Cryogenic Fill Hose Safety Reliefs- An absolute necessity

Why are safety reliefs installed on all cryogenic liquid oxygen, nitrogen, argon or carbon dioxide fill hoses?

In fact- safeties are not only to be installed on all fill hoses. They are also installed on any cryogenic line that is sealed on both sides. This is because cryogenic liquid trapped in a line will vaporize and expand exponentially creating tremendous pressure in hoses, piping or tubing. This expanding liquid nitrogen, oxygen, argon, or CO2 can easily build enough pressure to cause the line or hose to explode with great force.

This is a danger that is easily overlooked and one that is not obvious to someone without prior knowledge or training. And- it is something that can be missed by even the most experienced personnel who are hooking up a new line out of necessity or otherwise in a hurry.

Whether you are filling medical oxygen bases, transfilling liquid from one DOT4L vessel to another or otherwise filling from a bulk source it is essential to have a relief for expanding vapor. So- never forget to be sure the hose you are using to fill has a properly rated safety relief installed somewhere between the valves or other connectinos that could trap liquid.