Hello our dear customers and site visitors. Today we will talk about steel welded flanges flat, collar and loose, about what it is, what they are for, according to what GOST they are made and from what materials, what types and types they have, designs, how they are designated, which have dimensions and weight, how to choose the right flange, find out the price, request a price sheet and buy in the end.

To begin with, let's see how flat steel welded flanges can look like in the photo below:

In the photo, we see that the flanges are somewhat different from each other because they are two different types: flat and collar, which and why we need to consider everything in detail.

flange connection

So what is the flange for? And its purpose is to organize a flange connection. Suppose there are two sections of the pipe and they can of course be welded together, but then it will be a rigid one-piece connection, and in order to organize a quick-release flange connection, flanges are used that are welded onto the ends of the pipes and tightened with bolts and nuts or studs with nuts, as on photo below.

The flange itself is a flat ring or is sometimes made in the form of a square or rectangle with a hole in the middle for inserting the end of the pipe and several holes evenly spaced closer to the outer diameter into which bolts or studs are inserted, nuts are screwed onto them and two flanges are pulled together. To seal the connection between the flanges, a gasket made of special rubber or other material for this purpose, such as fluoroplastic, is laid. By the way, there are different designs depending on the type of gaskets, it will be more correct, of course, on different types and different gaskets.

The pipes themselves are often joined to each other, but it is more necessary to connect any devices or devices, for example, heat exchangers with a section of the pipeline through which any medium is supplied. For example, look at the photo below there is an oil cooler mb 25-37 and two flanges number 1 are clearly visible at the ends, which are welded to the nozzles and additionally located on them mating flanges number 2 screwed with bolts and nuts, this is such a delivery set for the manufacture of the heat exchanger. Counter flanges are also needed by the customer in order to organize the connection of the apparatus with the pipeline section.

Suppose the customer ordered the manufacture of a heat exchanger, brought it to the place, installed it and needs to connect it. To do this, pipelines are brought to the apparatus, flat steel counter flanges are welded onto the ends of the pipes, and the flange on the cooler and at the end of the pipe are connected with bolts or studs, without forgetting, of course, to put a gasket between them for tightness. Conveniently! Because occurs periodically, for example, for repair or prevention, the need to stop the operation of the device and disassemble it. This oil cooler has four flat steel flanges. Two for inlet and outlet of cooling water and two for inlet and outlet of cooled oil.

In the same way, sections of pipelines are connected to various technological tanks. Flanges 1 and 2 refer to the type of valve flanges, fittings and pipelines.

Thus it can be said that flanges are needed to organize the connection or connection of a pipeline section to various technological apparatuses and devices: heat exchangers, tanks, etc., for the supply and removal of media, as well as for joining pipe sections to each other.

For a more detailed acquaintance, of course, you need to go to the corresponding guest.

Flanges of vessels and apparatuses:

Now it becomes clear what types of flanges are and what types are divided into depending on the purpose. All technical characteristics, drawings, design and dimensions of flanges can be viewed by clicking on the links above or select the appropriate GOST at the bottom of the article. Let's go investigate further.

Flange versions

Flanged version this is essentially a design or type of end surface of the flanges between which a flange connection is created. And here the geometry of surfaces is also regulated by GOST. Let's look at an example.

GOST 12815-80 contains 9 versions:

1. execution 1 - there is a connecting protrusion at an angle of 45 0 as a chamfer, by the way the most common.
2. version 2 - also with a ledge but at an angle of 90 0 .
3. execution 3 - with a ledge under 45 0 plus a cavity, a selection from the inside.
4. execution 4 - a flange with a spike, the same as the previous one, only a ledge 90 0.
5. execution 5 - with a groove. It has the form of an annular selection.
6. version 6 - under the lens gasket. Has an internal chamfer.
7. version 7 - for an oval section gasket. An oval-shaped groove on the end surface.
8. performance 8 and 9 - performance 8 is the same as the 4th, and the ninth, like the 5th. I don't understand the difference between them. I would be glad if someone writes in the comments to this article.

GOST 28759.2-90 contains 15 versions, and 28759.3-90 - twelve. It makes no sense to list them, so I ask you to follow the links to these GOSTs and see everything in detail how they look, etc.

Geometric dimensions and weight of flanges

Very important parameters, both at the stage of designing devices, containers, etc., and at the stage of operation and repair, including procurement, because you need to know what part to buy. Therefore, it is very important to know what connecting and overall dimensions available on certain flanges. There are a lot of sizes, but the main one is Du conditional passage. The choice of flange is based on it when buying, and when designing. Let's get a little more detailed.

Nominal diameter of flanges

Let's say there are two pipes that are joined together or a branch pipe on a heat exchanger or some kind of container. Pipes and spigots have an outer diameter and are sometimes thought to correspond to the inner diameter of the flange in the designation, but this is not the case. For example, DN 100 corresponds to an outer diameter of a pipe of 108 mm or 114 mm, by the way, according to Yandex statistics, the flange DN 100 is most often looked for, and with DN 125, the pipe diameter is 133 or 140 mm, for DN 150, a pipe with a diameter of 152, 159 or 168 mm is chosen, depending on execution and from the letter A, B, C indicated in the GOST table. When an order is made next to the flange, the letter must be indicated, if it is not there, then it is considered that the letter A is selected.

Such a dependence exists for flat and welded ring flanges, for collar flanges - there is no such a butt. If you enter the GOSTs, you will see everything in detail.

