Two recent incidents involving liquid nitrogen occurred at Penn.
The first incident occurred in Stellar-Chance Laboratories when a research group began using a wrench to open the liquid dispensing valve. The liquid dispensing valve was difficult to open and rather than having the tank serviced, research staff used a wrench to open the valve. The use of the wrench eventually sheared the liquid dispensing valve seat. The entire valve dislodged from the cylinder causing a violent release of liquid nitrogen from the cylinder.
The second incident also involved the use of a wrench to open the liquid dispensing valve. In this case the researcher completely unthreaded the valve from a cylinder, resulting in another uncontrolled release of liquid and gaseous nitrogen.
Nitrogen gas rapidly expands to approximately 700 times its liquid volume, displacing oxygen and posing a significant asphyxiation hazard. Skin contact with the liquid can result in serious burns. In both of the these incidents the researchers evacuated the area of the release and escaped unharmed, but the potential for injury was high.
The primary contributing factor in both cases was the deteriorated condition of the liquid nitrogen cylinder. When the liquid dispensing valve becomes difficult to open by hand, it is an indication that the equipment requires repair. Tools must never be used to force a valve open.
Other indicators that repairs may be needed include:
-Corrosion or damage to the cylinder body or valves
-Broken or inaccurate gauges
-Loss of product due to insufficient vacuum insulation
-Frequent venting of gas through the pressure release device
-Frost formation on the valve handles or tank body
A laminated tag containing important safety reminders and pertinent contact information will be affixed to each liquid nitrogen cylinder.
If you believe your liquid nitrogen cylinder is in need of repair, discontinue use immediately and contact Keen Compressed Gas at 302.594.4555 or www.keengas.com or Airgas at 1.866.718.0685 to arrange for maintenance to be performed.
All liquid nitrogen tanks filled by a Penn operated fill station must have a safety inspection by Keen Compressed Gas every five years. Tanks that are not inspected will not be filled.
If you have additional questions about liquid nitrogen use, consult the Cryogen and Dry-Ice Safety Fact Sheet or contact the EHRS office at 215-898-4453.