[introduction] pipe flange gasket, and the fasteners are collectively referred to as flange joint. Flange joints are widely used in engineering design, which involves a very wide range of parts. It is essential for piping design, pipe valve parts, but also equipment, equipment parts (such as manholes, mirror level gauge etc.) necessary components. In addition, other professional such as industrial furnace, thermal, water supply and drainage, heating ventilation, automatic control, etc., but also often use the flange joint.
Basic flange profile
Material: stainless steel, forged steel, WCB, 316L, 304L, 316, 304, 321, Cr Mo steel, chromium molybdenum vanadium, molybdenum, titanium, two fluorine rubber lining material.
Variety: flange, neck flange, welded flange, flange ring, socket flange, and blind plate.
A series of GB standards (national standard), JB series (Mechanical), HG series (Ministry of chemical industry), ASME B16.5 (American Standard), BS4504 (British Standard), DIN (German standard), JIS (Japan).
International standard pipe flange pipe flange system: international standard has two main systems, namely DIN in Germany (including the former Soviet Union) as the representative of the European and American ANSI system with pipe flange pipe flange pipe flange system represented by america. In addition, there are Japanese JIS pipe flange, but in the petrochemical plant is generally used only for public works, but also in the international impact on the smaller.
A brief introduction to the flange of each country
The American system pipe flange standard, with B16.5 ANSI and B ANSI 16.47 as the representative.
The British and French standard pipe flanges, between the two countries have two casing flange standard, to sum up, through the international standard pipe flange can be divided into two different, and not interchangeable flange system: one to Germany on behalf of the European pipe flange system; another is represented by the United States of America pipe flange system. IOS7005-1 is the international organization for Standardization in 1992 issued a standard, the standard is actually the United States and Germany, the two sets of series of pipe flanges and pipe flange standard. Two system of pipe flange connection size safety is different, can not match each other. Flange two system with pressure level to distinguish the most appropriate, the European system was 0.25, 0.6, 1, 1.6, 2.5, 4, 6.3, 10, 16, 25, 32, 40.0MPa, 1, 2, American system 5, 11, 15, 26, 42.0MPa.
Brief introduction to the situation of flange in our country
China's chemical industry, petrochemical industry, the use of the standard pipe flange
1 inch tube (International piping Series) GB 9112, SH 3406 ~ 9125
2, the metric tube (the diameter of the domestic steel pipe diameter series) HGJ44 ~ 76, JB/T74 ~ 90 DIN connection size and JB standards are different, specific see table below:

Note: the &ldquo within the brackets in the table; all ” that all specifications are replaced by second rows of fasteners. “ part ” indicates that there is a part of the specification of the fastener to be changed, but there is still a part of the specification of the fastener that is not changed, it is the same.
HG new standard and JB standard flange with the use of the old, should pay attention to the following points:
1, there are three flange bolts a number of inconsistencies, which have two specifications (PN0.25/DN500, PN0.6/DN500) directly affect the fit; PN1.0/DN80HG standard bolt number 8, JB standard bolt number is 4;
2, part of the old standard (JB 2) the best screw expanding 1 ~ 2mm, another part can add the washer in the installation;
3, PN16.0MPa high pressure pipe flange, the new JB and HG standard connection size is completely different.
Flange type and sealing surface form
A welding plate flange

Welding plate flange (chemical standard national standard HG20592, GB/T9119, JB/T81: convenient, mechanical) has the advantages of simple manufacture, low cost, wide use; but less rigid, it shall not be used for supply and demand, flammable, Yi Baohe high vacuum requirements of chemical process piping system and height, is extremely harmful to the occasion. Seal type plane and surface process.

Two, hubbed flange


Hubbed flange to flange standard system gb. Is one of the national standard flange (also known as GB flange), which is one of the performance of the device or pipe is commonly used in one of the flange.
Hubbed flange neck low height, stiffness, bearing capacity of flange is improved. Compared with the welding, welding workload, electrode consumption is not high, high temperature and high pressure and repeated bending and temperature fluctuations, but the site is convenient to install and can be omitted the weld process take rub injury.

Three, hubbed flange

The full name of hubbed flange hubbed steel pipe flanges English Name: Slip-on SO
Hubbed flange with flange plate is the same as the steel pipe and pipe fittings into the flanges are connected by fillet welds and equipment or pipeline flanges.
Hubbed flange sealing surface form:
Raised face (RF), (FM), concave convex surface (M), (T), tenon groove (G), the whole plane (FF).
Hubbed flange diameter range: DN10~DN600
Scope of application: PN2.5~PN40 series Class; PN series Class150~Class1500
Flange material: carbon steel, steel, 304, Luo 316, 304L, 316L, 321, 347, CF8C.Manufacturing process: forging.
Advantages: hubbed flange also belongs to the flange, because there is a short neck, so as to improve the strength and improve the load bearing strength of flange flange. So it can be used in a higher pressure pipe.
Disadvantages: a welding plate flange cost is higher, because of the characteristics of the shape are more likely to bump in transit.

