August 25 (Xinhua) The Liaoning Provincial Emergency Management Department released the investigation report on the "1·15" major explosion and fire accident of Panjin Haoye Chemical Co., Ltd. on the 25th. The accident investigation team determined that this was a major production safety accident.

 At around 13:25 on January 15 this year, Panjin Haoye Chemical Co., Ltd. had an explosion and fire accident during the pressure sealing operation of the inlet pipe of the washing tank of the alkylation unit, resulting in 13 deaths, 35 injuries, and direct economic losses of approximately 87.99 million yuan.

The investigation report stated that after the accident, on-site inspection, expert technical analysis and public security investigation ruled out the possibility of the accident caused by factors such as man-made sabotage and natural disasters. After comprehensive analysis by the expert group, it was determined that the ignition source causing the explosion was: One is the connection energy of the intercom when talking, and the other is the high-temperature hot surface of the exhaust pipe of the crane at the work site.

The investigation found that the four walkie-talkies used for operation command are non-explosion-proof walkie-talkies. The minimum operating voltage is 4.5V. The passing current is estimated as a lower value of 100mA. If the on-time lasts for 0.1s, the spark energy is E=UIt=45mJ.

 1. How the accident occurred

On January 11, 2023, Haoye Chemical discovered a leak at the edge of the elbow fixture of the accident pipeline (the location of the leak on April 19, 2022). Haoye Chemical Equipment Department organized maintenance and organized leak plugging three times on January 11, 12, and 14, but failed.

                                                                                                                △Leakage at the edge of the accidental pipe elbow clamp

At around 13:00 on January 15, Haoye Chemical and the maintenance unit once again began to organize and implement pressure sealing operations. Two cranes are used on site to lift a hanging basket each, and two leak-stopping workers are arranged in each hanging basket to be lifted to the leakage point by the crane. The crane is commanded by an intercom (the intercom is non-explosion-proof).

At 13:24:10, when one set of bolts were installed and tightened on each side of the new clamp, the pipe weld at the horizontal end of the original clamp suddenly broke, and a large amount of medium spurted out from the fracture. The on-site monitoring personnel immediately evacuated the outside and arranged an emergency stop for the operators inside the alkylation unit.

At 13:25:53, an explosion and fire occurred in the alkylation unit area.

2. Direct cause of the accident

The accident pipeline leaked and broke during the pressure sealing operation. The reaction effluent in the water washing tank spurted out in large quantities, mixed with air to form an explosive vapor cloud, exploded and caught fire when encountering an ignition source, causing heavy casualties in on-site operations, monitoring, and within the scope of the explosion shock wave.

The investigation found that the four walkie-talkies used for operation command are non-explosion-proof walkie-talkies. The minimum operating voltage is 4.5V. The passing current is estimated as a lower value of 100mA. If the on-time lasts for 0.1s, the spark energy is E=UIt=45mJ. In addition, there are two working cranes on site, and the high-temperature hot surface temperature of their exhaust pipes can be as high as 800 to 900°C. In the leakage medium, the minimum ignition energy of n-butane is 0.25mJ, and the ignition temperature is 405℃ ； The minimum ignition energy of isobutane is 0.52mJ, and the ignition temperature is 460°C.

After comprehensive analysis by the expert group, it was determined that the ignition source causing the explosion was: One is the connection energy of the intercom when talking, and the other is the high-temperature hot surface of the exhaust pipe of the crane at the work site.

Indirect causes of the accident also include: The construction unit decided to use 20 steel instead of 316 stainless steel for the accident pipeline without any design changes. ； The pressure sealing operation failed to formulate construction plans and emergency measures, conduct on-site surveys and handle operation approvals in accordance with the specifications. ； There is a serious lack of daily management of enterprise special equipment.

3. Suggestions on handling relevant responsible persons and responsible units

Fines and written inspections were imposed on 12 responsible units including accident-related enterprises, Panjin Municipal Emergency Management Bureau, Panjin Municipal Market Supervision Bureau, Panshan County Party Committee, County Government, Panjin Municipal Party Committee, and Municipal Government.

Two persons responsible for the accident were exempted from liability due to death, and 14 persons responsible for the accident were subject to compulsory measures by the public security organs.； The 48 public officials involved in the accident were held accountable and the relevant liability facts have been handed over to the Commission for Discipline Inspection and Supervision for handling in accordance with regulations, disciplines and laws. ； 11 persons responsible for the accident received administrative penalties.

It is understood that after the accident, Panjin City immediately organized a team of experts to carry out comprehensive risk identification and hidden danger investigation on the accident enterprise, comprehensively rectify the enterprise's safety management issues, and update relevant equipment and facilities. The Provincial Emergency Department organized and carried out special inspection and rectification work on equipment diseases in chemical enterprises across the province, comprehensively rectified the problems of equipment operation with diseases, and strictly prevented similar accidents from happening.

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