At present, the most common pipe cutting method for spiral steel pipe manufacturers is plasma cutting, which will generate a large amount of metal vapor, ozone, and nitrogen oxide smoke during cutting, which will seriously pollute the surrounding environment. The key to solving the root problem is how to inhale all the plasma soot into the dust removal equipment, to prevent air pollution.
For plasma cutting of spiral steel pipe, the difficulty of dust removal is:
1. The cold air around the suction port enters the suction port from outside the machining gap and the air volume is large so that the total amount of smoke and cold air in the steel pipe is greater than the effective air volume inhaled by the dust collector, so it becomes impossible to completely absorb the cutting smoke and dust.
2. When the nozzle of the plasma gun is cutting, the air is blown out in two opposite directions at the same time, so that the smoke and dust emerge from both ends of the steel pipe, and the suction port is installed in one direction of the steel pipe is difficult to recover the smoke and dust well.
3. Since the cutting part is far away from the dust suction inlet, it is difficult for the wind reaching the suction inlet to draw the smoke and dust.
To this end, the design principles of the hood are:
1. The air volume inhaled by the dust collector should be greater than the total amount of smoke and dust generated by plasma cutting and the air inside the pipe. It should form a certain amount of negative pressure cavity inside the steel pipe, and try not to let the outside air enter the steel pipe in large quantities. Suck the fumes into the dust collector.
2. Block the smoke and dust at the position after the cutting point of the steel pipe, try to avoid cold air from entering the inside of the steel pipe at the suction port, and form a negative pressure cavity in the inner space of the steel pipe to prevent the smoke and dust from emerging. The key is to design the facilities to block the smoke and dust. The production is reliable, does not affect normal production, and is convenient to use.
3. The shape and installation position of the suction port. To achieve the effect, the suction port must suck more smoke and dust inside the steel pipe into the pipe to achieve the effect. Add a baffle at the position after the cutting point of the plasma gun to keep the smoke and dust inside the steel pipe, and it can be completely absorbed after buffering for some time.
Install the soot baffle on the accompanying trolley inside the steel pipe and place it about 500mm from the cutting point of the plasma gun. After the steel pipe is cut, stay for a while to absorb all the soot. Note that the fume baffle needs to be accurately positioned in the cut-off position. In addition, to match the rotation of the accompanying trolley supporting the fume baffle with the steel pipe, the wheel angle of the accompanying trolley must be consistent with the angle of the inner roller.
For plasma cutting of large-diameter spiral welded steel pipes with a diameter of about 800mm, this method can be used; for a diameter of less than 800mm, the smoke and dust with small pipe diameters cannot emerge from the direction of the pipe, and there is no need to install an internal baffle. However, at the fume suction port of the former, there must be an external baffle to block the entry of cold air.