| Case Name |
Fire of leaked oil from a heat exchanger caused due to slow action of an emergency cut-off valve at a fluidized catalytic cracking unit |
| Pictograph |
|
| Date |
January 17, 1998 |
| Place |
Kawasaki, Kanagawa, Japan |
| Location |
Refinery |
| Overview |
On January 17th, 1998. An instrument air failure of a fluidized catalytic cracker (FCC) unit at a refinery occurred, and an emergency shutdown procedure was performed by the emergency shutdown (ESD) system. The internal pressure of the feedstock preheating system rose abnormally, oil leaked from the flange, made contact with the hot wall of the heat exchanger, and ignited. The cause of the internal pressure rise was that the emergency valve for the return flow line of the pump could not function quickly because of a viscosity rise of feedstock caused by a temperature lowering. The cause of the instrument air failure was a problem with the solenoid valve of the dehumidification system for the instrument air. Inadequate management of the facility seems to have been the true cause. |
| Incident |
An instrument air failure occurred at a fluidized catalytic cracker (FCC) unit in a refinery. The emergency shutdown (ESD) system of the feedstock-preheating system of FCC operated. Desulfurized vacuum gas oil leaked from the flange of the feedstock supply system heat exchanger (E-3104), and ignited. The heat insulation cover of the heat exchanger and about 50 square meters of the second floor were destroyed by fire. Refer to Fig2.
A problem with an automatic switching valve of a dehumidifier for instrument air was the cause of the instrument air failure. Instrument air must be dehumidified to prevent problems with condensed water. |
| Processing |
Manufacture |
| Individual Process |
Charge and feed |
| Process Flow |
Fig3.Unit process flow
|
| Chemical Reaction |
Other |
| Substance |
Vacuum gas oil |
| Type of Accident |
Leakage, fire |
| Sequence |
On October 17th, 1998, 16:02. Instrument air stopped by a problem with the solenoid valve of the dehumidification unit for instrument air of FCC, and the ESD system operated.
16:03-04. An operator found oil leakage from E-3104 heat exchanger during patrol. Simultaneously, it was noticed that smoke rose from the heat exchanger near E-3103. At that time, flames had already appeared around the E-3103 heat exchanger flange.
16:04-09. Fire extinguishing activities by manufacturing group members were carried out.
16:09. The fire was confirmed to have been extinguished. |
| Cause |
Main cause: Delayed operation of the pressure relief valve (FICV-3106 in Fig3) due to viscosity rise of the flowing liquid.
The ignition source was a hot surface. |
| Response |
A fire was extinguished and a flow of feedstock stopped. |
| Countermeasures |
The heating steam trace must be enhanced to maintain an adequate temperature.
The orifice diameter of the feedstock return line must be widened to prevent a pressure increase.
Safety management must be improved. (The refinery had three accidents at FCC unit in these three years.) |
| Knowledge Comment |
The leakage of flammable material near a high-temperature device immediately leads to the accident. Therefore, sufficient consideration is necessary to prevent an abnormal increase of the inside pressure. |
| Background |
The reason why the viscosity of vacuum gas oil was abnormally high is that the temperature of the feedstock lowered. The temperature of the feedstock was abnormally low because ambient temperature was low and the heat insulation of the piping was insufficient. It is considered that functioning of the pressure relief valve was delayed by the oil viscosity. Therefore, heating facilities such as a steam trace was needed to maintain an adequate temperature even in winter. Management including design might have been insufficient. The response time of an emergency valve must be taken into account.
A little delay in the emergency valve operation may cause a trouble. Therefore, response time of some kind of emergency valves has to be studied by process engineers and instrument engineers at the design stage. |
| Incidental Discussion |
The response time of some emergency valves must be short. It is important that process designers and instrumentation designers understand this. |
| Reason for Adding to DB |
Example of leakage and fire caused due to duplication of inadequate management of facilities |
| Scenario |
| Primary Scenario
|
Insufficient Analysis or Research, Insufficient Practice, Lack of Imagination, Poor Value Perception, Poor Safety Awareness, Inseufficient safety measure, Planning and Design, Poor Planning, Poor Design, Usage, Maintenance/Repair, Wrong heat insulation, Failure, Large-Scale Damage, Leakage, Secondary Damage, External Damage, Fire
|
|
| Sources |
High Pressure Gas Safety Inst. of Japan. High-pressure gas protection overview. p.146(2000).
Kawasaki City Fire fighting station. Prevention division. Peace section. Fire at heat exchanger of feed stock preheating system. Material of the Kawasaki City complex safety countermeasures committee. (1998)
Fire and Disaster Management Agency. Fluidized catalytic cracker. Feed stock preheating system heat exchanger fire. Accident cases of dangerous materials. pp.58-60.
|
| Physical Damage |
About 1.8 L of vacuum gas oil was lost by fire. A heat insulation cover of a heat exchanger and about 50 square meters of the second floor burned. |
| Financial Cost |
¥ 2 million. (Material of the Kawasaki City complex safety countermeasures committee) |
| Multimedia Files |
Fig2.Sketch of the accdent site
|
| Field |
Chemicals and Plants
|
| Author |
DOBASHI, Ritsu (School of Engineering, The University of Tokyo)
TAMURA, Masamitsu (Center for Risk Management and Safety Sciences, Yokohama National University)
|
