What is Flange?

Flange (sae flange JBZQ 4187-97) is also called flange or flange. Parts that connect pipe to pipe to each other, attached to pipe ends. There are holes in the flange, and the bolts tightly connect the two flanges. The flanges are sealed with gaskets. Flange pipe fittings refer to pipe fittings with flanges (flanges or lands). It can be cast, screwed or welded.


Flange connection (flange, joint) consists of a pair of flanges, a gasket and several bolts and nuts. The gasket is placed between the sealing surfaces of the two flanges. After the nut is tightened, the specific pressure on the surface of the gasket reaches a certain value and then deforms, and fills the unevenness on the sealing surface to make the connection tight. Flange connection is a detachable connection. According to the connected parts, it can be divided into container flange and pipe flange. According to the structure type, there are integral flange, loop flange and threaded flange. Common integral flanges include flat welding flanges and butt welding flanges. Flat welding flanges have poor rigidity and are suitable for occasions where the pressure p≤4MPa. butt welding flanges, also known as high neck flanges, have higher rigidity and are suitable for occasions with higher pressure and temperature.

There are three forms of flange sealing surface: flat sealing surface, suitable for occasions with low pressure and non-toxic medium. concave-convex sealing surface, suitable for occasions with slightly higher pressure , toxic media and high pressure occasions. The gasket is a ring made of a material that can produce plastic deformation and has a certain strength. Most of the gaskets are cut from non-metallic plates, or made by professional factories according to the specified size. The materials are asbestos rubber plates, asbestos plates, polyethylene plates,etc. There is also a metal-clad gasket made of wrapped non-metallic materials. there is also a wound gasket made of thin steel strips and asbestos strips. Ordinary rubber gaskets are suitable for occasions where the temperature is lower than 120°C. asbestos rubber gaskets are suitable for occasions where the temperature of water vapor is lower than 450°C, the temperature of oil is lower than 350°C, and the pressure is lower than 5MPa. Medium, the most commonly used is acid-resistant asbestos board. In high-pressure equipment and pipelines, lens-shaped or other-shaped metal gaskets made of copper, aluminum, No. 10 steel, and stainless steel are used. The contact width between the high-pressure gasket and the sealing surface is very narrow (line contact), and the processing finish of the sealing surface and the gasket is relatively high.

Flange classification: Flanges are divided into threaded (wired) flanges and welding flanges. The low-pressure small diameter has a wire flange, and the high-pressure and low-pressure large diameters use welding flanges. The thickness of the flange plate of different pressures and the diameter and number of connecting bolts are different. According to the different grades of pressure, flange pads also have different materials, ranging from low-pressure asbestos pads, high-pressure asbestos pads to metal pads.

1. Divided by material into carbon steel, cast steel, alloy steel, stainless steel, copper, aluminum alloy, plastic, argon, ppc, etc.

2. According to the production method, it can be divided into forged flange, cast flange, welding flange, rolled flange (oversized model) 3. According to the manufacturing standard, it can be divided into national standard (standard of the Ministry of Chemical Industry, petroleum standard, electric power standard) , American Standard, German Standard, Japanese Standard, Russian Standard, etc.

flange valve

Several systems of international pipe flange standards:

1. Flange connection or flange joint refers to a foldable connection consisting of flanges, gaskets and bolts connected to each other as a combined sealing structure. Pipeline flanges refer to flanges used for piping in pipeline installations. On the equipment, it refers to the inlet and outlet flanges of the equipment.

2. Several systems of international pipe flange standards

1) European flange system: German DIN (including the Soviet Union) British standard BS French standard NF Italian standard UNI

a. Nominal pressure: 0.1, 0.25, 0.6, 1.0, 1.6, 2.5, 4.0, 6.4, 10.0, 16.0, 25.0, 32.0, 40.0, Mpa

b. Calculated diameter: 15~4000mm (the maximum diameter varies with the selected flange specification and flange pressure level)

c. The structure type of the flange: flat welding plate type, flat welding ring loose sleeve type, curling loose sleeve type, butt welding curling edge loose sleeve type, butt welding ring loose sleeve type, butt welding type, neck threaded connection type, Integral and flanged covers

d. Flange sealing surfaces include: flat surface, protruding surface, concave-convex surface, tongue and groove surface, rubber ring connection surface, lens surface and diaphragm welding surface

e. The OCT pipe flange catalog standard issued by the Soviet Union in 1980 is similar to the German DIN standard, and will not be repeated here.

