Severity
Incident
Leak
Yes
Ignition
Yes
Ignition Source
unknown

A fire occurred in a continuous-feed autoclave system (fixed-catalyst-bed tubular reactor) when the rupture disc released, discharging hot oil, oil distillates, and hydrogen gas out a vent pipe into the autoclave cell. The flammable mixture was discharged directly into the cell because there was no system in place to catch or remotely exhaust the autoclave contents. The oil and gas ignited in a fireball that, in turn, ignited nearby combustibles (cardboard and paper), causing a sustained fire. The hydrogen gas and autoclave system were shutoff immediately. However, a lecture bottle containing hydrogen sulfide was heated by the surrounding fire and ultimately ruptured with enough force to cause facility structural damage. (Lecture bottles do not have a pressure-relief device.) The explosion occurred about five minutes after the rupture disc released.

One employee received minor burns on his arm from the initial fireball. No other injuries occurred. Fire damage to the laboratory and equipment was minimal, but the cost of the structural damage caused by the explosion was estimated at about $55,000.

Incident Date
Sep 01, 1983
Setting
Equipment
  • Pressure Relief Devices
  • Burst Disk
  • Hydrogen Storage Equipment
  • Gas cylinder
  • Process Equipment
  • Fixed-catalyst-bed tubular reactor
Characteristics
When Incident Discovered
Lessons Learned

The ignition of the fireball could have been caused by any of the following mechanisms:

The inverse Joule-Thompson effect of hydrogen (i.e., heating upon expansion)
Some of the oil and light ends were above their auto-ignition temperatures
Contact with hot surfaces of the autoclave
Static electricity
Electrostatic discharge of the mixture.

The possibility that the explosion may have been caused by the hydrogen discharged from the autoclave was thoroughly investigated. However, there were no signs of combustion in the upper part of the cell. Also, the explosion occurred approximately five minutes after the rupture disc release, long after the hydrogen source had been shut off and more than one air exchange had occurred in the cell.

The following were identified as lessons learned from the incident:

The reactor outlet line was plugged with viscous oil, which resulted in over-pressurization of the system. If the plug had been in the feed line, the rupture disc on the reactor would never have been over-pressurized. If the staff had added a second rupture disc near the pump outlet to relieve pressure before the reactor rupture disc, with a check valve in between the two, the release might have been avoided. This design change was incorporated into the system rebuild.
The fixed-catalyst-bed tubular reactor system should have been reviewed and approved by health and safety, facilities engineering, or building management staff.
The inadequate hazard analysis of the installation resulted in failure to anticipate the need for containment or remote discharge of the rupture disc effluent. A thorough hazard analysis should have been done before operating the system.
The operators were not adequately trained on the hazards of the system. - Combustible materials and gas lecture bottles should not have been stored in the autoclave cell (i.e., poor housekeeping).
The fire failed to activate the sprinkler system because the exhaust fan was turned on within seconds of the rupture disc release, so the air change volume minimized the temperature rise within the cell.
The roof pressure vent panel failed to adequately relieve the explosion pressure.

Key:

  • = No Ignition
  • = Explosion
  • = Fire
Hydrogen Incident Summaries by Equipment and Primary Cause/Issue
Equipment / Cause Equipment Design or Selection Component Failure Operational Error Installation or Maintenance Inadequate Gas or Flame Detection Emergency Shutdown Response Other or Unknown
Hydrogen Gas Metal Cylinder or Regulator   3/31/2012
4/30/1995
2/6/2013
4/26/2010 12/31/1969     3/17/1999
11/1/2001
12/23/2003
Piping/Valves 4/4/2002
2/2/2008
5/11/1999
4/20/1987
11/4/1997
12/31/1969
8/19/1986
7/27/1991
12/19/2004
2/6/2008
10/3/2008
4/5/2006
5/1/2007
9/19/2007
10/31/1980
2/7/2009 1/24/1999
2/24/2006
6/8/1998
12/31/1969
2/7/2009

9/1/1992
10/31/1980

10/3/2008  
Tubing/Fittings/Hose   9/23/1999
8/2/2004
8/6/2008
9/19/2007
1/1/1982 9/30/2004
10/7/2005
  10/7/2005  
Compressor   10/5/2009
6/10/2007
8/21/2008
1/15/2019
    10/5/2009 8/21/2008  
Liquid Hydrogen Tank or Delivery Truck 4/27/1989 12/19/2004
1/19/2009
8/6/2004 12/31/1969   1/1/1974 12/17/2004
Pressure Relief Device 7/25/2013
5/4/2012
1/15/2002
1/08/2007
12/31/1969        
Instrument 1/15/2019 3/17/1999
12/31/1969
2/6/2013
    11/13/73    
Hydrogen Generation Equipment 7/27/1999     10/23/2001      
Vehicle or Lift Truck   7/21/2011         2/8/2011
12/9/2010
Fuel Dispenser   8/2/2004
5/1/2007
6/11/2007
9/19/2007
  2/24/2006
1/22/2009
     
Fuel Cell Stack            

5/3/2004
12/9/2010
2/8/2011

Hydrogen Cooled Generator       12/31/1969
2/7/2009
     
Other (floor drain, lab
anaerobic chamber,
heated glassware,
test chamber,
gaseous hydrogen
composite cylinder,
delivery truck)
  11/14/1994
7/21/2011
7/27/1999
6/28/2010
8/21/2008
12/31/1969
3/22/2018
    6/10/2019
  • = No Ignition
  • = Explosion
  • = Fire