The conditional passage of flanges is a fundamental parameter on which all basic geometric dimensions depend. Those. knowing the magnitude nominal diameter of flanges all the rest are assigned automatically, except for one nuance called a series.

There are only two of them, 1st and 2nd, but they affect the overall dimensions. Depending on what flange row 1 or two dimensions depend on:

• diameters D3, D4, D5, D6.
• d - diameter of holes for studs or bolts.
• n is the number of these mounting holes.
• h1 - protrusion height and tenon depth.
• h2 - groove depth.
• h3 - depth of the groove of the oval section.
• nominal diameter of bolts or studs.

All other connecting or overall dimensions depend only on the conditional passage. Flanges must be manufactured in accordance with GOST according to the preferred row 2 if 1 is not specified.

All dimensions in the drawings and tables, depending on the conditional passage and series, can be found in GOSTs.

Weight or mass of flanges

Another important value is flange weight, rather from a practical point of view, for example, to determine the weight of the entire batch, if there are other options, please put your comments at the end of this material, I will be very grateful. This value can also be found in the tables of the required GOST.

So we got acquainted with the main, from my point of view, geometric and conditional dimensions and sizes of flanges. And all the rest can be found and viewed in the state standard, they have already been determined by various strength calculations of the strength of materials. It’s clear with the dimensions, but since the flange is steel and made of some kind of metal, of which there are a lot of grades, the question will accordingly arise: “What metal or steel grade are the flanges made of and how to choose the right one if necessary, or how to choose the grade of steel, cast iron and alloy flanges"?

Materials or grades of steel, cast iron or flange alloys

In order to pick material from which flanges are made exists and there is one wonderful table in it, seeing which everything becomes clear. Let's say we are interested in a collar flange or, in another way, a steel welded butt according to GOST 12821-80. The first thing we pay attention to is the conditional pressure at which it works. Let's say it is 150 kgf / cm2 or Ru 15MPa. We look where it is, we find that in the second column and the second part in the range from 0.1 to 20 MPa, because the first part does not suit us 0.1 to 10 MPa.

Next, we look at the temperature regime of operation, for example, from -40 0 C to +450 0 C and find that a stainless steel flange 12x18n9t is suitable for us, although 12x18n10t is now used as the most common brand of stainless steel, and studs, bolts and nuts and steel grade 20x13 are corrosive -resistant heat-resistant, used in power engineering. That's all science.

There are many different grades of steels and alloys, but the most popular are st20, st3, 09g2s, 12x18n10t and 15xm, as the most commonly used for the manufacture of flanges because. there are many more such working conditions. There are, of course, specific brands, but there are very few conditions where they should work. It is worth noting that there are many fittings made of cast or malleable iron, therefore flanges are used from the corresponding grades of cast iron SCh 15 and KCh 30. If necessary, we look at all other materials in GOST 12816-80. You can also download.

Features of connecting pipes or branch pipes with a flange

Here I will talk about the features of joining the pipeline or branch pipes of apparatuses or containers directly with the flange itself. Because the most common are steel welded flat, steel welded butt or collar and steel free on the welded ring, then we will stop at them.

Connection of steel flat welding flanges to a pipe or nozzle

During installation, the pipe is inserted into the flange and scalded with two seams, one inside and the other outside along the end surface. The most time-consuming connection, because. you need to make two welds and to align the holes you will have to twist the pipe.

Connection of steel welded flanges butt-collar

For installation, the end of the pipe is leaned against the end of the flange or the so-called collar, which is why they were called collar, the one that is cone and scalded with just one weld. Much faster and easier.

Connection of steel loose flanges on a welded ring

Here the pipe is taken, the flange itself is put on it, then the pipe is inserted into the ring and scalded. Similarly, the other part of the connection. It turns out that only rings are welded to the pipes, and the flanges rotate freely on pipes or nozzles. Further, the ends are brought to each other, rotating the flanges, the holes are matched along the contour and the studs or bolts are inserted and everything is tightened with nuts. Extremely convenient, because there is no need to rotate the pipe or achieve an exact match of the holes before welding, which is not always possible. Very practical in places that are difficult to access or where frequent checking of the flange connection is required, such as in the chemical industry. Maybe cheaper. it is allowed to use only a stainless steel ring, and the flange itself is made of ordinary carbon steel 3 or steel 20.

So we looked at how the most common types of flanges fit together and now we would like to show how to designate them correctly.

Flange designation

Designation of flat weld flanges

Flange 1-450-10 Art. 20 GOST 12820-80 - this is the designation of a conventional flat flange of execution 1 (with a connecting ledge) with a nominal bore of 450 mm, designed for a nominal pressure of 10 kgf / cm2 or 1 MPa, made of steel 20.

And if the flange is square, with Du 1200 made of steel 3, then: Square flange 1-1200-10 st. 3 GOST 12820-80.

When ordering flanges with nominal bore DN 100, 125 and 150 m, the corresponding pipe diameter is indicated.

When ordering thorn-groove flanges for fluoroplastic gaskets, the letter F is placed after the nominal pressure numbers.

Designation of collar flanges - butt welded

Flange 1-1000-100 st. 12x18n10t GOST 12821-80 - collar flange version 1, nominal bore Dts 1000 mm, PN 10 MPa or 100 kgf / cm2, stainless steel.

Flange square 1-800-10 Art. 12x18n10t GOST 12821-80 - if square. And here Du is 800, and Ru is 1 MPa.