It became clear from the previous article that flange is a great way to connect pipes, valves, valves and other items to create a piping system. This method equipment connection gives easy access for cleaning, inspection or modification of the piping system.
Everything flanges are distinguished by types: flat, collar, free on the welded ring. These types are regulated according to GOSTs, respectively, GOST 12820-80, GOST 12821-80 and GOST 12822-80 (see. Useful information--―> GOSTs).
Also flanges can be produced according to 2 standards:
DIN - German Institute for Standardization;
ANSI/ASME is an American standard.
Also flanges can be divided into types.
execution flanges are the geometric parameters of the connecting surface. Flanged versions there are different geometries. According to all GOSTs, the first version is the most common. First flanged the performance is considered basic, since any other performance can be produced and made from it.
In total there are 9 different designs for flat and collared flanges. Flanged versions are regulated by GOST 12815-80:
- Execution 1. with a connecting ledge.
- Execution 2. with ledge.
- Execution 3. with a hollow.
- Execution 4. with a spike.
- Execution 5. with a groove.
- Execution 6. for lens gasket.
- Execution 7. for oval section gasket.
- Execution 8. with a spike for a PTFE gasket.
- Execution 9. with a groove for a PTFE gasket.
Choosing one or the other flange design due primarily to the technological features of the application of the execution flange. It also depends on the geometry of the sealing surface of the attached element, operating pressure, nominal diameter, material of manufacture. flange connections
etc.
For almost every GOST on flanges there is a GOST for the performance of sealing surfaces. For example, for GOST 28759.4-90 ( flanges vessels and apparatuses for gaskets of octagonal section) versions of sealing surfaces of sizes flanges there are only two:
1 - for a gasket of an octagonal section, monometallic;
2 - under the gasket of octagonal cross-section welded with corrosion-resistant steel.
The main task of executions flanges is to ensure tightness flange connection, and various types of cushioning circles can be used for this. Gaskets can be metal (lens gaskets, oval section, octagonal section), and can be made of non-metallic materials (paronite, fluoroplast). The use of gaskets for flanges from various types performance, has a positive effect on ensuring tightness flanges And flange connections. As a rule, non-metallic gaskets are used up to 6.18 MPa of working pressure, and metal gaskets - over 6.18 MPa of working pressure flange connections. Use of gasket materials and various designs flanges, as well as fasteners (nuts, studs, bolts), provide a reliable tight flange connection.
Flange- a part of the pipeline designed for the installation of its individual parts, as well as for connecting equipment to the pipeline.
Areas of use
The flange is used in the installation of pipelines and equipment in almost all industries.
The variety of materials from which flanges are made today allows these products to be used as pipeline fittings in almost any conditions. external environment(temperature, humidity, etc.) and in accordance with the medium passing through the pipeline (including aggressive ones).
Distinctive features and characteristics of flanges
There are certain characteristics of flanges:
1. Constructive.
The basis of this group of characteristics is the design of the flange. Within the territory of Russian Federation and the CIS countries, the most widespread are three flange standards:
GOST 12820-80 - steel flat welded flange.
GOST 12821-80 - steel welded butt flange.
GOST 12822-80 - free steel flange on the welded ring.
Flanges according to the three most common standards mentioned above are designed to connect pipe fittings and equipment.
Due to the design features, the mounting conditions for these flanges are different.
Flange steel flat welded. During installation, the flange is “put on” on the pipe and welded with two welds around the circumference of the pipe.
Butt-welded steel flange. The installation of such a flange, compared to a flat welded flange, provides for only one connecting weld (in this case, it is necessary to butt the end of the pipe and the “collar” of the flange), which simplifies work and reduces time costs.
Steel loose flange on the welded ring consists of two parts - a flange and a ring. In this case, of course, the flange and the ring must be of the same nominal diameter and pressure. Compared to the above-mentioned flanges, such flanges differ in ease of installation, since only the ring is welded to the pipe, and the flange itself remains free, which ensures easy mating of the bolt holes of the free flange with the bolt holes of the valve or equipment flange without turning the pipe. They are often used when installing pipeline fittings and equipment in hard-to-reach places or when frequently repairing (checking) flange connections (for example, in the chemical industry).
