Flange

What is a flange?

A flange is a part that connects a pipe to a pipe, and is connected to a pipe end. There are holes in the flange, and bolts make the two flanges tight. The flanges are sealed with a gasket. Flanged pipe fittings are pipe fittings with flanges (flange or socket). It can be cast (not shown), it can also be threaded or welded. A flange joint consists of a pair of flanges, a washer, and 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 gasket surface is deformed after the specific pressure reaches a certain value, and the unevenness on the sealing surface is filled to make the connection tight. The flange connection is a detachable connection. According to the connected parts can be divided into container flanges and pipe flanges. According to the structural type, there are integral flanges, loose flanges and threaded flanges. The common integral flange has flat welding flanges and butt welding flanges. Flat welded flanges are less rigid and suitable for applications where pressure is ≤ 4 MPa. Butt welded flanges, also known as high neck flanges, are rigid and suitable for high pressure and temperature applications. There are three types of flange sealing surface: flat sealing surface, suitable for occasions with low pressure and non-toxic media; concave and convex sealing surface, suitable for occasions with slightly higher pressure; tongue and groove sealing surface, suitable for flammable and explosive , toxic media and high pressure occasions. The gasket is a ring made of a material that produces plastic deformation and has a certain strength. Most of the gaskets are cut from non-metal plates or made by professional factories according to the required size. The materials are asbestos rubber plate, asbestos plate, polyethylene plate, etc.; also use thin metal plate (tin plate, stainless steel) asbestos. Metal-clad gaskets made of non-metallic materials are wrapped; there is also a wound gasket made by winding a thin steel belt together with an asbestos belt. Ordinary rubber gaskets are suitable for applications where the temperature is below 120°C; asbestos rubber gaskets are suitable for applications where the vapor temperature is below 450°C, for oils below 350°C, and pressures below 5MPa, for general corrosion Medium, the most commonly used acid-resistant asbestos board. In high-voltage equipment and pipelines, lens-type 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 sealing surface and the gasket have a high processing finish.
The flange is divided into threaded (wired) flanges and welded flanges and ferrule flanges. Low-pressure and small-diameter wire-bonded flanges and ferrule flanges are used. High-pressure and low-pressure large-diameter welding flanges are used. The thickness of flanges and the diameter and number of connecting bolts are different for different pressures.

flg standards - Flange

Classification

1. According to chemical industry (HG) industry standard: integral flange (IF), Threaded Flanges (Th), Plate Flanges (PL), Welding Neck Flanges (WN), Slip-on Flanges (SO), Socket Weld Flanges (SW), Blind Flanges (BL)[2].
2. According to the petrochemical (SH) industry standard: Plate flange (PT), welded neck flange (WN), Slip On flange (SO), socket welded flange (SW), Lap Joint Flanges (LJ).
3, according to the national (GB) standard points: integral flange, threaded flange, butt welding flange, with welding neck flange, with neck socket welding flange, butt welded ring with loose collar flange, plate flat Welded flanges, butt-welded ring-type loose flanges, flat-welded ring-type loose flanges, flanging ring-type loose flanges, flange covers.

SPECIAL FLANGES

Except the most used standard flanges, there are still a number of special flanges such as:

Raw materials

Flange manufacturing materials: stainless steel plate, carbon steel plate, alloy plate, galvanized steel plate, stainless steel bar, stainless steel forgings, stainless steel profiles, etc.
Material: WCB (carbon steel), LCB (low temperature carbon steel), LC3 (3.5% nickel steel), WC5 (1.25% chromium 0.5% molybdenum steel), WC9 (2.25% chromium), C5 (5% chromium 0.5% molybdenum) , C12 (9% 1% chromium molybdenum), CA6NM (4 (12% chrome steel), CA15 (4) (12% chrome), CF8M (316 stainless steel), CF8C (347 stainless steel), CF8 (304 stainless steel), CF3 (304L stainless steel), CF3M (316L stainless steel), CN7M (alloy steel), M35-1 (Monel), N7M (Hast nickel alloy B), CW6M (Hasta nickel alloy C), CY40 (Inco nickel Alloy) etc.

flanges images - Flange

What is flange connection?
Flange connection can generally be divided into five kinds: flat welding, butt welding, socket welding, loose sets, threads.
The following is a detailed description of the first four types:
1. Flat welding: only welding the outer layer, no welding inner layer; generally used in medium and low pressure pipelines, the nominal pressure of the pipeline should be less than 0.25MPa. There are three kinds of sealing surfaces for flat welding flanges, namely, smooth, concave and convex, and tongue and groove. Among them, the most widely used is the smooth type, and the price is affordable and cost-effective.
2. Butt welding: The inner and outer layers of the flange are welded. They are generally used in medium and high pressure pipelines. The nominal pressure of the pipeline is between 0.25 and 2.5 MPa. The sealing surface of the butt welding flange connection is concave and convex, and the installation is complicated. Therefore, labor costs, installation methods, and auxiliary materials are all relatively high.
3 socket welding: generally used for nominal pressure less than or equal to 10.0MPa, nominal diameter less than or equal to 40mm in the pipeline.
4. loose sets: generally used for pressure is not high, but the medium is more corrosive in the pipeline, so this type of flange corrosion resistance, material mainly stainless steel.
This connection is mainly used for the connection of cast iron pipes, lining hoses, non-ferrous metal pipes and flange valves, and the connection of process equipment and flanges is also flanged.


