The “8·7” Asphyxiation Incident at Ningbo Jiangning Chemical Co., Ltd. (Case Analysis)

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(I) Overview of the accident 1. Brief description of the accident: At around 8 a.m. on August 7, 2013, employees of Ningbo Jiangning Chemical Co., Ltd. discovered three radiographic inspection workers from Hangzhou Huaan Non-Destructive Testing Technology Co., Ltd. lying on the inner tube sheet platform of Reactor No. 3 in the maleic anhydride workshop; they were taken to the hospital but died despite efforts to save them. The accident resulted in direct economic losses of 3.51 million yuan. 2. Cause analysis: (1) The direct cause was that the nitrogen pipeline connected to the reactor was not properly isolated; an operator on the gas phase side accidentally opened the valve of this pipeline, allowing nitrogen to flow into Reactor No. 3. As a result, radiographic inspection personnel who did not have the proper authorization entered Reactor No. 3, where they died from oxygen deficiency asphyxiation. (2) Indirect causes ① Failure to implement safety management responsibilities. Jiangning Company did not sign a safety management agreement with Huayi Company, and Jingtong Company did not sign such an agreement with Huaan Company ； Jingtong Company, Huayi Company, and Jiangning Company failed to fully fulfill their responsibilities regarding the coordinated safety management of relevant parties; thus, safety management responsibilities were not effectively implemented. ②Lack of safety management for relevant parties. Jiangning Company failed to provide training and education for the personnel responsible for radiographic inspection ； Huayi Company failed to urge Jingtong Company to sign a subcontract and a safety management agreement with Huaan Company ； The company failed to assign personnel to effectively manage the radiographic inspection site, and did not supervise the inspection quality of Huaan Company. ③Safety management regulations and operating procedures have not been implemented. Huaan Company failed to provide a radiation inspection plan, did not establish requirements for permits for working in confined spaces, and did not implement operating procedures for such work; moreover, the personnel carrying out radiation-related tasks were working without the necessary qualifications ； Proficient in developing radiographic inspection plans that were not requested by the company, and failed to verify the qualifications of the personnel carrying out on-site inspections ； Huayi Company did not request or review the radiography inspection plan, nor did it verify the qualifications of the on-site inspectors ； Jiangning Company failed to request and review the radiographic inspection plan, did not implement a management system for external personnel, and failed to obtain the necessary work permits as required. ④Safety education and training for employees are inadequate. Huaan Company failed to provide adequate safety training and education to Zhang Mengqing, Zhang Zhihu, and Zhang Guodong, resulting in a weak awareness of safety among them ； Jiangning Company lacks targeted and effective training for its employees, and the operators are not familiar with the on-site production processes and equipment. ⑤The management at the work site is inadequate. Jiangning Company failed to implement effective isolation for the nitrogen pipeline of Reactor No. 3, failed to label the equipment, facilities, and pipelines as required, and did not use tags to manage the important pipeline valves. (II) Basic Information 1. Information on the units involved in the accident: ① Ningbo Jiangning Chemical Co., Ltd. (hereinafter referred to as Jiangning Company) was established on June 25, 2007. It is a limited liability company wholly owned by Zhejiang Jiangshan Chemical Co., Ltd. Its registered address is No. 198, Haixiang Road, Ningbo Petrochemical Economic and Technological Development Zone. The registered capital is 450 million yuan. The legal representative is Mao Zheng, while the general manager (the main person in charge of the enterprise) is Mao Xue. The company produces 80,000 tons of maleic anhydride and its derivatives, as well as 90,000 tons of n-butane per year, with a workforce of 227 people. The integrated project for the annual production of 80,000 tons of maleic anhydride and its derivatives was approved and registered by the Ningbo Development and Reform Commission on October 17, 2011. In February 2012, China Tianchen Engineering Corporation (the general contractor) commenced construction (with the maleic anhydride reactor package designed, manufactured, and assembled on-site by Shanghai Huayi Group Equipment Engineering Co., Ltd.). By March 2013, the installation and commissioning of equipment, pipelines, and electrical instruments were essentially completed. On April 30, 2013, the construction project reached mechanical completion; on May 14, 2013, the trial production plan was duly registered. ②Shanghai Huayi Group Equipment Engineering Co., Ltd. (hereinafter referred to as Huayi Company) was