Four, the overall flange


Integral flange is a flange connection mode. Is a steel with welding neck flange. Material with carbon steel, stainless steel, alloy steel, etc.. In various domestic standards, using IF to represent the overall flange. Used in high pressure pipelines. Production process is generally cast.
In the flange type is to use a “ IF” to indicate the type of the integral flange. General process surface (RF), if the condition of the use of flammable, explosive, high or extreme harm, can choose the convex and concave surface except RF outside surface (MFM) and groove (TG) of the sealing surface of the form.

Five, socket welding flange


The socket welding flange is a flange which is connected with one end of the steel pipe to the other end of the pipe.
The sealing surface forms: process surface (RF), convex surface (MFM) and groove (TG) and ring junction (RJ)
Application: boiler pressure vessel, petroleum, chemical, shipbuilding, pharmaceutical, metallurgy, machinery, stamping elbow food and other industries socket welding flange: commonly used in 10.0MPa; DN&le, PN≤ 40 of the pipeline;

Six, threaded flange


The threaded flange is the inner hole of the flange is processed into the pipe thread, and is connected with the pipe with a thread, and is a non welding flange. Compared with the flange or welded flange, threaded flange has convenient installation and maintenance characteristics, in some field is not allowed to use the pipeline welding. Alloy steel flange has sufficient strength, but not easy to weld, or poor performance, can also choose a threaded flange. However, the temperature change in the pipe or temperature is higher than the temperature above 260 degrees Celsius below -45 degrees Celsius, it is recommended not to use the threaded flange, so as to avoid leakage.

Seven loose flange ring, butt welding


Loose flange ring butt welding flange is movable, generally supporting the drainage fittings factory, expansion joints at both ends have a flange bolt connection pipeline, directly and in engineering equipment.
Effect:
The use of welding ring loose flange of the general purpose is to save materials, the structure is divided into two parts, one part of the pipe head and the pipe head is made into a welding ring. The flange plate adopts the low grade material, and the pipe part uses the same material as the pipe, so as to achieve the purpose of saving material.
The advantages of the loose flange ring welding:
1, cost savings. When the pipe material is special, the price is expensive, the same material of the welding flange high cost.
2, is not easy to welding or not easy to process or the need of strength. Such as plastic pipes, glass pipes and the like.
3, ease of construction. If the connection is not easy to find the corresponding flange bolt hole flange bolt holes are the replacement of equipment or prevent the day after.
Disadvantages:
1, under low pressure.
2, the strength of the welding ring is low (especially when the thickness of 3mm)
Eight, with loose flange ring


Welding-on collar loose flange is a flange can be activities. Directly connected with the pipe and equipment in the project. Use the flat ring loose flange of the general purpose is to save the data, the structure is divided into two parts, a local pipe head and pipe head is made into a flange, the flange part is sheathed on the upper flange. Flange plate using the low level of information, and the use of pipes and pipes as the same as the information, to achieve the purpose of saving information.
Welding-on collar loose flange defect:
1, accept low pressure.
2, the strength of the welding ring is low (especially when the thickness of 3mm)
The advantages of welding-on collar loose flange:
1, convenient for welding or convenient in the processing or need the strength of large, such as plastic pipe, glass pipe and the like.
2, ease of construction, such as the connection of the flange bolt hole corresponding to the right to find a positive or to prevent the day after the replacement of the flange bolt and bolt, etc..
3, when the price is noble, save cost. When the pipe material is special, the cost of welding the same material is high.

Nine, flange cover


Blind flange, blind plate. Is the middle of the flange without holes, pipe plug for seal. With welding head and screw cap is the same, but the blind flange and screw cap can be unloaded, and the welding head. Sealing surface in the form of many types, with the entire plane, bursting surface, convex surface, groove, ring joint face. Major production areas in Mengcun area.
Flange cover cover
The plane (FF), (RF), sudden surface roughness (MFM) and groove (TG) and ring junction (RJ)

Ten, lining flange cover


The lining flange cover is a kind of blind flange, which is close to the side of the medium and is welded with stainless steel. The lining flange cover is used for blind plate on the pipeline with corrosive medium. The difference between the common flange cover and the common flange cover is that the anti-corrosion lining layer is added to the contact surface of the medium.
Eleven, American Standard hubbed flange


Hubbed flange connected to the pipe end. Is the main part of the pipe and the pipe connected to each other. Hubbed flange holes, wear bolts, the two flange, flange gasket seal. Hubbed flange composed of a pair of flanges, a gasket and a plurality of bolts and nuts. Gasket on the flange sealing surface between the two, tighten the nut, the gasket on the surface pressure reaches a certain value after the deformation, and fill uneven sealing surface, so that does not leak tight connection. Removable flange connection is a connection. According to the connection of the components can be divided into the container flange and pipe flange. Hubbed flange for nominal pressure of not more than 2.5MPa of steel pipe connection.
Hubbed flange for butt welding flange and pipe, reasonable structure, strength and stiffness to withstand high temperature and high pressure and repeated bending and temperature fluctuations, reliable seal. The nominal pressure is 0.25 ~ 2.5MPa hubbed flange seal surface using bump.

