(1) In the system, the inner and outer walls of hot-dip galvanized steel pipes or the inner and outer walls of hot-dip galvanized seamless steel pipes with pipe diameter < DN100 can be connected by threads. When the system uses hot-dip galvanized steel pipes on the inner and outer walls, the pipe fittings can use forged iron threaded pipe fittings (GB3287~3289); when the system uses hot-dip galvanized seamless steel pipes on the inner and outer walls, 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 connection.
(3) When the pipe adopts 55° tapered pipe thread (Rc or R), the threaded interface can be sealed with PTFE tape; when the pipe adopts 60° tapered pipe thread (NPT), it is advisable to use sealant as the seal of the threaded interface. ; The sealing tape should be applied on the male thread.
(4) Pipes with a pipe diameter > DN50 shall not use threaded joints, and single-piece reducing joints should be used at the pipe diameter reduction.
