Summary of various flange knowledge

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1. Classified according to chemical industry standards: integral flanges (IF), threaded flanges (Th), plate slip-on flanges (PL), wafer flanges (WN), socket weld flanges (SO), socket weld and butt weld flanges (SW), butt weld ring loose flanges (PJ/SE), slip-on ring loose flanges (PJ/RJ), lined flange covers (BL(S)), and flange covers (BL). 2. Classified according to petrochemical industry standards: threaded flanges (PT), butt-welded flanges (WN), socket-welded flanges (SO), slip-on weld flanges (SW), loose-flange types (LJ); flange covers (not specified). 3. Classified according to mechanical industry standards: integral flanges, butt-welded flanges, plate-type socket weld flanges, butt-welded ring plate-type loose flanges, plate-type socket weld ring plate-type loose flanges, flanged ring plate-type loose flanges, and flange covers. Flat welding steel flanges: Suitable for connecting carbon steel pipelines with a nominal pressure not exceeding 2.5 MPa. The sealing surfaces of flat welding flanges can be designed in three types: smooth, ribbed, and tongue-and-groove. Smooth flat welding flanges are the most widely used; they are employed in situations where the operating conditions are relatively mild, such as low-pressure, unpurified compressed air or low-pressure circulating water. Their advantage is their relatively low cost ； Butt-welded steel flanges: Used for welding flanges to pipes; they have a rational structure, high strength and stiffness, can withstand high temperatures and pressures as well as repeated bending and temperature fluctuations, and offer reliable sealing performance. Butt-welded flanges with a nominal pressure of 0.25–2.5 MPa feature male-female type sealing surfaces. Socket-welded flanges: Commonly used in pipes with PN≤10.0 MPa and DN≤40 ； Loose-flange: Also known as a flexible flange, loose-flanges are divided into weld-ring type flexible flanges, flanged-type flexible flanges, and butt-welded flexible flanges. They are commonly used in situations where the temperature and pressure of the medium are not high, but the medium has strong corrosive properties. When the medium is highly corrosive, the part of the flange that comes into contact with the medium (the flanged stub) is made of corrosion-resistant high-grade materials such as stainless steel, while the outer portion is secured by flange rings made of lower-grade materials such as carbon steel in order to achieve sealing ； Integral flange: The flange is often integrated with equipment, pipes, fittings, valves, etc.; this type is commonly used on equipment and valves. Seal surface type: flat (FF), raised face (RF), male face (M), female face (F), mixed face (MF), tenon face (T), groove face (G), tenon-groove face (TG), ring joint face (RJ). The flange materials include: 20#, A105, Q235A, 12Cr1MoV, 16MnR, 15CrMo, 18-8, 321, 304, 304L, 316, 316L, etc. 4. Classified by **standard type: integral flanges, threaded flanges, butt-welded flanges, necked slip-on flanges, necked socket-welded flanges, butt-welded ring-necked loose flanges, plate-type slip-on flanges, butt-welded ring-plate loose flanges, slip-on ring-plate loose flanges, flanged ring-plate loose flanges, and flange covers. Thus, the rigidity of the flange is further increased. Therefore, it is specified for higher pressure ranges (PN 0.6 MPa–6.4 MPa) and diameter ranges (DN300 mm–2000 mm), with an applicable temperature range of -20°C–450°C. As can be seen from Table 4-16, the specifications for Type B flat welding flanges with a diameter of 2000 mm or less are all included within the scope defined for long-neck butt welding flanges. The connection dimensions and flange thickness of these two types of flanges are exactly the same. Therefore, for Type B flat welding flanges with a diameter of 2000 mm or less, rolled long-neck butt welding flanges can be used as a substitute to reduce the production cost of flanges. Both flat-weld and butt-weld flanges are available in both lined and unlined versions. When the equipment is made of stainless steel, using carbon steel flanges 7 with stainless steel linings can save stainless steel. The schematic shows a Type A flat welding flange with a gasket ring. 　 