From the previous article it became clear that flange- This great way connections of pipes, gate valves, valves and other items to create a pipeline system. This method of connecting equipment allows easy access for cleaning, inspection or modification of the piping system.
All flanges They are distinguished by types: flat, collar, free on a welded ring. These types are regulated by GOSTs, respectively GOST 12820-80, GOST 12821-80 and GOST 12822-80 (see. Helpful information--―> GOSTs).
Also flanges can be manufactured according to 2 standards:
DIN - German Institute for Standardization;
ANSI/ASME - American standard.
Also flanges can be divided by type of execution.
Execution flanges are the geometric parameters of the connecting surface. Flange versions come in different geometries. According to all GOSTs, the first version is the most common. First flanged a design is considered basic because any other design can be produced and manufactured from it.
There are a total of 9 different designs for flat and collar flanges. Flange versions regulated by GOST 12815-80:
- Version 1. with connecting projection.
- Version 2. with projection.
- Version 3. with a cavity.
- Version 4. with a spike.
- Version 5. with groove.
- Version 6. for lens spacer.
- Version 7. for oval gasket.
- Version 8. with a spike for a fluoroplastic gasket.
- Version 9. with a groove for a fluoroplastic gasket.
Choosing one or the other flange version due, first of all, to the technological features of the application of the design flange. This also depends on the geometry of the sealing surface of the connected element, operating pressure, nominal diameter, material of manufacture flange connections etc.
For almost every GOST on flanges There is a GOST for the design of sealing surfaces. For example, for GOST 28759.4-90 ( flanges vessels and apparatus for gaskets of octagonal cross-section) designs of sealing surfaces dimensions flanges there are only two:
1 - monometallic for an octagonal gasket;
2 - under the octagonal cross-section gasket, deposited with corrosion-resistant steel.
The main task of execution flanges is to ensure tightness flange connection, and for this they can be used various types spacer circles. Gaskets can be metal (lens gaskets, oval gaskets, octagonal gaskets), or can be made of non-metallic materials (paronite, fluoroplastic). The use of sealing gaskets for flanges With 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 working pressure, and metal gaskets - above 6.18 MPa working pressure flange connections. Application of gasket materials and various designs flanges, as well as fastening elements (nuts, studs, bolts), provide reliable sealing flange connection .
Flange– a part of a pipeline intended 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 connecting parts under almost any environmental conditions (temperature, humidity, etc.) and in accordance with the environment 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 flange design. In the territory Russian Federation and CIS countries, three flange standards are most widespread:
GOST 12820-80 – steel flat welded flange.
GOST 12821-80 – steel butt welding flange.
GOST 12822-80 – loose steel flange on a welded ring.
Flanges according to the three most common standards mentioned above are designed to connect pipeline fittings and equipment.
Due to their design features, the installation conditions for these flanges vary.
Flat welded steel flange. During installation, the flange is “slipped” onto the pipe and welded with two welds around the circumference of the pipe.
Butt welded steel flange. Installation of such a flange, compared to a flat welded flange, requires 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 the work and reduces time costs.
Steel loose flange on a welded ring consists of two parts - a flange and a ring. In this case, naturally, the flange and ring must be of the same nominal diameter and pressure. Such flanges differ from the above in ease of installation, since only the ring is welded to the pipe, and the flange itself remains free, which ensures easy joining of the bolt holes of the free flange with the bolt holes of the flange of the fittings or equipment 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, the positive thing is that when selecting loose flanges for a stainless steel pipe, in order to save money, it is allowed to use a stainless steel ring and a carbon flange.
In addition to these three standards, special mention should be made of flanges manufactured according to customer drawings (non-standard flanges). Unlike the first three flanges mentioned above, this design is not permanent and can be changed depending on the client's expectations and requirements. Such flanges are individual and serve to meet any customer needs.
Flanges manufactured according to foreign standards differ structurally from Russian ones. Among imported ones, the most widely used in Russia are flanges made according to German standards 01M (standard adopted throughout Europe) and American AM51.
TO flanges according to other Russian standards, these include: threaded steel flanges, flanges of vessels and apparatus, insulating flanges for underwater pipelines. They differ from the above in design and applications.
Design features also include (using the example of the three most common GOSTs):
Conditional pass. It is designated as DN and measured in mm.
Conditional pressure. It is designated as Ru and measured in kgf/cm2.
Designs 1 to 9. Determines the type of surface for the gasket.
Material (represented by Russian steel grades).
2. Technological.
These characteristics are related to the characteristics 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. are produced for pipeline fittings that have a square flange as a connecting unit. Therefore, in accordance with GOST 12815-80, up to a nominal pressure of 4 MPa (40 kgf/cm2), both round and square flanges are provided by design. When ordering square flanges, you must remember 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 is worth immediately noting that the conditional diameter is not the outer diameter of the pipe, but designates the passage (section) through which the medium flows through the flange connection. One of the features of steel flat welded flanges and steel free flanges on a welded ring for nominal diameters DN 100, 125 and 150 mm is that three 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 indicated in the application (specification) for these flange sizes, then the flanges are manufactured for the following pipe diameters: 100A, 125A, 150B (Table 1).