Type of face flanges
There are different flanges profiles.

raised face flange rf - FlangeRaised Face Flanges (RF):
RF flanges seal with a flat gasket designed for installation between the raised faces of two mating flanges (both with raised faces). The raised faces have a prescribed texture to increase their gripping and retaining force on this flat gasket. Some users of raised face flanges specify the use of spiral wound gaskets.

ring type joint flange rtj - FlangeRing Type Joint Flanges (RTJ) or Ring Joint Facing Flanges (R-JF):
RTJ flanges have grooves cut into their faces which accept steel Ring Gaskets. RTJ flanges seal when tightened bolts compress the gasket between the flanges into the grooves, deforming (or “Coining”) the gasket to make Intimate Contact inside the grooves, creating a metal to metal seal.
An RTJ flange may have a raised face with a ring groove machined into it. This raised face does not serve as any part of the sealing means. For RTJ flanges that seal with BX ring gaskets, the raised faces of the connected and tightened flanges may contact each other. In this case the compressed gasket will not bear additional load beyond the bolt tension, vibration and movement cannot further crush the gasket and lessen the connecting tension.

Standards for Flanges

EN 1092-1:
Flanges and their joints – Circular flanges for pipes, valves, fittings and accessories, PN designated – Part 1: Steel flanges

This European standard specifies requirements for circular steel flanges in PN designations PN 2,5 to PN 400 and nominal sizes from DN 10 to DN 4000. This standard specifies the flange types and their facings, dimensions, tolerances, threading, bolt sizes, flange face surface finish, marking, materials, pressure/ temperature ratings and flange masses.

EN 1092-2:
Flanges and Their Joints – Circular Flanges for Pipes, Valves, Fittings and Accessories, PN Designated – Part 2: Cast Iron Flanges

The document specifies requirements for circular flanges made from ductile, grey and malleable cast iron for DN 10 to DN 4000 and PN 2,5 to PN 63. It also specifies the types of flanges and their facings, dimensions and tolerances, bolt sizes, surface finish of jointing faces, marking, testing, quality assurance and materials together with associated pressure/temperature (p/T) ratings.

EN 1092-3:
Flanges and their joints – Circular flanges for pipes, valves, fittings and accessories, PN designated – Part 3: Copper alloy flanges

This document specifies requirements for circular copper alloy flanges in PN designations from PN 6 to PN 40 and nominal sizes from DN 10 to DN 1800.

EN 1092-4:
Flanges and Their Joints – Circular Flanges for Pipes, Valves, Fittings and Accessories, PN Designated – Part 4: Aluminium Alloy Flanges

This standard specifies requirements for PN designated circular flanges for pipes, valves, fittings and accessories made from aluminium alloy in the range of DN 15 to DN 600 and PN 10 to PN 63. This standard specifies the types of flanges and their facings, dimensions and tolerances, bolt sizes, surface finish of faces, marking and materials together with associated P/T ratings. The flanges are intended to be used for pipework as well as for pressure vessels.

EN 1759-1:
Flanges and their joints – Circular flanges for pipes, valves, fittings and accessories, Class designated – Part 1: Steel flanges, NPS 1/2 to 24 

This European Standard specifies steel flanges, Class designated. The standard lists dimensions, tolerances, materials, P/T ratings and technical delivery conditions.

EN 1759-2:
Flanges and Their Joints – Circular Flanges for Pipes, Valves, Fittings and Accessories, PN Designated – Part 2: Cast Iron Flanges

The document specifies requirements for circular flanges made from ductile, grey and malleable cast iron for DN 10 to DN 4000 and PN 2,5 to PN 63. It also specifies the types of flanges and their facings, dimensions and tolerances, bolt sizes, surface finish of jointing faces, marking, testing, quality assurance and materials together with associated pressure/temperature (p/T) ratings.

EN 1759-3:
Flanges and their joints – Circular flanges for pipes, valves, fittings and accessories, Class designated – Part 3: Copper alloy flanges 

The document specifies requirements for circular copper alloy flanges in Class designations Class 150 and Class 300 and nominal sizes from DN 10 to DN 900 (NPS 1/2 bis NPS 36).

