I. Electrical Accidents
Case 1: Unauthorized powering of the welding machine by a welder leads to an electric shock
Incident Description
A factory welder worked outdoors at a temporary construction site. Due to the lack of a distribution box, he removed the rubber from the end of each power cord wire and connected them to the outdoor power line.
Because he mistakenly connected the neutral wire to the live wire, he was electrocuted and killed while adjusting the welding current and touching the box.
Primary cause analysis
The welder was not familiar with electrical safety knowledge, and the incorrect connection of the neutral wire and the live wire caused the housing of the welding machine to become electrified, causing a fatal electrocution accident.
Primary Preventive Measures
Only certified electricians should connect welding equipment. Welders should not perform this task alone.
Case 2: Electric shock due to touching the welding clamp while changing welding rods
Incident Description
A young welder at a shipyard was welding inside the cabin of a ship. Due to the high temperature in the cabin and the lack of ventilation, his work clothes and leather gloves were soaked with sweat.
She was electrocuted and fell backwards in a spasm as she touched the welding tongs while changing the welding rod. The welding tong fell on her neck and she was unable to remove it, leading to her death despite rescue efforts.
Primary cause analysis
(1) The no-load voltage of the welding machine has exceeded the safe voltage.
(2) The high temperature in the ship's cabin caused the welder to sweat a lot, reducing the body's resistance and increasing the risk of electric shock.
(3) The electric shock was not detected in time, allowing the electric current to pass through the body for a longer time, causing severe damage to vital organs such as the heart and lungs, leading to unsuccessful rescue efforts.
Primary Preventive Measures
While working in the booth, a supervisor must be appointed to monitor the welder's condition at all times. If there is any sign of danger, the power must be immediately cut off for rescue.
Case 3: Electrical accident caused by a burnt terminal board that electrified the welding machine housing
Incident Description
While spot welding an iron casing in a factory, welders A and B noticed a broken wire on the welding machine. An electrician only provided them with a piece of flexible wire for B to replace himself.
While B was changing the wire, he noticed that the screw on the primary line terminal board was loose, so he tightened it with a wrench (at this time, A was not there). After testing the welding a few times, B left the scene.
A returned later and, unaware of the situation, began welding points. After just one weld, A screamed and fell to the ground. Worker C immediately cut off the power, but A died because rescuers did not arrive in time.
Primary cause analysis
(1) The terminal board burned out, causing the welding machine coil and housing to collide and short circuit.
(2) The welding machine housing was not grounded.
Primary Preventive Measures
(1) Equipment maintenance must be carried out by an electrician.
(2) Welding equipment must be grounded.
Case 4: A welder failed to wear required protective equipment, resulting in fatal electrocution
1. Accident details
In a structural workshop of a machinery factory in Shanghai, several welding machines were used to weld product bases.
During a moment when a welder was turning on the circuit breaker with his right hand and holding the welding machine with his left, he suddenly screamed and fainted. Despite immediate medical intervention, he died.
2. Root cause analysis
(1) The welding machine housing has been electrified.
(2) The welder was not wearing insulated gloves or shoes.
(3) The grounding of the welding machine has failed.
3. Primary Prevention Measures
(1) Equipment insulation and grounding must be checked for damage before work.
(2) Welders must wear personal protective equipment.
(3) When pushing or pulling the power circuit breaker, wear insulated gloves, act quickly, and stand aside.
Fire Accident
Case 5: A welder causes a fire by using oxygen for displacement while welding inside a container
1. Accident details
A maintenance welder at a pesticide factory entered a reproduction vessel (1 m in diameter, 2 m in height) to weld a baffle. Without installing a smoke exhaust system, he blew oxygen into the pan to eliminate the smoke.
Upon entering the welding pan again, a loud bang was heard, and the welder suffered burns covering 88% of his body, 60% of which were third-degree burns. He succumbed to his injuries seven days later.
2. Root cause analysis
(1) Using oxygen as a source of ventilation is a serious violation.
(2) No ventilation device has been installed for welding inside the container.
3. Primary Prevention Measures
(1) A ventilation device must be installed for welding inside a container.
(2) The ventilation source must be compressed air.
Case 6: The regulator of an oxygen cylinder catches fire and is destroyed
1. Accident details
While welding, a gas welder on a construction crew used a leaky torch. The flame from the adjustment wheel burned the welder's palm, causing blisters. Despite applying badger oil and continuing to work, it backfired again during the welding process.
The oxygen hose exploded, the regulator caught fire and was destroyed. By the time the oxygen cylinder valve was closed, the top half of the cylinder was too hot to touch, posing a serious hazard.
2. Root cause analysis
(1) A leaky torch has a tendency to backfire.
(2) The valve and regulator of the oxygen cylinder were lubricated, causing it to backfire, which caused intense burning due to the strong oxidation effect of compressed pure oxygen.
3. Primary Prevention Measures
(1) Before gas welding, check the torch for leaks. If leak is found, discontinue use and continue welding only after repair.
(2) Do not use grease gloves to open the valve and regulator of the oxygen cylinder.
Case 7: Inadequate welding location leads to large fire
1. Accident details
A welder at a shipyard applied for a hot work permit. The firefighter approved the request without visiting the site.
After the welder used a torch to cut a piece of metal, sparks ignited the oil residue beneath the ship, causing a large fire.
Attempts to put out the fire with water and extinguishers were unsuccessful, resulting in five deaths, one serious injury and three minor injuries.
2. Root cause analysis
(1) The firefighter was negligent and approved the hot work without inspecting the site.
(2) There was oil residue below the hot work area.
(3) Personnel on site had no knowledge of firefighting.
3. Primary Prevention Measures
(1) Firefighters must inspect the site before approving hot work.
(2) Oil residues under the hot working area must be cleaned up.
(3) Employee safety education should be improved.
Case 8: Unauthorized operation results in a major fire disaster at the end of the century
1. Accident details
On the night of December 25, 2000, Christmas Eve, Dongdu Mall in Luoyang Old Town was brightly lit. Taiwanese businessmen recently rented a floor and basement in Dongdu Shopping Mall to open a Luoyang branch of Zhengzhou Dennis department store, which was scheduled to open for trial operation on the 26th.
While they were busy decorating, a nightclub on the 4th floor of the mall was organizing a Christmas carnival.
However, while everyone was immersed in Christmas cheer, some small sparks from electric welding downstairs set the basement under renovation on fire.
Fire and thick smoke quickly reached the top-floor nightclub, causing a massive disaster that claimed 309 lives.
2. Root cause analysis
(1) The direct cause of the fire was that the four welders hired by Dennis had not received safety training and were working in violation of regulations without special operating authorization.
(2) No preventive measures were taken. The reckless construction led to falling red-hot welding slag and the ignition of flammable items such as wooden furniture and sofas in the basement furniture store.
(3) In panic, some tried to put out the fire with a cage of water, but were unable to do so. Instead of alerting authorities, they fled the scene, delaying fire suppression and evacuation opportunities, causing 309 deaths from smoke inhalation.
3. Primary Prevention Measures
(1) Welders must have appropriate certification; Fire prevention should be a priority during the welding process.
(2) Suitable protective measures must be taken at the welding site.
(3) A dedicated safety officer must be assigned to monitor possible fire hazards.
