Explosion in an Ammonia Production Plant
The event occurred during welding works which ignited accidentally released hydrogen. The plant had been partially shut down for repairing works to a pipe affected by internal cracks. The repairing schedule foresaw grinding and external welding of the defective parts. Despite the purging phase to guarantee drying of the pipe section, further water leakage was hindering the work, so that additional measures was taken, also to avoid too much gas waste. The hydrogen entered the system by a leaking valve, undetected at the time of job preparation and during subsequent checks. A welder was slightly injured. There was no damage to the plant.
Event Date
August 3, 1987
Record Quality Indicator
Region / Country
Event Initiating System
Classification of the Physical Effects
Nature of the Consequences
Cause Comments
The direct cause of the incident was the failure to adequately isolate hydrogen from the section of the system which was undergoing repairing works.The root cause was the inadequate management system
Facility Information
Application Type
Application
Specific Application Supply Chain Stage
Components Involved
hydrogen pipe
Storage/Process Medium
Location Type
Location description
Industrial Area
Pre-event Summary
The plant had been partially shut down for repairing. The preparatory actions were not able to achieve the dry conditions necessary for the grinding and welding work. Additional measures were adopted, affecting also the sections still containing gases.
Lessons Learned
Lessons Learned
According to Nightingale (1989), the very complex mechanisms that led to this incident had not been foreseen. Even after its occurrence, the explanation was only found after two full days of intensive investigation. Among other findings related to the failure to ensure hydrogen tightness, the investigation explained why the gas measurements performed at the end of the purging could not detect hydrogen: the nitrogen flow was enough to reduce hydrogen concentration below the detection threshold of the instrument. As corrective measure, the instructions for the isolations of the process during maintenance were improved, adopting positive (slip plates) isolations for hazardous materials.
Event Nature
Emergency Action
Unknown
Release Type
Release Substance
Hydrogen Release Concentration (%)
100.00
Ignition Source
Detonation
No
Deflagration
No
High Pressure Explosion
No
High Voltage Explosion
No
Source Category
References
References
Source lost