established on November 30, 2005. It is a one-person limited liability company owned by a legal person. Its address is No. 1188, Canggong Road, Fengxian District, Shanghai. The registered capital amounts to 90 million yuan. The legal representative is Mr. Li. The company’s business scope includes the design, manufacturing, and installation of chemical machinery products and complete sets of equipment. In 2011, it obtained the Special Equipment Manufacturing License for the People’s Republic of China (pressure vessels) issued by the General Administration of Quality Supervision, Inspection and Quarantine, with the license number TS1210428-2015. Variety range: high-pressure containers ； Class III low and medium pressure vessels ； Automobile tankers, long-tube trailers ； Tank container. ③Shanghai Jingting Jiancheng Non-Destructive Testing Co., Ltd. (hereinafter referred to as Jingting Company) was established on June 4, 2004. It is a limited liability company of domestic joint venture type, located at Building 1, No. 1188 Canggong Road, Fengxian District, Shanghai. Its registered capital is 3.5 million yuan, and the legal representative is Mr. Chen. The company’s business scope includes non-destructive testing services for special equipment. On January 7, 2013, it obtained the Approval Certificate for Special Equipment Inspection and Testing Institutions in the People’s Republic of China issued by the General Administration of Quality Supervision, Inspection and Quarantine (Class B non-destructive testing institution), with the serial number TS7310094-2017. In 2012, it obtained a radiation safety license issued by the Shanghai Environmental Protection Bureau, with certificate number: Hu Huan Fu Zheng [22704]. The type and scope of this license permit the use of Class II and Class IV radioactive sources as well as Class II radiation devices. ④Hangzhou Huaan Non-Destructive Testing Technology Co., Ltd. (hereinafter referred to as Huaan Company) was established on February 25, 2002. It is a limited liability company located at Building 1, No. 56 Liuhe Road, Xihu District, Hangzhou. Its registered capital amounts to 10.556489 million yuan. The legal representative is Mr. Zhang. The company’s business scope includes non-destructive testing of metal materials, testing of special equipment, and radiation testing. On February 17, 2012, it obtained the Approval Certificate for Special Equipment Inspection and Testing Institutions in the People’s Republic of China issued by the General Administration of Quality Supervision, Inspection and Quarantine (Class A non-destructive testing institution), with the serial number TS7310181-2016 ； In 2009, it obtained a radiation safety license issued by the Zhejiang Provincial Department of Environmental Protection; the license number is: Zhehuan Fu Zheng [A0009] (00445). The type and scope of this license permit the use of Class II and Class IV radioactive sources, as well as Class II radiation devices. 2. Basic information regarding project acceptance On September 29, 2011, Jiangning Company signed a contract with Huayi Company for the procurement of a maleic anhydride reactor package ； On June 3, 2013, Jiangning Company and Huayi Company signed a purchase and sale contract for the disassembly and assembly of the upper head of the maleic anhydride reactor ； On December 16, 2011, Huayi Company signed a non-destructive testing project contract with Jingting Company (Jingting Company was responsible for carrying out all of Huayi Company’s non-destructive testing tasks), with the contract valid from January 1, 2012, to December 31, 2017 ； On August 5, 2013, Jingzhong Company orally subcontracted the on-site radiographic inspection of the head welds on the four reactors in Jiangning Company’s maleic anhydride production workshop to Huaan Company. 3. Basic information on the maleic anhydride production facility: The maleic anhydride production plant of Ningbo Jiangning Chemical Co., Ltd. uses a process package supplied by the American company Huntsman. It is a fixed-bed butane oxidation process, in which raw butane is mixed thoroughly with air in a certain ratio before being fed into the reactor, where it reacts with a catalyst present in the tubular reactors to produce maleic anhydride. The optimal reaction temperature ranges from 440–470°C. Huntsman in the United States requested that the upper head be cut open to load the catalyst. Reaction equation: C4H10 + 7/2 O2 → C4H2O3 + 4 H2O
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Figure 1: Schematic diagram of Reactor No. 3 for maleic anhydride production
(III) Sequence of events surrounding the accident
Date/Time | Description
