Our current flange standards are divided into two systems, namely PN series (European system) and Class series (American system).
The nominal pressure level of PN series is expressed by PN, including the following nine levels: PN2.5, PN6, PN10, PN16, PN25, PN40, PN63, PN100, PN160.
Class series nominal pressure level using Class, including the following six levels: Class150, Class300, Class600, Class900, Class1500, Class2500.
Because the pressure level itself should be no second, just a different class standard, interchangeable in addition to consider the conversion relationship between LB and MPa, probably MPa = 0.007 × LB. LB and PN is the pressure level, not a simple unit of pressure, that is, LB can be converted to each other with the MPa, but the LB and PN can not be simply converted.
HG/T20592-2009 and HG/T20592-97 flange standard nominal pressure difference.
Pressure conversion formula: 1 bar (bar) = 100000 Pa (Pa) = 10 Newton / square centimetre = 0.1 MPa (MPa is megapascals) is the unit defined by the International Standards Organization.
In HG/T20592-2009 flange standard pressure for PN16, and HG/T20592-97 flange standard pressure PN1.6 pressure is the same, that is, we usually say 16 kg pressure.
2009 version of the nominal pressure is by bar as a unit, 97 version of the nominal is by MPa as a unit, 16bar = 1.6MPa.
Concept and Classification of Flanges
Flanges are also called flanges or flanged discs. Flange is to make the pipe and pipe interconnection parts, connected to the pipe end; also used in the equipment import and export of the flange, used for two equipment before the connection. Flange connection or flange joint, refers to the flange, gasket and bolt three interconnected as a group of combined sealing structure of the detachable connection, pipe flange refers to the piping device in the piping with the flange, used in equipment refers to the import and export of equipment flange. There are holes on the flange, and the bolts make the two flanges tightly connected. The flanges are sealed with gaskets.
Flanges can be divided into threaded flanges and welded flanges according to the connection method.
1, according to the chemical industry standards, the flange is divided into:
Plate type flat welding flange, necked flat welding flange, necked butt welding flange, integral flange, socket welding flange, threaded flange, butt welding ring loose set flange, flange cover, flat welding ring loose set flange, lining flange cover.
2, according to the petrochemical (SH) industry standards, flanges are divided into:
Threaded flanges, butt-welding flanges, flat welding flanges, socket welding flanges, loose flanges, flange covers.
3、According to machinery (JB) industry standards, flanges are divided into:
Integral flange, butt-welding flange, plate welding flange, butt-welding ring-plate loose set flange, flat welding ring-plate loose set flange, flanging ring-plate loose set flange, flange cover.
4、According to the national (GB) standard, the flange is divided into:
Integral flange, threaded flange, butt-welding flange, necked flat welding flange, necked socket welding flange, butt-welding ring necked loose flange, plate type flat welding flange, butt-welding ring plate loose flange, flat welding ring plate loose flange, flanging ring plate loose flange, flange cover.
5, according to the connection method flange connection type to points, the flange is divided into:
Plate type flat welding flange, necked flat welding flange, necked butt welding flange, socket welding flange, threaded flange, flange cover, necked butt welding ring loose set flange, flat welding ring loose set flange, ring groove surface flange and flange cover, large diameter flat plate flange, large diameter high-necked flange, eight blind, butt welding ring loose set flange and so on.
Concept and Classification of Flanges
Flanges are also called flanges or flanged discs. Flange is to make the pipe and pipe interconnection parts, connected to the pipe end; also used in the equipment import and export of the flange, used for two equipment before the connection. Flange connection or flange joint, refers to the flange, gasket and bolt three interconnected as a group of combined sealing structure of the detachable connection, pipe flange refers to the piping device in the piping with the flange, used in equipment refers to the import and export of equipment flange. There are holes on the flange, and the bolts make the two flanges tightly connected. The flanges are sealed with gaskets.
Flanges can be divided into threaded flanges and welded flanges according to the connection method.
1, according to the chemical industry standards, the flange is divided into:
Plate type flat welding flange, necked flat welding flange, necked butt welding flange, integral flange, socket welding flange, threaded flange, butt welding ring loose set flange, flange cover, flat welding ring loose set flange, lining flange cover.
2, according to the petrochemical (SH) industry standards, flanges are divided into:
Threaded flanges, butt-welding flanges, flat welding flanges, socket welding flanges, loose flanges, flange covers.
3、According to machinery (JB) industry standards, flanges are divided into:
Integral flange, butt-welding flange, plate welding flange, butt-welding ring-plate loose set flange, flat welding ring-plate loose set flange, flanging ring-plate loose set flange, flange cover.
4、According to the national (GB) standard, the flange is divided into:
Integral flange, threaded flange, butt-welding flange, necked flat welding flange, necked socket welding flange, butt-welding ring necked loose flange, plate type flat welding flange, butt-welding ring plate loose flange, flat welding ring plate loose flange, flanging ring plate loose flange, flange cover.
