【Haichuan Confined Space Incident】001-2018: 3 persons entered a confined space in violation of regulations by ignoring the oxygen deficiency alarm, resulting in asphyxiation due to argon accumulation

Panggu New Alloy Materials (Changzhou) Co., Ltd. has two production workshops, namely the amorphous alloy workshop and the titanium alloy powder workshop. The accident occurred in the titanium alloy powder workshop, which is divided into two sections: the upper section for titanium alloy atomization operations and the lower section for powder collection, with the floor separating these two levels. The lower level is located 5 meters below the ground surface; the powder collection room is 8 meters long and 9 meters wide, with stairs built to lead to it, and it is surrounded by metal railings. Panggu New Alloy Materials (Changzhou) Co., Ltd.’s titanium alloy atomization workshop is equipped with one arc melting furnace. This furnace runs through both the upper and lower levels of the workshop. In the titanium alloy atomization process, titanium alloy rods are placed inside the furnace; vacuum is created, argon gas is introduced simultaneously, and the mixture is heated by electrodes to high temperatures, resulting in the atomization of the material into titanium alloy powder. The titanium alloy powder remains in the powder collection box, while the argon gas is discharged outside this box through an exhaust valve and a bellows (see Figure 2). The lower powder collection room is equipped with gas exhaust ducts along each of the four columns; these ducts converge before discharging the air outside. The electrical control switch for the exhaust fan is located in the control cabinet on the upper level of the workshop. On July 31, an oxygen level detector was installed at a height of half a meter above the ground, at the bottom of a pillar located on the lower level of the workshop, near the stairs. The workshop is open from 7 a.m. until midnight the next day, with employees leaving at 12:30 a.m. During regular working hours, the exhaust fan is kept on, and it is turned off after work; the oxygen level detector remains on at all times. At 00:30 on August 5, after the employees left work, the exhaust fan was turned off. According to Qin Wangbo, the shift supervisor, the oxygen level detector was in alarm mode; there was no interlock between the oxygen level detector and the exhaust fan.

Course of the accident and emergency response (I) Course of the accident: At 23:00 on August 4, 2018, four employees on duty began the atomization process for a titanium alloy rod numbered A20180719PWAS63; this work was completed by 00:00 the following day, after which the four employees left their posts at 00:30. Qin Wangbo, the shift supervisor, turned off the control power supply, stopped the exhaust fans, and closed the workshop doors; however, the oxygen level detector remained on and in alarm mode. According to the accident reconstruction tests, the oxygen concentration in the powder collection room was below 12.8% (the alarm threshold for the oxygen detector is below 19.5%). On the morning of August 5, 2018 (a factory holiday), equipment specialist Mi Aiping, along with Wu Jinhong and Zhuang Laping whom she had gathered, went to the entrance of the titanium alloy atomization workshop in order to enter the powder collection room on the lower floor of that workshop to carry out waterproofing work. The surveillance footage shows that at around 6:22, Mi Aiping walked half a circle in the workshop adjacent to the titanium alloy atomization workshop; 6 minutes later, Zhuang Laping appeared at the entrance of the workshop next to the titanium alloy atomization workshop. At 6:30, the three entered the powder collection room on the lower floor of the titanium alloy atomization workshop. At around 22:00 that day, Wu Jinhong’s brother received a call from his sister-in-law saying that no one was answering his brother’s phone. The two of them then found Xu Conglin, the delivery worker from the building materials store, and Xu led them to the location where waterproof materials had been delivered the previous day. There, they found Mi Aiping lying on the ground near the stairs in the powder collection area beneath the titanium alloy atomization workshop; Wu Jinhong was lying on the ground behind Mi Aiping. Zhuang Laping was lying face up on the ground near the oxygen level detector. They immediately called 120 and 110 for help. At around 22:34, the Xuebu Town Police Station in Jintan District received a 110 call. The Jintan Xuebu Fire Brigade and the police station rushed to the scene, where they found three people lying on the floor of the powder collection room on the lower level of the titanium alloy atomization furnace workshop (the oxygen level detector had been turned off, and it was not possible to determine who among the three people had done so). They immediately requested additional fire support. Wearing protective gear, the firefighters arrived at the scene and carried the three people out one by one. After an examination by medical staff from 120, it was confirmed that the three had no vital signs. Subsequent autopsy reports conducted by police forensic experts determined that the deaths were caused by asphyxiation due to lack of oxygen.

【Haichuan Confined Space Incident】002-2023 Accident in a Rice Processing Plant in Tongcheng https://bbs.hcbbs.com/thread-3905601-1-1.html (Source: Huahai Chuanliu – Haichuan Network)