July 25, 23:00 | Catalyst was being loaded into Reactor No. 3 in the maleic anhydride production facility (hereafter referred to as Reactor No. 3). Since the catalyst needed to remain dry, instrument air had to be supplied to the reactor. Workers from Jiangning Company, namely Jiang and Chang, opened the valves for the instrument air pipelines connected to the reactor. As the instrument air could not reach the reactor, rubber hoses were used temporarily to supply air from the hose station to Reactor No. 3. On July 26, it was discovered that the instrument air pipelines connecting all four reactors had been short-circuited; Qiu, the supervisor of the maleic anhydride production facility, ordered staff to replace those short-circuited pipelines for Reactors No. 1, No. 2, and No. 4. On August 1, the catalyst was loaded into Reactor No. 3. On August 2, Huayi Company arranged for personnel to carry out lifting and welding work on the top head of Reactor No. 3. At 15:00 on August 5, the welding work on the upper head of Reactor No. 3 was completed. On August 4, Lu, the person in charge of Huayi Company’s succinic anhydride project in Jiangning, contacted Chen, the general manager of Jingtong Company, and requested non-destructive testing of the welds on the heads of the 4 reactors in the succinic anhydride production facility. On August 4, Chen contacted Zhang, the general manager of Huaan Company, via the mobile phone of Zheng, the office director at Jingtong Company, to discuss the radiographic testing of the welds on the reactor’s head cover at Jiangning Company. Zhang asked Chen to get in touch with Lang, the manager of Huaan Company’s Ningbo project team, and provided him with Lang’s contact number. Chen then passed on Lang’s number to Lu, asking him to contact Lang directly. On the afternoon of August 4, Lu got in touch with Lang and agreed to meet at the company in Jiangning at 8 a.m. on August 5 to inspect the site. At 8:30 on August 5, Lang and Zheng from Huaan Company, accompanied by Lu, went to the maleic anhydride production workshop to inspect Reactors No. 2 and No. 3. Lang suggested taking a photo for 50 yuan, and Lu agreed. Immediately afterwards, Lang, Zheng Hong, and Lu went together to the office of Zheng, the deputy manager of Jiangning Company’s production department, and submitted an application to carry out radiographic testing on the welds of the heads of Reactors No. 2 and No. 3 from 20:00 on the 5th to 06:00 on the 6th. Zheng agreed and asked someone to draft a notice informing the chief dispatcher in the control room and other relevant personnel of the time, location, and precautions for the radiographic testing. At 20:00 on August 5, Zheng Hongmou (a non-destructive testing specialist holding an intermediate certificate in RT – radiographic inspection, certificate number: 330821198412190014) together with Zhang Mengmou (an assistant), Zhang Guomou (an assistant), and Zhang Zhimou (an assistant) went to the succinic anhydride production workshop of the Jiangning company to carry out radiographic inspections on the welds of the upper heads of Reactors No. 2 and No. 3. The radiographic inspection was completed at 4:00 on August 6. On the morning of August 6, Zheng Hong informed Lu that there were 11 weld defects related to certain negative films that needed to be repaired and re-shot (6 of these related to Reactor No. 3). Lu immediately arranged for personnel to carry out the repairs, and informed Zheng Hong as well as Zheng, the deputy manager of the production department, that the radiographic inspection was scheduled to take place from 8 p.m. on the 6th to 6 a.m. on the 7th ； Zheng, the deputy manager of the production department, had someone draft a notice regarding ray inspection operations, to inform the chief dispatcher in the control room and other relevant personnel. At 15:00 on August 6, the welders from Huayi Company completed the repair of the welds. At 17:30 on August 6, Qiu, the director of the maleic anhydride workshop at Jiangning Company, assigned He, an operator working on the gas side of that workshop, to check the flow rate of instrument air in the maleic anhydride reactor, specifying that this flow rate should be no less than 320 (unit: Kg/H; 1.25 Kg/Nm3). At 18:26 on August 6, He summoned Liu, the operator in charge of the gas phase section, to go together to the maleic anhydride workshop to check the flow rate of instrument air in the reactors. The two went to the third floor where the reactor was located, but could not find the instrument air flow meter; they then went down to the first floor and found that the flow rate of instrument air for reactors No. 1 and No. 2 was both above 320. They proceeded to reactor No. 3, where the flow meter showed a value of 0. Liu tried to open the valve by hand without success, so he went to look for a wrench nearby. While Liu was looking for the wrench (for about 2 minutes), He opened the valve by hand (actually the nitrogen pipeline valve) and adjusted the flow rate to above 320, informing Liu that it had been adjusted properly. The two then went to reactor No. 4 to check the instrument air flow rate; finding it too high, they reduced the flow rate. After completing the inspection, they returned to the control room. At 20:01 on August 6, Zhang from Huaan Company led Zhang Guo and Zhang Zhi to the succinic anhydride reactor site to carry out radiographic inspection work. At 7:40 on August 7, Qiu received a call from Ke of China Chemical Engineering Tenth Fourth Construction