The “9·14” collapse accident at Baoliyuan Coking Co., Ltd. in Tangshan, Hebei

Thread Content

I. Accident Investigation and Analysis (I) Overview of the Accident 1. Introduction to the Accident Around 12:40 on September 14, 2013, while workers in the coal preparation workshop of Tangshan Baoliyuan Coking Co., Ltd. were clearing the coal accumulation above the No. 3 disk feeder, the No. 3 coal receiving bin suddenly collapsed, resulting in 3 deaths and 1 injury, with direct economic losses amounting to 2 million yuan. 2. Cause analysis: (1) Direct cause – After years of use, the welding areas where the steel plates surrounding Bin No. 3 and the angle steel at its upper edge were joined suffered severe rusting. As a result of continuous contact during coal loading operations using a truck loader, the western edge of the upper opening became severely deformed and separated from the angle steel; the other two sides (south and north) also became detached. Only the eastern side remained partially welded to the angle steel at the upper opening, resulting in insufficient connection strength. At the same time, the large amount of coal accumulated at the top of the coal receiving bin, combined with increased coal moisture due to recent rain, led to increased pressure on this bin. Under the effect of gravity, the coal receiving bin and the large quantity of coal attached to it suddenly detached, resulting in the accident. (2) Indirect causes: ① Inherent defects in design and production. The connection method using angle steel at the four corners of the top of the No. 3 coal receiving bin is simple, and does not meet the requirements of design and construction specifications ； The coal bin and the corner steel members were not welded on both sides; only single-sided, intermittent welding was performed ； The coal bin and the top angle steel lack longitudinal reinforcement plates as required by the specifications ； The reinforced concrete beams in the underground batching tank, as well as the upper parts of the walls, lack steel structural embedments that should be welded to the angle steel at the four corners of the coal bin’s top; as a result, the angle steel at the top of the coal bin can easily become detached from the reinforced concrete beams and walls. ②Equipment management is inadequate. Tangshan Baoliyuan Coking Co., Ltd. has not established management systems for the inspection and maintenance of coal storage areas ； The coal receiving hoppers in operation were not inspected or maintained, and there was a lack of proper daily management for them ； After the gantry crane grab used in the original design was taken out of service, it was not repaired or replaced in a timely manner; instead, a truck loader was used for coal loading. This led to collisions with the angle steel at the top of the coal receiving bin during the loading process, resulting in deformation at the upper edge on the western side of those angle steels, as well as a separation between those angle steels and the reinforced concrete beam ； After the angle steel became detached from the coal bin, no inspection or repair was carried out in a timely manner ； Proof of the qualifications of the design firm, construction firm, and supervision firm was not provided, nor were the design drawings or any related documents for construction and supervision available. ③Safety hazard inspections are not thorough enough. Tangshan Baoliyuan Coking Co., Ltd. failed to conduct a thorough inspection for potential safety hazards; there were blind spots and areas that were not covered, and long-standing accident risks went unnoticed, resulting in those hazards remaining unaddressed for a long time. ④Safety training is inadequate. The safety education and training provided to the employees of Tangshan Baoliyuan Coking Co., Ltd. was merely a formality; retraining in safety matters was also superficial. Training was not carried out within the specified time frames or according to the required content, as a result of which the employees had poor safety awareness and skills, and lacked an adequate understanding of the hazard factors present at the work site. ⑤Safety supervision is inadequate. The people’s government of Shaheyi Town in Qian’an City, as well as the Qian’an City Work Safety Supervision Bureau, failed to fulfill their responsibilities for safety supervision properly; they did not ensure that Tangshan Baoliyuan Coking Co., Ltd. carried out thorough investigations and rectifications of safety hazards in accordance with the requirement of \"full coverage\". (II) Basic Information 1. Information on the units involved in the accident: Tangshan Baoliyuan Coking Co., Ltd. was established in December 2003; it is a limited liability company with the registration number 130283000009621. The company