Freeze plugs or Freeze seals are regularly used in nuclear reactor fluid systems to drain or isolate components that, for various reasons, cannot be conveniently isolated by valving. Once they are isolated, they are able to perform maintenance or upgrades without shutting down an entire system.
The United State Navy utilizes a large vortex tube to supply -50°F cooled air stream into a freeze jacket around the pipe. A time frame is chosen based on pipe size and fluid in the pipe to verify they are generating adequate cooling. Temperature monitoring is put in place, flow through the pipe is stopped, and cooling of the freeze seal begins. The water near the walls of the pipe freezes first. Next, the frozen liquid continues towards the center until a solid plug of ice exists. The freeze seal is then subcooled to a pre-determined temperature at which point the freeze is considered equivalent to a shut valve. Between the Ice plug and the small bit of pipe shrinkage at the point of cooling these seals are able to hold back thousands of pounds! (See drawing below, Shrinkage exaggerated for viewing)
In the attached photo bellow, (Provided by the U.S. Navy, photo by John Lenzo) this is a Freeze seal training Rig! You will see three colored lines, Blue is the cold air flow supplied by the vortex tube, red is the hot air from the vortex tube is exhausting away from the application location, and yellow is the pipe they are creating the freeze seal on. Surrounding that pipe is a jacket that holds the -50°F air in contact with the pipe.
With careful temperature monitoring in place and backup cooling methods on standby the work up stream can start. Coolant flow throughout the rest of the system can now be reestablished. Following the repair, flow will again be stopped for several hours while the freeze seal is given time to melt. This ensures that the ice plug is not shot through the now repaired machine.
If you think you have an application that would benefit from Vortex tube technology, give us a call! We have a team of Application Engineers in from 7AM-4PM EST M-F! Or shoot us an email to firstname.lastname@example.org and one of those Engineers will reach out to you!
Freeze Seal Image Provided by the U.S. Navy