Cutting method of thick wall spiral steel pipe

　　The most common pipe cutting method of spiral steel pipe manufacturers is plasma cutting. When cutting, there will be a lot of metal vapor, ozone, nitrogen oxide smoke and dust, which will severely pollute the surrounding environment. The key to deal with the problem of dust is how to inhale all the plasma dust into the dust removal equipment, and then avoid air pollution.

　　As for plasma cutting of spiral steel pipe, the difficulties of dust removal are as follows:

　　1. When the nozzle of plasma gun is cut, the air blows out in two opposite directions together, and then the smoke and dust will come out from both ends of the spiral steel pipe. However, it is difficult to recover the smoke and dust from the suction port of the device in one direction of the spiral steel pipe.

　　2. The cold air outside the suction inlet enters the suction inlet from the outside of the machine open space, and the air volume is large, so that the total amount of smoke and cold air in the spiral steel pipe is larger than the effective air volume inhaled by the dust remover, and then it is impossible to completely absorb the cut smoke.

　　3. Because the cut part is far away from the dust suction inlet, the wind force reaching the suction inlet is difficult to pump the dust.

　　For this reason, the design principle of the dust cover is:

　　1. The air volume inhaled by the precipitator should be larger than the total amount of smoke and dust produced by plasma cutting and the air inside the pipe. A certain amount of negative pressure cavity should be formed inside the spiral steel pipe, and a lot of external air should not be allowed to enter the steel pipe as far as possible, so as to effectively absorb the smoke and dust into the precipitator.

　　2. In the future, the smoke and dust shall be blocked at the cutting point of the spiral steel pipe, and the cold air at the suction inlet shall be avoided to enter the spiral steel pipe as far as possible. A negative pressure chamber shall be formed in the internal space of the spiral steel pipe to prevent the smoke and dust from emerging. The key is that the equipment to prevent the smoke and dust shall be designed and manufactured firmly, which will not affect the normal production and convenient use.

　　3. Shape of suction inlet and device position. It is necessary for the suction inlet to absorb more smoke and dust inside the steel pipe into the pipe to achieve the effect. A baffle shall be added in the future direction of the plasma gun cutting point to retain the smoke and dust inside the steel pipe, and it can be completely removed after a period of buffer.

　　Specific measures:

　　Put the dust baffle device on the traveling trolley inside the steel pipe and place it at the cutting point of the plasma gun about 500mm. After the spiral steel pipe is cut off, stay for a while to absorb all the dust. Note that the soot baffle should be precisely positioned in the cut-off position. In addition, in order to make the traveling trolley supporting the soot baffle and the spiral steel tube roll in accordance with each other, the traveling wheel angle of the traveling trolley must be consistent with the inner roll angle.

　　This method can be used for plasma cutting of large-diameter spiral welded pipe with a diameter of about 800mm; as for the pipe with a diameter less than 800mm, the smoke and dust with a small diameter can not be emitted from the direction of the pipe outlet, and it is not necessary to install internal baffles. However, there must be an external baffle to block the cold air at the smoke suction inlet of the shaper.