When determining the dimensions of a flange using flange standards, it is necessary to know the flange’s nominal diameter and nominal pressure. The nominal diameter of the pressure vessel flange shall be from the same series as that of the pressure vessel. For example, a pressure vessel with a diameter of DN 1000 mm should be equipped with a pressure vessel flange of DN 1000 mm. The nominal pressure of a flange is determined by the flange’s maximum operating pressure, operating temperature, and flange material. This is because the flange size series and the calculation of flange thickness are based on the mechanical properties of 16MnR at 200°C. Therefore, the maximum allowable operating pressure at 200°C for a flange size determined based on this standard is considered to be the nominal pressure of that flange size. For example, a flange with a so-called nominal pressure of PNO.6MPa refers to a flange of specific dimensions; it is made of 16MnR, and its maximum allowable operating pressure at 200°C is 0.6MPa. If this PN0.6MPa flange is used at temperatures above 200°C, its maximum operating pressure will be lower than its nominal pressure of 0.6MPa. Conversely, if it is used at temperatures below 200°C, its maximum operating pressure is still determined based on 200°C. If the material of the flange is changed to Q235-A, then the mechanical properties of Q235-A steel are inferior to those of 16MnR. For this flange with a nominal pressure of PN0.6MPa, even when operating at 200°C, its maximum allowable operating pressure will be lower than its nominal pressure. Conversely, if the material of the flange is changed from 16MnR to 15MnVR, then due to the superior mechanical properties of 15MnVR compared to 16MnR, the maximum allowable operating pressure of this flange with a nominal pressure of PN0.6MPa at an operating temperature of 200°C will be higher than its nominal pressure. In short, once the nominal diameter and nominal pressure of the flange are determined, the dimensions of the flange are also determined. As for the maximum operating pressure allowed by this flange, it depends on the operating temperature of the flange and the material from which it is made. The flange materials specified in the standards for pressure vessels are low-carbon steel (Q235-A, 20g, etc.) and ordinary low-alloy steel (16Mn, 16MnR, and 15MnVR, etc.). Table 4-17 shows the conversion relationship between the nominal pressure and the maximum allowable operating pressure for Type A butt-weld flanges and Type B butt-weld flanges at different temperatures. Using this table, the operating temperature and design pressure specified in the design conditions can be converted into the nominal pressure required to consult the flange standards. For example, select flanges for a vessel with an operating temperature of 300°C and a design pressure of 0.6 MPa. As can be seen from Table 4-17, if the flange material is 15MnVR, the flange dimensions can be obtained using a nominal pressure of 0.6 MPa. If the flange material is 20R, the flange dimensions must be obtained based on a nominal pressure of 1.0 MPa. For example, select flanges for a vessel with an operating temperature of 300°C and a design pressure of 0.6 MPa. As can be seen from Table 4-17, if the flange material is 15MnVR, the flange dimensions can be obtained using a nominal pressure of 0.6 MPa. If the flange material is 20R, the flange dimensions must be obtained based on a nominal pressure of 1.0 MPa. II. Standards for pipe flanges: Due to the different actual dimensions represented by the nominal diameter of the container cylinder and that of the pipe, container flanges and pipe flanges with the same nominal diameter also have different dimensions, and therefore they cannot be used interchangeably. In addition to butt-welded and socket-welded flanges, there are also cast steel flanges, cast iron flanges, slip-on flanges, threaded flanges, and other types of pipe flanges. The methods and steps for selecting pipe flange standards are the same as those for pressure vessel flanges. In addition to GB9119.7-88, other common standards for pipe flanges include the Ministry of Chemical Industry standards HG20592～HG20602-97 ； Sinopec