What should I do when a liquid nitrogen tank is continuously venting?

According to the Praxair’s State College employee Jennifer at the extension 7003, it is perfectly normal; all you have to do is to connect the tank and start using the nitrogen. “Pressure builds up and the tank is venting”, Jennifer tells me, as if this was my first delivery of high-pressure LN2. (Translation: “Praxair got your money, now it’s your problem”.)

Normal liquid-to-gas conversion is about 2-3%, when not in use; the tank I received yesterday has already managed to convert about 50% of its 240 L to gas. When high-pressure cylinders are not being used, they will vent occasionally. Unlike other liquid nitrogen cylinders of the same make and model delivered by Praxair , this one suffers from incontinence: it has already lost half of its volume within 24 hours because it vents non-stop through a faulty valve. Thankfully, we have good ventilation, otherwise we’d suffocate.

What I expected from Praxair was an apology for delivering a defective product and an offer to replace it with a usable one. Instead, I got a childish explanation of the workings of a liquid nitrogen cylinder.

The serial number of the poor leaky guy is M699-009-GD (Part No. GL65-OC 14-EZ-MG M, Taylor-Wharton). If it shows up in my lab again, venting away – it goes straight back where it came from.