EN 1759-4:
Flanges and their joints – Circular flanges for pipes, valves, fittings and accessories, Class designated – Part 4: Aluminium alloy flanges

This standard specifies requirements for Class designated circular flanges for pipes, valves, fittings and accessories made from aluminium alloy in the range of DN 15 to DN 600 (NPS 1/2 to NPS 24) and Class 150 to Class 300. This Standard specifies the types of flanges and their facings, dimensions and tolerances, bolt sizes, surface finish of faces, marking and materials together with associated p/T ratings.

EN 1515-1:
Flanges and their joints. Bolting. Selection of bolting

EN 1515-2:
Flanges and their joints. Bolting. Classification of bolt materials for steel flanges, PN designated

EN 1515-3:
Flanges and their joints. Bolting. Classification of bolt materials for steel flanges, class designated.

ANSI/ASME B16.1 -2005
Gray Iron Pipe Flanges and Flanged Fittings: Classes 25, 125, and 250 

This Standard covers Classes 25, 125, and 250 Gray Iron Pipe Flanges and Flanged Fittings. It includes: 
(a) pressure-temperature ratings 
(b) sizes and method of designating openings of reducing fittings 
(c) marking 
(d) material 
(e) dimensions and tolerances 
(f) bolting and gaskets 
(g) coatings 

ANSI/ASME B16.3 -2006
Malleable Iron Threaded Fittings: Classes 150 and 300 

This Standard for threaded malleable iron fittings Classes 150, and 300 provides requirements for the following: (a) pressure-temperature ratings 
(b) sizes and method of designating openings of reducing fittings 
(c) marking 
(d) material 
(e) dimensions and tolerances 
(f) threading 
(g) coatings 

ANSI/ASME B16.4 -2006
Gray Iron Threaded Fittings, Classes 125 and 250

This Standard for gray iron threaded fittings, Classes 125 and 250, covers (a) pressure-temperature ratings 
(b) sizes and method of designating openings of reducing fittings 
(c) marking 
(d) material 
(e) dimensions and tolerances 
(f) threading 
(g) coatings 
Mandatory Appendix I provides table values in U.S.
Customary units. 

ASME B16.5 -2009
Pipe Flanges and Flanged fittings: 1/2″ through 24″ NPS. 

This Standard covers pressure-temperature ratings, materials, dimensions, tolerances, marking, testing, and methods of designating openings for pipe flanges and flanged fittings. Included are:
• Flanges with rating class designations 150, 300, 400, 600, 900, and 1500 in sizes NPS 1/2 through NPS 24 and flanges with rating class designation 2500 in sizes NPS 1/2 through NPS 12, with requirements given in both metric and U.S. Customary units with diameter of bolts and flange bolt holes expressed in inch units.
• Flanged fittings with rating class designation 150 and 300 in sizes NPS 1/2 through NPS 24, with requirements given in both metric and U.S. Customary units with diameter of bolts and flange bolt holes expressed in inch units.
• Flanged fittings with rating class designation 400, 600, 900, and 1500 in sizes NPS 1/2 through NPS 24 and flanged fittings with rating class designation 2500 in sizes 1/2 through NPS 12 that are acknowledged in Nonmandatory Appendix E in which only U.S. Customary units are provided.
This Standard is limited to: 
• Flanges and flanged fittings made from cast or forged materials 
• Blind flanges and certain reducing flanges made from cast, forged, or plate materials
• Also included in this Standard are requirements and recommendations regarding flange bolting, gaskets, and joints.

ANSI/ASME B16.20 -2007
Metallic Gaskets for Pipe Flanges: Ring-Joint, Spiral-Wound, and Jacketed 

This Standard covers materials, dimensions, tolerances, and markings for metal ring-joint gaskets, spiral-wound gaskets, and metal-jacketed gaskets. These gaskets are dimensionally suitable for use with flanges described in reference flange standards ASME B16.5, ASME B16.47, API Specification 6A, and ISO 10423. This Standard covers spiral-wound metal gaskets and metal-jacketed gaskets for use with raised-face and flat-face flanges.

ANSI/ASME B16.21 -2005
Nonmetallic Flat Gaskets for Pipe Flanges 

This Standard covers types, sizes, materials, dimensions, tolerances, and markings for nonmetallic flat gaskets. These gaskets are dimensionally suitable for use with flanges described in the referenced flange standards.

ANSI/ASME B16.24 -2006
Cast Copper Alloy Pipe Flanges and Flanged Fittings: Classes 150, 300, 600, 900, 1500 and 2500 

This Standard for cast copper alloy pipe flanges and flanged fittings covers:
(a) pressure-temperature ratings;
(b) sizes and methods of designating openings for reduced fittings;
(c) marking;
(d) materials;
(e) dimensions;
(f) bolting and gaskets;
(g) tolerances;
(h) tests. 
This Standard covers pressure temperature ratings, materials, dimensions, tolerances, gaskets, and tests for Classes 150, 300, 600, 900, 1500, and 2500 Cast Copper Pipe Flanges and Flanged Fittings.

