Cryogenic Freeze Plug Using Alternative Fluid.

The use of ice or freeze plugs for isolating piping systems has gained wide acceptance throughout the plumbing, nuclear and petroleum industries. The reliability of the process as well as the significant cost avoidances that freeze plugs provide can benefit the cryogenics industry also. The standard method of repairing a cryogenic or high purity line was to empty the line and make the repair. The cryogenics industry also has to allow the piping to come to ambient temperature before repairs can be made. This paper describes a new process for creating a freeze plug within a pipe utilizing an alternative fluid. This process is ideally suited for application on systems where the fluid is either extremely difficult to freeze, or possibly hazardous to do so. The method can also be used on high purity systems to help maintain quality requirements. The specific application described herein provides a means for isolating components in a liquid oxygen pipeline while in service, allowing the change out of components without draining the system. The cost savings, reduced handling risks and additional thermal cycling of the associated equipment and the dewar are significant. The process has been successfully employed on a large Liquid Oxygen Dewar at the Kennedy Space Center. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]