2) American flange system: American ANSI B16.5 "Steel Pipe Flanges and Flanged Fittings" ANSI B16.47A/B "Large Diameter Steel Flanges" B16.36 Orifice Flanges B16.48 Character Flanges wait.

a. Nominal pressure: 150psi (2.0Mpa), 300psi (5.0Mpa), 400psi (6.8Mpa), 600psi (10.0Mpa), 900psi (15.0Mpa), 1500psi (25.0Mpa), 2500psi (42.0Mpa).

b. Calculated diameter: 6~4000mm

c. Flange structure type: bar welding, socket welding, threaded connection, loose sleeve, butt welding and flange cover

d. Flange sealing surface: convex surface, concave-convex surface, tongue and groove surface, metal ring connection surface

3) JIS pipe flange: it is generally only used in public works in petrochemical plants, and has little influence internationally, and has not formed an independent system internationally.

3. my country's national standard system for steel pipe flanges GB

1) Nominal pressure: 0.25Mpa~42.0Mpa

a. Series 1: PN1.0, PN1.6, PN2.0, PN5.0, PN10.0, PN15.0, PN25.0, PN42 (main series)

b. Series 2: PN0.25, PN0.6, PN2.5, PN4.0 where PN0.25, PN0.6, PN1.0, PN1.6, PN2.5, PN4.0 have 6 levels of methods The flange size belongs to the European flange system represented by the German flange, and the rest is the American flange system represented by the American flange. In the GB standard, the maximum nominal pressure level of the European flange system is 4Mpa, and the maximum nominal pressure level of the American flange system is 42Mpa.

2) Nominal diameter: 10mm~4000mm

3) The structure of the flange: integral flange unit flange

a. Threaded flange

b. Welding flange, butt welding flange, flat welding flange with neck, socket welding flange with neck, plate type flat welding flange

c. Loose sleeve flange, butt welding ring loose sleeve neck flange, butt welding ring loose sleeve flange, flat welding ring loose sleeve flange, plate type turned over loose sleeve flange

d. Flange cover (blind flange)

e. Swivel flange

f. Anchor flange

g. Overlay welding / overlay welding flange

4) Flange sealing surface: flat surface, convex surface, concave-convex surface, tongue and groove surface, ring connection surface.

flange valve

Standard system of pipe flanges commonly used in instruments

1. DIN standard

1) Commonly used pressure levels: PN6, PN10, PN16, PN25, PN40, PN64, PN100, PN160, PN250 2) Flange sealing surface: raised face DIN2526C raised face flange grooued acc. DIN2512N tongue and groove face

2. ANSI standard

1) Commonly used pressure ratings: CL150, CL300, CL600, CL900, CL1500

2) Flange sealing surface: ANSI B 16.5 RF flanges raised face flange

3. JIS standard: not commonly used

Commonly used pressure levels: 10K, 20K.

Flange production standard

National standard: GB/T9112-2000 (GB9113·1-2000~GB9123·4-2000)

American Standard: ANSI B16.5 Class150, 300, 600, 900, 1500 (WN, SO, BL, TH, LJ, SW)

Japanese standard: JIS 5K, 10K, 16K, 20K (PL, SO, BL, WN, TH, SW)

German standard: DIN2573, 2572, 2631, 2576, 2632, 2633, 2543, 2634, 2545 (PL, SO, WN, BL, TH)

Ministry of Chemical Industry standard: HG5010-52~HG5028-58, HGJ44-91~HGJ65-91, HG20592-97 series, HG20615-97 series

Standards of the Ministry of Machinery: JB81-59~JB86-59, JB/T79-94~JB/T86-94, JB/T74-1994

Pressure vessel standard: JB1157-82~JB1160-82, JB4700-2000~JB4707-2000 B16.47A/B B16.39 B16.48

Post time: Mar-31-2023