| Case Name |
Leakage and fire of heavy gas oil from an opening in vent piping of a reflux pump at a distillation column |
| Pictograph |
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| Date |
October 30, 1978 |
| Place |
Kawasaki, Kanagawa, Japan |
| Location |
Refinery |
| Overview |
A fire occurred near the screw of vent piping of a reflux pump at a distillation column of the ADU. The screw portion broke due to corrosion, and high-temperature heavy gas oil leaked, resulting in a fire. Fire fighting activities began at once after the fire occurred, and the fire was controlled. The valve was closed and the fire was extinguished afterwards. It was speculated that a piping breakage occurred because the following four factors were piled up.
1. Reduced thickness near the screw caused by corrosion.
2. Piping material selection error.
3. Excessive load due to insufficient support.
4. Cyclic vibration stress during operating. As a result, high-temperature heavy gas oil leaked and ignited. The standard for a small-diameter branch pipe like this piping should be regulated by a design standard. |
| Incident |
The screw portion of a vent nozzle of a reflux pump at a distillation column of an atmospheric distillation unit (ADU) broke due to corrosion. High-temperature heavy gas oil leaked and burned. |
| Processing |
Manufacture |
| Individual Process |
Distillation |
| Substance |
Heavy gas oil |
| Type of Accident |
Leakage, fire |
| Sequence |
Turnaround shutdown maintenance was carried out for the unit from September 26th to October 27th in 1978.
On October 28th: The unit started.
About 09:34, on October 30th: The unit entered usual operation. A cavitation problem in a reflux pump of the distillation column occurred, and an alarm operated in the control room.
About 09:35: The operator who patrolled the unit found foggy oil spouting from the pump, and emergency shutdown operation was conducted.
About 09:38. Spouting oil ignited, and there was a fire. It was announced to the public fire station by an emergency call, and fire extinguishing activities started.
About 09:45. As the fire had died down, the valve in the vicinity of the pump was closed. As a result, the fire was extinguished completely. |
| Cause |
The vent piping (nominal 3/4 inch) had been used for 11 years. Therefore, its thickness was reduced due to corrosion. In addition, the piping material was not a thick wall pipe as specified originally, but was normal thickness. Moreover, the entire load was put on the screw portion because there was not enough support for this piping. Therefore, cyclic vibration stress was placed during operation, and cracks were caused near the screw. It is presumed that high-temperature heavy gas oil spouted from there. The temperature of the leaked oil seems to have caused ignition after mixing with air because the oil temperature was higher than the ignition point. Moreover, the vent hole of the pump usually has a nominal diameter of 1/2 inch. Perhaps, 1/2-inch piping was screwed into the vent hole and was connected there with 3/4-inch piping through a 1/2-3/4 inch reducer. |
| Response |
An emergency shutdown. Fire extinguishing activities. Valves were closed. |
| Countermeasures |
The vent piping was taken out from the process piping. The vent hole of the pump casing was sealed with a plug. A standard for design, installation, and inspection of small piping were reviewed. |
| Knowledge Comment |
The peripheral part of the system is not considered to be so important, and inspection and management are apt to be inadequate. This might be a cause of the accident. |
| Background |
The vent piping was hardly maintained during operation management because it had not been considered to be so important. The wall thickness of the piping, the support of the piping, and the seal welding of the screw part, etc. should be provided according to the design standard. It is uncertain whether the design standard was established, or if it was standardized in the design of this plant at that time. |
| Sequel |
All similar piping was checked. |
| Incidental Discussion |
For steel piping with resisting pressure of 10 kg/cm2 level, schedule 40 for normal piping and schedule 30 for large piping are used. For small pipes of 1and 1/2 inch or less or 2 inches, it is safer to have a thick wall pipe of schedule 80, considering strength. A vent of a pump usually has a 1/2-inch plug hole. When 3/4-inch piping is connected, it is common sense to support it sufficiently. Why was the support insufficient?
Schedules 30, 40, and 80 are United States standards that decide the thickness of piping, and are generally used in the refinery and petrochemical field. The larger the figure, the thicker wall it has. |
| Reason for Adding to DB |
Example of leakage and fire caused due to a break of small piping from corrosion |
| Scenario |
| Primary Scenario
|
Poor Value Perception, Poor Safety Awareness, Insufficient Safety Measure, Organizational Problems, Poor Management, Slackness of Management, Planning and Design, Poor Planning, Poor Design, Usage, Maintenance/Repair, No Inspection in 11 Years, Bad Event, Mechanical Event, Vibration, Failure, Abrasion, Corrosion, Secondary Damage, External Damage, Leakage/Fire, Loss to Organization, Economic Loss
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| Sources |
Fire and Disaster Management Agency, Heavy light oil spouting from topping plant pump attachment piping, Exampled of fire accidents at hazardous materials manufacturers, 1978 pp.46-47.
Kawasaki City, Fire fighting station, Yoshida Sueo, Case of fire accident with the small diameter piping breakage, 27th national fire-fighting engineer conference paper, (1979).
High Pressure Gas Safety Inst. of Japan, The topping plant, Fire accident caused by vent line breakage at side reflux pump, Accident examples in complexes, pp.149-151(1991).
Hazardous materials safety research association of the Kawasaki City, Heavy gas oil spouting from a topping plant pump attachment piping and fire, Examples of accidents at hazardous facilities with FTA, pp.20-22(1997).
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| Physical Damage |
A pump, a motor, piping on a pipe rack, electrical instrumentation within a radius of about 10 m burned. |
| Financial Cost |
¥ 295,000. (Fire and Disaster Management Agency). |
| Field |
Chemicals and Plants
|
| Author |
OGAWA, Terushige (Graduate School of Environment and Information Sciences, Yokohama National University)
TAMURA, Masamitsu (Center for Risk Management and Safety Sciences, Yokohama National University)
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