In addition, it is positive that when selecting free flanges for a stainless steel pipe, in order to save money, it is allowed to use a stainless steel ring, and a carbon steel flange.
In addition to these three standards, special attention should be paid to flanges manufactured according to customer drawings (non-standard flanges). Unlike the first three above-mentioned flanges this design is not constant and may change depending on the expectations and requirements of the client. These flanges are customized and serve to meet any customer needs.
Flanges manufactured according to foreign standards differ from Russian ones structurally. Among imported ones, the most widespread in Russia are flanges made according to German standards 01M (the standard is accepted throughout Europe) and American AM51.
TO flanges other Russian standards include such as: steel threaded flanges, vessel and apparatus flanges, insulating flanges for underwater pipelines. They differ from those mentioned above in terms of design and applications.
Also, design features include (using the example of the three most common GOSTs):
Conditional pass. Designated as Du and measured in mm.
conditional pressure. It is designated as Ru and is measured in kgf / cm2.
Execution from 1 to 9. Determines the type of surface for the gasket.
Material (represented by Russian steel grades).
2. Technological.
These characteristics are associated with the peculiarities of production (from what blanks and by what technologies the flange is made).
Round and square flanges. Currently, a small number of gate valves, valves, etc., pipeline fittings are produced, which have a square flange as a connecting unit. Therefore, in accordance with GOST 12815-80, up to a conditional pressure of Ru 4 MPa (40 kgf / cm2), both round and square flanges are provided by design. When ordering square flanges, it must be remembered that there is a direct dependence of the flange diameter on the nominal pressure: the higher the pressure, the smaller the diameter of the flange can be produced.
Conditional pass. Features of its designation
It should be noted right away that the conditional passage is not the outer diameter of the pipe, but denotes the passage (section) through which the medium flows through the flange connection. One of the features of steel flat welded flanges and steel loose flanges on a welded ring for nominal bore diameters DN 100.125 and 150 mm is that three of their designs are possible for different outer diameters of the pipe.
Therefore, when ordering these flanges for DN 100, 125 or 150 mm, it is necessary to indicate the letter corresponding to the required pipe diameter. If the letter is not specified in the application (specification) for these standard sizes of flanges, then the flanges are manufactured for the following pipe diameters: 100A, 125A, 150B (Table 1).
Tab. one
The next feature of flanges with a nominal bore diameter DN > 200 mm is that, due to different accuracy classes for the manufacture of pipes and flanges, boring of the inner diameter of flat, free and its ring flanges is allowed according to the actual outer diameter of the pipe with a gap of no more than 2 per side, 5 mm, i.e. over the entire inner diameter of the flange and ring no more than 5.0 mm. In other words, pipe manufacturing may deviate from the ideal circle shape, so the pipe may not match the inner diameter of the flange, which in turn makes it difficult to connect the pipe and flange.
Taking into account the accumulated experience and processing of a large statistical material, Orbita-M LLC developed drawings of such flanges, where changes were made to their design for DN > 200 mm along the inner diameter c1v.
ranks
If the design features of the connecting dimensions (row 1 or 2) are not specified when ordering, then the flange is manufactured by default in accordance with row 2. The design difference between row 1 flanges and row 2 flanges is different amount holes in it for mounting bolts (studs) and their diameters.
For example, a flange for DN 300 mm and PN 63 kgf / cm2 row 1 has a mounting hole diameter of 36 mm, and row 2 - 39 mm. Similarly, the flange for DN 80 mm and PN 10 kgf / cm2 of row 1 has a mounting hole diameter of 18 mm with a total of 8 pcs., And row 2, respectively - 18 mm and 4 pcs. Therefore, this feature must be taken into account when ordering flanges as counterparts for stop valves.
