I. National standard marking 

 The flange should be marked according to the nominal diameter, nominal pressure, sealing surface code, the matching steel pipe series code (the meter pipe code is "Series 2", and the British pipe is not marked) and the standard number. 

 Example of label: nominal diameter 80mm, nominal pressure 4.0MPa (25bar) convex welded steel pipe flange (with metric pipe) 

 Flange DN80-PN40 M (series 2) GB/T9115.2-2000, nominal diameter 100mm, nominal pressure 5.0MPa (25bar) with neck flat welded steel pipe flange (with English pipe) flange DN100-PN50 RF GB/T9116.1-2000. 

 II. Standard Mark of the Ministry of Machinery 

 Label example: nominal diameter 500mm, nominal pressure 1.6MPa, series 2 flat welded steel pipe flange 

 Flange 500-16 JB/T81-94 

 The nominal diameter is 300mm, the nominal pressure is 6.4MPa, and the concave face-to-weld steel pipe flange of Series 1 

 Flange 300-64B (Series 1) JB/T82.2-94 

 (Note: The standard default pipe outer diameter of the Ministry of Machinery is series 2, and the classification of butt welding flange: A-type convex surface, B-shaped concave surface, C-type tention surface, D-type groove surface) 

 III. Standard Mark of the Ministry of Chemical Industry 

 The flange should be marked according to the following provisions (this marking method is recommended) 

 A. Standard number: All types of pipe flanges are uniformly marked with the standard number of this standard: HG20592. 

 B. The flange type code is in accordance with the provisions of Table 5.0.1. 

 When the threaded flange is threaded according to GB/T7306, it is marked as "Th(Rc)" or "Th(Rp)"; 

 When the threaded flange adopts the conical pipe thread specified in GB/T12716, it is marked as "Th(NPT)"; 

 If the thread flange is unmarked, it is Rp (GB/T7306.1). 

 C. Flange nominal diameter DN (mm) and applicable steel pipe outer diameter series: 

 Overall flange, flange cover, lining flange cover, threaded flange, suitable for the marking of the outer diameter series of steel pipe can be omitted; 

 Flanges suitable for international series steel pipes (commonly known as British pipes), marked "DN(A)"; 

 It is suitable for domestic flanges that continue to use series of steel pipes (commonly known as metric pipes), marked as "DN(B)". 

 D. The nominal pressure of the flange is PN,MPa. 

 E. The sealing surface code is according to the provisions of Table 6.0.1. The protruding flange, such as the car-made dense water line, is marked as "RF(A)". 

 F. The wall thickness of the steel pipe should be provided by the user. 

 The wall thickness of the steel pipe should be marked with the neck butt welding flange and the loose sleeve flange of the butt welding ring. 

 G. Material brand. 

 H, others. Adopt requirements or additional requirements that are inconsistent with the provisions of this standard series, such as the surface roughness of the sealing surface. 

 Product parameters 

 The nominal diameter is 1200mm, the nominal pressure is 0.6MPa, and the protruding panel flat welded steel pipe flange with metric pipe is made of Q235A, HG20592 flange PL1200(B)-0.6 RF Q235A 

 The nominal diameter is 300mm, the nominal pressure is 2.5MPa, and the convex belt neck flat welded steel pipe flange is equipped with British pipe. The material is 20 steel HG20592 flange SO300(A)-2.5 M 20 

 The nominal diameter is 150mm, the nominal pressure is 16.0MPa, and the ring connection surface of the English pipe is equipped with neck butt welded steel pipe flange. The material is 16Mn, and the wall thickness of the steel pipe is 10mm. 

 HG20592 Flange WN150(A)-16.0 RJ S=10mm 16Mn 

 The nominal diameter is 200mm, the nominal pressure is 1.0MPa, and the protrusion face welding ring loose sleeve steel pipe flange with metric pipe, the material is: flange 20, butt welding ring 316, steel pipe wall thickness is 4mm, HG20592 flange PJ/SE200(B)-1.0 RF S=4m 20/316