【Accident Case Analysis】The “4·25” Hydrogen Sulfide Poisoning Incident at Shenyang Paraffin Chemical Co., Ltd. (Case Analysis)

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I. Accident Investigation and Analysis (I) Overview of the Accident 1. Introduction to the Accident At around 15:30 on April 25, 2013, China National Chemical Engineering Corporation No. 13 (hereinafter referred to as “CNCEC No. 13”) experienced an poisoning accident at the site of partial maintenance work on the gas separation unit at the DCC joint plant owned by Shenyang Paraffin Chemical Co., Ltd. (hereinafter referred to as “Shenyang Paraffin Chemical”). This accident resulted in 3 deaths and direct economic losses of 2.5 million yuan. 2. Cause analysis: (1) Direct cause – Three workers from the Shenyang Waxification Project Department of \"Thirteen Chemical Construction\" carried out work involving the installation and removal of blind flanges without wearing gas masks, in violation of safety regulations, while the on-site safety supervisor was not present. This was the direct cause of the accident. (2) Indirect cause ①: Three workers from the Shenyang Waxification Project Department of \"Thirteen Modernization Projects\" failed to conduct a thorough identification of hazardous factors in the working environment at the construction site prior to carrying out the operations related to removing and installing blind flanges, in violation of Article 51 of the \"Work Safety Law\" and Article 5.4 of the \"Safety Standards for Operations Involving the Removal and Installation of Blind Flanges in Chemical Production Units\" (AQ 3207-2008, an industry standard for work safety in the People’s Republic of China). As a result, Guan failed to fill in any information in the \"Pre-operation Inspection Comments\" section of the \"Safety Permit for Operations Involving the Removal and Installation of Blind Flanges\" before signing it. It also failed to comply with the provision of Article 6.2, Paragraph 2 of the Safety Agreement, which states that \"Party B shall formulate a safety construction plan prior to commencement of work.\" ②“\"Shisan Hua Jian\" failed to assign full-time on-site safety management personnel in compliance with Article 6.2 of the \"Safety Agreement\" signed with \"Shenyang Luhua\" in 2013, as well as Article 2 of the \"Contractor’s HSE Safety Commitment Letter\". “Although on-site supervisors were assigned for the \"Shenyang waxing\" project, the supervisors went to look for the workers, resulting in no one being present to oversee the construction site. ③“The Dalian branch of \"Thirteen Chemical Construction\" subcontracted the maintenance and operation project for the production facilities at \"Shenyang Waxification\" in 2013 to an individual named Sun who did not possess the necessary qualifications. No contract or agreement regarding safe production was signed, and the rights and obligations of both parties in terms of safe production were not clearly defined. As a result, Sun hired temporary workers to carry out the construction work on site, which violated paragraphs 9 and 13 of Article 6.2 of the \"Safety Agreement\" signed by both parties, as well as Articles 41 and 86 of the \"Safe Production Law\". ④“The safety management at the Shenyang Waxification Project Department of Thirteen Chemical Construction was chaotic; it failed to properly implement the safety production responsibility system and relevant regulations, did not assign full-time safety managers to the site, and failed to comply with the safety provisions outlined in Article 6 on \"Safety Responsibilities\" of the \"Production Facility Maintenance and Operation Agreement\" signed with Shenyang Waxification, as well as Article 6.2 of the Safety Agreement (2013) ； The provisions of paragraphs 5.3.1, 5.3.2, and 7.1 of the \"HSE Management (Measures) Plan for the Maintenance Project of the Production Facilities at Shenyang Paraffin Chemical Co., Ltd.\" were not implemented, nor were the commitments set out in paragraphs 2 and 5 of the \"Contractor’s SHE Safety Commitment Letter\" fulfilled. ⑤“The safety management system at the Dalian branch of \"Thirteen Chemical Construction\" is inadequate; it fails to properly implement the responsibilities related to safe production as well as relevant regulations, resulting in a lack of effective safety management. The person in charge of the maintenance and operation projects for the production facilities at \"Shenyang Wax Chemical\" does not have the necessary qualifications for this role, and his responsibilities are unclear. As a result, effective supervision of safe production at the Shenyang Wax Chemical project site is not ensured, which constitutes a violation of Articles 17 and 19 of the Safety Production Law. ⑥“\"Thirteen Chemical Construction\" failed to effectively supervise its Dalian branch and the projects under it with regard to the establishment of proper safety production responsibilities and regulations. It also failed to provide guidance, conduct inspections, or carry out evaluations regarding safety production at the \"Shenyang Wax Chemicals\" construction site. The various safety agreements signed with \"Shenyang Wax Chemicals\" were merely formalities; they were not properly implemented. Moreover, illegal subcontracting activities were not detected or stopped in a timely manner. ⑦“Shenyang Luhua failed to carry out effective supervision, inspection, and management of Shisanhua Jian’s compliance with laws, regulations, rules and regulations related to work safety, as well as various agreements. It failed to