The \"9·24\" pressure vessel accident in Jiyang, Shandong
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Shandong “September 24” pressure vessel accident1. Brief description of the accident
On the morning of September 24, 2020, on the west side of National Highway 220 in Qudi Subdistrict, Jiyang District, Jinan City, Shandong Province, an autoclave belonging to a building materials company in Jinan was in normal operation for the processing of aerated concrete blocks. During the production process, the equipment was sealed and pressurized with steam to 1 MPa; after maintaining this pressure for 3 hours, it was depressurized. Once the pressure returned to normal levels, the autoclave was opened to remove the aerated concrete blocks. At noon on the 24th, when the pressure in the autoclave reached 1 MPa, operator Xu Da immediately stopped increasing the pressure; after maintaining that pressure for over 10 minutes, an explosion occurred. The explosion caused the autoclave lid to fly about 102 meters north, passing through the northern building before hitting the ground; the autoclave itself moved southward, breaking through the production workshop and office spaces, resulting in casualties and damage to those facilities. After the explosion of the R-2 autoclave, it separated into a lid and a body; both the lid and the body flew away from their original installation positions in a north-south direction. The lid on the north side of the autoclave flew 102 meters northward from its fixed position, while the autoclave’s cylinder and the lid on the south side moved 88 meters southward from their fixed positions. The kettle lid and the kettle body are largely intact; the kettle body is deformed and cracked due to collisions, the pressure gauge and safety valve have fallen off, the safety interlock device has been damaged, and the steam pipe connected to the autoclave is broken. The explosion caused the color steel sheet roof of the building above the autoclave to collapse, the cement base to be damaged, and the insulation surrounding the autoclave to be ruined as well. The northern lid collapsed the north wall of the company’s premises; after hitting the south wall of the workshop belonging to a neighboring company located to the north of the said company, it fell inside that neighboring company’s workshop. As the cylinder of the R-2 autoclave and its cover on the south side moved backward, they struck the south wall of the workshop; after passing through the factory roads and the restaurant located on the west side of the first floor of the office building on the south side of the road, they came to a stop. This caused the south wall of the workshop to collapse and partial damage to the first floor of the office building, as well as broken glass in that office building. The accident resulted in 4 deaths, 3 injuries, and direct economic losses of 5.75 million yuan. 2. Direct cause of the accident: Due to the failure of the safety interlock device, the kettle lid slid circumferentially during equipment operation and detached from the autoclave; steam inside the kettle escaped rapidly, resulting in an explosion that caused casualties. 3. Indirect causes of the accident
1) The company failed to adequately fulfill its primary responsibilities regarding workplace safety. Its safety management responsibilities were not clearly defined, and its safety management system was incomplete. It did not establish job responsibilities for special equipment safety managers, procedures for regular maintenance and periodic self-inspections, relevant record-keeping systems, mechanisms for identifying and rectifying potential hazards, or systems for managing and training safety personnel and workers. Operators violated procedures; the autoclave operators failed to fulfill their responsibilities regarding on-site operational safety, allowing the autoclave to operate while faulty despite the failure of its safety interlock system. 2) Wang Moujun, the contractor for this company, failed to conduct regular inspections of the condition of the autoclave, did not address any issues that were identified in a timely manner, and was slow to carry out equipment repairs; as a result, the autoclave continued to operate despite the failure of its safety interlock devices. 3) Zhang, the legal representative of the company, failed to properly fulfill the responsibilities inherent to a unit that operates special equipment, which led to the autoclave being operated despite the failure of its safety interlock devices.
A painful price; safety is no trivial matter
Nine out of ten safety interlock devices in autoclaves have problems: 1. In dusty environments, these interlock devices cannot remain functional over the long term; the requirement under technical specifications to conduct tests at least once a month is hardly ever met by users, and some design specifications even require testing once a year； 2. Management is chaotic or non-existent; unlicensed personnel often take it upon themselves to operate the equipment, and some workers even destroy safety interlocks in an attempt to increase production speed ； 3. Training is a mere formality; there is no actual training provided within the factory. The certification authorities’ reliance on private training institutions also serves no real purpose. Even those who hold certificates are unaware of the scope of responsibilities outlined in TSG 08-2017, as well as the safety requirements related to safety interlock devices as specified in TSG 21-2016; in some cases, they don’t even know what safety interlock devices are ； 4. The manufacturer is not responsible; it often informs the users through technical documents, contracts, instruction manuals, etc., that it is up to the users to take care of the safety interlock devices. Users generally do not read such written materials or fail to understand them. In reality, the equipment that reaches the users is defective, and the effectiveness of the safety interlock devices added later for inspection purposes is questionable ； 5. Most bosses are new-rich people who have no sense of safety and are even less willing to invest heavily in it. Regarding such accidents, my personal opinion is: 1. Identify the responsible parties clearly at each level, and ensure that proper explanations are provided ； 2. Training should focus on key areas; explanations of laws, regulations, and technical standards need to be detailed. It is not sufficient to focus only on the teaching process without considering its effectiveness, and social training institutions should be eliminated ； 3. The user unit is required to shorten the calibration cycle for safety interlock devices, and these devices must pass calibration in accordance with technical specifications ； 4. Increase the frequency of inspections; if anything might go wrong, carry out special inspections, and it is necessary to conduct targeted, long-term, planned inspections ； 5. Implement effective systems to enable certified personnel to manage things properly; where possible, use physical measures such as enclosed management via fences, and construct explosion-proof walls at the front and back to reduce the risks associated with accidents.
Due to the failure of the safety interlock device, the kettle lid slid circumferentially during operation and detached from the autoclave; steam inside the kettle escaped rapidly, resulting in an explosion that caused casualties.