is located west of Liutaizi Village, Shaheyi Town, Qian’an City, and its legal representative is Mr. Sang. The company obtained its safety production license in June 2010; the license number is: (Ji) WH Anxu Zhi No. 020196. The second renewal took place on June 19, 2012, with a validity period from June 19, 2012, to June 18, 2015. The company’s business scope includes coking, production of crude benzene and tar, as well as the wholesale of iron ore powder, pelletized iron ore, dolomite, limestone, and steel products. The main production facilities include two TJL80-4355CD type coke ovens, which produce 600,000 tons of coke, 8,000 tons of crude benzene, and 25,000 tons of tar per year. The company has 15 departments, including a coking workshop, a chemical products workshop, a coal preparation workshop, a machinery and transportation workshop, an electrical and instrumentation workshop, a production department, a safety department, a logistics department, and a general office. There are over 450 employees, including 9 full-time safety managers. The accident occurred below Silo No. 3 in the coal blending section of the coal preparation workshop at Tangshan Baoliyuan Coking Co., Ltd. The coal preparation workshop is located in the eastern part of the company’s facility; it was completed and put into use at the end of 2007. The coal blending section is located on the east side of the coal yard in the coal preparation workshop. The coal preparation workshop mainly consists of a coal yard, coal blending, crushing, grinding, belt conveyors, and transfer stations. The main equipment in the coal blending section includes 7 coal receiving hoppers, 7 disk feeders (2 of which are spare), belt conveyors, and electronic scales (for small belts), which are used to deliver blended coal to the coal hoppers on top of the coke ovens. The 7 coal receiving bins are arranged in sequence from north to south; among them, bins #1, #2, #3, #4, and #5 are in normal use, while bins #6 and #7 are reserved. All of these coal receiving bins have a semi-underground structure. The coal preparation workshop currently has 36 employees, including 1 full-time safety manager. (III) Timeline of the accident: On September 14 at 7:45, Zhang, the shift leader of Shift B in the coal preparation workshop at Tangshan Baoliyuan Coking Co., Ltd., organized a pre-shift meeting attended by 10 workers including Tang, Zhang, Deng, Shang, and others, to arrange the tasks for that shift. At 8:00 on September 14, all employees went to their posts to load coal into the coal bunker on top of the coke oven. According to the division of duties for that shift, Deng was responsible for monitoring bins No. 1 and No. 2 as well as the disk feeder in the pit, Tang was in charge of monitoring bins No. 3 and No. 4 along with the disk feeder, while Shang was responsible for monitoring bin No. 5 and the disk feeder. At 10:00 on September 14, coal feeding was halted due to the filling of the coke oven roof coal bin, and the equipment stopped operating. Coal loading was resumed into the coke oven roof coal bin at 11:50 on September 14. During that time, Chai, a maintenance worker from Shift B in the coal preparation workshop, conducted inspections of the equipment’s operation and found no abnormalities. At 12:20 on September 14, Tang discovered that the No. 3 coal receiving bin was blocked and could not accept coal, so he reported this situation to Zhang by phone. At 12:25 on September 14, Zhang called Chai to inform him of a fault in Silo No. 3 for receiving coal. At 12:30 on September 14, Zhang and Chai went into the pit one after another. After checking bin No. 3 for coal storage, Chai found no abnormalities in the equipment and told Zhang and the other four people to remove the coal sludge from the bottom of the bin; thereafter, Chai returned to the ground-based control room. Zhang, Shang, and Deng discussed taking turns to help Tang remove the sludge coal from the bottom of the coal bin. Shang stood on the support structure beneath the electronic scale (small belt) next to the disk feeder at the bottom of Bin No. 3, using a small rake to remove coal from that area. Tang, Deng, and Zhang stood on the operation platform in the belt corridor below Bin No. 3, waiting their turn to carry out the cleaning task (as the space was too limited for more than one person to work at a time). At 12:40 on September 14, the 3# coal receiving bin collapsed suddenly. The upper opening of this bin landed against the east wall of the pit, while its lower opening hit the west wall of the pit. The 3# coal receiving bin and the coal stored inside it buried Tang, Deng, and Zhang. Angle iron that fell from the upper opening of the bin injured Shang. (IV) Accident losses: The accident resulted in 3 deaths and 1 injury, with