implement the relevant provisions of Articles 5.1 and 5.2 of the Safety Agreement signed with Shisanhua Jian in 2013; safety oversight at the construction site was inadequate, the filling out of Safety Permits for blind plate installation and removal was not done properly, and there were shortcomings in training and management. (II) Basic Information 1. Information on the units involved in the accident ① China Chemical Engineering 13th Construction Co., Ltd. Address: No. 2, North Ring East Road, Xinhua District, Cangzhou City, Hebei Province. Economic type: Limited liability. Nature of the enterprise: Central state-owned enterprise. Registered capital: 322.8 million yuan. Legal representative: Mr. Li. Business scope: Construction of chemical, petroleum, and petrochemical projects, etc. Qualifications: First-class general contractor for chemical and petroleum project construction ； Grade 1 Professional Contracting for the Installation of Chemical and Petroleum Equipment Piping ； Grade 1 professional contracting for pipeline engineering, etc. ② Shenyang Paraffin Chemical Co., Ltd. Address: No. 888, Shenda Road, Shenyang Economic and Technological Development Zone, Liaoning Province. Economic type: Limited liability company. Nature of the enterprise: Central state-owned enterprise. Registered capital: 1.82138 billion yuan. Legal representative: Mr. Wang. Business scope: Gasoline ； Liquefied petroleum gas ； naphtha ； Propylene ； Production of compressed mixtures of hydrogen and methane, etc. ③ Situation regarding the contracting out of maintenance work: Since 2011, “Shisan Hua Jian” has undertaken projects related to the maintenance and operation of Shenyang Wax Chemical’s production facilities through bidding processes. These projects are bid for on an annual basis, with contracts signed each year as well. “Shisan Hua Jian” won the bids for two consecutive years; the implementation of these projects was handled by its Dalian branch. In 2013, no agreement could be reached due to cost issues, and the two parties have yet to sign a contract for the maintenance and operation of the production facilities for that year. Starting from January 1, 2013, “Shenyang Luhua” awarded the maintenance and repair work to “Shisan Hua Jian” through a bidding process; “Shisan Hua Jian” continued to be responsible for carrying out the maintenance and operation work for “Shenyang Luhua”. A de facto agreement was thus established between the two parties. On January 14, 2013, they signed a “Safety Agreement” regarding the maintenance and operation of the production facilities for that year. On the same day, the project management team of “Shisan Hua Jian” at Shenyang Luhua submitted an “HSE Management (Measures) Plan” for the maintenance and operation work, and also signed a contractor HSE safety commitment letter. This project was under the overall responsibility of Zhao, the manager of Dalian Branch of \"Thirteen Chemical Construction\". On-site management was handled successively by the project leader ** and Jin. Meanwhile, Dalian Branch of \"Thirteen Chemical Construction\" subcontracted the on-site construction work of this project to Sun, an individual without any qualifications, who was responsible for hiring workers to carry out the construction tasks. (III) Time sequence of the incident: Date and time – April 24. Due to internal leaks in the top condenser E9003 of the depropanization unit and the top condenser E9006 of the deethanization unit at the \"Shenyang Luhua\" plant, hydrocarbon materials entered the circulating water, contaminating its quality and resulting in a decrease in the plant’s yield. On April 24, operations were halted according to a partial shutdown plan; after the system was purged and replaced, \"Shisan Hua Jian\" carried out repairs and replaced the heat exchanger tubes. At 9:00 on April 25, Yu Jiao, the main operator of the gas separation unit at the DCC branch of \"Shenyang Luhua\", as well as the on-site supervisor, began to prepare the \"Safety Permit for Blind Flange Installation/Removal Operations\". A total of 9 blind flanges were planned to be installed or removed. After being approved by shift leader Xiang and the process specialist Lu, the worker Guan (one of the deceased) signed for the safety permit and started working. In the morning, a total of 5 blind flanges were removed: the P9010B pressure relief line blind flange and the P9010A pressure relief line blind flange, which were used to connect to the nitrogen pipeline during the shutdown process; two high-pressure nitrogen pipeline blind flanges used to connect to the nitrogen supply source; and the P9003B pressure relief line blind flange, which was also used to connect to the nitrogen pipeline during the shutdown process. At 13:10 on April 25, three workers from \"Thirteen Chemical Construction\" removed the blind flanges on the E9007 shutdown extraction line, which are used for material withdrawal and replacement, as well as the blind flange on the T9002 nitrogen supply line used for nitrogen purging, and the blind flange on the E9003 shutdown extraction line, all under the supervision of supervisor Mr. Mou from \"Shenyang Waxification\". At 14:20 on April 25, after 8 blind flanges had already been removed or installed, three workers from \"Thirteen Chemical Construction\" and the supervisor from \"Shenyang Waxification\" arrived at the blind flange located on the pressure relief pipeline of the gas separation unit, numbered WB9017, in order to remove or install another blind flange there. Due to the inappropriate maintenance tools, the workers went to