Explosion at Outlet Piping of a Hydrodesulfurization Reactor
The incident affected at an indirect oil desulfurization unit, and originated at a piping at the outlet of a heat exchanger. The exchanger was located in the furthermost downstream of the reactor. The dead-end cap of the piping failed due to corrosion and opened, releasing high-pressure hydrogen which leaked, ignited and exploded. Due to the explosion, the heat exchanger was damages and oil leaked out contributing to spread the damage. Approximately 1200 kg of hydrogen and 30000 l of oil were burned. No injuries.
Event Date
March 6, 1989
Record Quality Indicator
Region / Country
Event Initiating System
Classification of the Physical Effects
Nature of the Consequences
Cause Comments
The IMMEDIATE CAUSE was corrosion at the dead-end of a piping, decreasing its thickness. The corrosion was caused by corrosive substances such as ammonium hydroxide and chlorine which was included in the injection water. In addition, a dummy support had been welded to the cap, so that thermal stress might could have also contributed to the loss of containment. The ROOT CAUSE is a not optimal risk assessment and management of changes. Four years before the incident, a heat exchanger had been added and a rearrangement of heat exchangers at the outlet of the reactor was carried out to rationalize energy recovery. This caused an increase of the concentration of corrosive substances at the heat exchanger outlet. Despite that fact that the plan was controlling the concentration of corrosive substances, no one believed the wall thickness at the piping dead-end part would be reduced by corrosion. Therefore it was not so the part of the plan for wall thickness measurements.
Facility Information
Application Type
Application
Specific Application Supply Chain Stage
Components Involved
dead-end piping, heat exchanger
Storage/Process Medium
Location Type
Location description
Industrial Area
Operational Condition
Pre-event Summary
Four years before the incident, a heat exchanger had been added and a rearrangement of heat exchangers at the outlet of the reactor was carried out to rationalize energy recovery.
Lessons Learned
Lessons Learned
LESSON LEARNEDA. The possibility of a failure due to corrosion had clearly not considered when performing a risk assessment of the modifications executed on the facility. B. Plants with same processes are not necessarily characterized by exactly the same hazards and risks. A full understanding of each plans is crucial to guarantee its safety.C. Specifically regarding dead-end piping, they are the cause of several problems, because concentrations of corrosive substances increases locally quicker than in part characterized by high flows of liquid or gases. Therefore, specific safety provisions are required for these areas.CORRECTIVE MEASURES1. The management system of operations and facilities was strengthened to be able to monitor abnormal phenomena such as local corrosion and to respond properly.2. The safety review system for modifying new facilities was improved. 3. The risk assessment of existing facilities was re-evaluated.4. All refineries with the same kind of desulfurization unit were required to inspect dead-end piping in the areas similar to those where the incident occurred. 5. They were also recommended to perform a safety review of thir operational and facilities management system.
Event Nature
Emergency Action
An operator shut down the plant immediately after the accident. The fire brigade arrived and sprayed water to cool peripheral equipment. They also used foam fire extinguishers to extinguish the fire.
Release Substance
Hydrogen Release Concentration (%)
1200.00
Detonation
No
Deflagration
No
High Pressure Explosion
No
High Voltage Explosion
No
Source Category
References
References
JST failures database:
https://www.shippai.org/fkd/en/cfen/CC1000003.html
(accessed Dec 2023)
JST failures database:
https://www.shippai.org/fkd/en/cfen/CC1000003.html
(accessed Dec 2023)