- Flange is a disc-shaped part, which is the most common in pipeline engineering. Flanges are used in pairs. In pipeline engineering, flanges are mainly used for the connection of pipelines. In the pipelines that need to be connected, install a flange. Low-pressure pipelines can use wire flanges, and welding flanges can be used with pressures above 4 kg. Add a sealing point between the two flanges and tighten them with bolts.
- Flanges for different pressures have different thicknesses and use different bolts. When water pumps and valves are connected to pipelines, some parts of these equipment are also made into corresponding flange shapes, also called flange connection. Any connecting parts that are bolted on two planes and closed together at the periphery are generally called “flanges”, such as the joints 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 water pump, It is not easy to call the water pump “flange parts”. Relatively small ones, such as valves, can be called “flange parts”.
- 12 flange types
1. Plate flat welding flange
Plate flat welding flange (HG20592, GB/T9119, JB/T81).
Advantages: Convenient materials, simple manufacturing, low cost, widely used
Disadvantages: Poor rigidity, so it cannot be used in chemical process piping systems with supply and demand, flammable, explosive and high vacuum requirements and in highly and extremely hazardous situations.
The sealing surface types include flat and raised surfaces.
2. Flat welding flange with neck
Neck flat welding flange belongs to the national flange standard system. It is one of the manifestations of the national standard flange (also called GB flange) and is one of the flanges commonly used on equipment or pipelines.
Advantages: On-site installation is more convenient, and the process of patting and rubbing the welds can be omitted.
Disadvantages: The neck height of the flat-welded flange with neck is low, which improves the stiffness and load-bearing capacity of the flange. Compared with butt welding flanges, the welding workload is large, the welding rod consumption is high, and it cannot withstand high temperature and pressure, repeated bending and temperature fluctuations.
3. Butt welding flange with neck
The sealing surface forms of neck butt welding flange are:
Raised surface (RF), concave surface (FM), convex surface (M), tenon surface (T), groove surface (G), full plane (FF).
Advantages: The connection is not easy to deform, the sealing effect is good, and it is widely used. It is suitable for pipelines with large fluctuations in temperature or pressure or pipelines with high temperature, high pressure and low temperature. It is also used for pipelines transporting expensive media, flammable and explosive media, and toxic gases. superior
Disadvantages: The necked butt welding flange is bulky, heavy, expensive, and difficult to install and position. Therefore, it is more likely to be bumped during transportation.
4.Integral flange
The integral flange is a flange connection method. It is also a type of neck butt welded steel pipe flange. Materials include carbon steel, stainless steel, alloy steel, etc.
Among various domestic standards, IF is used to represent the integral flange. It is mostly used in pipelines with high pressure. The production process is generally casting.
In the flange type, an “IF” is used to represent the overall flange type.
Generally it is raised surface (RF). If it is used in flammable, explosive, highly and extremely hazardous working conditions, you can choose convex and concave surface (MFM) and tongue and groove surface (TG) seals in addition to the RF surface. surface form.
5. Socket welding flange
Socket welding flange is a flange with one end welded to the steel pipe and the other end connected with bolts.
Sealing surface form: raised surface (RF), concave and convex surface (MFM), tongue and groove surface (TG), ring connection surface (RJ)
Scope of application: Boiler and pressure vessels, petroleum, chemical industry, shipbuilding, pharmaceutical, metallurgy, machinery, stamping elbow, food and other industries. Commonly used in pipelines with PN≤10.0MPa and DN≤40.
6. Threaded flange
Threaded flange is a non-welded flange that processes the inner hole of the flange into pipe threads and connects it with threaded pipes.
Advantages: Compared with flat welding flanges or butt welding flanges, threaded flanges are easier to install and maintain, and can be used on some pipelines where welding is not allowed on site. Alloy steel flanges have sufficient strength, but are not easy to weld, or have poor welding performance. Threaded flanges can also be selected.
Disadvantages: It is recommended not to use threaded flanges to avoid leakage when the pipe temperature changes rapidly or when the temperature is higher than 260°C and lower than -45°C.