Pressure
Another important design feature of all products that make up a flange connection is the nominal pressure that the connection can withstand. The pressure values depend on the geometric dimensions of the flange and the design of the sealing surface. A flat welded steel flange (GOST 12820-80) and a loose steel flange on a welded ring (GOST 12822-80) can withstand pressure up to 25 kgf/cm2, but a butt-welded steel flange (GOST 12821-80) can withstand pressure up to 200 kgf/cm2. cm2.
At the same time, a feature of this indicator is that it can be expressed in various units of measurement: kgf / cm2, Pa, MPa, atm, bar. The unit of measurement in the production and designation of flanges is kgf / cm2. To avoid confusion, always specify the pressure unit when ordering products.
Flange versions
In accordance with the requirements of GOST, there are nine versions of the flange surface, and for a free flange, various designs are possible only for the weld ring. Therefore, when selecting mating flanges of pipeline valves, in addition to conditional pass and pressure, the design of the sealing surface must be specified.
Execution 1. It is used at nominal pressure not higher than 63 kgf/cm2. For pipelines transporting substances A and B of technological facilities of category I explosive ™, it is not allowed to use flange connections with version 1 sealing surface, except for the cases of using spirally wound gaskets with a restrictive ring.
At conditional pressures of Ru over 2.5 MPa (25 kgf / cm2), to ensure greater tightness of the system, flange sealing surface designs 2,3,4,5,6 and 7 are more often used. Flanges of various designs are connected to each other as follows:
Version 1 (raised face) with version V,
Execution 2 (with a ledge) with execution 3 (with a hollow);
Execution 4 (with a thorn) with execution 5 (with a groove);
Version 6 (for lens gasket) with version 6;
Version 7 (for oval gasket) with version 7;
Execution 8 (with a stud) with execution 9 (with a groove) with the obligatory use of a fluoroplastic gasket.
Material Grades
The final distinguishing design characteristic of the flange is the material used. Flanges can be made of carbon and alloy steels, as well as stainless steels. Currently, a large number of steel grades are used for the manufacture of flanges, the most widely used of which are Art. 20, Art. 09G2S, Art.
Steel grades are selected taking into account the use of flanges for a given operating temperature, nominal pressure and transported medium in the pipeline. The requirements for the steel grade of the flange, depending on the operating pressure and medium temperature, are given in GOST 12816-80 (Table 1).
A flange is a hardware item. Its purpose is to connect pipes, glands or similar hollow metal structures of a cylindrical shape. To firmly and securely connect two objects, you must additionally use soft pads. Soft materials are used for their manufacture. And to the question: "Flange - what kind of detail is this?" - you can answer that this is a hardware (short for "metal product"), which creates good sealing at the junctions of cylindrical elements.
Device
Standard flanges appearance reminiscent of a metal ring, on which there are special holes for studs or bolts. On some types of these elements there may be protrusions, depressions, spikes, grooves.
Flange manufacturing
Various steel grades are used for manufacturing: 13XFA, 20/09G2S, 12X18H10T, 15X5 M and others. In addition, they can be steel and stainless. The technology used is different. Manufacturers use forging, stamping, casting. For each method, special equipment and molds are used. When releasing their products, manufacturers carefully check their quality. Applying special tests in their work, QCD employees check them for durability and reliability. Flanges are also checked for moisture resistance. What it is? Since they are fasteners and are involved in connecting metal parts that may come into contact with water, it is important that they are not susceptible to corrosion. That is why waterproof metal alloys are used. Often manufacturers cover the surface of the flanges with an additional protective layer. 
Types of flanges
So, the flange is, first of all, hardware. Depending on the application, these parts can be flat, collar, free. The design is not much different. On the collar flanges there is a small protrusion resembling a cone. It is often referred to as a collar. This type of flange is used when it is necessary to weld parts end-to-end. This protrusion helps to tightly connect the connecting parts of the pipelines. They are also necessary when pipelines are brought to tanks or other technical equipment. The main advantage of such flanges is that they can be used several times. These hardware are made of durable materials, and this allows them to be used in work where the temperature ranges from -253 to +600 degrees Celsius. 
