Connection mode and characteristics of spiral steel pipe

　　The allowable deviation of the wall thickness of spiral steel pipe shall not exceed plus or minus 10% of the nominal wall thickness when the wall thickness is less than 10 mm, and it shall be plus or minus 8% of the wall thickness when the wall thickness is greater than 10 mm, except for the wall thickness of the bending angle and weld area. Generally, the delivery length of spiral steel pipe is 4000mm-12000mm, with the majority of 6000mm and 12000mm. Spiral steel pipe is allowed to deliver short and non fixed length products not less than 2000mm, and can also be delivered by interface pipe.

　　However, the Demander shall cut off the interface pipe during operation. The weight of short and non fixed length products shall not exceed 5% of the total delivery quantity, and the spiral steel pipe with theoretical weight greater than 20kg / m shall not exceed the total delivery quantity. According to the different connection modes, spiral steel pipe can be divided into adhesive socket pipe fitting, elastic sealing pattern socket fitting, threaded joint fitting and flange connecting pipe fitting.

　　According to different processing methods, pipe fittings are divided into injection molding pipe fittings and pipe bending forming pipe fittings. The reduction factor of nominal pressure and temperature is due to the sensitivity of plastic products to pressure and temperature.

　　When the water delivery temperature is different, the working pressure should be corrected according to the reduction coefficient of different temperatures given. The technical requirements are that the internal and external surfaces of various pipe fittings should be smooth and no delamination is allowed. Obvious bubble, mark, cold spot and uneven color and other defects. For the injection molded spiral steel pipe, the wall thickness of the main body outside the socket connection part shall not be less than the wall thickness of the pipe with the same specification and pressure grade; the average outer diameter of the pipe fitting socket shall comply with the provisions on the average outer diameter and deviation of the pipe.