At the beginning of external blowing and zinc wiping for galvanized steel pipes, it is required to double the gas flow rate to ensure the pipes enter the gas field. There are two reasons for this:
(1) The end of the galvanized steel pipe that first leaves the zinc bath cools longer in the air, resulting in a quicker solidification of the galvanized layer. Therefore, a larger gas flow rate is needed to increase the blowing and wiping force, in order to blow off and smooth out the excess zinc liquid on the nearly solidified galvanized layer.
(2) When the galvanized steel pipe has not yet entered the nozzle ring opening, the gas diffuses rapidly and cannot be concentrated on the head of the pipe end for blowing and wiping, leading to insufficient blowing and wiping force. Therefore, the gas flow rate must be increased to rectify this. Once the galvanized steel pipe enters the nozzle ring opening, the gas is effectively blown onto the outer surface of the galvanized steel pipe, significantly increasing the blowing and wiping force. At this point, the blowing gas volume can be appropriately reduced.