ANSI/ASME B16.34 -2009
Valves Flanged, Threaded and Welding End 

This Standard applies to new construction and covers pressure.temperature ratings, dimensions, tolerances, materials, nondestructive examination requirements, testing, and marking for cast, forged, and fabricated flanged, threaded, and welding end and wafer or flangeless valves of steel, nickel-base alloys, and other alloys shown in Table 1. Wafer or flangeless valves, bolted or through-bolt types, that are installed between flanges or against a flange are treated as flanged-end valves. 
Alternative rules for NPS 2 1/2 and smaller valves are given in Mandatory Appendix V.

ANSI/ASME B16.42 -1998
Ductile Iron Pipe Flanges and Flanged Fittings, Classes 150 and 300 

This Standard covers minimum requirements for Class 150 and 300 cast ductile iron pipe flanges and flanged fittings. The requirements covered are as follows:
(a) pressure-temperature ratings 
(b) sizes and method of designating openings
(c) marking
(d) materials 
(e) dimensions and tolerances 
(f) bolts, nuts, and gaskets 
(g) tests Codes and Regulations. 
A flange or flanged fit- ting used under the jurisdiction of the ASME Boiler and Pressure Vessel Code, the ASME Code for pressure Piping, or governmental regulation is subject to any limitation of that code or re- gulation. This includes any maximum temperature limitation, any rule governing the use of a material at low temperature, or provisions for operation at a pressure exceeding the pressure- temperature ratings in this Standard.

ANSI/ASME B16.48 -2009
Valves Flanged, Threaded and Welding End 

This Standard covers pressure-temperature ratings, materials, dimensions, tolerances, marking, and testing for operating line blanks in sizes NPS 1/2 through NPS 24 for installation between ASME B16.5 flanges in the 150, 300, 600, 900, 1500, and 2500 pressure classes. The dimensions are suitable for blanks made of materials listed in Table 1.


Flange connection process
The flange connection process is as follows:
First, the connection between the flange and the pipeline must meet the following requirements:
1. The center of the pipeline and the flange must be on the same horizontal line.
2. The center of the pipe and the sealing surface of the flange are 90 degrees vertically.
3, the location of the flange bolts on the pipe should be consistent.
Second, the pad flange gasket requires the following:
1. In the same pipe, the gaskets of the same pressure flange should be the same, so that they can be exchanged later.
2, for the use of rubber plate pipe, the gasket is also best to choose rubber, such as water lines.
3. The selection principle of the gasket is: Select as close to the small width as possible, this is the principle that should be followed in determining the gasket will not be crushed.
Third, connecting flange
1. Check whether the specifications of flanges, bolts, and gaskets meet the requirements.
2, the sealing surface should be kept smooth and clean, there can be no glitches.
3, bolts to be complete thread, can not be a defect, chimeric to be natural.
4, the gasket texture should be flexible, not easy to aging, the surface is not damaged, folds, scratches and other defects.
5, before assembling the flange, it is necessary to clean the flange, remove oil, dust, rust and other debris, remove the seal line clean.
Fourth, assembly flange
1. The flange sealing surface is perpendicular to the center of the pipe.
2, the same size of bolts, the installation direction is the same.
3. The installation position of the flange installed on the branch pipe should be more than 100 mm from the outer wall of the riser, and should be 200 mm or more from the wall of the building.
4, do not bury the flange directly in the ground, easy to be corroded, if must be buried in the ground, we must do anti-corrosion treatment.

Welding quality
As iron plate welding flanges, many customers questioned whether the quality of the iron plate welding flange outweighs the forged welding flange. In fact, the quality of the welded flange of the iron plate is the same as the quality of the forged welding flange, but the iron plate welding flange cannot be protected in any place. That is, the material of the iron plate welding flange is the most unprotected, because In the general process, the density of the welded flange of the iron plate is not a problem. However, during the production process, the blanks of the welded flange of the iron plate are rarely detected. Therefore, after being produced, the thickness is not passed. The material of the welded iron flanges tested cannot be guaranteed. [1] 

Welding process
Required equipment
A set of manual welding equipment, a handle angle grinder, an electric hammer, a flat surface.
Prepare for welding
1. Check the debugging equipment to ensure the normal operation of the equipment. 2. Prepare the φ4.0J402 electrode for drying at 300°C-350°C for one hour.
Welding process
1. Assembly The vertebral body and the large flange are assembled together according to the requirements of the drawings, and the flange is divided equally into 8 equal parts. 2. Because the flange is thicker and the groove is larger, it adopts segmental symmetry and multi-layer welding.
Weld quality
The weld strength is required to be at least that of the base metal. The surface of the weld is smooth and smooth, with no defects such as burn-through, porosity, weld leakage, slag inclusion, undercut, and full welding. The remaining height is less than 2mm.
Precautions
1. Be sure to use the J506 electrode for hand build-up and make use of low current welding. In strict accordance with the welding process welding. 2. After each welding position, use the horizontal ruler to check the deformation of the flange plane. 3. One side of the welding side is hammered with a pneumatic hammer to achieve the effect of eliminating stress.