the tool storage room to get replacement tools, taking the \"Safety Permit for Blind Flange Installation and Removal Operations\" with them. At 15:10 on April 25, someone went to the logistics room to look for the workers who hadn’t returned, and informed Qu, the person in charge of production processes, about it. At 15:20 on April 25, Qu did not see Ni or the workers return, so he went to the logistics room and the pump house to look for them, but found no workers there. When Qu reached the semi-enclosed pump house located below the site of the accident and detected an unusual odor, he immediately tried to find its source. Upon arriving at the site where the blind flanges were being handled, he found that three workers from \"Shisan Hua Jian\"—Guan, Zhao, and Liu—had fainted at the work site. He promptly reported the situation to the management of \"Shenyang Luhua\" and organized rescue efforts. At the same time, he informed Jin, the project manager of \"Shisan Hua Jian\", to arrive at the scene as soon as possible. By the time the supervisor Yu returned to the work site, the three workers had already fainted due to poisoning. (IV) Accident losses: The accident resulted in 3 deaths and direct economic losses of 2.5 million yuan. http://www.chemicalsafety.org.cn/uploads/allimg/161031/7-1610311H932550.jpghttp://www.chemicalsafety.org.cn/uploads/allimg/161031/7-1610311H94O64.jpghttp://www.chemicalsafety.org.cn/uploads/allimg/161031/7-1610311I004323.jpg Figure 1: Accident scene (V) Analysis of accident causes 1. Analysis of direct causes Three workers from the Shenyang Waxification Project Department of “Thirteen Chemical Construction” carried out operations related to removing and installing blind flanges without wearing gas masks, as there was no on-site safety officer present; this illegal behavior was the direct cause of the accident. 2. Analysis of indirect causes: ① Three workers from the Shenyang Waxification Project Department of \"Thirteen Modernization Construction\" failed to conduct a thorough identification of hazardous factors in the working environment at the construction site prior to carrying out the operations related to installing and removing blind flanges, in violation of Article 51 of the Work Safety Law and Article 5.4 of the Safety Standards for Installing and Removing Blind Flanges in Chemical Production Units (Industry Standard AQ 3207-2008 of the People’s Republic of China). As a result, Guan filled in no information in the \"Pre-operation Inspection Comments\" section of the Safety Permit for Installing and Removing Blind Flanges before signing it. It also failed to comply with the provision of Article 6.2, Paragraph 2 of the Safety Agreement, which states that \"Party B shall formulate a safety construction plan prior to commencement of work.\" ②“\"Shisan Hua Jian\" failed to assign full-time on-site safety management personnel in compliance with Article 6.2 of the \"Safety Agreement\" signed with \"Shenyang Luhua\" in 2013, as well as Article 2 of the \"Contractor’s HSE Safety Commitment Letter\". “Although on-site supervisors were assigned for the \"Shenyang waxing\" project, the supervisors went to look for the workers, resulting in no one being present to oversee the construction site. ③“The Dalian branch of \"Thirteen Chemical Construction\" subcontracted the maintenance and operation project for the production facilities at \"Shenyang Waxification\" in 2013 to an individual named Sun Jihua who did not possess the necessary qualifications. No contract or agreement regarding safe production was signed, and the rights and obligations of both parties in terms of safe production were not clearly defined. As a result, Sun hired temporary workers to carry out the construction work on site, which violated paragraphs 9 and 13 of Article 6.2 of the \"Safety Agreement\" signed by both parties, as well as Articles 41 and 86 of the \"Safe Production Law\". ④“The safety management at the Shenyang Waxification Project Department of Thirteen Chemical Construction was chaotic; it failed to properly implement the safety production responsibility system and relevant regulations, did not assign full-time safety managers to the site, and failed to comply with the safety provisions outlined in Article 6 on \"Safety Responsibilities\" of the \"Production Facility Maintenance and Operation Agreement\" signed with Shenyang Waxification, as well as Article 6.2 of the Safety Agreement (2013) ； The provisions of paragraphs 5.3.1, 5.3.2, and 7.1 of the \"HSE Management (Measures) Plan for the Maintenance Project of the Production Facilities at Shenyang Paraffin Chemical Co., Ltd.\" were not implemented, nor were the commitments set out in paragraphs 2 and 5 of the \"Contractor’s SHE Safety Commitment Letter\" fulfilled. ⑤“The safety management system at the Dalian branch of \"Thirteen Chemical Construction\" is inadequate; it fails to properly implement the responsibilities related to safe production as well as relevant regulations, resulting in a lack of effective safety management. The person in charge of the maintenance and operation projects for the production facilities at \"Shenyang Wax Chemical\" does not have the necessary qualifications for this role, and his responsibilities are unclear. As a result, effective supervision of safe production at the Shenyang Wax Chemical project site is not ensured, which constitutes a violation of Articles 17 and 19 of the Safety Production Law. ⑥“\"Thirteen Chemical Construction\" failed to effectively supervise its Dalian branch and the projects under it with regard to the