Flat flange - what is it? This is a hardware that resembles a flat disk with holes. It is used when it is necessary to connect parts of fittings, shafts, vessels, pipelines, devices and the like. With this element, parts of pipelines can be tightly fixed.
Loose flange - what is it? This species is not much different from the above. It consists of two parts: a conventional flange and a ring. It is important that they are made of the same material and have the same diameter and pressure. They are used where the work is most difficult, where it is difficult to perform installation. Due to the two parts, the connection will be tight and durable. First, a conventional flange is connected (it is welded), and the other ring can then be safely rotated during operation.
Other classification
For some, special types of elements are made. Special flange - what is it? These are the same hardware, but in order to make some work convenient, their design is slightly modified. They can also be welded, loose, cast, threaded. Only grooves are cut out on them or protrusions are welded. For their manufacture, special drawings are first developed and molds are cast. Such hardware is made by order of enterprises.
From afar, huge and long main pipelines (gas, water, oil, steam) seem to be solid and continuous lines. But it is worth coming closer, and the joints of the pipes become noticeable. It is there that the answer to the question of what flanges are is located. They are different: round and square, steel flat welded or steel collar flanges. But all are very important to ensure the safety of pipelines.
What are flanges?
They are usually used in pairs. Simply put, this is a round or square fastener into which a pipe or other pipeline elements are inserted. The next pipe is inserted into the other flange, after which the two fasteners are bolted together. For this, a large number of holes are provided along the outer perimeter of the part. Other types of products are put on the end of the pipe. The junction of the pipe and the flange is welded. Thus, it is a connecting element of pipelines, tanks, vessels, shafts, devices, etc. For it, you also need to choose the right flange fasteners (bolts, nuts, washers, studs), the type and strength of which directly depend on the same pressure, temperature and type of transported medium.
What are they needed for?
- to hermetically join pipes together, incl. different diameter;
- to fix various devices or fittings on the pipeline;
– to lead the pipe safely to the inlet of tanks, pressure vessels or other apparatus.
What are they made of?
Flanges are made of steel. Depending on the working pressure, temperature and type of medium (steam, gas, oil, water), they are produced either from a special alloyed or from ordinary grades of carbon and stainless steel.
Main types:
- the most common are conventional flat welded flanges;
– more durable and comfortable steel collar flanges;
- for installation in hard-to-reach places, a free flange on the welded ring is most often used;
- non-standard flanges, which are made according to individual drawings for a specific order.
Consider the most popular product options.
Steel flat weld flanges
Main parameters:
– operating temperature from -70 C to 450 C;
- working pressure from 0.1 MPa to 2.5 MPa;
They come in various designs, for example, with a ledge, with a cavity, with a groove, with a tenon, etc. During installation, the flange is put on the end of the pipe and welded twice along the joint contour.
Steel collar flanges
Main parameters:
– operating temperature from -253 C to 600 C;
- working pressure from 0.1 MPa to 20 MPa;
– pipe diameter from 10 mm to 1600 mm.
Such a flange has a protrusion in the form of a truncated cone, into which the pipe is inserted. Here you need to make only one weld, which, with a large amount of work, saves time. When using this type of product, it will subsequently be possible to quite easily upgrade a separate part of the pipeline or completely dismantle the system. To do this, you do not need to cut the pipe, you just need to remove the collar flange, which can be called a reusable connecting element. Due to the presence of a collar and the fact that its cone has different wall thicknesses in height, the product is able to withstand more pressure than a conventional flat welded flange.
Now you know what flanges are, what they are for, and you can distinguish steel collar flanges from flat welded ones. This knowledge will be useful even in Everyday life, because there are also such connecting elements on small pipelines that carry natural gas or water to your home.