Flange gasket
The gasket is a ring made of a material that produces plastic deformation and has a certain strength. Most gaskets are cut from non-metal plates or manufactured by professional factories according to the required size. The materials are asbestos rubber plate, asbestos plate, PTFE plate, polyethylene plate, etc.; also use thin metal plate (tin plate, (Stainless steel) Metal-clad gaskets made of non-metallic materials such as asbestos; there is also a wound gasket made by winding a thin steel belt together with asbestos belt. The most commonly used is stainless steel tape and graphite wound. The metal spiral wound gaskets can also be made of asbestos depending on the use environment. Ordinary rubber gaskets are suitable for applications where the temperature is below 120°C; asbestos rubber gaskets are suitable for applications where the vapor temperature is below 450°C, for oils below 350°C, and pressures below 5MPa, for general corrosion Medium, the most commonly used acid-resistant asbestos board. In high-voltage equipment and pipelines, lens-type 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 sealing surface and the gasket have a high processing finish.
Low-pressure and small-diameter wire-reinforced flanges, high-pressure and low-pressure large-diameter welding flanges are used, and the flanges of different pressures have different thicknesses and diameters and numbers of connecting bolts.
Flange gasket standard
According to the different levels of pressure, flange gaskets also have different materials, from low-pressure asbestos pads, high-pressure asbestos pads to metal gaskets.
1. Carbon steel, cast steel, alloy steel, stainless steel, copper, aluminum alloy, plastic, argon and pound, ppr, etc. are divided by material.
2. It can be divided into forging flanges, casting flanges, splicing flanges, cutting flanges, and rolling flanges (oversized models) by the manufacturing method.
3. The division into manufacturing standards can be divided into national standards (Ministry of Chemical Industry Standards, Petroleum Standards, Electric Power Standards, Machinery Standards, Marine Standards), American Standards, German Standards, Japanese Standards, and Russian Standards.

Related species
(1) Reducing Flange
Product name: Reducing flange
Technical parameters: In accordance with national standards
Quality standards: manufacturing strictly in accordance with relevant standards formulated by the country
Product Specifications: DN15-DN2000
Product packaging: wooden box or other
Product color: Metal color
Product features: anti-corrosion, acid and alkali, long service life, reasonable price calculation, smooth surface, acid and alkali resistant, high temperature, beautiful appearance, strong texture and performance
Production process: professional overall forging, forging manufacturing, medium board cutting, medium board rolling, etc.
Processing methods: high-precision CNC lathe turning, ordinary lathe finishing, argon arc welding and other processing
Nominal pressure sch5s, sch10s, sch20s, sch30s, sch40s, etc.
Manufacturing standards: national standard, American standard, Russian standard, Japanese standard, etc.
Material: 201,304.316.316L.0Cr18Ni9.321.202, etc.
Uses: Widely used in water conservancy, power, power stations, pipe fittings, industrial, pressure vessels, etc.
Connection method: flange nut, bolt connection.
(2) Stainless Steel Flanges
Product Name: Stainless steel flanges
Specification: 1/2′′~240′′(10-6000)
Pressure rating: 0.6Mpa to 32Mpa, 150Lb to 2500Lb, PN0.25-PN42.0
Material: 304, 304L, 321, 316, 316L, 310S and other materials
Ministry of Chemical Industry Standards: HG5010-52 ~ HG5028-58, HGJ44-91 ~ HGJ65-91, HG20592-2009 (PN Series), HG20615-2009 (Calss Series)
Applications: Boiler pressure vessels, petroleum, chemicals, shipbuilding, pharmaceuticals, metallurgy, machinery, food and other industries.
(3) Pressure vessel flange
Product Name: Pressure Vessel Flange
Specifications: DN300~3000
Product Remarks: Pressure Vessels Flange Application Industry: HVAC Power Building Water Supply Pressure Vessel Accessories, Pressure Pipe Fittings.
Product Category:Flange Series
Application Industry: HVAC Power Building Water Supply Pressure Vessel Fittings, Pressure Pipe Fittings.
Applied technical parameters
Seal Nominal pressure PN, MPa(bar) 0.6 1.0 1.6 2.5 4.0 6.4
Concave Surface (MFM) DN1300~3000 DN300~3000 DN400~2000 DN300~800
Cutting surface (TG) DN1300~3000 DN300~3000 DN300~3000 DN300~800
Full Plane (FF) DN300~3000 DN300~3000 DN300~3000 DN300~800


