Flange

Flange joint is a connection of pipes, where the connecting pieces have flanges by which the parts are bolted together.Pipe flange refers to the flange used for piping in the pipeline device, and when used on equipment, refers to the inlet and outlet flange of the equipment. There are holes in the flange, and the bolts tightly connect the two flanges. The flanges are sealed with gaskets. Flanges are divided into threaded connection (threaded connection) flange, welding flange and clamping flange. Flanges are always used in pairs, low-pressure pipelines can use wire flanges, and welding flanges can be used with pressures above four kilograms.

Specifications of Flange

Type	weld neck flange, slip on flange, blind flange, tube sheet, threaded flange,
Type	socket weld flange, plate flange, spectacle blind, LWN, Orifice flange, anchor flange.
OD/SIZE	15mm-6000mm 1/2”-60” NPS (DN15-DN3000)
Pressure	150#-2500#,PN0.6-PN400,5K-40K,API 2000-15000
Standard	ANSI B16.5,EN1092-1, SABA1123, JIS B2220, DIN, GOST,UNI,AS2129, API 6A, etc.
Wall thickness	SCH5S, SCH10S, SCH10, SCH40S,STD, XS, XXS, SCH20,SCH30,SCH40, SCH60,
Wall thickness	SCH80, SCH160, XXS and etc.
Material	Stainless steel: A182F304/304L, A182 F316/316L, A182F321, A182F310S, A182F347H, A182F316Ti, A403 WP317, 904L,
	1.4301,1.4307,1.4401,1.4571,1.4541, 254Mo and etc.
	Carbon steel: A105, A350LF2, Q235, St37, St45.8, A42CP, E24 , A515 Gr60, A515 Gr 70
	Duplex stainless steel: UNS31803, SAF2205, UNS32205, UNS31500, UNS32750 , UNS32760, 1.4462,1.4410,1.4501 and etc.
	Pipeline steel: A694 F42, A694F52, A694 F60, A694 F65, A694 F70, A694 F80 etc.
	Nickel alloy: inconel600, inconel625, inconel690, incoloy800, incoly 825, incoly 800H, C22, C-276, Monel400, Alloy20 etc.
	Cr-Mo alloy: A182F11, A182F5, A182F22, A182F91, A182F9, 16mo3 etc.
Application	Petrochemical industry;avation and aerospace industry;pharmaceutical industry;
Application	gas exhaust;power plant;ship building;water treatment,etc.

Types of Flange

There are numerous types of flanges, and commonly used materials include carbon steel, stainless steel, alloy steel, etc. In addition, the thickness, number of screw holes, and aperture all require the selection of flanges of appropriate specifications and sizes according to the operational requirements.

Common types of flanges can be divided into sliding flanges (also known as flat-neck flanges) (SO), butt-weld flanges (WN), threaded flanges (THDF), loose flanges (LJ), socket-weld flanges (SW), blind flanges (BL), and other special types according to their shapes and welding methods. The following basically introduces several major flange types.

Weld Neck Flange

The most common type of flange is the weld neck flange, which has a weld bevel on the end of the neck extension. This type of flange is designed to be butt welded directly to the pipe to provide a quality and relatively natural connection. This type of flange connection is almost exclusively used in larger sizes and higher pressure classes. If only one drilled flange style exists in a modern application, the weld neck flange will be your first choice.

Slip-On Flanges

The slip-on flange is a common type of pipe flange designed to place the pipe into the hole/center of the flange to be welded on the outside diameter (OD) of the pipe and the inside of the connection. The slip-on flange is a simple and excellent alternative to weld neck because it does not have a weld bevel, so the length of the pipe can be adjusted to the position of the flange. The hole diameter of the slip-on will provide ample space for the matching pipe. This provides enough working space for the welder and fabricator to make the connection.

Blind Flanges

A blind flange is a solid steel piece without a hole (inside diameter) and is mainly used to close off pipeline lines. Since most flange connections allow air or fluid to pass through the internal opening, the blind flange provides a good termination point for the end of the pipe connection, or to redirect the media of interest to another part of the pipeline assembly. In these cases, and when the pipe requires future modifications, such as installing valves or fittings to redirect the flow, choose a blind flange.

