Cryogenic Bulk Tanks- Vacuum and Leaks

"Nature abhors a vacuum."

When conducting cryogenic vessel classes we often discuss the fact that, other than occassional flashes between my ears, natural vacuums do not exist within the earth's atmosphere. Given time and opportunity, all vacuums will draw in molecules to the point that atmospheric balance is restored.

It is no great wonder then that vacuum insulated cryogenic bulk tank and other liquid cryogenic vessels lose their vacuums and related insulation capacity over time. And, when the vacuum is lost, the vessel loses all or the greatest part of its insulating capacity and can no longer protect the liquid from heat resulting in excessive loss of oxygen, argon, or nitrogen liquid product. The mystery (and fun CSI part) of the job comes from determining the how, where, and why of a lost vacuum.

All too often, vessels with bad vacuums are hooked up to a vacuum pump until a good reading is once again achieved. The pump is then disconnected and the vessel returned to use only to find that it is again losing product within days, weeks or months. The process is repeated with the unsurprising recurrence of the problem.

There is another way and we'll discuss it next.....