establishment of proper safety production responsibilities and regulations. It also failed to provide guidance, conduct inspections, or carry out evaluations regarding safety production at the \"Shenyang Wax Chemicals\" construction site. The various safety agreements signed with \"Shenyang Wax Chemicals\" were merely formalities; they were not properly implemented. Moreover, illegal subcontracting activities were not detected or stopped in a timely manner. ⑦“Shenyang Luhua failed to carry out effective supervision, inspection, and management of Shisanhua Jian’s compliance with laws, regulations, rules and regulations related to work safety, as well as various agreements. It failed to implement the relevant provisions of Articles 5.1 and 5.2 of the Safety Agreement signed with Shisanhua Jian in 2013; safety oversight at the construction site was inadequate, the filling out of Safety Permits for blind plate installation and removal was not done properly, and there were shortcomings in training and management. II. After the three workers from “Thirteen Chemical Construction” fainted in an accident emergency rescue situation, they were given preliminary first aid on the spot by Zhao, the deputy director of the DCC joint factory of “Shenyang Waxification”, a person in charge of process operations, and Jin, the project manager for “Thirteen Chemical Construction”. Subsequently, “Shenyang Waxification” arranged for vehicles to transport the three poisoned workers to a nearby hospital; they arrived at Shenyang Occupational Disease Hospital around 4 p.m. After 50 minutes of attempts to save them, the three workers died at 4:50 p.m. due to the failure of the rescue efforts. One hour after the accident occurred, an investigation team was promptly established at the request of Shenyang **. Under the unified coordination of this investigation team, and with the cooperation of Shenyang Luhua, \"Shisan Hua Jian\" provided continuous support and comfort to the families of the victims; the families remained calm and did not engage in any extreme behavior. While fully respecting the opinions of the families, compensation agreements were reached with the families of the three victims by May 2. All bodies of the victims were cremated by that date, the families left, and the follow-up procedures were completed. III. Reflections and Recommendations (1) The “Thirteen Modernization Projects” should earnestly learn from the lessons of these accidents, apply those lessons to similar situations, and make significant efforts to address the gaps in safety management. The following tasks should be given priority: 1. Immediately correct the illegal subcontracting practices by the Shenyang Waxification Project Department; such illegal subcontracting must be eliminated. The safety management department should conduct thorough reviews of the qualifications of subcontractors, sign specialized safety agreements that define their rights and obligations, and ensure that these agreements are strictly followed. 2. Thoroughly implement laws and regulations such as the Work Safety Law, as well as those issued by relevant departments; establish responsibility systems in accordance with relevant requirements, further improve corresponding safety management systems and operating procedures; in particular, strengthen supervision over the implementation at grassroots project sites to resolutely eliminate any instances of illegal operations. 3. For similar projects, the company requires that the project teams, in addition to attending safety training provided by the client, carry out their own safety training in strict accordance with relevant regulations, to ensure that the relevant personnel have a thorough understanding of applicable laws and regulations and fulfill their respective responsibilities regarding safe production. 4. Strengthen safety management institutions at all levels, enhance the safety management capabilities of branch offices, and raise safety awareness. Whether it is large-scale or small-scale projects, it is essential to ensure that safety inspections can be carried out effectively and in a timely manner. The qualifications of workers must be carefully verified, and construction personnel must be supervised to follow regulations strictly, in order to prevent similar accidents from occurring again. 5. Strengthen safety supervision at construction sites; dedicated safety managers must be present on-site. Comprehensive inspections for potential safety hazards must be carried out at existing construction sites, and any identified hazards must be rectified promptly. (II) \"Shenyang Luhua\" should earnestly learn from the lessons of this accident, further implement relevant laws and regulations on work safety. In particular, it needs to strengthen management of projects assigned to others, standardize procedures, and strictly fulfill the safety-related rights and obligations agreed upon by both parties. It should also supervise the contractor to ensure strict compliance with all contracts and agreements signed by both parties, and carry out proper supervision and management at the construction site ； Strengthen training for all employees on the laws, regulations, and rules related to safe production, with a focus on those responsible for filling out various work permits. Emphasize detailed management and apply lessons learned to various situations, ensuring full compliance with all relevant laws, regulations, and rules regarding safe production, so as to guarantee the safety of the company’s operations, maintenance activities, and any outsourced projects.