Shrink fitting | Stirling Cryogenics
Shrink fitting is a technique in which pieces of a structure are heated or cooled, employing the phenomenon of thermal expansion, to make a joint. An example is fitting an iron strip around the edge of a cartwheel. The strip is heated and expands to the wheel's diameter. The rim is then fitted around the wheel. After cooling, the iron rim contracts, binding tightly in place.
A common shrink fitting method used in industry is to pre-heat large metal components thereby causing them to expand slightly and allow for the insertion of another component.
The heated part expands beyond its intended size and after insertion of the component contracts thus guaranteeing a tight fit.
The cryogenic method avoids the energy consuming and costly heating of the larger part too higher temperatures in order to obtain the same insertion freedom.
Cryogenic shrink fitting consists of cooling the smaller parts so far that these shrink to the size required for force-free insertion.
This method of assembly has only a temporary effect on the mechanical properties of the component. It is quite straightforward and is used for fitting components as valve seats, gear wheels and cylinder liners. It results in economical clean operations and scale-free products without the drawback of metal softening due to high temperatures. Sub-zero cooling is a treatment which nowadays finds wide application in the metal working industry for constructional purposes.
For use in applications as described the following Stirling Cryogenics products may be considered: