Case Ditails

Scenario
Case Name Fire of a raw material feed pump caused due to incorrect operation during emergency shutdown procedure at a fuel oil direct desulfurization unit
Pictograph
Date October 10, 1991
Place Ichihara, Chiba, Japan
Location Refinery
Overview Because of a recycle gas compressor failure, an emergency shut-down was carried out at a fuel oil direct desulfurization unit. A feed pump stopped before a discharge valve of the pump was closed, so high-temperature stock oil flowed backward from the process to the pump, a mechanical seal was damaged, and a fire broke out. There were questions as to whether the shutdown instruction manual was sufficiently examined, or the check valve's malfunction was predictable or not.
Incident An emergency shutdown was conducted at a fuel oil direct desulfurization unit because of a malfunction of a recycle gas compressor of hydrogen, which was used for a reaction system. During shutdown operations, stock oil flowed backward to a feed pump, and part of the mechanical seal was damaged. Then, leaked stock oil spontaneously ignited. The condition of the pump at that time was 17 MPa, 310 °C.
Processing Manufacture
Individual Process Reaction
Chemical Reaction Hydro-desulfurization
Substance Fuel oil
Type of Accident Fire
Sequence 02:10 on October 10th, 1991; An alarm lamp of a recycle gas compressor lit, and an operator rushed to the site.
02:20; He found that the degree of vacuum had decreased at a steam turbine's condenser for driving the compressor.
02:23; An emergency shut down of the unit was decided.
02:25; All operators were gathered in the control room, and after confirming the work procedure, they started shutdown procedure with remote control.
02:35; When they went to the site, a fire was found at the part of a mechanical seal of a feed pump.
04:15; The fire around the pump was extinguished. Fire fighting for a fin-fan cooler continued.
08:55; The fire at the pump and the fin-fan cooler were extinguished completely.
Cause During shutdown operations, closing of a flow control valve at the upstream preheating furnace was delayed and done after stopping the pump. Then, stock oil in the process flowed backward. Furthermore, because of carbon adhesion, a check valve mounted at the pump discharge did not work properly, and the stock oil flowed backward as far as the pump. Then, the pump rotated reversely and a mechanical seal was exposed to a high-temperature. Therefore, the mechanical seal was damaged, the stock oil flowed ou, and l ignited. After that, the fire spread to a fin-fan cooler in the upper part of the pump, tubes of the cooler were damaged, and an inside liquid flowed out and ignited. In short, as the procedure was wrong and the check valve did not work properly, a fire occurred.
Response The company's fire fighters turned out. They put out the fire and sprayed water for cooling. Public fire fighters also turned out.
Countermeasures The pump discharge valve was changed into a remote control type.
Review of operation and instruction manuals for the whole unit at a shut-down.
Making a manual of periodic unit checks and replacement.
Installation of a leakage sensor.
The upper part of the pump was changed into a heat-proof type.
Improvement of patrols, paying attention to pumps.
Knowledge Comment If countermeasures against emergencies were not sufficiently studied, it might cause an accident.
Background The procedure of stopping the pump and closing the valve was reversed. This might have been caused due to human error or an operation instruction error. The check valve is mounted to prevent a backflow, but sometimes it fails. Moreover, in the case of fuel oil, the probability of leakage is high due to solids or sticky materials. An instruction manual for shutdown operations, which is based on a recognition that a leak occurs at a check valve, would be required.
Incidental Discussion There was no information about the recycle gas compressor's malfunction, which caused the shutdown, in any reports.
Reason for Adding to DB Example of fire caused due to a reverse flow through a check valve
Scenario
Primary Scenario Poor Value Perception, Poor Safety Awareness, Inadequate Risk Recognition, Carelessness, Insufficient Precaution, Inadequate Handling, Organizational Problems, Inflexible Management Structure, Insufficient Education/Training, Non-Regular Operation, Emergency Operation, Emergency Shutdown, Malfunction, Poor Hardware, Check Valve Leakage, Secondary Damage, External Damage, Leakage/Fire, Loss to Organization, Economic Loss, Manetary Damage 90 million yen
Sources Fire and Disaster Management Agency. Fire at mechanical seal of pump in fuel oil direct hydro-desulfurization unit. Accident cases of dangerous materials. 1991. pp.68-70
Aoki Yasuhiko, Fire at atmospheric distillation unit, Report from High Pressure Gas Safety Inst. of Japan No,36, pp.61-63 (1992)
National dangerous object safety association. Fire at heavy oil spouting from fuel oil direct desulfurization unit pump mechanical seal. Cases of accidents at 100 dangerous facilities. -No.2- pp.10-11(1994).
High Pressure Gas Safety Inst. of Japan. Fuel oil direct desulfurization unit. Leakage and fire caused by mechanical seal damage to raw material feed pump. Accident examples of Petroleum refinery and Petrochemical units. pp.54-56(1995).
Number of Deaths 0
Number of Injuries 0
Physical Damage At the No.10 fuel oil direct desulfurization unit, 200 square meters were destroyed by fire. A pump mechanical seal, a fin-fan cooler, connection piping etc, burned and were deformed.
Financial Cost ¥ 90 million (Fire and Disaster Management Agency)
Field Chemicals and Plants
Author WADA, Yuji (National Institute of Advanced Industrial Science and Technology)
TAMURA, Masamitsu (Center for Risk Management and Safety Sciences, Yokohama National University)
Scenario