Twelve, American Standard hard welding flange


American Standard flange is to make pipe and pipe interconnected parts, connected to the pipe end. American Standard by welding flange forged and cast into two methods. According to the American Standard flange with a neck can be divided into American Standard welded flange hubbed welding flange and American Standard without a neck. American Standard consists of two welded flange flange with flange pad, fastened together with bolts to complete the connection. The holes are American Standard flange bolt, the two flange connect the flange gasket seal.

Flange foundation knowledge ask
A, what is a live cover flange, the flange is used in what place and what kind of pipe fittings?
Loose flange is a flange can be activities, generally supporting the drainage accessories (the most common slip joint), the factory expansion joints at both ends have a flange bolt connection pipeline, directly and in engineering equipment.
Two, the flange is how and the pipeline connected to the welding in what part?
Flange classification. Generally use a flat flange, welded flange (neck flange), loose flange etc.. Flange for low pressure, using plug welding, both sides of the welding, welding depth from the flange sealing surface 2-5mm can be welded directly welded flange, loose flange bolt connection without welding.
Three, what is the meaning of the flange type?
The flange is a link, to connect the valve and piping, valves and pipe connections that when the junction is connected by bolts, so the valve end of two months with a uniform N is the flange bolt holes.
1, the flange flange is flange: transliteration, meaning that, with flange parts, the parts can be alone, is the flange, can also be combined, such as pipe end or ends with flange, flange on several through holes for mounting screws, some bearing outer ring with flange. The flange can have holes, can not only block with holes, edge positioning.
2, flange type: valve and pipeline or equipment is connected with flange connection, also known as the connection mode is a flange type.
Four, what is the flange?
Flange is a disc - shaped parts, in the pipeline project is the most common, the flange is used in pairs. In the pipeline project, the flange is mainly used for the connection of pipes. In the need to connect the pipe, a variety of installation of a flange plate, low pressure pipe can be used wire connection flange, 4 kg or more pressure on the use of welding flange. Between the two pieces of flange and the sealing point, and then tighten the bolts. Different pressure flange have different thickness and use different bolt. Pumps and valves, in connection with the pipe, the parts of the equipment, but also made corresponding to the flange shape, also known as the flange connection. In two planes in the surrounding the use of bolts at the same time the closed connecting parts, generally referred to as &rdquo, such as “ flange; ventilation pipeline connection, the parts can be called “ flange parts ”. But this connection is only a part of the equipment, such as the flange and the water pump connection, it is not good to pump called “ flange parts ”. Relatively small, such as valves, can be called “ flange parts ”.
Five, the flange is how to connect a way?
Flange connection is an important connection way of pipeline construction.
Flange connection is the two pipes, fittings or equipment, the first fixed on a flange plate, the two flanges, plus the flange gasket, bolts fastening together, complete the connection. Some pipe fittings and equipment have own flange, but also belong to the flange connection.
Flange connection (wire connection) flange and welding flange. Low voltage and small diameter wire connecting flange, high pressure and low pressure and large diameter are welded flange, the thickness of the flange plate of different pressure and the connecting bolt diameter and the number is different.
According to the different levels of pressure, the flange gasket also has different materials, from the low pressure asbestos gasket, high pressure asbestos pad to the metal pad.
Flange connection is convenient to use, able to withstand greater pressure.
In industrial pipelines, the use of flange connections is very wide. In the family, the pipe diameter is small, moreover is the low pressure, can not see the flange connection. If you are in a boiler room or in the production site, all the pipes and equipment are connected to the flange. Flange connection is the two pipes, fittings or equipment, the first fixed on a flange plate, the two flanges, plus the flange gasket, bolts fastening together, complete the connection. Some pipe fittings and equipment have own flange, but also belong to the flange connection.
Note that the connection of the time, especially when the bolt is tightened to do all the same bolt.
Six, the use of the flange is what?
Flange is used to locate the.
For example, there is an installation of the cylinder is called the flange installation, that is, such as a rectangle around the four to playThe middle hole, there is a big hole and cylinder diameter, the cuboid is set in the cylinder between them can be welded after other fixed together, is connected with the cylinder and other things are connected by four holes around the cuboid, the cuboid can be called flange.
Connection seven, orifice flange and ordinary flange?
Is the two pipes, fittings or equipment, the first fixed on a flange plate, the two flanges, plus the flange gasket, with bolts fastening together, complete the connection.
