Explosion at Oil Storage Tank in a Refinery
This incident occurred unit at a demonstration of a new technology for the catalytic cracking of vacuum residual oil. An oil storage tank failed due to high pressure. The overpressure in the tank was the result of a backflow of compressed hydrogen gas. When operators reduced the discharge pressure of the feedstock feed pump, high-pressure hydrogen gas in the reaction system flowed back into a feedstock surge drum and then into the cooling oil receiver. The pressure of the cooling oil receiver increased and the oil blew out and the feedstock surge drum ruptured and a fire occurred. Detailed incident evolution: The shutdown of the unit was performed to replace substituted with heavy gas oil piping in the morning.13:00; a shift leader ordered two operators to stop the feedstock feed pump.13:08; one of the operators checked the discharge pressure, which was 19 MPa, and directed the other operator to open the circulation line valve to the feedstock surge drum.After they informed the control room, they started the operation of opening the valve on the circulation line.13:15; as the discharge pressure fell to 1.65 MPa, they began to close the valve at the discharge side of the pump.13:16; when the spindle stroke of the discharge valve was 50%, they found oil blowing out from the manhole of the cooling oil receiver.13:17; they informed to the control room of the oil blowout. When they ran to the site to check what had happened, the feedstock surge drum burned out.````
Event Date
March 18, 1988
Record Quality Indicator
Region / Country
Event Initiating System
Classification of the Physical Effects
Nature of the Consequences
Cause Comments
The immediate cause of the incident was backflow of compressed hydrogen gas to the oil storage tank, which ruptured due to overpressure. The backflow itself was either caused (i) because of the outlet valve on the pump was not completely closed or (ii) because a combination of a pressure decrease at the outlet of the pump and the non-return value failure as a result of excessive opening of the valve. According to the analysis of the source, the root cause was a combination of:(1) The procedure was wrong (the valve operations should have been inverted) (2) the overall manual character of the operation increases the chance to mistakes,(3) possibly lack of specific knowledge could be as well a contributing cause.
Facility Information
Application Type
Application
Specific Application Supply Chain Stage
Components Involved
oil storage tank, oil and hydrogen line, non-return valve
Storage/Process Medium
Actual Pressure
19
Location Type
Location description
Industrial Area
Operational Condition
Pre-event Summary
The unit was shutdown, to allow for piping replacement.
Lessons Learned
Lessons Learned
TECHNICAL CORRECTIVE MEASURES A restriction orifice shall be installed in the circulation line piping.A check valve shall be replaced.The back-flow monitoring system shall be changed. The emergency shutdown valve should be reviewed.Operation procedures have to be revised. LESSON LEARNEDCheck valves sometimes do not work well when it is necessary. An operation manual on actions to be taken assuming the check valve does not work is needed.Basic knolwedge on gas dynamics isrequires: for example, it should not be forgotten that fluid flows from high-pressure to low-pressure.
Event Nature
Emergency Action
The plant was put in mergency shutdown.
Detonation
No
Deflagration
No
High Pressure Explosion
No
High Voltage Explosion
No
Source Category
References
References
Originally in RISCAD, now in JST Failure Knowledge Database:
https://www.shippai.org/fkd/en/cfen/CC1000135.html