Introduction to flange types and models

Steel pipe flanges include plate-type butt weld flanges. Plate flat welding flanges are named according to their flange type. Steel pipe flanges are named according to their purpose. Basically, the former is a certain form of the latter. That is, it includes a relationship of being included.

Thank you to the original poster for sharing. It would be even better if different pipeline pressure standards could also be shared

GB50236-1998 and JB4708-2000 classify base metals in different ways; in GB50236, low-alloy structural steels with a tensile strength threshold of 480–550 MPa are placed in one group, such as 16Mn, 16MnR and 15MnV, 15MnVR, while in JB4708 they belong to separate groups； In JB4708, 12CrMo, 15CrMo, and 12Cr1MoV belong to the same group, whereas in GB50236 they are not ； In GB50236, the 18Cr-8Ni austenitic stainless steels belong to the same group as the 18Cr-12Ni-2Mo and 18Cr-13Ni-3Mo series, whereas in JB4708 they are classified into different groups ； Different groups have distinct rules for the evaluation of welding procedure qualifications, and inspectors should pay close attention to these differences when reviewing such qualifications.

For the piping fittings required for this project, our company strictly adheres to GD87 and other relevant specifications in its implementation. 1.1 Suppression Fitting Section 1. Materials: 1) The materials used are seamless steel pipes and steel plates that comply with the specifications set out in GB3087, GB5310, and GB713 – specifically 20# steel seamless pipes and plates, as well as 12Cr1MoV steel seamless pipes; in addition, seamless pipes and plates made from other steel grades that meet the required standards are also used as raw materials. 2) Steel pipes with a positive deviation and steel plates of greater thickness are used as the blanks for pipe fittings. Since the wall thicknesses of the pipe fittings specified in the standards correspond to the actual wall thicknesses required for the finished products, the blank thickness must be determined by the company after applying an appropriate reduction based on the processing method, and the technical documents accompanying the steel materials must also be reviewed. 2. Manufacturing 1) The inner and outer surfaces of the steel pipe must be cleaned thoroughly, and inspections of both the inside and outside are to be carried out after cleaning ； 2) The inner and outer surfaces of the steel pipe must be free from defects such as cracks, scars, tears, delaminations, and folds. Such defects must be completely removed, and removing them must not result in a wall thickness reduction exceeding the specified tolerance values ； 3) The steel pipe can be spun on a machine tool or cut into tube blanks using an oxy-acetylene flame, and all burrs and uneven edges must be removed by mechanical means ； 4) Tube billet heating method and heating temperature: 4.1) For 12Cr1MoV steel, the upper heating limit is 1050–1100, with the final rolling temperature above 850 ； 4.2) For 20# steel, the upper heating temperature is 1050–1100, with the final rolling temperature above 800 ； 4.3) Other steel grades shall be processed at their specified hot working temperatures and final rolling temperatures ； 4.4) For alloy steel grades, if the final rolling temperature is used in place of normalizing, this temperature is determined by the company based on the characteristics of the steel grade. 5) The heat treatment procedures for pipe fittings are as follows:
Steel grade | Heat treatment procedure
20# | Normalizing at 870~900°C for 15 minutes
10CrMo910 | Quenching at 900~960°C, followed by air cooling or oil cooling; tempering at +700~750°C (air cooling)
12Cr1MoV | If δ≤40: Normalizing at 1000~1020°C for 30 minutes, followed by air cooling; tempering at +720~760°C with a holding time of 3 hours. If δ>40: Normalizing at 1000~1020°C for 30 minutes, followed by oil cooling or forced air cooling; tempering at +720~760°C with a holding time of 3 hours. The holding time for normalizing is determined at 1 minute per mm, while the holding time for tempering is determined at 2 minutes per mm. For other steel grades, our company can decide the appropriate procedures based on specific circumstances. 6) Our company measures the wall thickness reduction for the fittings of each parameter, and conducts random hydraulic pressure tests on batches of fittings. 3. Dimensions and tolerances: Strictly comply with the requirements of GD87 standard ； 4. Inspection and acceptance: 1) Our company’s quality control department conducts inspections in the following order: a) Check the quality of raw materials based on the purchasing conditions ； b. Check the external dimensions ； c. Use an ultrasonic thickness gauge to measure the wall thickness of the high-pressure pipe fittings and keep a record of it ； d. Perform non-destructive testing on the high-pressure fittings to determine whether there are any cracks or other defects, and measure the hardness value after heat treatment ； e. Check the markings and paint on the pipe fittings, etc. 2) After each fitting is inspected, a stamp from the quality control department indicating that the inspection is complete is applied to it ； 3) The data and inspection results related to the pipe fittings are included in the factory technical documents. 5. Packaging markings and documents: 1) Pipe fittings should be painted or coated with grease to prevent rusting during storage and transportation ； 2) Mark the labeling position on each fitting ； 3) The pipe fittings are supplied with factory technical documents in a format specified by the company at the time of shipment.

Base metal grade Welding rod grade Welding wire grade Welding equipment Preheating of welding materials 20Gst45.8 A106B A672B70CL32 J507 (grade) AWS E7015 (model) J50 TIG welding for root pass Manual arc welding Drying at 350°C for 2 hours; holding at 150°C A335 P91 CHROMET9m (E9015-B9) E9018-B9-H4 (model) AWS A5 5-96 (grade) TGS-9cb TIG welding for root pass Manual arc welding Drying at 300–350°C for 2 hours; holding at 150°C 12Cr1 MoV 10CrMo910 E5515-B2 AWS E9015-B3 R317 R407 TIG-R31 TIG welding for root pass Manual arc welding Drying at 350°C for 2 hours; holding at 130°C A335 P22 E6015-B R407 R40 TIG welding for root pass Manual arc welding Drying at 300–420°C; holding at 150°C WB36 AWSA5.5 T065E555 E9018-G-H4 DMO-IG TIG welding for root pass Manual arc welding Drying at 340–380°C; holding at 120–150°C Cr5Mo, Cr9, Cr13, Cr28 AWSE310-15 A407 (O407) TIG welding Drying at 300°C for 1 hour