Inadequate safety management and electric shock accidents

On July 14, 2000, in the construction of the renovation project of the Lijialing cottage, a construction company, a migrant worker who was responsible for operating the mortar machine died of electrocution due to mechanical leakage during operation.

After the accident:

At about 13:30 on July 14th, during the construction of the Lijialing cottage renovation project of a construction company, Yang Moumou, a migrant worker, was working on a mortar machine. He used a steel pipe weighing about 27 kg and a length of 7.2 m to send water into the mortar tank to mix the mortar. After that, he put the mortar on both hands and tried to pour the mixed mortar out. At this moment, he suddenly got an electric shock and fell to the ground. After finding out from the four-story scaffolding, the migrant worker who was drinking water from the four-story scaffolding quickly rushed to the switch box and took a power off. However, Yang Moumou died after being rescued, causing huge damage to the deceased's family.

Accident analysis:

According to the analysis of the investigation results, the technical reasons leading to this electrocution accident are as follows:

The direct cause of the charging of the mortar machine: The mortar machine as a whole is entirely of metal construction and is tightly integrated with the motor. The motor terminal box is square, and there should be 4 screws to connect the bottom of the box with the lid. However, only 1 screw was found after the accident and it was loose (the other 3 screws were never found in the field), resulting in the motor terminal box cover and box. The bottom connection is not strong. When the deceased, after using the 7. 2 m long iron pipe, Yang Moumou randomly (just right) dumped one end of the iron pipe on the cover of the motor terminal box. The junction box had only one screw in the lower left corner and was not tightened. Such a large load is “forced” to shift downward, causing the inner wall of the metal terminal box cover to touch the right phase terminal (both exposed in the box) on the bottom of the terminal box, causing the mortar machine and the motor to become electrically charged as a whole.

The indirect reasons that cause the mortar machine to be charged are as follows: 1 When the operator prepares to pour the mixed mortar out of the mixing tank, only the stop stirring button is pressed, and the three-phase knife gate in the electric gate box is not pulled open (the electric gate box No lock during door usage.) 2 The protection neutral line should be connected to the reliable connection of the casing of the electrical equipment, but the site electrician inserts one end of the protection neutral wire into the gap between the junction box cover of the motor and the bottom of the box and there is a rubber seal apron, so when the iron is When the tube cover is on the cover of the motor terminal box, when the cover is offset downward, the end point of the protection zero line also shifts off and falls off at the same time and loses its protective effect. 3 According to the relevant provisions on safe electrical use, each electrical equipment should be equipped with a current-type leakage protection device separately, but not only the leakage protection device is installed on the electrical circuit of the mortar machine, but also the protective repeated grounding has not been done, resulting in the Mortar machine is charged for a long time.

The direct cause of death from electrocution by Yang Moumou was: Yang Moumou wore rubber-soled shoes on the day and the ground around the mortar machine was quite moist. The cloth shoes were already soaked. He used naked and wet hands with water drops without any protection. Under the touch of the charged mortar machine, the accident current was formed from the deceased's hands through the heart and other parts and grounded by the feet, causing Yang to suffer serious step voltage hazards.

Yang Moumou indirect causes of electrocution are: 1 Yang Moumou wear rubber sole shoes, but has been watered through the morning work. Working in such an environment, if you wear insulated boots, you can completely avoid the death of the disaster. 2 The mortar supporter is not equipped with a rubber insulation cover. If a rubber insulating sleeve is installed, an electric shock will occur and it will not cause death. 3 The protection neutral line is disconnected (detached) and there is a phase collision (leakage). Because the human body resistance is much larger than the natural grounding resistance of the device, the human body almost bears all the hazards of the phase voltage. 4 Electricians (farmer contract workers) are of low quality and weak technical knowledge. In the case of quite damp and possibly splashed with water, the zero line is actually sandwiched between the bottom of the terminal box and the lid. No consideration should be given to sealing the terminal box with an insulating waterproof tape or to the box. In the three phase line connections, we did not think of protecting the zero line in the motor terminal box. This shows that the site technicians have low technical quality and poor safety awareness.

Site management reasons. In addition to the above technical reasons, the following causes of electrocution deaths still exist in the following management aspects: 1 The concept of the legal system in the three aspects of the project is weak, and safety inspections are in the form. According to the requirements of the relevant documents, the construction (investment) units, the general contracting companies, and the engineering subcontracting companies shall perform regular, regular, general, and professional inspections on the safety conditions at the construction site. However, the three aspects of on-site safety inspection records are blank, and it is indifferent to whether or not a special operator is holding a certificate, and the motor terminal box screw is not a shortage of motors for the mortar machine. 2 The quality of personnel is low. In addition to project managers and other responsible persons at the site, most of the actual operators are contract farmers for recruitment, and none of them are specially trained special operators. The agricultural contract workers who provided the motor wiring for the accidental mortar machine had neither an electrician certificate nor a rackwork worker's license. However, at the site, both the electrician and the scaffolding were erected. 3 equipment is not standardized. The mortar was placed at a distance away from the water pipe, and after being diverted with a rubber hose, it was short (about 4. 7 m long) and could not reach the mortar machine. The on-site management personnel did not pay attention to this problem, resulting in the deceased's Yang Moumou finding the iron pipe (heavy and unwieldy). One end was connected to the rubber hose and the other end was filled with water in the mortar machine. The tube flung sideways and touched the junction box of the motor. It was the fuse that caused the accident of electrocution.

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