Orifice flange is orifice flowmeter orifice connection (measuring part, orifice flowmeter) to the pipe, flange on both sides of the hole plate is fixed in the middle, the pressure measuring point on the flange, leads to a differential pressure transmitter, to measure flow rate.
Eight, to ensure that the installation of the flange does not leak oil leak, the installation of attention to what the problem?
1, the flange should have enough strength, can not be deformed when tightening. The flange sealing surface should be smooth and clean, to seriously clean up oil and rust during installation.
2, the sealing gasket should have good oil resistance and aging resistance, as well as good flexibility and mechanical strength. Installation should be based on the shape of the connection of different sections and sizes of sealing gasket, and placed correctly.
3, flange fastening force should be uniform, rubber pad compression should be controlled at 1 / 3.
Nine, welding flange flange and what is the difference?
Welded flange is interface end diameter and wall thickness and welding pipe, pipe welding on two.
Flange interface is slightly larger than the outer diameter machining a concave point, pipe inside welding.
Butt welding performance is good, corrosion is relatively small.
Welding and butt welding is the welding flange and pipeline connection, flange welding only one side welding without welding pipe and flange connection inside the mouth, butt welding flange welding installation requires double welding flange. So the flange generally used for low and medium pressure pipeline, welded flange for connection, high pressure pipe, butt welding flange is at least PN2.5MPa, use the welding in order to reduce the stress concentration of welded flange general is also called the nipple flange neck flange. Installation welding flange so that the labor cost and material fee is high, because the more a process.
Welded flange not all need inside and outside the double welding, not only the general outside welding a special requirements, have not seen 1/2" the welding flange, welding): what is good for welding, because the pipe and flange of the vertical pipe, not inclined.
Ten, the difference between the flange and the valve?
Valve is the same thing as the faucet, or that the faucet is a kind of valve. You can turn on, water or gas can flow out; can be closed, the water does not flow.
Home tap water is screwed on the tube, but the factory with some pipe inside the water or gas, high pressure, with a threaded connection is not solid, directly welded or connected with other methods. Flange is one kind of connection method.
Eleven, the choice of the main principle of the flange is what?
Answer: to design a temperature of 300 DEG C and nominal pressure of less than or equal to 2.5MPa pipeline, should choose the flange for design temperature greater than 300 degrees or greater than or equal to the nominal pressure 4.0MPa pipe, welding flange should be used.
Twelve, what circumstances can be used thread connection?
A: when the design pressure is less than or equal to 1.6MPa and the design temperature is not more than 200 degrees Celsius, in the "low pressure fluid delivery welded steel pipe" GB / T 3091 can be used on the thread connection.
Thirteen, what are the reasons for the leakage of the flange?
Flange leakage, more common in the following 7 reasons.
1, partial mouth
Partial mouth, refers to the pipe and the flange is not vertical, not concentric, not parallel to the flange. Flange leakage occurs when the pressure of the internal medium is greater than the load of the gasket. This situation is mainly caused by the installation of construction or maintenance process, more easily found. As long as the project is completed in order to really check, you can avoid the occurrence of such accidents.
2, wrong mouth
Wrong mouth, refers to the pipe and flange vertical, but the two flange is not concentric. The flange is not concentric caused around the bolts are not free to penetrate into the bolt hole. In the case of no other way, only with a smaller size or reaming the bolt through the bolt hole, and this method will reduce the tension of the two flanges. Also, the sealing surface of the sealing surface has a deviation, it is very easy to leak.
3, mouth
Mouth, refers to the flange clearance is too large. Flange clearance is too large and caused by external loads, such as axial or bending load, the gasket will be subjected to shock or vibration, lose the compression force, which gradually lost the seal of kinetic energy and lead to failure.
4, wrong hole
The wrong hole, refers to the pipe and the flange concentric, but the distance between the two flanges relative to the bolt hole is larger. The wrong hole will make the bolt stress, the force is not eliminated, the bolt will cause shear stress, a long time will cut off the bolt, resulting in seal failure.
5, the effect of stress
In the flange, flange butt joint two are relatively standard, but in the production system, the pipeline into the medium after the pipeline caused by temperature change, make the pipe expansion or deformation, so that the flange by bending or shear force, easy to cause the gasket failure.
6, corrosion effect
Due to the erosion of the corrosion medium for long time, the gasket has a chemical change. The corrosive medium penetrated into the gasket, the gasket began to become soft, lose the compression force, causing the flange leakage.
7, expansion and contraction
The fluid expansion and contraction effect caused by bolt expansion or contraction, it will produce gasket gap, the medium pressure leak.