Improper design caused chlorine gas leakage, and the design unit was punished

1. Basic information of the project. XXXX Company’s 30,000 tons/year (1st phase 10,000 tons/year) sodium bleaching powder technological transformation project passed the construction project safety facility design review on October 24, 2016. The design unit is Hebei XXXX Engineering Design Co., Ltd., and the main construction content is: There is one liquid chlorine tank area, tablet press workshop, and packaging material warehouse. There are three 35m liquid chlorine storage tanks (one for dual use and one for backup) indoors in the liquid chlorine tank area. The total liquid chlorine storage capacity is 77.8t. Two sets of accident absorption tower systems are set up on the south side of the outdoor outdoor area of ​​the liquid chlorine tank area, which are used in series (secondary absorption). Two sets of liquid chlorine gasification devices (for production) ； On the west side of the liquid chlorine tank area, there is a liquid chlorine gasification device (for unloading trucks), two liquid chlorine pumps, a sewage collection tank and a liquid chlorine unloading platform. ； The original calcium hydroxide storage warehouse was converted into a tableting workshop ； The south side of the original parts warehouse and the west side of the finished product warehouse are the packaging material warehouse. XXXX Company's 30,000 tons/year (first phase 10,000 tons/year) sodium bleaching powder technical transformation project was completed in July 2019. The Cangzhou Municipal Emergency Management Bureau issued trial production plan demonstration review opinions on August 5, and the company began to organize trial production on August 16.

2. The accident and rescue situation (1) The accident occurred at 21:22:07 on September 6, 2019. The overcurrent protection action switch of the 110KV Shannan Station 10KV Shanjing Line 5614 of the xx County Power Supply Company tripped, and the XXXX Company factory lost power. Operator Liu xx, who was near the liquid chlorine tank area, heard an abnormal noise coming from the liquid chlorine tank area. With the help of the emergency lighting and flashlight of the liquid chlorine tank area, he looked into the tank area through the glass of the tank area workshop and found that there was yellow-green gas in the workshop, which was suspected of chlorine leakage. (2) The emergency response situation at the accident site shall be verified after verifying the leakage of chlorine gas. At 22:05, after the power supply was restored, the alkali absorption device was immediately started to absorb and neutralize the leaked chlorine gas and decontaminate the tank area. The emergency response was completed around 23:00. The accident did not cause poisoning or injury to anyone in the factory. 17 villagers near the company felt unwell and went to XX County Hospital for medical treatment. Among them, 13 villagers went home the same day after being diagnosed as fine, and 4 villagers stayed in the hospital for observation and treatment. They were all discharged before 11:00 on September 10.

2. The accident and rescue situation (1) The accident occurred at 21:22:07 on September 6, 2019. The overcurrent protection action switch of the 110KV Shannan Station 10KV Shanjing Line 5614 of the xx County Power Supply Company tripped, and the XXXX Company factory lost power. Operator Liu xx, who was near the liquid chlorine tank area, heard an abnormal noise coming from the liquid chlorine tank area. With the help of the emergency lighting and flashlight of the liquid chlorine tank area, he looked into the tank area through the glass of the tank area workshop and found that there was yellow-green gas in the workshop, which was suspected of chlorine leakage. (2) The emergency response situation at the accident site shall be verified after verifying the leakage of chlorine gas. At 22:05, after the power supply was restored, the alkali absorption device was immediately started to absorb and neutralize the leaked chlorine gas and decontaminate the tank area. The emergency response was completed around 23:00. The accident did not cause poisoning or injury to anyone in the factory. 17 villagers near the company felt unwell and went to XX County Hospital for medical treatment. Among them, 13 villagers went home the same day after being diagnosed as fine, and 4 villagers stayed in the hospital for observation and treatment. They were all discharged before 11:00 on September 10.

(3) Weather conditions According to data provided by the Qingxian Farm Meteorological Observation Station of the xx County Meteorological Bureau, the wind direction was southeast from 21:15 to 21:40 on September 6, with a wind speed of level 1-2； From 21:45 to 23:05, the wind direction is southeast, with wind speed of level 1-2. ； The wind direction was southeast from 23:10 to 0:15 the next day, with wind speed of level 1. (4) Mains power supply contract and power outage situation According to data provided by the xx County Power Supply Company, at 21:22:07 on September 6, 2019, the overcurrent protection action switch of the 110KV Shannan Station 10KV Shanjing Line 5614 that supplied power to XXXX Company tripped. After inspection by Xiaoshan Power Supply Station personnel, no line fault was found. At 22:05, the line switch was turned on and the line returned to normal.

