Release of Hydrogen from a Storage Tank
A leak occurred at a of a liquid withdrawal valve of a liquid hydrogen storage tank. The hydrogen escaped at the flange between the valve body and the upper part of the valve (flange with tongue and groove). 40 kg of hydrogen were lost.The accidental release was due to the use of bolts different from those prescribed. By using the wrong ones (old bolts), the bolt material was able to flow at the specified tighteningtorque. This meant that there was insufficient tightening torque, which led to a leak.
Event Date
September 9, 2004
Record Quality Indicator
Region / Country
Event Initiating System
Classification of the Physical Effects
Nature of the Consequences
Causes
Cause Comments
The immediate/direct cause was the erroneous use of bolts on a flange. The root cause is related to a human error, to lack of knowledge and to the absence of clear procedures.
Facility Information
Application Type
Specific Application Supply Chain Stage
Components Involved
flange, bolts
Storage/Process Medium
Location Type
Location description
Unknown
Operational Condition
Pre-event Summary
The source does not mention when the wrong installation of the old bolts, and how much tine intercurred between that moment and the start of the release.
Lessons Learned
Lessons Learned
LESSON LEARNEDAlthough the source does not provide details regarding the moment when the wrong bolts were installed, it is plausible to conclude from the available evidence that this happed during a repair or replacement phase. If correct, the event is a typical example of "things gone wrong during maintenance". The human error is only a component of the root cause, the other being a shortcoming of measures able to prevent the human error. CORRECTIVE MEASURE1. Replace bolts, nuts and spring washers according to manufacturer's instructions.2. Check the bolts after 12 hours and re-tighten if necessary.3. Weekly check of the tightening torques for 4 weeks, then every six months.4. If bolts need to be tightened during the above checks, replacement of the seal should be planned.5. Plant-specific training for staff. The number must be determined so that trained people are continuously available.6. Setting up a camera system that provides insight into the areas of the valves and the filter skid.7. Renewed awareness training for the local fire department.8. Minimizing the time by which a competent person from a specialist company is on site.9. Creation of work instructions for the fitters, which stipulate that when using refurbishment kits, the kit is checked and only the new components are used.
Event Nature
Emergency Action
Closure of the adjacent streetClosure of airspace
Release Type
Release Substance
Hydrogen Release Concentration (%)
100.00
Release Amount (kg)
40.00
Detonation
No
Deflagration
No
High Pressure Explosion
No
High Voltage Explosion
No
Source Category
References
References
Event from Germal database ZEMA
https://www.infosis.uba.de/index.php/en/site/13947/zema/index.html
https://www.infosis.uba.de/index.php/en/binaries/asset/zema_ereignis/33…
(accessed December 2023)