Case Ditails

Scenario
Case Name Fire of naphtha caused due to an operator who went another site to do other work leaving a drain valve opened at an ethylene plant
Pictograph
Date December 15, 1992
Place Kashima, Ibaragi, Japan
Location Chemical factory
Overview The drain valve was opened slightly to check the residue during preparatory work for decoking at the cracking furnace of an ethylene manufacturing plant. The operator left the site with the valve open, because only water flowed out. Residual naphtha leaked afterwards, and a fire occurred. Background of work is as follows.
1. The residue inside was neglected.
2. An inadequate decoking operation manual (The procedure was not described clearly in the manual, and the work was carried out inadequately).
3. The inadequate mounting position of the control valve (A2) in ethane piping. (The structure in which liquid easily accumulate).
4. Operation was considered easy work as it was usually done.
Incident A fire occurred during preparing for decoking work at a cracking furnace of an ethylene plant. The drain valve was opened slightly to check a residual in ethane piping connected to the cracking furnace. At that time, only water flowed out. The operator then left the site to make a report. Soon, naphtha that had remained inside leaked out, being scattered in a high-temperature part of the furnace, and ignited. It is usual in Japan that there are multiple units in a cracking furnace and that naphtha bought from the outside and ethane generated as a byproduct are used as raw materials.
Decoking is work to burn and remove carbon adhering to an internal wall in a cracking tube with a steam-air mixture.
Processing Manufacture
Individual Process Maintenance
Substance Naphtha
Type of Accident Leakage, fire
Sequence 10:50 on December 14th, 1992. In preparation for decoking, ethane feed to the furnace stopped.
10:00 on December 15th. Naphtha feed stopped, and steam purging started.
15:00. A blind plate was inserted into the naphtha piping.
16:00. There was a change of shifts. Unfinished purging work for ethane piping was reported to the next shift. To confirm purging of ethane piping, the next shift was directed to check the drain.
About 16:30. Steam purging of ethane piping started.
16:48. By opening the drain valve in 1/4 rotation, purging was confirmed. Purging was judged good because only drain water flowed out. The valve was left open, and the operator went to make a status report.
16:50. A fire occurred. The main steam valve was closed immediately.
16:52. An emergency shutdown of the furnace and adjacent furnaces was carried out. The fire at the drain valve was confirmed.
17:50. The upstream valve in the ethane piping was closed by an operator with fireproof gear.
18:07. The fire was confirmed to have been extinguished.
Cause The fire was caused by human error. An operator did the drain checking without expecting naphtha to be drained, and at first only water was drained as expected. So, the operator thought checking work had been completed and left the site with a valve still open. After that, residual naphtha leaked, made contact with a high-temperature flange, and ignited. The principle is that an operator must not leave a valve open until all the drain has flowed out.
Response An emergency shutdown was carried out. Office disaster prevention headquarters was set up, and the fire brigade stood by. The upstream valve of the ethane piping was closed by an operator wearing fireproof gear, and the leakage stopped.
Countermeasures 1. Safety education.
2. Improving an operation manual.
3. Relocating the ethane piping control valve A2.
4. Executing inspection and repairs based on inspection results.
Knowledge Comment Several accidents were considered to have been caused due to operators leaving a work place before the operation finished. At the drain work where water and oil co-exist, it is natural that first water comes out from the drain valve, and oil flows after the water. The operator must keep paying attention until all the process finishes.
Background The main cause was the assumption that a drain containing residual naphtha would not flow out. The following are factors related to the accident.
1. Neglect of a residue inside. The operator left the site without confirmation stopping of the drain.
2. Errors in the manual of decoking operation procedure. The procedure was not clear. Operators did a different way of operation.
3. The mounting position of the adjusting valve in ethane piping was inadequate. (The structure in which liquid easily accumulated)
1 and 2 above seem to be the result of lack of concentration of operators, and the manager also has a responsibility.
Reason for Adding to DB Example of fire caused due to inadequate operation of a drain valve
Scenario
Primary Scenario Carelessness, Insufficient Precaution, Carelessness of Operator, Organizational Problems, Inflexible Management Structure, Insufficient Education/Training, Organizational Problems, Poor Management, Poor Operation Management, Malicious Act, Rule Violation, Safety Rule Violation, Secondary Damage, External Damage, Fire, Loss to Organization, Economic Loss, Direct Monetary Damage 40 million yen
Sources High Pressure Gas Safety Inst. of Japan. High-pressure gas protection overview. pp.195-197, 204-205(1993).
Dangerous object safety research association of Kawasaki City. Examples of accidents. Examples of accidents at dangerous facilities with FTA. pp.29-31(1997).
Fire and Disaster Management Agency. Major examples of accidents. Second ethylene plant cracking furnace (2F-203) fire. Accident examples of dangerous materials. pp.33, 50-53.
Physical Damage Burn-out of valves, piping, structures, heat insulation materials, paint, instrumentation devices, cables, and electric cables. A mixture of naphtha and water burned.
Financial Cost ¥ 40 million (Accident examples of dangerous materials)
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)
Scenario