Socket Weld Flange

A less common but equally effective flange connection style, the socket weld flange requires less overall available space than a traditional weld neck flange and features a countersunk hole in the center to cleanly weld the pipe into the socket. Typically available in smaller nominal pipe sizes, it is an excellent alternative to weld necks and slip-on sleeves when necessary.

Threaded Flange

A threaded flange, sometimes referred to as a mating flange/screw flange/NPT flange, contains a female NPT thread in the center for connection to male NPT pipe. Threaded flanges are common when creating reduced-diameter connections. In addition to the standard NPT form specified by the ASME B16.5 specification, other thread styles are available for machining.

Lap Flange

Lap flanges are also known as backup flanges, loose ring flanges, loose hub flanges, and Van Stone flanges. Choosing the right flange for your industrial application is critical. It all depends on the requirements of the intended application. Lap flanges are ideal for piping systems and are easy to disassemble, while rolled angle rings are ideal for structural applications to create bends or circles within various structures.

Standard of Flange

Flange Standards
There are a variety of standards used in the design and selection of flanges. The following codes and standards relate to pipe flanges:

American standards for flanges:ASME Codes and Standards

ASME B16.1 --> Cast Iron Flanges and Flanged Fittings
ASME B16.5 --> Pipe Flanges and Flanged Fittings
ASME B16.24 --> Bronze Flanges and Fittings–150 and 300 Classes
ASME B16.42 --> Ductile Iron Pipe Flanges and Flanged Fittings–150 and 300 Classes

ASME B16.47 --> Large Diameter Steel Flanges

ASTM A 105--> Carbon Steel Flange

ASTM A 182-->Stainless Steel Flange

ASTM A350-->Carbon and Low Alloy Steel Flanges for Low Temperature Services

European standard EN 1092: Flanges and Their Joints (Circular Flanges for Pipes, Valves, Fittings and Accessories, PN designated)
Steel flanges, PN 2.5 to PN 400
Cast iron flanges, PN 2.5 to PN 63
Copper alloy flanges, PN 6 to PN 40
Aluminium alloy flanges, PN 10 to PN 63

Production Process of Forged Flange

Select high-quality steel billets for blanking, heating, forming, and cooling after forging. Forging process methods include free forging, die forging, and tire die forging. During production, different forging methods are selected according to the quality of the forgings and the production batch.

Basic process of free forging: During free forging, the shape of the forging is gradually forged into the billet through some basic deformation processes. The basic processes of free forging include upsetting, drawing, punching, bending, and cutting.

Upsetting is the process of forging the original billet along the axial direction to reduce its height and increase its cross-section. This process is often used to forge gear billets and other disc-shaped forgings. Upsetting is divided into full upsetting and partial upsetting.

Drawing is a forging process that increases the length of the billet and reduces the cross-section. It is usually used to produce shaft blanks, such as lathe spindles, connecting rods, etc.

Punching is a forging process that uses a punch to punch through or non-through holes in the billet.

Bending is a forging process that bends the blank into a certain angle or shape.

Twisting is a forging process that rotates one part of the blank relative to another part at a certain angle.

Cutting is a forging process that splits the blank or cuts off the head.

Die forging is the full name of model forging, which places the heated blank in a forging die fixed on the die forging equipment for forging and forming. Basic processes: blanking, heating, pre-forging, final forging, punching, trimming, quenching and tempering, shot peening. Common processes include upsetting, drawing, bending, punching and forming. Common die forging equipment Common die forging equipment includes die forging hammer, hot die forging press, flat forging machine and friction press. Generally speaking, forged flanges are of better quality and are generally produced by die forging. They have fine crystal structure and high strength, and of course, they are more expensive.

Cutting flanges:Directly cut the inner and outer diameters and thickness of the flange on the middle plate, and then process the bolt holes and waterlines. The flange produced in this way is called a cut flange, and the maximum diameter of this type of flange is limited by the width of the middle plate.

Rolled flange:The process of cutting strips from the middle plate and then rolling them into a circle is called rolling, which is mostly used in the production of some large flanges. After the rolling is successful, it is welded, then flattened, and then the waterline and bolt hole processes are processed.