Production standards
GB: GB/T9112-2000 (GB9113·1-2000~GB9123·4-2000)
American Standard: ANSI B16.5 Class 150, 300, 600, 900, 1500, 2500 (WN, SO, BL, TH, LJ, SW) ANSI B16.47, ANSI B16.48
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
Machinery department standards: JB81-59 ~ JB86-59, JB/T79-94 ~ JB/T86-94, JB/T74-1994 pressure vessel standards: JB1157-82 ~ JB1160-82, JB4700-2000 ~ JB4707-2000
Ship Standards: GB568-65, GB569-65, GB2503-89, GB2506-89, GB/T10745-89, GB2501-89, GB2502-89
Pressure vessel standards: JB1157-82 ~ JB1160-82, NB/T47020-2012 ~ NB/T47027-2012, B16.47A/B B16.39 B16.

Standard system
There are two main international standards for pipe flanges, namely the European pipe flange system represented by German DIN (including the former Soviet Union) and the American pipe flange system represented by the American ANSI pipe flange. In addition, there are Japanese JIS pipe flanges, but they are generally used only for public works in petrochemical plants, and they have a smaller international impact. Now introduce the flanges of each country in the following:
1. European system pipe flange represented by Germany and the former Soviet Union
2. American system pipe flange standard, represented by ANSI B16.5 and ANSI B 16.47
3, the United Kingdom and France pipe flange standards, the two countries have two casing flange standards.
In summary, the internationally accepted standards for pipe flanges can be summed up in two different and not interchangeable pipe flange systems: a European pipe flange system represented by Germany; the other is represented by the United States. American pipe flange system.
IOS 7005-1 is a standard promulgated by the International Organization for Standardization in 1992. This standard is actually a pipe flange standard formed by merging the two sets of pipe flanges of the United States and Germany [5].

Instrument commonly used
1, DIN standard
1) Commonly used pressure levels: PN6, PN10, PN16, PN25, PN40, PN64, PN100, PN160, PN250
2) flange sealing surface: raised face DIN2526C protruding surface flange grooued acc. DIN2512N grooved surface
2, ANSI standards
1) Commonly used pressure levels: CL150, CL300, CL600, CL900, CL1500
2) Flange seal face: ANSI B 16.5 RF flanges Faceted flange (RF), Full face flange (FF)
3, JIS standard: not commonly used
1) Commonly used pressure levels: 5K, 10K, 20K

