Also called flange or flange. The part that connects the tube to the tube. Connected to the pipe end. There are holes in the flange, and bolts can be worn to tightly connect the two flanges. The flanges are sealed with gaskets.

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Flange

There are two types of connection between container parts: non-detachable (welded) and detachable. Due to the production process requirements, and for the convenience of manufacturing, transportation, installation and maintenance, between the cylinder and the cylinder, the cylinder and the head, the pipeline and the pipeline, and the pipeline and the valve, a removable flange connection is commonly used.

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Although the detachable structure has flange connection, threaded connection and socket connection. However, the flange connection is most widely used in chemical, pharmaceutical equipment and pipelines due to its unique sealing reliability, high strength and wide adaptability.

Flange connection structure and sealing mechanism

Working mechanism: By pre-tightening the bolts, the gasket between the flange sealing surfaces is compressed and solidified, and fills the uneven gap on the flange sealing surface, preventing the leakage of the medium through the capillary holes of the gasket and leakage The interface between the gasket and the sealing surface is leaking. Thus achieving pre-sealing.

The conditions for ensuring the sealing of the flange connection are leak-proof: when pre-tensioning, the pre-tension specific pressure acting on the gasket is not lower than the pre-tightening specific pressure; when working, the remaining specific pressure acting on the gasket is not Below the specific pressure of the working seal.

Flange type

According to the integrity of flange and equipment or pipeline connection:

1. Integral flange

Flat welding flange: used for occasions where temperature and pressure are not too high. (The standard has specific temperature and pressure values)

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Butt welding flange: suitable for important occasions with high pressure, high temperature, toxic, flammable and explosive. The cost is high.

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The difference between flat welding flange and butt welding flange:

1. The welding seam forms are different: the flat welding seam can not be detected by radiography, but the butt welding seam can be; the flat welding is two corner joint welding seams, butt welding is one butt joint welding seam.

2. The nominal pressure is different: the nominal pressure of the neck-welded flange is: 0.6---4.0MPa, while the nominal pressure of the neck-welded flange is: 1--25MPa, obviously, the neck-welded flange The adaptive pressure level is lower.

3. Different connection methods: flat welding flanges can generally only be connected to pipes, but not directly to butt-welded fittings; butt-welded flanges can generally be connected to all butt-welded fittings (including elbows, tees, reducers, etc.) Etc.) Direct connection, of course including pipes.

2. Loose flange

Features: The flange cannot be connected with the pipeline or container, which is suitable for the occasion with low pressure, and does not produce additional bending stress on the non-ferrous metal and stainless steel equipment and pipeline shell; when it is made of carbon steel, it can save the consumption of precious metals. But the rigidity of the loose flange is poor.

Connection method of flange and container or pipeline:

Put on the cuff

Put on the welding ring

Put on the belt loop

3. Threaded flange

Widely used in small-diameter high-pressure pipelines, the additional stress generated by the flange on the pipe wall is small.

Flange shape

In general, the shape of the flange is disc-shaped or disc-shaped with a neck, and partly square or oval (waist-shaped).

Square flange

Round flange

Oval flange

Factors affecting flange sealing

The main factors affecting the flange sealing are: bolt preload, sealing surface form, gasket performance, flange stiffness and operating conditions.

The form of the sealing surface:

Flat type: simple structure, convenient processing, easy to anti-corrosion or lining. However, the gasket is easy to extrude and is not easy to be compressed. It is used in low pressure, small size, non-toxic, and low sealing requirements.

Concavo-convex type: good neutrality, good sealing performance, used in medium pressure and high temperature occasions.

Tongue and groove type: good neutrality, reliable sealing, small gasket width, and small required pressing force, suitable for flammable, explosive, toxic and high pressure occasions. Processing and maintenance are more difficult.

Three important parameters in flange standard

1. Nominal diameter DN:

The nominal diameter of the flange refers to the nominal diameter of the container or pipe that matches the flange. The nominal diameter of the container refers to the inner diameter of the container (except for containers that use tubes as cylinders). The nominal diameter of the tube refers to its nominal diameter, which is a value between the inner and outer diameter of the tube, most of which are close to the the inside diameter of. For steel pipes with the same nominal diameter, the outer diameter is the same, because the thickness changes, so the inner diameter also changes. See Table 14-1.

2. Nominal pressure PN:

Nominal pressure is the pressure level divided for the purpose of setting standards. See Table 14-2.

3. Maximum allowable working pressure:

The nominal pressure in the pressure vessel flange standard is determined according to the flange material 16Mn (or 16MnR) and the design temperature 200oC. When the flange material and temperature change, the maximum allowable working pressure of the flange will increase or decrease . For example, the maximum allowable working pressure of the long neck butt welding flange in Table 14-3.

How to choose pressure vessel flange

It is an optional flange for a container cylinder or head with an inner diameter of Di, a design pressure of p, and a design temperature of t.

1. According to the nominal diameter DN of the container and the design pressure p, refer to JB/T4700 Table 1 to determine the structure of the flange. (Type A flat welding flange, type B flat welding flange or long neck butt welding flange)

2. According to the design pressure p of the vessel, the design temperature t and the flange material to be used, determine the PN of the selected flange according to Table 6 or Table 7 (maximum allowable working pressure gauge) of JB/T4700.

3. Check table 1 of JB/T4700 according to PN and DN to verify whether the flange type determined initially meets the requirements. If it does not comply, you need to change the flange type or material and re-determine the PN.

4. Check the flange size according to JB/T4701 (Type A) or 4702 (Type B) or 4703 (Long neck butt welding).

Baoji Hongyada Nonferrous Metal Material Co., Ltd.

Contact: Zhang Hongbin

Mobile: 13809171560 (same number on WeChat)

Tel: 0917-3854158

E-mail: hongyadajinshu@163.com

Skype: carrolyn851

Q Q: 379855550