Classification and brief introduction of flanges

Flange basic introduction
Flange, also known as flange flange or flange. Flanges are the interconnected parts between shafts and are used for the connection between pipe ends; they are also used as flanges on the inlet and outlet of equipment for the connection between two equipment, such as reducer flanges. Flange joint is an appliance used for flange sealing.

1. Application:
Flange joint is a kind of component that is extremely commonly used in engineering design and involves a wide range of surfaces. It is an essential part of piping design, pipe fittings and valves, and an essential component of equipment and equipment parts (such as manholes, sight glass level gauges, etc.). In addition, other professions such as industrial furnaces, thermal engineering, water supply and drainage, heating and ventilation, automatic control, etc., also often use flange joints.
2. Material:

Forged steel, WCB carbon steel, stainless steel, 316L, 316, 304L, 304, 321, chrome molybdenum steel, chrome molybdenum vanadium steel, molybdenum titanium, rubber-lined, fluorine-lined material.

10 Flange Types and Features
1. Plate flat welding flange
Plate type flat welding flange (chemical standard HG/T20592, national standard GB/T9119, mechanical JB/T81).
advantage:
The material is convenient to obtain, the manufacture is simple, the cost is low, and the utility model is widely used.
shortcoming:
The rigidity is poor, so it should not be used in chemical process piping systems with supply and demand, flammable, explosive and high vacuum requirements and in highly and extremely hazardous occasions.
2. Flat welding flange with neck
Flat welding flange with neck belongs to the national standard flange standard system. It is one of the manifestations of national standard flange (also known as GB flange).
advantage:
On-site installation is more convenient, and the process of slapping and rubbing the welding seam can be omitted.
shortcoming:
The neck height of the flat welding flange with neck is lower, which improves the rigidity and bearing capacity of the flange. Compared with butt welding flanges, the welding workload is large, the consumption of welding rods is high, and it cannot withstand high temperature and high pressure, repeated bending and temperature fluctuations.
3. Butt welding flange with neck
advantage:
The connection is not easy to be deformed, the sealing effect is good, and it is widely used. It is suitable for pipelines with large fluctuations in temperature or pressure or high temperature, high pressure and low temperature pipelines.
shortcoming:
Neck butt welding flanges are bulky, heavy, expensive, and difficult to install and position, so they are more likely to be bumped during transportation.
4. Integral flange
Integral flange is a flange connection method. It is also a kind of necked butt welded steel pipe flange. Materials are carbon steel, stainless steel, alloy steel, etc.
In various domestic standards, IF is used to represent the overall flange. It is mostly used in pipes with high pressure, and the production process is generally casting.
In the flange type, an "IF" is used to represent the type of integral flange. Generally, it is a raised surface (RF). If it is used in flammable, explosive, highly and extremely hazardous operating conditions, the convex and concave surface (MFM) and the tongue and groove surface (TG) can be selected in addition to the RF surface. face form.
5. Socket welding flange
Socket welding flange is a flange with one end welded to the steel pipe and the other end connected by bolts.
Application range:
Boiler and pressure vessel, petroleum, chemical, shipbuilding, pharmaceutical, metallurgy, machinery, food and other industries.
Commonly used in pipelines with PN≤10.0MPa and DN≤40.
6. Threaded flange
Threaded flange is a kind of non-welding flange, which processes the inner hole of the flange into pipe threads and connects with the threaded pipe.
advantage:
Compared with the flat welding flange or the butt welding flange, the threaded flange has the characteristics of convenient installation and maintenance, and can be used on some pipelines where welding is not allowed. Alloy Steel Flange has sufficient strength, but it is not easy to weld, or the welding performance is not good, threaded flange can also be selected.
shortcoming:
When the temperature of the pipeline changes rapidly or the temperature is higher than 260℃ and lower than -45℃, it is recommended not to use threaded flanges to avoid leakage.
7. Butt welding ring loose flange
The butt welding ring loose flange is a movable flange, which is generally matched to the water supply and drainage accessories. When the factory leaves the factory, there is a flange at each end of the expansion joint, which is directly connected with the pipeline and equipment in the project with bolts.
effect:
The purpose of using butt welding ring loose flange is to save materials. The flange is made of low-grade material, and the pipe part is made of the same material as the pipe, so as to save material.
advantage:
Cost saving. When the pipe material is special and expensive, the cost of welding flanges of the same material is high.
It is inconvenient for welding or processing or requires high strength, such as plastic pipes, glass steel pipes and the like.
It is convenient for construction. For example, it is not easy to align the flange bolt holes when connecting or to prevent the flange bolt holes from changing in the future when the equipment is replaced.
shortcoming:
Low pressure and low strength at the welding ring (especially when the thickness is less than 3mm)
8. Flat welding ring loose flange
The flat welding ring loose flange is a movable flange, which is directly connected with the pipeline and equipment in the project with bolts.
The purpose of using flat welding ring loose sleeve flange is generally to save materials. Its structure is divided into two parts. One end of the pipe is connected to the pipe, and the other end is made into a flange, and the flange part is sleeved on the flange.
advantage:
It is convenient for welding or processing or needs high strength, such as plastic pipes, glass steel pipes and the like.
It is convenient for construction. For example, the corresponding flange bolt holes are convenient for alignment or to prevent the flange bolt holes from changing in the future when the equipment is replaced.
Save money when the price is high. When the pipe material is special, the cost of welding flanges of the same material is high.
shortcoming:
Accept low pressure.
The strength of the welding ring is low (especially when the thickness is less than 3mm).
9. Flange cover
Also known as blind flange and blind flange, it is a flange without a hole in the middle, which is used to seal the pipe plug. The function is the same as the welding head and the screw cap, except that the blind flange and the screw cap can be removed at any time, but the welding head cannot.
10. Lining flange cover
The lining flange cover is a kind of blind flange, and the side close to the medium is surfacing stainless steel as a whole. The lining flange cover is used as a blind plate on the pipeline with corrosive medium. The difference from the ordinary flange cover is that the anti-corrosion lining is added to the contact surface with the medium.
Plate type flat welding flanges are commonly used in volumetric Heat Exchangers and heat exchange units in hot water systems.