Severity
Near-Miss
Leak
No
Ignition
No

A safety research laboratory experienced two similar air-actuated ball valve failures in a 6-month period while performing hydrogen release experiments. The hydrogen release system contains a number of air-actuated ball valves which are sequenced by a Programmable Logic Controller (PLC) in order to obtain the desired release parameters. During an experimental release sequence, a PLC valve command failed to open the valve even though the PLC valve position confirm signal indicated the valve had opened. On further investigation, the valve actuator and valve stem were found to be moving correctly, but the valve was not opening. The system was depressurized and purged with nitrogen, and the valve was removed for inspection. Inspection required dismantling the valve, and in both incidents a sheared valve stem was found. The valve stem failures occurred after 8 to 14 months of continuous hydrogen operation at pressures of 800 to 850 bar (11,603 to 12,328 psi). The two failed hydrogen valves were identical and rated by the valve manufacturer for hydrogen service.

The cause of this incident has not been determined, but valve stem material incompatibility with hydrogen (causing a material weakening) is suspected, although it could also have been a design flaw. Review of the valve manufacturer's drawings showed the valve stem material to be 17-4 precipitation hardening stainless steel that has been reported in the literature (Attachment 1) as having a 90% reduction in fracture toughness in a hydrogen environment. No metallurgical analysis was done on the failed valve stems to confirm a material failure. The valves were repaired with new valve stems made from 316 stainless steel, placed back in service, and have operated satisfactorily for 18 months without failure.

Incident Date
Feb 06, 2008
Setting
Equipment
  • Piping/Fittings/Valves
  • Valve
Damage and Injuries
Probable Cause
Contributing Factors
When Incident Discovered
Lessons Learned

1. Ensure that equipment and materials exposed to hydrogen are compatible with a hydrogen environment (even hydrogen-service-rated equipment).

2. Equipment designs in a hydrogen environment that use the fracture toughness for 17-4 precipitation hardening stainless steel may want to consider a 90% derating in published values (see Attachment 1).

Additional discussion of materials selection for compressed gas storage vessels can be found in the Hydrogen Safety Best Practices Manual. Similar discussion of materials selection for cryogenic liquid storage vessels can be found in the Hydrogen Safety Best Practices Manual.

A web-based resource developed by Sandia National Laboratories to provide data on hydrogen embrittlement of various materials is available at Technical Reference for Hydrogen Compatibility of Materials.

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