Table 1
The next feature of flanges with nominal diameter DN > 200 mm is that due to various classes precision in the manufacture of pipes and flanges, boring of the internal diameter of the flanges of the flat, free and its ring is allowed according to the actual outer diameter of the pipe with a gap on the side of no more than 2.5 mm, i.e. along the entire internal diameter of the flange and ring no more than 5.0 mm . In other words, when making a pipe, there may be a deviation from the ideal circle shape, so the pipe may not match the internal diameter of the flange, which in turn makes it difficult to connect the pipe and the flange.
Orbita-M LLC, taking into account the accumulated experience and processing of large statistical material, has developed drawings of such flanges, where changes have been made to their design for DN > 200 mm in internal diameter c1v.
Rows
If the design features of the connecting dimensions (row 1 or 2) are not specified when ordering, then the default flange is manufactured in accordance with row 2, Constructive difference The flanges of row 1 from the flanges of row 2 are different in the number of holes in it for mounting bolts (studs) and their diameters.
For example, a flange for DN 300 mm and PN 63 kgf/cm2 of row 1 has a mounting hole diameter of 36 mm, and of 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 number of 8 pcs., and row 2, respectively, has 18 mm and 4 pcs. Therefore, this feature must be taken into account when ordering flanges as counter flanges for shut-off valves.
Pressure
Another important design feature of all products that make up a flange connection is the nominal pressure that the connection can withstand. Pressure indicators depend on the geometric dimensions of the flange and the design of the sealing surface. The steel flat welded flange (GOST 12820-80) and the steel free flange on a welded ring (GOST 12822-80) can withstand pressure up to 25 kgf/cm2, but the steel butt welded flange (GOST 12821-80) can withstand pressure up to 200 kgf/cm2 cm2.
Moreover, the peculiarity 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 misunderstandings, when ordering products, always indicate the pressure unit.
Flange versions
In accordance with the requirements of GOST, there are nine designs of the flange surface, and for a free flange, different designs are possible only with a welded ring. Therefore, when selecting mating flanges for pipeline fittings, in addition to the nominal bore and pressure, it is necessary to indicate the design of the sealing surface.
Execution 1. Used at a nominal pressure not higher than 63 kgf/cm2. For pipelines transporting substances A and B of technological objects of category I explosive™, the use of flange connections with design 1 sealing surface is not allowed, except in cases of using spirally wound gaskets with a restrictive ring.
At nominal pressures 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 (with connecting projection) with version V,
Execution 2 (with projection) with execution 3 (with recess);
Execution 4 (with a tenon) with execution 5 (with a groove);
Version 6 (for lens gasket) with version 6;
Execution 7 (for oval gasket) with execution 7;
Version 8 (with a tenon) with version 9 (with a groove) with the obligatory use of a fluoroplastic gasket.
Material grades
The final distinguishing design characteristic of a 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 common of which are St. 20, St. 09G2S, St. 15Kh5M IST.12Kh18N10T.
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 temperature of the medium are given in GOST 12816-80 (Table 1).
From a distance huge and long main pipelines(gas, water, oil, steam) appear as solid and continuous lines. But as soon as you get closer, the pipe joints become noticeable. This is where the answer to the question of what flanges are. They come in different types: round and square, steel flat welded or steel collar flanges. But all are very important to ensure pipeline safety.
What are flanges?
They are usually used in pairs. Simply put, it 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 purpose, 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 connection between the pipe and the flange is welded. Thus, it is a connecting element of pipelines, tanks, vessels, shafts, instruments, etc. You also need to choose the right one for it. flange fastener(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 diameters;
– to secure various devices or fittings to the pipeline;
– to safely lead the pipe to the entrance to tanks, pressure vessels or other apparatus.
What are they made of?
Flanges are made of steel. Depending on the operating pressure, temperature and type of fluid being moved (steam, gas, oil, water), they are made either from special alloyed or from ordinary grades of carbon and stainless steel.
Main types:
– the most common are ordinary flat ones weld flanges;
– steel ones are more durable and comfortable collar flanges;
– for installation in hard-to-reach places, a loose flange on a welded ring is most often used;
– non-standard flanges, which are made according to individual drawings for a specific order.
Let's look at 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 projection, with a depression, with a groove, with a tenon, etc. During the installation process, the flange is placed on the end of the pipe and welded twice along the contour of the joint.
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 only need to make one weld, which saves a lot of time when the volume of work is large. When using this type of product, it will be quite easy to modernize 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 the collar and the fact that its cone height has different wall thicknesses, the product is able to withstand greater pressure than a conventional flat welded flange.
Now you know what flanges are, what they are needed for, and you can distinguish steel collar flanges from flat welded ones. This knowledge will be useful even in everyday life, because such connecting elements are also on small pipelines that carry into your home natural gas or water.
