Release of a Pressure Release Valve
A hydrogen safety sensor went into alarm at a hydrogen demonstration facility. The early morning temperature was near freezing and there was a trace of precipitation on exposed surfaces. Upon further inspection following the sensor alarm, a 3,500 psig (approximately 24 MPa) stationary storage vent was found to be releasing hydrogen through the PRD vent stack (PRD = Pressure Relief Device). The alarming sensor was at an adjacent building but responded to hydrogen 20 yards (18 m) downwind from the vent location. The vent release location is 10 feet (3 m) above ground level. No ignition was detected. [Source: Burgess et al., Technical Report NREL/TP-5400-67381]
Event Date
November 1, 2014
Record Quality Indicator
Region / Country
Event Initiating System
Classification of the Physical Effects
Nature of the Consequences
Causes
Cause Comments
Review of pressure data did not show a pressure above the PRD set point. Freezing temperatures and moisture are suspected as contributing factors to spurious opening of the valve. Once the valve popped open, the cold temperatures of the escaping gas could have caused the valve to freeze in the open position.
Facility Information
Application Type
Application
Specific Application Supply Chain Stage
Components Involved
PRD, vent stack
Storage/Process Medium
Location Type
Location description
Inhabited Area
Operational Condition
Pre-event Summary
The early morning temperature was near freezing and there was a trace of precipitation on exposed surfaces.
Currency
Lessons Learned
Lessons Learned
Following the investigation, the following CORRECTIVE ACTIONS were proposed: (1) Consider the removal of PRDs from stationary storage where appropriate. the quantitative risk associated with a PRD failure has been compared against the risk of not having a PRD in the case of stationary hydrogen storage. It has been argued that the overall risk is lower with no PRD on the stationary storage. (2) PRD predictive maintenance program. As part of the corrective action surrounding this PRD failure, the R&D facility operator initiated a pilot program to test and recertify compressed gas PRDs across the lab.
Event Nature
Emergency Action
Unknown
Release Type
Release Substance
Hydrogen Release Concentration (%)
100.00
Detonation
No
Deflagration
No
High Pressure Explosion
No
High Voltage Explosion
No
Source Category
References
References