With time, cryogenic and vacuum seals wear out and lose their ability to perform. Sometimes the need for replacement is due to heat or constant thermal cycling, while other times it is due to the constant pressure on the seal as the joint is periodically tightened to maintain the integrity required. If the device is still usable, the seal can be, in most cases, renewed by following the steps below.
After the seal is broken and dismantled, there will likely be remnants of the gasket material previously used on the flanges or mating materials. This must be removed prior to the placement of a new gasket or wire that will create the new seal.
With care, remove as much of the old gasket material as possible using a razor blade, scrapper or putty knife. On very critical seals, the old material can be removed using a soft cloth, instead of mechanically removing it. Sometimes it is necessary to gently warm the area to soften the gasket material allowing for easier removal with the cloth.
In the case with indium as gasket material, if any remains on the flanges after scrapping and/or wiping with a soft cloth, a 10% solution of HCL can be used to remove the remaining small traces of indium. The HCl should always be followed by a good rinse in DI water followed by an acetone rinse and an air dry or blow dry with nitrogen.
Once the above preparation is complete, the new gasket material can be placed.
Our Technical Support Engineers are can assist with any questions regarding hermetic, vacuum or cryogenic seal applications.
15 October 2012