What is a flange?

A flange is a type of piping component that is used to connect pipes or other equipment components in various industries.

duplex 2205 flanges
duplex 2205 flanges

Flanges are typically flat, round, or square-shaped plates with holes in the center through which bolts can be passed to connect the flange to another component.

Flanges are available in many different sizes, shapes, and materials, and they can be classified based on their design, face type, or pressure class. The most common types of flanges include:

  1. Weld Neck Flanges: These flanges have a long, tapered neck that is welded to the pipe, providing excellent strength and support for high-pressure applications.
  2. Slip-On Flanges: These flanges slip over the end of the pipe and are then welded in place, making them easy to install and suitable for low-pressure applications.
  3. Blind Flanges: These flanges are used to seal the end of a pipe or fitting, rather than connecting it to another component.
  4. Threaded Flanges: These flanges have threads on the inside bore, allowing them to be connected to pipes or fittings with matching threads.
  5. Lap Joint Flanges: These flanges are used in conjunction with a stub end to allow the pipe or fitting to rotate during installation or maintenance.

Flanges can be made from various materials, such as stainless steel, carbon steel, and other alloys. The choice of material depends on the application, the environment, and the required performance characteristics.

Overall, flanges are an essential component of industrial piping systems, providing a means to connect pipes and other equipment components in a secure and leak-proof manner.

Flange is a part connected between the pipe and the pipe, used for the connection between the pipe ends; It is also useful in the inlet and outlet of the equipment flange, used for the connection between two equipment, such as reducer flange. Flange connection or flange joint refers to the detachable connection of flange, gasket and bolt connected with each other as a group of integrated sealing structure. Pipe flange refers to the flange of the pipe fitting in the pipe installation, and refers to the inlet and outlet flange of the equipment. There are holes in the flange, and bolts make the two flanges tightly connected. Flanges are sealed with gaskets.

Flanges are connected by thread (wire connection) flange, welding flange and clamp flange. Flanges are used in pairs, wire flanges can be used for low pressure pipes, welding flanges can be used for pressure over 4 kg. Add a gasket between the two flanges and tighten with bolts. Flanges with different pressures have different thicknesses, and they use different bolts. Pumps and valves, when connected with pipes, parts of these equipment are also made into corresponding flange shapes, also known as flange connections. The connection parts that are closed at the same time using bolts around the two planes are generally called “flanges”, such as the connection of ventilation ducts. This kind of parts can be called “flange parts”. But this connection is only a part of the equipment, such as the connection between the flange and the pump, it is not good to call the pump “flange parts”. Smaller ones, such as valves, can be called “flange parts”.

Reducer flange, used for connecting motor and reducer, as well as connecting reducer and other equipment.

Classification method

1: According to the standard of chemical industry (HG), it can be divided into: integral flange (IF), threaded flange (Th), plate welding flange (PL), butt-welded flange (WN), butt-welded flange (SO), socket welding flange (SW), butt-welded ring loose flange (PJ/SE), butt-welded ring loose flange (PJ/RJ), lining flange cover (BL(S)), flange cover (BL).

2: According to petrochemical (SH) industry standards: threaded flange (PT), butt welding flange (WN), flat welding flange (SO), socket welding flange (SW), loose sleeve flange (LJ), flange cover (not indicated).

3: According to the mechanical (JB) industry standards: overall flange, butt welding flange, plate flat welding flange, butt welding ring plate loose sleeve flange, flat welding ring plate loose sleeve flange, flanging ring plate loose sleeve flange, flange cover.

4: According to national (GB) standards: overall flange, threaded flange, butt welding flange, flat welding flange with neck, socket welding flange, butt welding ring with neck loose sleeve flange, flat welding flange, butt welding ring plate loose sleeve flange, flat welding ring plate loose sleeve flange, flanged ring plate loose sleeve flange, flange cover.

The material

Carbon steel (WCB), LCB (low temperature carbon steel), LC3 (3.5% nickel steel), WC5 (1.25% 0.5% chrome molybdenum steel), WC9 chromium (2.25%), C5 (0.5% 5% chromium molybdenum), C12 (9% 1% chromium molybdenum), CA6NM (4 (12% chromium steel), CA15 (4) (12% chromium), CF8M (3 16 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(Haster nickel alloy B), CW6M(Haster nickel alloy C), CY40(Inco nickel alloy), etc.

The connection method

Flange connection is the two pipes, pipe fittings or equipment, first respectively fixed on a flange, between the two flanges, plus flange pad, bolted together, complete the connection. Some fittings and equipment have come with flanges, also belong to the flange connection. Flange connection is an important connection mode in pipeline construction. Flange connection is easy to use and can withstand large pressure. Flanged connections are widely used in industrial pipelines. In the home, the pipe diameter is small, and the low pressure, the flange connection is not visible. If you’re in a boiler room or a production site, there are flanged pipes and equipment everywhere.

According to the connection flange connection types can be divided into: plate flat welding flange, with flat welding neck flange, butt welding neck flange, socket welding flange, threaded flange, flange cover, with neck butt welding ring flange, ring flat welding flange come loose, ring groove surface flange, flange cover, large diameter plate flange, large diameter high blind flange, butt welding neck flange, eight words ring flange, etc.

The welding quality

As for iron welded flanges, many customers question whether the quality of iron welded flanges is better than forged welded flanges. Actually iron plate welding quality and the quality of the welding flange forging flange is the same, but the iron plate welding flange exactly what place can not be guaranteed, is also the most insecure iron plate welding flange material, because the process of general, the density of iron plate welding flange is no problem, but in the process of producing, Iron welded flange blanks are rarely tested, so the material of untested iron welded flanges cannot be guaranteed after production.

Welding process

The required equipment

A set of manual welding equipment, a handle type Angle mill, an electric hammer, a plane ruler.

Weld preparation

1. Check and debug the equipment to ensure the normal operation of the equipment;
2. Prepare φ4.0J402 electrode preferably in 300℃-350℃ drying for one hour.

Welding process

1. Assemble the vertebral body and the large flange together according to the drawing requirements, and then divide the large flange into 8 equal parts on average.
2. Since the flange is thick and the groove is large, the piecewise symmetric and multi-layer welding is adopted.

Weld quality

The weld strength is required to reach the base metal strength at least. The weld surface is flat and smooth, without defects such as burn through, porosity, welding leakage, slag inclusion, edge biting and incomplete welding. Residual height less than 2mm.

Matters needing attention

1. J506 electrode must be used for manual surfacing when laying the bottom, and small current welding shall be adopted. Welding in strict accordance with welding process.
2. After each welding position, use a level to clamp the deformation of the flange plane.
3. Hammer the welding seam with air hammer while welding to eliminate stress.