5, according to the connection method flange connection type to points, the flange is divided into:
Plate type flat welding flange, necked flat welding flange, necked butt welding flange, socket welding flange, threaded flange, flange cover, necked butt welding ring loose set flange, flat welding ring loose set flange, ring groove surface flange and flange cover, large diameter flat plate flange, large diameter high-necked flange, eight blind, butt welding ring loose set flange and so on.
Forms of flange connection
Flange connection (flange, joint): consists of a pair of flanges, a gasket and a number of bolts and nuts. Flange connection is a detachable connection.
Principle: the gasket is placed between the two flange sealing surface, tighten the nut, the gasket surface pressure reaches a certain value after the deformation, and fill the sealing surface on the unevenness, so that the joint is tight and not leakage.
Performance: good strength and sealing, simple structure, low cost, can be repeatedly disassembled, widely used.
Failure form: the main manifestation of leakage, leakage control in the process and the environment within the scope of the allowable.
According to the connected parts can be divided into container flange and pipe flange.
According to the structure type, there are whole flange, threaded flange, flat welding flange, butt welding flange, live set (loose set, live tongue) flange and flange cover.
The whole flange refers to the pump, valve, machine and other mechanical equipment and pipeline connection of the import and export flange, usually and these pipeline equipment made into one, as part of the equipment.
Threaded flange is a non-welded flange in which the inner hole of the flange is processed into a pipe thread and is matched with the pipe with thread to achieve connection. Compared with the welding flange, it has the characteristics of easy installation and maintenance, and can be used in some occasions where welding is not allowed on site. However, under the condition of temperature higher than 260℃ and lower than -45℃, it is recommended not to use threaded flange to avoid leakage.
Flat welding flange is also known as lap welding flange. The flat welding flange is connected with the pipe by inserting the pipe into the inner hole of the flange to the proper position, and then lap welding, the advantage of which is that it is easier to be centred in the welding assembly and is cheaper, thus it is widely used. Calculated by internal pressure, the strength of flat welding flange is about two-thirds of the corresponding butt welding flange, and the fatigue life is about one-third of the butt welding flange. Therefore, flat welding flanges are only suitable for piping systems with relatively low pressure ratings, where pressure fluctuations, vibrations and oscillations are not serious.
Flat welding definition: the surface to be welded is in an approximately horizontal position, welding from above the joint.
Horizontal direction welding Horizontal plate welding is generally called flat welding. Weld inclination angle of 0 ° ~ 5, weld turn angle of 0 ° ~ 10 ° of the welding position is called flat welding position, and welding in the flat welding position is called flat welding. This welding position is one of the easiest welding positions in the whole welding position.
Flat welding flange: a kind of flange that is welded directly to the equipment or pipeline through the fillet weld. Its structure is simple and easy to process.
(1) Used on the container and divided into type A flat welding flange and type B flat welding flange. Type A flat welding flange is welded directly to the container, and the size of its unwelded seam is small or not open bevel welding, which can not ensure that the flange and the container at the same time force; type B flat welding flange is attached with a thicker short section, the flange and the short section of the weld quality is reliable, which can ensure that the flange and the container at the same time force. Flat welding flanges are widely used in the connection of medium and low pressure containers and pipelines.
Butt-welding flanges, also known as high neck flanges are more rigid and suitable for occasions with higher pressure and temperature.
(2) There are three types of plate flat welding flanges, necked flat welding flanges and necked butt welding flanges used on the receiver. Plate type flat welding flange: because the flange is directly welded to the steel pipe, the flange is subjected to poor force condition during operation and is prone to deformation. It is suitable for low pressure occasions. Necked Flat Welding Flange: Due to the increase of a thick-walled short section flange neck, the stiffness of the flange is increased, and the deformation of the flange is greatly reduced. Suitable for medium and low pressure occasions.
Butt-welding flange, also known as high neck flange, which is different from other flanges in that there is a long and inclined high neck from the welding of flange and pipe to the flange, and the wall thickness of this section of the high neck gradually transitions to the thickness of the pipe wall along the direction of the height, which improves the discontinuity of the stress, and thus increases the strength of the flange. Butt-welding flanges are mainly used in harsh working conditions, such as thermal expansion of the pipeline or other loads that cause the flange to be subjected to greater stress, or repeated stress changes; pressure, temperature fluctuations in large amounts of pipelines and high temperature, high pressure and sub-zero low temperature pipelines.
Butt welding: Butt resistance welding (referred to as butt welding) is a class of resistance welding method that uses resistance heat to weld two workpieces simultaneously along the entire end face. Butt welding is widely used because of its high productivity and ease of automation.
Butt welding is divided into resistance butt welding and flash butt welding two kinds.
Loose flange connection is actually achieved by welding, only this flange is loose in the pipe has been welded together with the ancillary components, and then through the connecting bolts will be ancillary components and gasket compression to achieve sealing, the flange (i.e., loose) itself does not contact the medium. The advantage of this flange connection is that the flange can be rotated, easy to align the bolt holes, easy to install in the use of large-diameter pipelines, but also applies to the pipeline needs to be frequently disassembled for cleaning and inspection of the place. Its flange accessory element material and pipe material, and flange material can be different from the pipe material, so it is more suitable for conveying corrosive media pipeline.
