1. After the accident
A welder in a hardware store was repairing the compressor and condenser in the shop. During the final air pressure test, because there was no compressed air, the welder replaced it with oxygen. When the pressure test reached 0.98mpa, the compressor leaked, and the welder immediately repaired the welding. At the moment of arc striking, the compressor exploded immediately, the shop was blown up, the welder was killed on the spot and many people were injured.
2. Analysis of main reasons
(1) The shop can't be used as a welding place.
(2) All hole covers should be opened before welding repair, and welding must be repaired without pressure.
(3) Oxygen is a combustion-supporting substance and cannot replace compressed air.
3. Main preventive measures
(1) The shop can't be used as a welding place. If it is urgent to weld, practical protective measures should be taken, that is, there are no flammable items in the hot spot 10m, and corresponding fire extinguishing equipment is available.
(2) When repairing welding, the pressure shall be relieved.
(3) It is forbidden to use oxygen instead of compressed air for pressure test.
Example 12: The stevedores violated the rules, causing the oxygen cylinder to explode.
1. After the accident
A unit used a truck to transport the newly filled oxygen. For convenience, the stevedores pedaled the oxygen cylinder from the car. The first cylinder just fell, and the second cylinder just hit it, which immediately caused two cylinders to explode, causing one death and one injury.
2. Analysis of main reasons
Two gas cylinders collide with each other, and the compressed gas is violently vibrated when the oxygen cylinders collide, causing the pressure to rise, so that the pressure generated somewhere in the gas cylinder exceeds the strength limit of the bottle wall, which causes the gas cylinder to explode.
3. Main preventive measures
(1) When handling oxygen cylinders, avoid collision and violent vibration, and wear safety helmet and shockproof ring.
(2) It is forbidden to roll when loading and unloading oxygen.
Example 13: welding repair acid tank explosion
1. After the accident
When the bottom of the tank carrying sulfuric acid leaked in a certain unit, when repairing welding, the tank bottom was placed on the ground with the manhole down. When the welder started the arc, the acid tank exploded, burning the welder on the spot and killing one worker present.
2. Analysis of main reasons
Through sampling analysis, it is known that the tank material is not acid-resistant steel, and under the action of dilute sulfuric acid, iron in the tank material can react with acid as follows:
fe + h2so4＝feso4 + h2↑
According to the above formula, the acid tank will be filled with the mixed gas of hydrogen and air, and the content of hydrogen in the air exceeds the explosion limit range, so it is obvious that the mixed gas in the tank is exploded by electric welding sparks.
3. Main preventive measures
Before welding acid and alkali tanks, it is necessary to know the situation in the tanks first, and then clean them with (alkali) water. Only when the liquid or gas in them is exhausted and the weldments are not sealed can welding be carried out. The tank containing dilute sulfuric acid shall be made of acid-resistant steel plate or lead-lined steel plate.
Example 14: welding repair diesel tank exploded.
1. After the accident
The oil outlet pipe of a diesel tank loaded by a car in a tractor factory is damaged near the oil valve and needs welding repair. After the operator discharged the diesel oil in the tank, he did not clean it, but only opened the manhole cover to carry out welding repair, which immediately exploded, killing three people at the scene.
2. Analysis of main reasons
(1) After the diesel oil in the oil tank is discharged, there is still an oil film on the inner surface of the tank wall, and the volatile oil gas enters the tank and forms an explosive mixed gas with the air, which is detonated by welding at high temperature.
(2) The welder blindly welds and repairs, resulting in an accident.
3. Main preventive measures
(1) The diesel tank must be replaced before welding, and can only be repaired after reaching the standard of cleaning.
(2) When welding, all covers and valves of the oil tank should be opened, and compressed air should be introduced.
Example 15: explosion of alcohol barrel repaired by welding.
1. After the accident
The pharmaceutical workshop of a factory sent a leaking alcohol barrel to the machine repair group for welding repair. Shortly after the welder A welded, the alcohol barrel exploded, and the flying barrel cover cracked the head of the armor and died on the spot.
2. Analysis of main reasons
The alcohol barrel is not cleaned before welding, and there is still alcohol in the barrel. Alcohol is volatile and forms explosive mixed gas with air in a closed container, which is ignited and exploded during gas welding.
3. Main preventive measures
(1) The container containing alcohol must be cleaned with clean water before welding, and the lid of the barrel should be opened for welding.
(2) Before welding, the welder must find out what inflammable and explosive articles have been installed in the container and the cleaning situation, and don't blindly use hot welding to repair them.
