Explosion of Several Hydrogen Bottles
Hydrogen gas cylinders exploded at the same time in three industrial locations, when the opening valve was opened. The overpressure generated by the explosion caused the walls of the hydrogen cylinder storage room to collapse, six workers were killed. The hydrogen cylinders used by the three companies were filled by the same company.The investigation found that a large amount of air was mixed with hydrogen in many of the delivered cylinders, the air accounting for 50% of the total volume. When the operator opened the cylinder valve, the friction between the air flow and the bottle valve generated static electricity, which directly detonated the cylinder. The company delivering the cylinders fills more than 1,000 cylinders in the same batch. These 20 MPa compressed hydrogen cylinders are filled from a hydrogen storage tank using two buffers tanks and two hydrogen compressors in parallel. According to the scientific article quoted in the references, the night before the accident, the company has experienced a reduction of the power supply. Answering to this, the operator ordered to close both the two valves delivering hydrogen to the compressors, after confirming that the compressors had stopped working. When the hydrogen compressor restarted, one of the valves was open, while the other was still close. This caused the development of vacuum in front of one of the hydrogen compressor, which continuously increased with time. After the pressure difference reached a certain level, the explosion-proof film in the buffer tank cracked and a large amount of air was sucked by the compressor and pumped into the hydrogen cylinders, mixed with hydrogen. A contributing cause was the rain of the night before, which dampened the explosion-proof membrane in the buffer tank.
Event Date
July 23, 2004
Record Quality Indicator
Region / Country
Event Initiating System
Classification of the Physical Effects
Nature of the Consequences
Causes
Cause Comments
The root cause dates back to the moment when the hydrogen cylinders were filled at the gas delivery company. The incident is related in first instance to an operative mistake, but additional environmental and technical causes contributed to it. Moreover, it is evident that that specific accidental scenario was not considered in during the designing phase.
Facility Information
Application Type
Application
Specific Application Supply Chain Stage
Components Involved
Quartz manufacturing, standard 20 MPa hydrogen bottles, refillable
Storage/Process Medium
Actual Pressure
20
Design Pressure
20
Location Type
Location description
Industrial Area
Operational Condition
Pre-event Summary
The companies where the incidents occurred were producing quartz rods. To reach the melting point of quartz, tungsten crucibles are used for melting. Since tungsten is easily oxidized at high temperatures, a nitrogen protective atmosphere is used, containing small amount of hydrogen as reducing gas.The hydrogen gas bottles which caused the incidents had been delivered by the dame company, where air was accidentally added to hydrogen during the filling of those specific bottles.
Currency
Lessons Learned
Lessons Learned
The investigation findings provide the following recommendations:(a) Strictly control the inspection before filling the hydrogen cylinder. The gas in the cylinder is randomly sampled for detection to determine the type of gas.(b) Enterprises should not combine two lines into one pipeline. An additional hydrogen filling line should be installed and each line should be filled separately. (c) Management change is required (d) Improve the maintenance and repair of equipment, to guarantee at every time the integrity of the equipment.(e) Unqualified products shall not be used. Specialised personnel should be in charge of repairing and maintenance of the equipment.(f) Operators should keep records of shifts and strictly implement the process rules.(g) Units using pressure vessels should be equipped with reinforced concrete explosion-proof walls and lightweight ceilings. In this accident, the use of a reinforced concrete ceiling in some locations caused the development of such an overpressure that the explosion-proof wall collapsed and caused secondary injuries.
Event Nature
Emergency Action
Unknown
Emergency Evaluation
Release Type
Release Substance
Hydrogen Release Concentration (%)
50.00
Ignition Source
Detonation
No
Deflagration
No
High Pressure Explosion
No
High Voltage Explosion
No
Source Category
References