direct economic losses of 2 million yuan. http://www.chemicalsafety.org.cn/uploads/allimg/161128/7-16112Q54642120.jpg Figure 1: Feed bin during normal operation. http://www.chemicalsafety.org.cn/uploads/allimg/161128/7-16112Q54A43Z.jpg Figure 2: 3# aggregate bin-1 after separation. http://www.chemicalsafety.org.cn/uploads/allimg/161128/7-16112Q54F4136.jpg Figure 3: Angle iron section of 3# aggregate bin. (V) Analysis of accident causes 1. Analysis of direct causes: After years of use, the welding areas where the steel plates on all four sides of 3# coal receiving bin met the angle irons at its upper edge were severely corroded. Due to continuous contact during coal loading operations using a truck loader, the western edge of the upper portion became severely deformed and separated from the angle irons; the other two sides (south and north) also became detached. Only the eastern side remained partially welded to the upper edge angle irons, resulting in insufficient connection strength. At the same time, the large amount of coal accumulated at the top of the coal receiving bin, combined with increased coal moisture due to recent rain, led to increased pressure on this bin. Under the effect of gravity, the coal receiving bin and the large quantity of coal attached to it suddenly detached, resulting in the accident. 2. Analysis of indirect causes: ① Inherent defects in design and production. The connection method using angle steel at the four corners of the top of the No. 3 coal receiving bin is simple, and does not meet the requirements of design and construction specifications ； The coal bin and the corner steel members were not welded on both sides; only single-sided, intermittent welding was performed ； The coal bin and the top angle steel lack longitudinal reinforcement plates as required by the specifications ； The reinforced concrete beams in the underground batching tank, as well as the upper parts of the walls, lack steel structural embedments that should be welded to the angle steel at the four corners of the coal bin’s top; as a result, the angle steel at the top of the coal bin can easily become detached from the reinforced concrete beams and walls. ②Equipment management is inadequate. Tangshan Baoliyuan Coking Co., Ltd. has not established management systems for the inspection and maintenance of coal storage areas ； The coal receiving hoppers in operation were not inspected or maintained, and there was a lack of proper daily management for them ； After the gantry crane grab used in the original design was taken out of service, it was not repaired or replaced in a timely manner; instead, a truck loader was used for coal loading. This led to collisions with the angle steel at the top of the coal receiving bin during the loading process, resulting in deformation at the upper edge on the western side of those angle steels, as well as a separation between those angle steels and the reinforced concrete beam ； After the angle steel became detached from the coal bin, no inspection or repair was carried out in a timely manner ； Proof of the qualifications of the design firm, construction firm, and supervision firm was not provided, nor were the design drawings or any related documents for construction and supervision available. ③Safety hazard inspections are not thorough enough. Tangshan Baoliyuan Coking Co., Ltd. failed to conduct a thorough inspection for potential safety hazards; there were blind spots and areas that were not covered, and long-standing accident risks went unnoticed, resulting in those hazards remaining unaddressed for a long time. ④Safety training is inadequate. The safety education and training provided to the employees of Tangshan Baoliyuan Coking Co., Ltd. was merely a formality; retraining in safety matters was also superficial. Training was not carried out within the specified time frames or according to the required content, as a result of which the employees had poor safety awareness and skills, and lacked an adequate understanding of the hazard factors present at the work site. ⑤Safety supervision is inadequate. The people’s government of Shaheyi Town in Qian’an City, as well as the Qian’an City Work Safety Supervision Bureau, failed to fulfill their responsibilities for safety supervision properly; they did not ensure that Tangshan Baoliyuan Coking Co., Ltd. carried out thorough investigations and rectifications of safety hazards in accordance with the requirement of \"full coverage\". II. Emergency rescue in case of accidents: Upon hearing the sound of a collapse coming from the coal storage area, Chai immediately ran towards the pit. When he reached the entrance of the pit, he encountered Shang coming out of it. After learning about the accident, Chai immediately reported it by phone to Liu, the section