Production Process of Flange
The production process is mainly divided into forging, casting, cutting and rolling.
(1) Cast and Forged Flanges
The cast flange has a precise shape and size, a small amount of processing, and a low cost, but it has casting defects (swells, cracks, inclusions); the internal streamline of the casting is poor (if it is a cutting part, the streamlined shape is worse);
Forged flanges are generally lower in carbon content than cast flanges, are less likely to rust, have better streamlined forgings, denser structures, and have better mechanical properties than casting flanges.
Improper forging process will also appear large or uneven grain, hardening crack phenomenon, forging caused by the higher than the casting flange.
Forgings can withstand higher shear and tensile forces than castings.
The advantage of castings is that they can produce more complex shapes with lower cost.
The advantage of forgings is that the internal structure is uniform and there are no harmful defects such as blowholes and inclusions in the castings.
Different from the production process, the difference between the cast flange and the forged flange, such as a centrifugal flange, is a kind of cast flange.
Centrifugal flanges are flanges produced by precision casting methods. This type of casting is much thinner than ordinary sand casting structures. The quality is improved a lot and problems such as loose structure, porosity, and trachoma are less likely to occur.
First of all, we need to understand how centrifugal flanges are manufactured and manufactured. Centrifugal casting methods and products for making flat welded flanges are characterized by the following process steps:
1 The selected raw material steel is placed in an MF melting furnace so that the temperature of the molten steel reaches 1600-1700°C;
2 pre-heat the metal mold to 800-900 °C to maintain constant temperature;
3 Start the centrifuge and inject the molten steel in step 1 into the metal mold after preheating in step 2;
4 castings are naturally cooled to 800-900°C for 1-10 minutes;
5 Cool to near room temperature with water and remove the mold from the mold.
Let’s look at the production process flow of the forged flange:
The forging process is generally composed of the following processes, namely, selecting the blank for high quality steel, heating, forming, and cooling after forging. Forging processes include free forging, die forging, and film forging. During production, different forging methods are selected according to the size of the forging mass and the number of production batches.
Forging productivity is low, and the machining allowance is large, but the tool is simple and versatile. Therefore, it is widely used for forging single-piece and small batch production forgings with relatively simple shapes. Free-forging equipment includes air hammers, steam-air hammers and hydraulic presses, which are suitable for the production of small, medium and large forgings, respectively. Die forging productivity, simple operation, easy to implement mechanization and automation. Die forgings have high dimensional accuracy, small machining allowances, and more reasonable distribution of fiber structure for forgings, which can further increase the service life of parts.
The basic process of free forging: When forging freely, the shape of the forging is gradually forging the blank through some basic deformation processes. The basic processes of free forging include upsetting, pulling, punching, bending and cutting.
1. Upsetting Upsetting is the operation of forging the original billet in the axial direction to reduce its height and increase its cross section. This process is often used for forging gear blanks and other disk-shaped forgings. Upsetting is divided into full upsetting and partial upsetting.
2. Pulling Long Pulling is the forging process that increases the length of the blank and reduces the cross section. It is usually used to produce shaft type blanks, such as lathe spindles and connecting rods.
3. Punching A forging process in which a punch punches a through hole or a blind hole in a blank.
4. Bending A forging process that bends a blank into a certain angle or shape.
5. Torsion A forging process that rotates a portion of a blank relative to another portion.
6. Cutting The forging process of dividing blanks or cutting heads.
(2) Die forging
Die forging is called model forging and the heated billet is forged into a forging die fixed on a die forging apparatus.
1. Basic procedure of die forging Die forging process: blanking, heating, pre-forging, final forging, lapping, trimming, tempering, shot peening. Commonly used processes include upsetting, pulling, bending, punching and forming.
2. Common die forging equipment Common die forging equipment includes die forging hammers, hot die forging presses, flat forging presses, and friction presses.
In layman’s terms, forged flanges are of better quality and are generally produced by die forging. The crystals are finely organised and the strength is high. Of course the price is also higher.
Both cast flanges and forged flanges are commonly used in flange manufacturing. See the strength requirements of the parts that need to be used. If the requirements are not high, flanges can also be selected for turning.
(3) Cutting flange
In the middle plate, the discs with the inner and outer diameters and thickness of the flanges are directly cut out, and then the bolt holes and the water line are processed. The flange thus produced is called a cut flange. The maximum diameter of such a flange is limited to the width of the middle plate.
(4) Rolling flange
The process of cutting a strip from a medium plate and then rolling it into a circle is called rolling, and it is used for the production of some large flanges. After successful rolling, welding is carried out and then flattening, followed by processing of the water line and bolt hole process [6].
Metric editing
National standard flange (English: national standard flange) refers to the flange according to the provisions of the People’s Republic of China national standard “GB/T 9112 ~ 9124-2010 steel pipe flange” production.
The national standard flange standard was jointly issued by the General Administration of Quality Supervision, Inspection and Quarantine of the People’s Republic of China and the Chinese National Standardization Administration Committee on 2011-01-10, and the recommended standards implemented from 2011-10-01 [7].
The GB/T 9112~9124-2010 contains a total of the following 13 criteria:
Replaced the national standard GB/T9112-2000; GB/T10745-1989 standard
GB/T 9112-2010 Steel Pipe Flange Types and Parameters
GB/T 9113-2010 Integral Steel Pipe Flange
GB/T 9114-2010 with steel threaded pipe flange
GB/T 9115-2010 butt welded steel pipe flange
GB/T 9116-2010 Steel flat-welded pipe flange
GB/T 9117-2010 Steel tube flange with neck socket weld
GB/T 9118-2010 butt-welded ring with loose tube steel pipe flange
GB/T 9119-2010 Flat welded steel pipe flange
GB/T 9120-2010 butt welded plate loose tube steel flange
GB/T 9121-2010 flat welded ring plate loose tube steel flange
GB/T 9122-2010 Flanged Ring Type Loose Steel Pipe Flange
GB/T 9123-2010 Steel pipe flange cover
GB/T 9124-2010 Steel pipe flange
Technical conditions
The pressure marks specified in this standard are classified into PN marks and Class marks.
PN mark has 12 pressure levels
Are: PN2.5; PN6; PN10; PN16; PN25; PN40; PN63; PN100; PN160; PN250; PN320; PN400
Class Mark has 6 pressure levels
They are: Class 150; Class 300; Class 600; Class 900; Class 1500; Class 2500
The other meaning of the national standard flange is: The flange produced according to the requirements of the national standard, such as size, tolerance, etc., is different from the flange piece that is not produced according to the standard size and is also called the second standard flange. It is not correct. Usually some unscrupulous merchants will reduce the flange thickness and outer diameter to achieve the purpose of material saving. There are also the use of scrap steel or scrap steel processing flanges, usually the chemical composition and mechanics of this steel. Wastes that do not meet the standards of performance, and even those produced by the private steel-making flanges of the Black Steel Plant, are not able to guarantee mechanical properties and welding performance due to the old steel-making technology used in private steelmaking. They may not be able to be welded to steel pipes during use, or Cracks in the steel itself, pores, etc. will also leak after welding, so when buying a flange, try to use the national standard flange. If the funds are limited, it is necessary to carefully observe and measure the flange size so as not to be fooled.
Processing professional equipment
Manufacturing large-diameter flanges requires professional equipment to do more with less. Professional equipment includes CNC disc milling machines and big head lathes.