Co., Ltd., who was carrying out lifting work at the company in Jiangning, reporting that the warning barriers set up for the radiographic inspection task had not yet been removed ； Qiu called Tang, the chief dispatcher in the control room, to inquire and learned that it was impossible to get in touch with the inspectors. At 7:50 on August 7, after arriving at the control room, Qiu learned that the inspectors had still not been reached, so he asked Tang to contact Zheng, the deputy manager of the production department, while he himself rushed to the reactor site in the maleic anhydride workshop to take a look. At 8:01 on August 7, I met Zheng downstairs from the maleic anhydride workshop; we then went together to the upper head of the reactor on the third floor of the workshop. There, we found Zhang Mengmou, Zhang Guomou, and Zhang Zhimou lying on the tube sheet platform inside Reactor No. 3. Qiu immediately called the chief dispatcher in the control room, requesting that air respirators be brought to the scene. Zheng, the deputy manager of the Production Department, promptly notified nearby workers to assist in the rescue efforts. At 8:16 on August 7, employees from Jiangning Company carried the 3 people out and took them to Zhenhai Refining & Chemical Hospital, where they died despite efforts to save them. (IV) Details of accident losses: The accident resulted in 3 deaths, with direct economic losses amounting to 3.51 million yuan. http://www.chemicalsafety.org.cn/uploads/allimg/161121/7-161121152F0G4.jpg Figure 2: Overview of the top part of Reactor No. 3 for maleic anhydride processing. http://www.chemicalsafety.org.cn/uploads/allimg/161121/7-161121152G1245.jpg Figure 3: Overview of the center area of the partition inside Reactor No. 3 for maleic anhydride processing. (V) Analysis of the causes of the accident: 1. Direct cause: The nitrogen pipeline connected to the reactor was not properly isolated; the operator on the gas side accidentally opened the valve of this pipeline, allowing nitrogen to enter Reactor No. 3. As a result, unqualified personnel carrying out radiation inspection work entered the reactor illegally and died from oxygen deficiency. 2. Analysis of indirect causes: ① Failure to implement safety management responsibilities. Jiangning Company did not sign a safety management agreement with Huayi Company, and Jingtong Company did not sign such an agreement with Huaan Company ； Jingtong Company, Huayi Company, and Jiangning Company failed to fully fulfill their responsibilities regarding the coordinated safety management of relevant parties; thus, safety management responsibilities were not effectively implemented. ②Lack of safety management for relevant parties. Jiangning Company failed to provide training and education for the personnel responsible for radiographic inspection ； Huayi Company failed to urge Jingtong Company to sign a subcontract and a safety management agreement with Huaan Company ； The company failed to assign personnel to effectively manage the radiographic inspection site, and did not supervise the inspection quality of Huaan Company. ③Safety management regulations and operating procedures have not been implemented. Huaan Company failed to provide a radiation inspection plan, did not establish requirements for permits for working in confined spaces, and did not implement operating procedures for such work; moreover, the personnel carrying out radiation-related tasks were working without the necessary qualifications ； Proficient in developing radiographic inspection plans that were not requested by the company, and failed to verify the qualifications of the personnel carrying out on-site inspections ； Huayi Company did not request or review the radiography inspection plan, nor did it verify the qualifications of the on-site inspectors ； Jiangning Company failed to request and review the radiographic inspection plan, did not implement a management system for external personnel, and failed to obtain the necessary work permits as required. ④Safety education and training for employees are inadequate. Huaan Company failed to provide adequate safety training and education to Zhang Meng, Zhang Zhi, and Zhang Guo, resulting in a weak sense of safety among them ； Jiangning Company lacks targeted and effective training for its employees, and the operators are not familiar with the on-site production processes and equipment. ⑤The management at the work site is inadequate. Jiangning Company failed to implement effective isolation for the nitrogen pipeline of Reactor No. 3, failed to label the equipment, facilities, and pipelines as required, and did not use tags to manage the important pipeline valves. II. Emergency rescue in case of an accident: At 8:01, I met Zheng, the deputy manager of the production department, downstairs in the maleic anhydride workshop. Together we went to the top head of the reactor on the third floor of that workshop, where we found Zhang Meng, Zhang Guo, and Zhang Zhi lying on the inner tube sheet platform of Reactor No. 3. Qiu immediately called the chief dispatcher in