chief of the coal preparation workshop, and at the same time organized the people on site to carry out rescue efforts right away. After lifting bin No. 3 using a mobile crane by about half a meter, the on-site personnel promptly cleared the coal accumulation from the operating platform in the belt corridor. At around 2 p.m., Zhang, Deng, and Tang were successively rescued and taken to Qian’an City Traditional Chinese Medicine Hospital for treatment. Despite efforts to save them, Tang, Zhang, and Deng died one after another on the same day. Shang suffered minor injuries and is not in life-threatening condition. III. Reflections and Recommendations (1) Tangshan Baoliyuan Coking Co., Ltd. should draw lessons from this incident, earnestly learn from it, and strengthen enterprise safety management. It should carry out a thorough inspection of potential safety hazards throughout the company, in order to identify and eliminate all types of such hazards promptly. To carry out thorough improvements to all coal receiving bins, a qualified design firm should be engaged to redesign them, ensuring that the relevant technical parameters of these bins meet the specified standards. Construction should then be carried out by a competent construction company in accordance with the design requirements. (II) Tangshan Baoliyuan Coking Co., Ltd. should strengthen equipment management, carefully improve and implement various rules and regulations, promptly identify and eliminate potential hazards related to equipment, and prevent the recurrence of production safety accidents caused by such hazards. It is necessary to establish management systems for the inspection and maintenance of coal receiving bins, keep inspection records, and strengthen the daily management of the equipment and facilities in these bins. It is necessary to repair or update the gantry crane grab lifters in a timely manner to resume using them for loading coal. Excessive accumulation of coal at the top of the coal receiving bin should be avoided, so as to prevent excessive pressure in that bin and stop similar accidents from occurring again. (III) Tangshan Baoliyuan Coking Co., Ltd. must strengthen the \"three-level safety education\" for its employees, focusing on the training of those working in key positions and those engaged in special types of work. Employees should be retrained within the specified time frames and according to established guidelines, so as to ensure that they have the ability to identify various potential safety hazards and risks associated with their roles, thereby enhancing their safety awareness and skills fundamentally. Key personnel, safety managers, and workers engaged in special operations must hold valid certificates to work. (IV) Tangshan Baoliyuan Coking Co., Ltd. must attach great importance to work safety, carefully study laws, regulations and document provisions such as the \"Regulations on the Reporting, Investigation and Handling of Production Safety Accidents\" (State Council Decree No. 493) and the \"State Council’s Notice on Further Strengthening Enterprise Work Safety\" (Guo Fa No. 23), and earnestly carry out the task of reporting information on production safety accidents; it is prohibited to delay, omit, misreport or conceal such accidents. (5) The people’s government of Qian’an City must earnestly learn from the lessons of this accident, strictly implement the requirements that \"the Party and the government share equal responsibilities, each position has dual responsibilities, and those in charge of certain industries must also be responsible for safety, those in charge of specific tasks must ensure safety, and those in charge of production and operations must prioritize safety.\" It is necessary to strengthen organizational leadership, refine work measures, and ensure that responsibilities are properly fulfilled. By taking into account local conditions, it is important to carefully analyze the prominent contradictions and problems existing in current work related to safety production, and to develop effective solutions so as to achieve comprehensive supervision of safety production. The people of Shaheyi Town and the Work Safety Supervision Bureau of Qian’an City must fulfill their safety supervision duties in accordance with the law. Following the general principles of \"full coverage, zero tolerance, strict enforcement, and emphasis on practical results,\" they should thoroughly supervise all types of production and business entities within their jurisdiction and under their supervision to carry out thorough inspections and rectifications of potential hazards, ensuring that such efforts are conducted on a regular and standardized basis, thus establishing an effective long-term mechanism for identifying and addressing potential hazards.