(3) Other forms of flange connection
Flange connection is also the HVAC industry in the valve with the most connection form. According to the shape of the bonding surface can be divided into the following types:
Smooth type: used for valves with low pressure. Processing is more convenient.
Convex type: higher working pressure, can use medium-hard gaskets.
Tongue and groove type: available plastic deformation of the gasket, more widely used in corrosive media, the sealing effect is better.
Trapezoidal groove type: oval metal ring for the gasket, used in the working pressure ≥ 64 kg / cm2 of the valve, or high temperature valves.
Lens type: the gasket is lens shape, made of metal. Used for high pressure valves with working pressure ≥100kg/cm2, or high temperature valves.
O-ring type: this is a newer form of flange connection, it is with the emergence of a variety of rubber O-ring, and the development of the sealing effect is more reliable than the general flat gasket.
Sealing Forms of Flanges
Flange sealing face forms include: flat face (FF); raised face (RF); concave-convex face (MFM), convex face (M), concave face (FM); tongue-and-groove face (TG), tongue-and-groove face (T), groove face (G); and ring joint face (RJ).
Scope of Use and Designation of Flanges
Flange Marking
Steel pipe OD series is the basis of pipe flange size. China's current production and use of steel pipe, from the outer diameter of two series: standard labelled as ‘Series Ⅰ’ and ‘Series Ⅱ’, or ‘A series’ and ‘B series’. ‘Series B’. Series A of steel pipe for the ‘imperial pipe’, commonly known as ‘large outer diameter pipe’; series B of steel pipe for the ‘metric pipe’, commonly known as ‘small outer diameter pipe Series B tubes are metric tubes, commonly known as ‘small OD tubes’.
The so-called ‘large outer diameter pipe and small outer diameter pipe’ means: in the same pipe nominal diameter conditions, pipeline accessories (such as flanges, valves, pipe fittings and pipe filters, etc.) with the size of the outer diameter of the size of the steel pipe, the size of the large size is called the ‘large outer diameter’ pipe; the size of the small size is called the ‘small outer diameter’ pipe. Smaller called ‘small outer diameter’ pipe.
For example: the nominal through DN100 flange, piping outside diameter of 114.3mm and 108mm two, 114.3mm outside diameter of the steel pipe is called ‘large outside diameter’ pipe or ‘A series’ pipe; 108mm outside diameter of the steel pipe is called ‘Small OD’ or “B series” pipe.
PN Series
Flanges are marked according to the following regulations:
HG/T 20592 Flange (or flange cover)
Where, b is the type of flange. c is the nominal size of the flange and the applicable steel pipe outer diameter series. It can be omitted if it is A series, and B series shall be indicated at the end. In addition, the overall flange, threaded flange, flange cover of the applicable steel pipe outside diameter series can be omitted. d for the nominal pressure level PN. e for the sealing form code. f for the wall thickness of the steel pipe, provided by the user, with a neck butt-welding flange, butt-welding ring (loose-set flange) should indicate the wall thickness of the steel pipe. g for the material grade. h for other, such as additional requirements.
Flanges are marked according to the following regulations:
HG/T 20615 Flange (or flange cover)
Among them, b is the type of flange. c is the nominal size of the flange. d is the nominal pressure class Class. e is the sealing form code. f is the wall thickness of the steel pipe, which is provided by the user, and the wall thickness of the steel pipe should be indicated for the butt-welding flanges with neck and butt-welding ring (loose-set flanges). g is the material grade. h denotes others, such as the additional requirements.
Common failures of flanges
In the continuous production of modern industry flange by media corrosion, scouring, temperature, pressure, vibration and other factors, will inevitably appear leakage problems. Due to the error of sealing surface processing size, aging of sealing elements and improper installation and fastening, etc. are very likely to cause flange leakage. If the flange leakage problem can not be managed in time, the leakage will expand rapidly under the medium washout, resulting in the loss of materials, the destruction of the production environment, leading to the shutdown of the enterprise, resulting in huge economic losses. If the leakage is toxic, hazardous, flammable and explosive media, it may cause poisoning, fire and explosion and other major accidents.
The traditional method to solve the flange leakage for the replacement of sealing elements and sealant coating or replacement of flanges and pipelines, but the method has great limitations, and some leakage by the safety requirements of the working environment, can not be resolved on-site. Now you can use polymer composite materials for on-site leakage plugging, is a very ideal method, especially in flammable and explosive occasions, more show its unique superiority. Polymer composite material technology construction process is simple, safe, and low cost, can solve most of the flange leakage problems for the enterprise, to eliminate potential safety hazards, for the enterprise to save more maintenance costs.
Disclaimer: The contents reproduced in this article are from the Internet and are for reference only. We are not responsible for its accuracy, completeness or timeliness, nor are we liable for any loss arising from its use. If you think the content of this website violates your rights and interests, please contact us and we will deal with it promptly.