Example 16: aft cabin explosion caused by arc striking by welder.
1. After the accident
Two oilers in a shipyard sprayed paint for the last time in a closed stern compartment, and the painting work was finished by noon. When leaving the aft cabin, leave with the manhole cover half open and half closed. There are no signs around the hatch cover that suggest danger (such as the cabin has been painted and the fire can't get close, etc.). At about 3 pm, an outfitting riveter boarded the ship to install a small frame, and the working position was close to the stern cabin. When the gas cutting was ignited, the riveter found that he didn't bring the electronic lighter, so he asked the welder to help him light the fire. The welder conveniently picked up the electrode holder and struck an arc on the stern hatch cover. Then there was a loud noise and the stern hatch exploded. Eight people were killed and six injured on the spot.
2. Analysis of main reasons
(1) The flammable gas of benzene in paint mixed with air reached the explosion limit. In addition, the hot weather aggravated the concentration of flammable gas in benzene, so it exploded immediately in case of fire.
(2) Warning signs and guardians are not set after the stern cabin is painted.
(3) No ventilation measures were taken in the aft cabin after painting.
3. Main preventive measures
(1) Warning signs and guardians should be set around the stern compartment.
(2) Compressed air should be introduced into the stern cabin to reduce the concentration of combustible gas.
(3) When the welder strikes the arc, pay attention to the surrounding environment (i.e. inflammable and explosive substances).
Example 17: welding-filled gasoline tank explosion
1. After the accident
An empty gasoline tank with cracks in the motorcade of a factory needs to be repaired by welding. The welder class suggested that it was dangerous to weld directly without taking measures, but the motorcade said that the empty tank was dry and not dangerous. Results Without taking any safety measures; Even if the cover of the oil filler is not opened, it will be repaired by welding. The situation at the scene is that a welder is squatting on the ground to burn gas welding, and another worker is holding a petrol tank with his hand. At the beginning of welding, the gasoline tank exploded, the heads at both ends flew out, the tank body was blown into an iron plate, and the gas welder who was operating was killed.
2。 Main cause analysis
The explosion limit of motor gasoline is 0.89% ~ 5.16%, and the lower explosion limit is very low. Therefore, although the empty barrel is dry, as long as the micropores on the rust surface of the inner wall of the barrel absorb a small amount of residual oil, or the residual oil or even gasoline vapor volatilized and diffused in the seam of the barrel, it is easy to reach and exceed the lower explosion limit, and it will explode in case of welding flame or arc. In addition, the lid of the hole that can be opened is not opened, and the explosion is more powerful.
3. Main preventive measures
(1) It is forbidden to repair and cut fuel containers and pipelines without safety treatment.
(2) It is forbidden to repair and cut sealed containers without holes by welding.
(3) The welding repair of fuel container shall take relevant safety organization measures according to regulations.
Example 18: Gas-cut petrol tank exploded.
1. After the accident
An army somewhere pulled an empty barrel filled with gasoline by car. Without any formalities, directly find the gas welder's armor and ask to cut the empty oil drum from the middle. At that time, A asked for cleaning before cutting. Two soldiers took the oil drum away. L hours later, the two soldiers pulled the oil drum back again and said to A, "Wash it twice with 2 Jin of alkali and hot water, and then wash it twice with clear water." A will open the big and small hole covers of the oil drum; Put it horizontally on the ground and stand at one end of the bottom of the barrel for cutting. No sooner had a small hole been cut through than the oil drum exploded. The bottom of the barrel was exploded, crushing the legs of A into comminuted fractures. The bottom of the barrel flew out nearly 5 meters, and the barrel moved back1.5 meters.
2. Analysis of main reasons
(1) The gasoline barrel was not cleaned thoroughly, and there was still residual gasoline and its vapor in the barrel. The cutting flame ignited the gasoline in the barrel and exploded.
(2) The oil drum is cut blindly without gas analysis after cleaning; Cause an accident.
3. Main preventive measures
(1) Before welding and cutting the container containing fuel oil, it must undergo strict safety treatment such as cleaning and replacement, and it can only be repaired or cut when it is hot after gas analysis and testing.
(2) When repairing or cutting an empty oil drum, the hole cover should be opened, and the oil drum should be placed horizontally on the ground. The operator should stand on the side of the drum to avoid the operation of the oil drum cover, in case of explosion, the oil drum end cover (weak strength here) will burst and hurt people.