At present, the most common pipe cutting method used by spiral steel pipe manufacturers is plasma cutting. During cutting, a large amount of metal vapor, ozone, and nitrogen oxide smoke will be produced, which will seriously pollute the surrounding environment. The key to solving the smoke problem is how to inhale all the plasma smoke into the dust removal equipment to prevent air pollution.

For plasma cutting of spiral steel pipes, the difficulties in dust removal are:
1. The cold air from the periphery of the suction port enters the suction port from outside the machine gap and the air volume is very large, making the total amount of smoke and cold air in the steel pipe greater than the effective air volume inhaled by the dust collector, making it impossible to completely absorb the cutting smoke.
2. The nozzle of the plasma gun blows air in two opposite directions at the same time during cutting, so that smoke and dust emerge from both ends of the steel pipe. However, it is difficult to recover the smoke and dust well with the suction port installed in one direction of the steel pipe.
3. Since the cutting part is far from the dust suction inlet, the wind reaching the suction inlet makes it difficult to move the smoke and dust.

To this end, the design principles of the vacuum hood are:
1. The air volume inhaled by the dust collector must be greater than the total amount of smoke and dust generated by plasma cutting and the air inside the pipe. A certain amount of negative pressure cavity should be formed inside the steel pipe, and a large amount of outside air should not be allowed to enter the steel pipe as much as possible to effectively Suction the smoke into the dust collector.
2. Block the smoke and dust behind the cutting point of the steel pipe. Try to prevent cold air from entering the inside of the steel pipe at the suction inlet. A negative pressure cavity is formed in the internal space of the steel pipe to prevent smoke and dust from coming out. The key is to design the facilities to block the smoke and dust. It is made reliably, does not affect normal production, and is easy to use.
3. The shape and installation location of the suction inlet. The suction port must be used to suck more smoke and dust inside the steel pipe into the pipe to achieve the effect. Add a baffle behind the cutting point of the plasma gun to retain the smoke and dust inside the steel pipe. After a period of buffering, it can be completely sucked out.

specific measure:
Install the smoke baffle on the trolley inside the steel pipe and place it about 500mm from the cutting point of the plasma gun. Stop for a while after cutting the steel pipe to absorb all the smoke. Note that the smoke baffle needs to be accurately positioned at the position after cutting. In addition, to make the rotation of the traveling trolley supporting the smoke baffle and the steel pipe coincide with each other, the angle of the traveling wheel of the traveling trolley must be consistent with the angle of the inner roller. For plasma cutting of large-diameter spiral welded pipes with a diameter of about 800mm, this method can be used; for pipes with a diameter less than 800mm, smoke and dust with small diameters cannot emerge from the direction of the pipe exit, and there is no need to install an internal baffle. However, at the smoke suction inlet of the former, there must be an external baffle to block the entry of cold air.