Fire steel piping connection method

1. Groove type (clamp) connection

(1) The grooved connector (pipe joint) and the depth of the steel pipe groove should meet the requirements of "Grooved Pipe Joint" (CJJ/T156-2001). The working pressure of grooved pipe joints with a nominal diameter of DN≤250mm is 2.5MPa, and the working pressure of grooved pipe joints with a nominal diameter of DN≥300mm is 1.6MPa.

(2) Flexible joints should be used in places with vibration and buried pipelines. Rigid joints should be used in other places. When rigid joints are used, a flexible joint should be set every 4 to 5 rigid joints.

2. Threaded connection

(1) In the system, the inner and outer wall hot-dip galvanized steel pipes or inner and outer wall hot-dip galvanized seamless steel pipes with pipe diameters less than DN100 can be connected by a thread. When the system uses inner and outer wall hot-dip galvanized steel pipes, the pipe fittings can use forged cast iron threaded pipe fittings (GB3287~3289); when the system uses inner and outer wall hot-dip galvanized seamless steel pipes, the pipe fittings can use forged steel threaded pipe fittings (GB/T14626). ).

(2) If the wall thickness of the steel pipe is less than δ<Sch30 (DN≥200mm) or the wall thickness is less than δ<Sch40 (DN<200mm), threaded connectors shall not be used for the connection.

(3) When the pipeline adopts 55° tapered pipe thread (Rc or R), the threaded interface can be sealed with PTFE tape; when the pipeline adopts 60° tapered pipe thread (NPT), the sealant should be used as the seal of the threaded interface; The sealing tape should be applied on the male thread.

(4) Threaded unions shall not be used for pipes with diameters> DN50, and single reducing joints shall be used at the pipe diameter change.

3. Welding or flange joints

(1) Flange types can be divided into flat welding flanges, bimetal welding, butt welding flanges, and threaded flanges according to the connection form. Bimetallic welded steel pipe is a new type of pipe. The flange selection must comply with steel pipe flanges (GB9112～9131), steel butt welded seamless pipe fittings (GB/T12459), and pipe flanges are covered with PTFE Gasket (GB/T13404) standard.

(2) If the hot-dip galvanized steel pipe adopts a flange connection, a threaded flange should be used. When the system piping adopts a non-corrosion-resistant inner wall, it can be connected by welding. Pipeline welding should comply with the "Code for Construction and Acceptance of Field Equipment and Industrial Pipeline Welding Engineering".