RECHARGING OXYGEN CYLINDERS


Produced by:
Mining Health and Safety Program,
Ontario Ministry of Labour
Alert #6/0395
ISSN 1195-5228


HAZARD SUMMARY:

Two workers at a quarry were injured while transferring oxygen 
from a large oxygen cylinder to a portable cylinder.  Both a 
rubber connecting hose and a pressure gauge mounted on the small 
oxygen cylinder exploded, causing serious injuries.  The accident 
was caused by the use of materials not compatible with oxygen.

The transfer was from a standard-size oxygen cylinder containing 
6.9 standard cubic metres (244 scf) at a pressure of 2400 psig to 
a small portable cylinder with a capacity of 0.57 standard cubic 
metres (20 scf) at 2215 psig.

The equipment used -- the transfer hose, the pressure gauge, a 
tee fitting and the valve connectors -- had been assembled by 
staff at the quarry.  Except for the nipples connecting directly 
to the two cylinder valves, this equipment was for handling 
hydraulic oil.  The steel-braided rubber transfer hose contained 
nitrile rubber, and the pressure gauge contained glycerin.  Both 
of these materials will ignite with relatively little applied 
energy in an oxygen atmosphere.  Ignition occurred inside the 
rubber transfer hose, caused by friction heat generated by the 
rapid movement of oxygen through the hose.

LOCATIONS AND SECTORS:

Mining, Construction, Industrial, Health Care.

RECOMMENDATIONS:

-  Use only appropriate equipment to handle oxygen.

-  Workers handling oxygen should be aware that in an oxygen 
   atmosphere it takes very little applied energy to cause an 
   explosion. 

-  Before attempting to transfer oxygen between cylinders, 
   consult and oxygen-supply company.

The Compressed Gas Association, Inc., (1235 Jefferson Davis 
Highway, Arlington, VA, 22202, USA) publishes guidelines on this 
subject, including CGA G4.4-1980 "Industrial Practices for 
Gaseous Oxygen Transmission and Distributing Piping Systems".