| Case Name |
Fire of a vacuum residue leaked from an opening of pipe caused due to corrosion in the bottom recycling line at a vacuum distillation unit. |
| Pictograph |
|
| Date |
July 19, 1990 |
| Place |
Tokuyama, Yamaguchi, Japan |
| Location |
Refinery |
| Overview |
At a refinery under usual operation, an opening was formed in a recycling pipe for a vacuum residue in a vacuum distillation column, from which the vacuum residue leaked. A fire occurred. A mistake had been made on the location at which the piping material was changed from anticorrosive material to carbon steel. As the carbon steel piping that was not sufficiently corrosion resistant was used for a position at which the vacuum residue including a sulfur compound was treated, corrosion was generated. Leakage and a fire occurred. |
| Incident |
The discharge piping of a furnace recycle pump of a vacuum distillation unit was corroded by a sulfur compound contained in a residue under high-temperature conditions. An opening was formed, from which fuel oil leaked. The leaked vacuum residue ignited, and a fire occurred. |
| Processing |
Manufacture |
| Individual Process |
Distillation |
| Process Flow |
Fig2.Unit process flow
|
| Substance |
Vacuum residue |
| Type of Accident |
Leakage, fire |
| Sequence |
May, 1975. The plant was completed, and operation started.
October, 1989. The last turnaround shutdown maintenance before the accident was carried out. However, there is no record of the piping being checked.
About 12:00 on July 19th, 1990. A vacuum residue suddenly leaked from the discharge piping of the furnace recycle pump of the second vacuum distillation unit during usual operation, and a fire occurred. The plant was shut down immediately. A disaster countermeasures office was established. After reporting to the City Fire Headquarters, disaster-prevention activities started.
12:10. When the city fire engine arrived, the private fire brigade was placed under the command of the public fire brigade.
12:10. The first step of an emergency shutdown of the plant was finished.
12:23. Introduction of nitrogen gas started to the vacuum distillation unit.
12:48. The fire was confirmed to have been extinguished. |
| Cause |
The leakage cause was estimated that the furnace recycle piping was corroded and opened due to a sulfur compound including heavy residue oil under high temperature conditions. Moreover, many solid particles are included in the flowing liquid, so the erosion might occur.
The ignition sauce was estimated the high temperature of leaked oil itself. |
| Response |
After the fire was detected, an emergency shutdown was done immediately at the vacuum distillation unit. Private and public fire brigades sprayed water for cooling. |
| Countermeasures |
The material of the piping was changed to a corrosion-resistant material. In terms of design, there should be reeducation on the piping selection standard. |
| Knowledge Comment |
Individual decision on piping material must be made taking into account operating environment and conditions.
The positions at which piping material is changed must be determined from basic conditions such as presence of a corrosive medium, temperature, and pressure. Even if the change point does not match the piping shape, it should not be set at a convenient position such as a valve or a flange. High-grade material should be used up to a safer position even if it is more expensive. |
| Background |
It is regarded as an error in piping material selection or application of the piping selection standard. The piping was used for recycling from the bottom of the vacuum distillation column to the feed furnace, and joined with a fresh feed liquid, which was bottom oil of the topper, at just downstream the accident position. High-grade material of above 5Cr-0.5 Mo steel is necessary for recycling piping considering the temperature and fluid properties, while ordinary carbon steel can be used for the fresh feed. As the location of the accident was upstream from the confluence, material above 5Cr-0.5 Mo steel should have been used. However, the piping material was changed at the position of a check valve downstream flange, which was upstream from the location of the accident, and carbon steel had been used at the location of the accident. Apparently, there was an error in selection and design of material.
One of the causes is considered to be the fact that changes in piping material selection often set flanges as a boundary. It seems that the designer of this piping selected carbon steel to cut cost because there were no suitable flanges downstream from the check valve. Originally, a material above 5Cr-0.5 Mo steel should have been chosen as the piping material around the confluence at the fresh feed side. The location of the accident was the heaviest part of the crude oil distillation system. There were a lot of solids and corrosive mediums present, and the temperature was high.
Thus, material selection should have been done carefully. If corrosion had been detected in the inspection of piping beforehand, generation of the
opening could have been avoided. |
| Reason for Adding to DB |
Example of leakage and fire caused due to corrosion from incorrect application of piping material selection standards |
| Scenario |
| Primary Scenario
|
Poor Value Perception, Poor Safety Awareness, Insufficient Recognition of Risk, Misjudgment, Misjudgment of Situation, Misjudgment of Using Environment, Carelessness, Insufficient Precaution, Carelessness of Operator, Planning and Design, Poor Planning, Wrong Material Selection, Usage, Maintenance/Repair, Insufficient Inspection, Failure, Abrasion, Corrosion, Secondary Damage, External Damage, Leakage/Fire, Loss to Organization, Economic Loss, Manetary Damage 45 million yen
|
|
| Sources |
Ministry of Labor. The piping was added to periodic voluntary inspection item for chemistry facilities. Ministry of Labor. Industry and protection. Vol.6. No.36. p.2(1990).
Fire and Disaster Management Agency. Selection of unsuitable pipe material and abrasion of tube wall caused by erosion. Industry and protection. Vol.7. No.22. pp.2-3(1991).
High Pressure Gas Safety Inst. of Japan. Vacuum distillation unit. Leakage and fire of vacuum residue caused by pipe opening. Accident examples of Petroleum refinery and Petrochemical units. pp.30-33(1995)
|
| Physical Damage |
Piping around a recycling pump of a heating furnace and a pump burned. Peeling of heat insulation and paint. Peripheral electrical equipment and instrumentation were damaged by fire. |
| Financial Cost |
¥ 45 million (High Pressure Gas Safety Inst. of Japan) |
| 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)
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