new helium processing plants are going up throughout the world. The cryogenic treatment of helium uses a great deal of aluminum pipe as critical members in the transferring of the helium liquid and gas as it is being processed throughout the facility. A large majority of the piping specified in the constructing of these facilities is stock-size aluminum pipe. This material can be found available on the floor of most aluminum suppliers. But due to the rarity of a number of the larger pipe diameters, some of the piping specified will not be able to be located as floor stock from your aluminum supplier. So what is done when only 30ft of 28in diameter, schedule 30, aluminum, grade 6061 pipe is needed?
In this instance a specialty fabricator known as a roller/bender is used to make the pipe by curving 10ft long, 5/8″ thick aluminum 6061 plate to a 28″ outside diameter. This is done through a curving process known as plate rolling. The fabrication of the pipe is done in multiple steps. First the plates are rolled into 10ft long cylinders which are known in the industry as cans. Each can is fully welded and tested. The welding is usually done by highly skilled, specialty welders. In order to successfully produce the cans, roller/benders must be set up for this type of work.
Due to the pipes’ specific use, carbon contamination of the aluminum cans must be avoided at all costs. Special polymer coatings are used in order to protect the can from any contamination during the rolling process.
Trimming off excess material on each end of the can’s weld seam, which is used to achieve complete roundness of the finished cans, is done with a specialty cutting/shielding gas plasma mixture. This mixture consists of Hydrogen/Argon (H35) for the cutting gas and uses Nitrogen (N2) as the shielding gas. This mixture gives the highest cut quality possible for aluminum and leaves the cut edge with excellent weldability. The can’s seam is then cleaned and tack welded.
The cans are shipped to the welders, who perform full-penetration weld seam. Each weld is then tested and certified at which point the cans become pipe. The pipes are the shipped to the fabricator/erector for use in constructing the helium processing facility.
The most important property of Helium is its extremely low boiling point of -452°F or – 269°C. At this point Helium is liquid, and can be used, for example, to cool magnets used in MRIs to these extremely low temperatures where electrical resistance is virtually non-existent, and the magents become superconducting.