7. Butt welding ring loose flange
Butt welding ring loose sleeve flange is a movable flange piece, which is usually matched with water supply and drainage fittings. When the manufacturer leaves the factory, there is a flange at both ends of the expansion joint, which is directly connected with the pipelines and equipment in the project with bolts.
Function: The purpose of using a butt welding ring loose flange is generally to save materials. Its structure is divided into two parts. One end of the pipe part is connected to the pipe, and the other end is made into a butt welding ring. The flange is made of low-grade materials, while the pipe part is made of the same material as the pipe to save material.
Advantages: cost savings. When the pipe material is special and expensive, the cost of welding flanges of the same material is high. It is not easy to weld or process or requires high strength. Such as plastic pipes, fiberglass pipes, etc. Easy to construct. For example, it is difficult to align the flange bolt holes when connecting or prevent the flange bolt holes from changing when replacing equipment in the future.
Disadvantages: Low stress tolerance. The strength of the welding ring is low (especially when the thickness is less than 3mm)
8. Flat welding ring loose sleeve flange
Flat welding ring loose sleeve flange is a movable flange piece. Directly connect with the pipelines and equipment in the project with bolts. The purpose of using a flat welding ring loose flange is generally to save materials. Its structure is divided into two parts. One end of the pipe part is connected to the pipe, one end is made into a flange, and the flange part is placed on the flange. The flange is made of low-grade materials, while the pipe is partially made of the same material as the pipe to save material.
Advantages: Convenient for welding or processing or requiring high strength, such as plastic pipes, fiberglass pipes, etc. It is convenient for construction. For example, the corresponding flange bolt holes make it easier to align when connecting or prevent the flange bolt holes from changing when replacing equipment in the future. When prices are high, save money. When the pipe material is special, the cost of welding flanges of the same material is high.
Disadvantages: Low acceptance pressure. The strength of the welding ring is low (especially when the thickness is less than 3mm)
9.Flange cover
Also called blind flange and blind plate. It is a flange without a hole in the middle, used to seal pipe plugs.
The function is the same as that of welded heads and threaded pipe caps, except that the blind flange and threaded pipe caps can be removed at any time, but the welded heads cannot.
There are many types of sealing surfaces, including full plane, raised surface, concave and convex surface, tongue and groove surface, and ring connection surface. The main production area is in Mengcun area.
Flange cover sealing surface: flat surface (FF), raised surface (RF), concave and convex surface (MFM), tongue and groove surface (TG), ring connection surface (RJ)
10. Lined flange cover
The lining flange cover is a blind flange, with stainless steel surfacing on the side close to the medium, forming a whole. Lined flange covers are used as blind plates on pipelines with corrosive media. The difference from ordinary flange covers is that an anti-corrosion lining is added to the contact surface with the medium.
11. American standard flat welding flange with neck
The necked flat welding flange is connected to the pipe end. Mainly the parts that connect pipes to each other. There are holes on the flat welding flange with neck, and bolts can be inserted to tightly connect the two flanges, and the flanges are sealed with gaskets.
The neck flat welding flange connection is composed 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, filling the uneven spots on the sealing surface to make the connection tight and leak-proof. Flange connection is a detachable connection. According to the connected parts, it can be divided into container flange and pipe flange. Neck flat welding flange is suitable for steel pipe connections with nominal pressure not exceeding 2.5MPa.
Neck flat welding flange is used for butt welding of flange and pipe. It has reasonable structure, high strength and rigidity, can withstand high temperature and pressure, repeated bending and temperature fluctuations, and has reliable sealing performance. The neck flat welding flange with nominal pressure of 0.25~2.5MPa adopts concave and convex sealing surface.
12. American standard neck butt welding flange
American standard flange is a part that connects pipes to each other and is connected to the pipe end. American standard butt welding flanges are made by forging and casting.
American standard butt welding flanges can be divided into American standard butt welding flanges with necks and American standard butt welding flanges without necks.
American standard butt welding flange consists of two flange plates plus flange pads, which are fastened together with bolts to complete the connection. There are holes in the American standard flange, and bolts tightly connect the two flanges.
The flanges are sealed with gaskets. - Implementation standards: GB series, JB series, HG series, ASME B16.5 (American standard), BS4504 (British standard), DIN (German standard), JIS (Japanese standard).
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