Common malfunctions
In the continuous production of modern industry, the influence of factors such as medium corrosion, erosion, temperature, pressure and vibration will cause inevitable leakage. Due to the error in the processing dimensions of the sealing surface, the aging of the sealing element, improper installation and fastening, etc., it is easy to cause leakage of the flange. If the problem of flange leakage cannot be solved in time, under the scouring of the medium, the leakage will rapidly expand, causing the loss of materials and the destruction of the production environment, resulting in the shutdown of the enterprise, resulting in huge economic losses. If it is a toxic, hazardous, inflammable and explosive medium, it may cause serious accidents such as poisoning, fire and explosion.
The traditional way to solve the flange leakage is to replace the sealing components and apply sealant or replace flanges and pipes. However, this method has great limitations, and some of the leaks are limited by the requirements of the working environment and cannot be solved on site. . Polymeric composite materials can now be used for on-site plugging, in which a more mature system with bluish blue is applied. It is a very ideal method, especially in flammable and explosive situations, showing its unique advantages. The technology of polymer composite materials construction is simple, safe, and cost-effective. It can solve most of the flange leakage problems for enterprises, eliminate potential safety hazards, and save more maintenance costs for enterprises.

Scope of application
Due to its good overall performance, flanges are widely used in chemical, construction, water supply, drainage, petroleum, light and heavy industry, refrigeration, sanitation, plumbing, fire protection, power, aerospace, shipbuilding and other basic projects.

Where to buy high quality stainless steel flange?

For those who are looking for flanges, Yaang can provide them best quality Monel Flanges, Inconel Flanges, Haselloy Flanges, Stainless Steel Flanges, Duplex Stainless Steel Flanges, Super Duplex Steel Flanges and so forth. You can buy high quality stainless steel flange from Yaang Pipe Industry Co., Limited (www.metallicsteel.com)

Source: China Flange Manufacturer – Yaang Pipe Industry (www.metallicsteel.com)

(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)

If you want to have more information about the article or you want to share your opinion with us, contact us at sales@metallicsteel.com

Please notice that you might be interested in the other technical articles we’ve published:

  • WHERE TO BUY HIGH QUALITY STEEL PIPES

  • WHERE TO BUY HIGH QUALITY FLANGES

  • WHERE TO BUY HIGH QUALITY PIPE FITTINGS

  • ADVANTAGES OF DUPLEX STAINLESS STEEL PIPE AND SELECTION

  • WHERE TO BUY HIGH QUALITY BELLOW EXPANSION JOINTS

  • Difference Between Pipe Elbow And Pipe Bend

  • Where to get high quality alloy steel pipes

  • Distinguish Inferior Steel Pipes

  • WHERE TO GET HIGH QUALITY HEAT EXCHANGER TUBES

  • How to get high quality forged flanges

  • WHERE TO GET HIGH QUALITY STUB ENDS

  • WHERE TO GET HIGH QUALITY CARBON STEEL PIPES

  • Where to get high quality blind flanges

  • Where to get high quality orifice flanges

  • Where to get high quality lap joint flanges

  • Where to get high quality plate flanges

  • Where to get high quality ring type joint flanges

  • Where to get high quality slip on flanges

  • Where to get high quality spacer rings and spade flanges

  • Where to get high quality socket welding flanges

  • Where to get high quality Threaded Flanges

  • Where to get high quality Spectacle Blind Flanges

  • Where to get high quality welding neck flanges

  • Where to get high quality expander flanges

  • Where to get high quality reducing flange

References:

  • [1]. The flanged forging national export quality and safety demonstration zone is scheduled to be listed. Netease [reference date 2017-11-21]
  • [2]. Wei Jun, Ying Dao Ban. HG “Steel Pipe Flanges, Gaskets and Fasteners” Standards Introduction (I) [J]. Chemical Equipment and Pipeline, 1998(1): 54-62.
  • [3]. Guo Hongwei. Treatment of Leakage without Stopping and Pressure Plugging[J]. Science & Wealth, 2011(8):201-201.
  • [4]. Management Committee. GB/T9112-2010 Steel Pipe Flanges. Types and Parameters [M]. China Quality Inspection Press, 2011.
  • [5]. Cao Yan, Bai Biao. Mechanical Standard Flange Manual and Three-Dimensional Library: Pro/ENGINEER Edition/Cao Yan, White Pei.[M]. Chemical Industry Press, 2012.
  • [6]. Li Ying, Xu Fang, Feng Caiqin. Optimization Design of Large Flange Production Process[J]. Machinery, 2001, 28(s1):150.
  • [7]. Yan Ming. The recently released national standard for steel pipe flanges [J]. Valves, 2001(5):43.
  • [8]. https://www.yaang.com

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