Explosion from the Hydrogen Recycle Line T Are Finery
Localized corrosion of a FCCU (Fluid Catalytic Cracking Unit) feed Hydrotreater recycle hydrogen line by-pass around a hydrogen pre-heat exchanger led to an explosion and fire.The failed part of the line had been identified by inspection as a dead leg. After investigation it was found that the mechanism of corrosion was ammonium chloride under deposit corrosion. The source of chloride has not been traced, but hydrogen from the catalytic reformer was strongly suspected. Inadequate inspection of the dead leg was identified as the cause of this incident. There was damage to equipment, material loss and product loss.
Event Date
April 6, 1996
Record Quality Indicator
Region / Country
Event Initiating System
Classification of the Physical Effects
Nature of the Consequences
Causes
Cause Comments
Corrosion by ammonium chloride. Its source unclear, hydrogen suspected.
Facility Information
Application Type
Application
Specific Application Supply Chain Stage
Components Involved
recycle hydrogen line, pre-heat exchanger
Location Type
Location description
Industrial Area
Pre-event Summary
.
Currency
Lessons Learned
Lessons Learned
Inadequate inspection of the dead leg was identified as the cause of this incident. Localized corrosion mechanisms are difficult to detect with fixed point ultra-sound testing (UT), and dead leg corrosion can have several different corrosion mechanisms.
Event Nature
Emergency Action
Unknown
Detonation
No
Deflagration
No
High Pressure Explosion
No
High Voltage Explosion
No
Source Category
References
References
Extract from the ICHEME database "ICHEME consequences-explosion-details", available at (accessed May 2020):
https://www.icheme.org/knowledge/safety-centre/resources/accident-data/