the control room to request that air respirators be sent to the scene, while Zheng, the deputy manager of production, promptly informed the workers nearby to assist with the rescue efforts. At 8:16, employees from Jiangning Company carried the three people out and took them to Zhenhai Refining & Chemical Hospital, where they died despite efforts to save them. At 8:22, Song, the shift supervisor of the maleic anhydride workshop, closed the valve on the nitrogen pipeline of Reactor No. 3 at the request of Shuai, the production department manager, who asked him to check whether nitrogen had entered the reactor. On the evening of the 7th, Qiu installed stop-signs on the instrument air valves in the nitrogen pipeline and hose station of Reactor No. 3. III. Reflections and Recommendations: All units must thoroughly draw lessons from this incident, apply these lessons to similar situations, and conduct a comprehensive review of any weak points in their work safety management. They must strictly adhere to work safety laws, regulations, standards, and norms, and earnestly implement corrective measures to prevent the recurrence of similar accidents. (1) Jiangning Company: 1. Establish and improve, as well as strictly implement, safety production responsibility systems for managers at all levels and employees. 2. Strictly comply with laws, regulations, standards related to work safety, as well as the company’s safety management systems and safety operating procedures, and take measures to ensure their proper implementation. 3. Further strengthen the safety management of special operations such as entering confined spaces, strictly enforce work permits, and implement on-site supervision measures to ensure the safety of such operations. 4. Strengthen safety production education and publicity among relevant parties, enhance safety training, and improve the safety knowledge and skills of managers at all levels as well as all employees. 5. Comprehensively strengthen the management of relevant parties. Revise and improve the regulations governing the management of relevant parties, clarify the management responsibilities of leaders at all levels, various departments, and workshops regarding such parties. Intensify safety supervision throughout the entire construction process involving relevant parties, ensure that safety briefings are conducted at work sites, and review the safety operating procedures, construction plans, and emergency response plans of relevant parties, so as to provide them with a safe and reliable working environment. 6. Strengthen safety management at the work site, improve signage for equipment, facilities, pipelines, and hazardous areas, implement labeling systems for important valves, and enhance the level of detail in on-site management. 7. Personnel at all levels must strictly fulfill their respective safety responsibilities, carry out effective supervision and inspection at the work sites, and put an end to all forms of violations of safety regulations. (II) Huaan Company: 1. Establish and improve, as well as strictly implement, safety production responsibility systems for managers at all levels and employees. 2. Strictly enforce laws, regulations, and standards related to work safety, further improve the company’s safety management systems and safety operating procedures, and take measures to ensure their proper implementation. 3. Strengthen safety production education and publicity, enhance safety training, and improve the safety knowledge and skills of managers at all levels as well as all employees. 4. Improve the on-site non-destructive testing procedures; operators must work with valid certificates, and it is prohibited for unlicensed personnel to carry out such tasks. 5. Managers at all levels, on-site supervisors, task leaders, and actual workers must strictly fulfill their respective safety responsibilities, carry out effective supervision and inspection at the work site, and prevent all forms of violations of safety rules. (III) Have a thorough understanding of the company’s operations; strictly fulfill the primary responsibilities for safety production, sign safety management agreements with relevant parties as required, clarify each party’s responsibilities in terms of safety management, and strengthen the unified coordination and management of safety production efforts by subcontractors. (IV) Huayi Company shall earnestly fulfill its responsibilities as the general contractor for safety management, and strengthen the unified coordination and supervision of the safety work carried out by the subcontractors. (5) The Management Committee of Ningbo Petrochemical Zone should draw serious lessons from this accident. In light of the safety management challenges associated with the construction phase of hazardous chemical enterprises, it should promptly improve the safety supervision framework, clarify the safety supervision responsibilities of relevant departments, and enhance the relevance and effectiveness of safety supervision during the construction phase in order to prevent similar accidents from occurring.