In 2020, there was a heat treatment accident in the United States, which resulted in the death of two employees. The reason was that safety procedures Lock Out Tag Out (LOTO) and Restricted Space Code were not followed.

This accident tells us that heat treatment is a very dangerous industry, heat treatment can not be separated from water, gas, electricity, and other dangerous factors are everywhere. Some equipment misoperation, carelessness, and so on can lead to fatal danger. As environmental protection and quality requirements become more and more strict, more and more enterprises buy and use true air quench furnaces, which involve the safety of vacuum furnaces and the safety of inert gas. This accident brings us back to another case. The accident occurred at 9:30 a.m. on May 17, 2001, when a maintenance worker was working on a hydraulic line in a vacuum furnace. The furnace is open to the side and has a quenching tank 6 feet in diameter and 9 feet deep. Once the workpiece is placed in the quenching tank lift, the furnace is filled with inert gas or nitrogen instead of vacuum. In order to repair the hydraulic line, the oil tank was drained three days ago and the motor was installed at the bottom of the quenching tank. The repairman fell into an empty tank at work and his supervisor heard the call for help and climbed into the stove to try to help him. Colleagues who heard the call for help arrived at the scene to find the maintenance man lying on the lift with the supervisor lying beside him. At this point, the furnace control panel is turned on and the argon and nitrogen switches are turned on. Gas release is usually controlled by a solenoid valve during the heat treatment process. It was not clear why it had started or what kind of gas was being pumped into the furnace. Later witnesses said the switch in the electric control cabinet pointed to argon gas. Maintenance workers and supervisors were not wearing helmets or safety cables, and by the time the fire department arrived too late to take them to the hospital, the autopsy report said the cause of death was asphyxiation.

Loto, which is spelled lockout-tagout. OSHA is an OSHA compliant method of preventing personal injury by isolating or locking certain hazardous sources of energy. It has been widely used in the world, and now it has emerged at the right moment in China. There are also relevant explanations in the Safety Production Law. There are also specific provisions in the only national mandatory heat treatment industry standard GB 15735 2012, Safety and Hygiene Requirements for Metal Heat Treatment Production Process. Its purpose is to protect employees from machine energy damage, involving every employee who needs to contact or work near a machine or equipment with or stored energy. The specific method is to lock the power when installing the \ maintenance \ adjustment \ inspection \ cleaning equipment, and to indicate that the maintenance work is being carried out with the tag when the lock is not available, and to try it out after doing the above work.