standards such as SH3406-96, etc. Among the standards set by the Ministry of Chemical Industry, there are those based on the European system and the American system, etc.; the European system is commonly used in China. Here is Example 4-6 to help readers understand the standards for flanges and their selection. Example 4-6: Provide a pair of flanges to connect the tower body and the head for a distillation tower. The inner diameter of the tower is 1000 mm, the operating temperature is 280°C, and the design pressure is 0.2 MPa. The material is Q235-A. Analysis: Based on the operating temperature, design pressure, and materials used, Table 4-17 indicates that the flange to be selected should have a nominal pressure of 0.6 MPa, and its dimensions should be determined accordingly. Due to the low operating pressure and small diameter, Type A flat welding flanges with a flat sealing surface can be used as shown in Table 4-16, and asbestos rubber sheets should be selected as the gasket material. The dimensions of various parts of the flange can be found in Appendix Table 9, and the flange is shown in the figure below. The connecting bolts are made of Q235-A material, with a total of 36 pieces of M20 size. Chinese-English Glossary of Flanges: Flange. Integral pipe flange: overall pipe flange. Steel pipe flange: flange for steel pipes. Threaded flange: flange with threads. Slip-on flange (SO): slip-on welding flange. Socket welding flange: flange for socket welding. Lap joint flange (LJF): flange with lap joint. Welding neck flange (WNF): flange with welding neck. Blind flange, blind: cover flange. Orifice flange: flange with orifices. Reducing flange: flange for reducing pipe diameters. Pad type flange: flange with a pad. Loose hubbed flange: flange with a loose hub. Welding plate flange: flange made of welded plates. Welding neck collar: similar to stub end. Welding-on collar: collar that is welded on. Stub end, lap: shortened end of a pipe with a lap joint. Lapped pipe end: pipe end with a lap joint. Loose plate flange: flange made of a loose plate. Pressure rating, pressure rating class: capacity to withstand pressure. Pressure-temperature rating: rating related to both pressure and temperature. Flange facing: surface of the flange. Raised face (RF): convex surface. Male face (MF): male-type surface. Female face (FMF): female-type surface. Tongue face: protruding surface on a flange. Groove face: grooved surface on a flange. Ring joint face: surface used for ring joint connections. Full plane: completely flat surface ； Flat face; Full face (FF). Smooth raised face (SRF). Facing finish. Roughness. Smooth. Serrated. Root mean square (RMS). Arithmetical average roughness height (AARH). Companion-flange. Bolt circle. Standards for flanges and accessories: GB/T9113–GB9124–2000. Flange standards: GB/T9113.1–GB/T9113.26–1988. Integral steel pipe flanges (1.6–42.0 Mpa). GB/T9113.1–.2: Integral steel pipe flanges (flat face) (1.6–2.0 Mpa). GB/T9113.3–.8: Integral steel pipe flanges (raised face) (1.6; 2.5; 4.0; 2.0; 5.0; 10.0 Mpa). GB/T9113.9–.15: Integral steel pipe flanges (raised and recessed face) (1.6; 2.5; 4.0; 5.0; 10.0; 15.0; 25.0 Mpa). GB/T9113.16–.20: Integral steel pipe flanges (keyway face) (1.6; 2.5; 4.0; 5.0; 10.0 Mpa). GB/T9113.21–.26: Integral steel pipe flanges (ring connection) (2.0; 5.0; 10.0; 15.0; 25.0; 42.0 Mpa). GB/T9115.1–.36–1988: Flat-face butt-welded steel pipe flanges (0.25–42.0 Mpa). GB/T9115.1–.5: Flat-face butt-welded steel pipe flanges (0.25 ； 0.6 ； 1.0 ； 1.6 ； 2.0 ； Mpa） GB/T9115.6～.16 (convex) butt-welded steel pipe flanges (0.25 ； 0.6 ； 1.0 ； 1.6 ； 2.5 ； 4.0 ； 2.0 ； 5.0 ； 10.0 ； 15.0 ； 25.0 ； Mpa) GB/T9115.17–.23 (ribbed surfaces) Welded steel pipe flanges (1.6; 2.5; 4.0; 5.0; 10.0; 15.0; 25.0 Mpa) GB/T9115.24–30 (mortise and tenon surfaces) Welded steel pipe flanges (1.6; 2.5; 4.0; 5.0; 10.0; 15.0; 25.0 Mpa) GB/T9115.31–.36 (ring connection) Welded steel pipe flanges (2.0; 5.0; 10.0; 15.0; 25.0; 42.0 Mpa) GB/T13402—1992 Flanges for large-diameter carbon steel pipes JB/T79.1–.4—1994 Integral cast steel pipe flanges (1.6–20 Mpa, including 6.4) ； (On behalf of JB79－59) JB/T79.1: Raised-face, fully cast steel pipe flanges; JB/T79.2: Ribbed-faced, fully cast steel pipe