The maximum water flow speed allowed in the spray pipe is mainly considered the economy of water supply, water head loss (energy loss is proportional to the square of the speed), when the flow rate is too large, the energy loss per unit length is too large, it is not economical, so the automatic spray design code (GB50084-2001) article 9.2.1 stipulates: The spray pipe water flow speed should be economic flow rate, if necessary, it can exceed 5m\/s, but not more than 10m\/s. The maximum water flow speed allowed in the spray pipe is not directly related to the size of the pipe diameter and the thickness of the pipe wall, but the size of the pipe diameter and the thickness of the pipe wall are related to the pressure in the pipe, which belongs to the calculation problem of the wall strength.