3. Cause and Nature of the Accident (1) Direct Cause Due to a sudden power outage, the UPS uninterruptible power supply and the self-contained generator did not provide power. The upper vent pipe cut-off valves PV0101A, B, and C of the liquid chlorine storage tanks A, B, and C opened due to the loss of power, resulting in the leakage of chlorine gas to the alkali solution absorption tower. Part of the leaked chlorine gas returns to the liquid chlorine storage tank area through the accident draft system of the liquid chlorine storage tank, and part of it enters the atmosphere through the exhaust pipe of the alkali absorption tower. (2) Indirect reasons 1. There are flaws in the safety facility design of Hebei XXXX Company. In the safety facility design logic diagram, the interlock action status of the liquid chlorine storage tank vent pipe segment valves PV0101A, B, and C is open after power failure. As a result, during a power outage, the liquid chlorine storage tank vent pipe cut-off valves PV0101A, B, and C are opened, and the chlorine gas in the storage tank enters the absorption tower.

2. XXXX Company’s main responsibility for safety production is not fully implemented. (1) The investigation and management of hidden dangers are not in place. The "Guidelines for the Investigation and Management of Safety Risks in Hazardous Chemical Enterprises" (Emergency [2019] No. 78) were not strictly implemented, and daily safety inspections became a mere formality. First, the emergency generator (diesel generator 200KW) switch failure was not found during the inspection. As a result, after a sudden power outage, the backup power supply automatically started, but due to the failure of the switching device, the power supply could not be switched. The vent pipe cut-off valves PV0101A, B, and C were still open after power loss. The emergency alkali pump of the chlorine absorption tower could not be started in time, the emergency alkali spray facilities could not work, and the chlorine entering the absorption tower could not be absorbed by the alkali solution. ； Second, it was not checked that the switches of the UPS uninterruptible power supply connected to the vent pipe cut-off valves PV0101A, B, and C were in the disconnected state, resulting in the UPS power supply not supplying power to the vent pipe cut-off valves PV0101A, B, and C after a sudden power outage.

(2) Risk identification and control measures are not in place. Failure to strictly comply with the "Regulations on Safety Production Risk Management and Hidden Hazard Management of Hebei Province" (Hebei Provincial People's * * Order [2018] No. 2, "Guidelines for the Investigation and Management of Safety Risks in Hazardous Chemical Enterprises" and "Cangzhou City Chemical Enterprises Interim Measures for Safety Production Management" (Cangzheng Office [2019] 32 No.) carried out hierarchical management and control of production safety risks and investigation and management of hidden dangers. In particular, the measures to control safety risks and the possible consequences of their failure were not fully and fully risk-identified. It was not recognized that if the emergency power supply was not supplied in time after a sudden power outage, the risk that the liquid chlorine storage tank vent pipe cut-off valves PV0101A, B, and C would be opened due to power loss, and the emergency alkali pump could not be started, resulting in the leakage of chlorine gas, and no corresponding risk control measures were formulated.

(3) Emergency drills are not in place and emergency response work is ineffective. First, there is a lack of professional emergency knowledge training, and emergency knowledge training and related simulation training under sudden power outages are not strictly carried out for personnel in electrical, instrumentation and other positions. ； Second, the professional quality of the on-duty personnel at the electrical instrument position was poor, and they were unclear about the working status of the UPS backup power supply. After the mains power outage, they did not check and confirm the working status of the UPS power supply. They were not familiar with the working status of the diesel generator. Although they checked that the diesel generator had started, they did not check and confirm whether the power supply was supplied, resulting in the vent pipe cut-off valves PV0101A, B, and C still being open in the absence of power.

3. The expert group participating in the design review of the safety facilities of the construction project did not strictly review the design of the safety facilities of the construction project and found no defects in the design of the safety facilities. (3) The nature of the accident determined that the accident was a production safety liability accident caused by design defects and inadequate safety management, and did not reach the level of general production safety accidents.

4. Opinions on handling the units responsible for the accident and relevant responsible persons 1. Hebei XXXX Company, the designed safety equipment did not meet the* * standards, which led to the occurrence of this accident. It is recommended that the Cangzhou City Safety Production Committee Office include it in the "blacklist" of production and business units with bad safety records. 2. XXXX Company failed to perform regular maintenance, maintenance and periodic testing on the emergency generator, and the UPS backup power supply was disconnected, which led to the accident. According to Article 96 (3) of the "Work Safety Law of the People's Republic of China", it is recommended that the Cangzhou Municipal Emergency Management Bureau impose an administrative penalty of RMB 30,000 and the XX County Emergency Management Bureau order it to suspend production and business for rectification. 3. According to Article 20, Item 3 of the "Expert Management Measures of the Hebei Provincial Emergency Management Department", it is recommended that the Cangzhou Municipal Emergency Management Bureau give a warning interview to the expert group headed by team leader XXX who participated in the design review of the safety facilities of the construction project.