Hydrocarbons and Hydrogen Fire in a Refinery
At around 9:15 a.m., during a routine inspection, a flame was observed at the bottom flange of a reactor in a refinery. A few moments later, sensors near the leak detected a rise in temperature.The facility was shut down in accordance with emergency procedures. The sprinkler system was triggered to protect the equipment. The rapid decompression of the plant towards the safety flare reduced the leak flow rapidly. At 10:12 am, the fire was extinguished. 15,7 t of hydrocarbons were sent to the flare for burning on the day of the accident.No injuries were reported on site and no inconvenience was felt outside. The leak involved naphtha, hydrocarbon gases and hydrogen. Due to the thermal effects of the ignited leak, cables, instruments and insulation materials were damaged.[ARIA event 58577]
Event Date
September 18, 2021
Record Quality Indicator
Region / Country
Event Initiating System
Classification of the Physical Effects
Nature of the Consequences
Causes
Cause Comments
The root cause lies in the decision of the operator to replace a defective component with another one with different operative characteristics. Also, the cause of the defect were not investigated. Initiating cause for the leak and the subsequent fire was the material incompatibility between flange and flange rods. DETAILS OF THE CAUSES:The leak was due to a loss of tightness at a flange, caused by an incompatibility of materials with operating conditions. Six months earlier, following a first leak on a flange seal, the flange rods had been replaced. As the specified replacement part was not available in stock, the supervisor and the modification coordinator validated the installation of rods with a higher chromium alloy because this metallurgy is compatible with the temperatures, pressures and substances of the process. However, they did not consider in the choice of the part, the difference of expansion coefficient between the flange and the rods. Moreover, during the modification, they did not open the flange and therefore did not notice that the lower metal ring seal was incompatible with the flange.
Facility Information
Application Type
Application
Specific Application Supply Chain Stage
Components Involved
reactor, flanges, bolts
Storage/Process Medium
Location Type
Location description
Industrial Area
Operational Condition
Pre-event Summary
Six months earlier, a first leak had already occurred on the same flange seal. The flange rods were replaced. However, because .the specified replacement part was not available in stock, rods with a higher chromium alloy were mounted.
Consequences
Number of Injured Persons
1
Currency
Lessons Learned
Lessons Learned
Although the ARIA report (see references) does not mention any lesson learned, the findings suggest the following corrective actions: (1) To improve procedure repair and maintenance procedures and guidelines, and the awareness/knowledge of them among the personnel, (2) To careful asses of materials compatibility when taking a decision deviating from the procedures(3) To secure the supply chain of spare materials
Event Nature
Emergency Action
Following the identification of the fire, the facility was shut down in accordance with emergency procedures. The sprinkler system was triggered to protect the equipment. The rapid decompression of the plant towards the safety flare allowed the release to be reduced rapidly. At 10:12 am, the fire was extinguished.
Release Type
Release Substance
Ignition Source
Detonation
No
Deflagration
No
High Pressure Explosion
No
High Voltage Explosion
No
Source Category
References