flanges; JB/T79.3: Grooved-face, fully cast steel pipe flanges; JB/T79.4: Ring-connected face, fully cast steel pipe flanges; JB/T82.1–JB/T82.4—1994: Butt-welded steel pipe flanges ； (Replaced by JB82-59) JB/T82.1 – Steel pipe flanges with convex mating surfaces; JB/T82.2 – Steel pipe flanges with convex-and-concave mating surfaces; JB/T82.3 – Steel pipe flanges with grooved mating surfaces; JB/T82.4 – Steel pipe flanges with ring-shaped mating surfaces. JB77-1959 – Types of flange sealing surfaces; JB78-1959 – Cast iron flanges; JB79-1959 – Cast steel flanges; JB80-1959 – Cast iron threaded flanges; JB82-1959 – Welded steel flanges. HGJ44–HGJ68-1999 – Steel flanges (Technical specifications for engineering construction issued by the Ministry of Chemical Industry); HG20592–HG20605-1997 – Steel flanges (Standards issued by the Ministry of Chemical Industry) ； European system) HG20613–HG20623—1997 Steel flanges (Ministry of Chemicals standard) ； European system) SH3406---1996 　　 Pipeline flanges for petrochemical enterprises ANSI B16.5---1996　　 Pipe flanges and flange fittings ANSI B16.25－1992 Welded connections MSS SP44--1991 Steel pipeline flanges API 605---1998 　 Large-diameter carbon steel flanges 　 Symbols for flange connection types: Welded: WN; Socket weld: SW ； Flat welding: SO; Threaded: PT ； Loose fit: LJ ； Flat surface: FF; Bossed surface: RF; Convex surface: LM; Concave surface: LF; Grooved surface: TG; Rabbeted surface: TF; Grooved surface: GF; Ring-shaped grooved surface: RJ. Insulated flange: An insulated flange is a general term for pipe flange joints that meet both the sealing requirements necessary for buried steel pipes and the electrical insulation requirements needed for projects aimed at preventing electrochemical corrosion. It includes a pair of steel flanges, an insulating seal between the two flanges, flange fasteners and insulating parts for those fasteners, as well as a pair of short steel tubes that have been welded to each of the two flanges. Insulated flanges and insulated joints are products that our factory has been manufacturing for many years for industries such as petroleum and chemicals. With their simple structure, safe usage, and reliable performance, they have been widely used and highly praised. Insulated flange products are available in a series; in case of special requirements, they can be designed and manufactured according to the customer’s specifications. We warmly welcome all users to choose our factory’s products. I. Product Applications: This product is suitable for the electrochemical corrosion protection and connection of buried pipelines carrying media such as oil, gas, and water. It also provides insulation protection. II. Classification: This product is classified into two types based on its insulation sealing elements: the specific pressure sealing type insulated flange (referred to as Type I insulated flange) and the self-sealing type insulated flange (referred to as Type II insulated flange). The application range of Type I insulated flanges is: nominal pressure Pn ≤ 2.5 MPa. III. Characteristics 1. It possesses the electrical insulation properties required for electrochemical corrosion protection projects of buried pipelines. 2. It can operate reliably for a long time at the temperature and pressure required by the pipeline medium, and possesses sufficient strength and sealing performance. 3. It has a reasonable structure, making assembly, disassembly, and part replacement easy. IV. Main technical parameters 1. Applicable temperature: ≤100°C 2. Pressure range: Pn0.6MPa～Pn16MPa 3. Product specifications: Dn50～Dn1200 Pressure vessel flanges are divided into flat-weld flanges and butt-weld flanges. Among them, flat-face flanges are further divided into Type A flanges and Type B flanges. The graphics and standard numbers are as follows: 1. Butt-weld flanges, necked butt-weld flanges. 1) Type B flanges have a short cylinder, which gives them better rigidity compared to Type A flanges; they can therefore be used in applications with higher pressures and larger diameters ； 　　2) Weld joint type: Type A features a V-shaped groove, while Type B has a U-shaped groove; therefore, Type B is easier to weld through, resulting in higher strength and stiffness.