The Class And Technical Requirements of Welding Neck Flanges
Welding neck flange is easy to use and can bear relatively large pressure. The materials for welding neck flange vary from low pressure asbestos pad, high pressure asbestos pad to metal pad due to the different pressure.
We use different ways and processes in the development and manufacturing. For example, we add a certain of elements in the actual production process, in order to increase the characteristics and value of carbon steel flange.
Welding neck flange is widely used in industrial pipelines. You can't see any welding neck flange in household, because the pipe has small diameter and low pressure. But if you are in a boiler room or production field, they are filled with flanges which connected with pipes or equipment.
We adopt a certain technical parameters and requirements in actual WN flange manufacturing process, in order to assure the correct use and promotion according to a certain ways and principles. Meanwhile, we produce and weld flanges by a certain techniques and principles so as to make sure the reliable quality of welding neck flanges.
The requirements of product level and techniques of welding neck flange should be consistent with the related specification of JB4726-4728. According to the standard, carbon steel or austenitic stainless steel forgings with nominal pressure of 0.25MP to 1.0MPa are allowed to be manufactured by ClassⅠforgings. For those forging pieces with nominal pressure of 1.6MPa-6.3MPa should meet the standard of Class II or above. As for the flange
forging piece with nominal pressure which is not lower than 10.0MPa, chromium molybdenum steel forgings with over 4.0MPa, ferritic steel forgings products with more than 1.6MPa and working temperature of no more than 20 ℃, they must comply with the requirements of Class III forgings.
Usually welding neck flanges are made from forging or forging and rolling technologies. And if you want to use steel plate or structural steel to produce welding neck flanges, they must comply with the related specification. Welding neck flange must be detected by ultrasonic flaw detecting, should have no laminar defects. You can cut the steels into strips based on the rolling direction, weld them into a ring by bending technique, and formed ring cylinder on the surface of the steel. You can't form the steel plate into welding neck flanges. You should adopt full penetration butt weld for the ring, and there should be a heat treatment after welding and 100% ray or ultrasonic flaw detection tests. And its ray detection results should fit the requirements of JB4730 concerning Class II, ultrasonic detection results should satisfy the requirements of JB4730 concerning Class I.