What slotted steel pipes are there in the fire fighting equipment?

There are seams on the pipe body of slotted steel pipe. According to the joint form, it can be divided into welded steel pipe, straight seam rolled pipe and spiral rolled pipe. (1) Welded steel pipe and galvanized welded steel pipe Welded steel pipe is formed by rolling steel strip or steel plate blank, high-frequency welding and finishing. Among the welded steel pipes, those that are not galvanized inside and outside are called black iron pipes and water gas pipes; Galvanized steel pipes, white iron pipes and galvanized water gas pipes are called galvanized steel pipes inside and outside, all of which are made of easily weldable steel. See table 3- 10 for the outside diameter, wall thickness, allowable deviation and theoretical weight of galvanized welded steel pipes and welded steel pipes. Galvanized welded steel pipes and welded steel pipes are divided into ordinary steel pipes and thickened steel pipes according to their wall thickness. See Table 3- 1 1 for their test pressure and maximum working pressure (temperature less than or equal to 2000C). For fire fighting with working pressure equal to or less than 1 M Pa, when the working pressure of the system is greater than 1 MPa, thick steel pipes or seamless steel pipes should be selected. (2) Large-diameter welded steel pipe for low-pressure fluid (straight-seam steel pipe) Large-diameter steel pipe for low-pressure fluid transportation is produced according to GB/T 14980-94 standard. See table 3-12 for the outside diameter, wall thickness and theoretical weight of the pipe; The allowable deviation of pipe outer diameter shall not exceed 0.8% DN；; The allowable deviation of pipe wall thickness shall not exceed12.5% s; The pipeline length is 6- 12m. See table 3- 13 for the pressure values of the hydrostatic test. (3) Spiral slit steel pipe for low-pressure fluid is a steel pipe with large diameter rolled by narrow steel strip. Its weld is not a straight seam along the axial direction of the pipeline, but a spiral wound around the central axis of the pipeline at a certain angle.