Comparison of dependent and independent heating systems. Types of fittings for connection to the pipeline Connection type coupling

V apartment buildings residents mainly use the services of the central heating network to heat the premises. The quality of these services is influenced by many factors: the age of the house, wear and tear of equipment, the condition of the heating main, etc. The special scheme according to which the connection to the heating network is carried out is also essential in the heating system.

Connection types

Connection schemes can be of two types: dependent and independent. Dependent connection is the simplest and most common option. The independent heating system has gained its popularity recently, and is widely used in the construction of new residential areas. What is the most effective solution for providing warmth, comfort and coziness to any room?

Dependent

Such a connection scheme, as a rule, provides for the presence of in-house heating points, often equipped with elevators. In the mixing unit of the heating station, overheated water from the main external network is mixed with the return one, while acquiring a sufficient temperature (about 100 ° C). Thus, the internal heating system of the house is completely dependent on the external heating supply.


Dignity

The main feature of such a scheme is that it provides for the flow of water into the heating and water supply systems directly from the heating main, while the price pays off quite quickly.

Flaws

Along with the advantages, this connection also has some disadvantages:

  • inefficiency;
  • adjustment temperature regime significantly difficult during weather changes;
  • overexpenditure of energy resources.

Connection methods

Connection can be made in several ways:


Independent

An independent heat supply system allows you to save consumed resources by 10-40%.

Operating principle

The consumer heating system is connected using an additional heat exchanger. Thus, heating is carried out by two hydraulically isolated circuits. The external heating circuit heats the water of the closed internal heating network. In this case, mixing of water, as in the dependent version, does not occur.

However, such a connection requires considerable costs for both maintenance and repair work.

Water circulation

The movement of the coolant is carried out in the heating mechanism thanks to circulation pumps, due to which there is a regular supply of water through the heating devices. An independent connection can have an expansion vessel containing a supply of water in case of leaks.

Components of an independent system.

Scope of application

Widely used to connect to the heating system multi-storey buildings or buildings that require increased level reliability of the heating mechanism.

For objects with available premises, where access of unauthorized service personnel is undesirable. Provided that the pressure in the return heating systems or heating networks above the permissible level - more than 0.6 MPa.

Advantages


Negative points

  • high price;
  • the complexity of maintenance and repair.

Comparison of the two types

The quality of heat supply according to the dependent scheme is significantly influenced by the operation of the central heat source. This is a simple, cheap, low maintenance and repair cost method. However, the advantages of a modern independent connection scheme, despite the financial costs and the complexity of operation, are obvious.

2018-01-16T15: 39: 03 + 03: 00

One of the main issues when choosing pipeline valves is the type of their connection to the system. Usually the already existing pipeline system dictates to us what type of connection to choose. But if you are faced with the task of designing such a system, then it is important to know all the possible types of connection of pipeline fittings to the system in order to choose the ideal option in your conditions. From our article you will learn about all types, their pros and cons, and you will be better guided in the types of connections. Let's start with the most popular ones.

Flange connection

This connection is made by two metal plates adjacent to each other. The plates have holes through which bolts or studs pass, and are tightened with nuts on the other side, thus pressing the flanges together. For greater reliability and tightness of the connection, protrusions, grooves, etc. are made on the plates, and gaskets are installed between the metal plates. Most often, the plates are rounded, but this is not necessary. Occasionally you can find square flanges, rectangular or with three corners, but their manufacture is more expensive. Such flange shapes are used only when urgently needed, for example, if space constraints require it. It is used on industrial pipelines with a diameter from DN 50 mm.

The word "flange" comes from the German flansch, which means the same thing as in Russian - a flat metal plate with holes.

A flange connection is one of the most popular connections in pipe fittings. For the manufacture of flanges, cast iron is most often used - gray or malleable, as well as steel of various grades. Gray cast iron is the most inexpensive solution, but ductile iron will generally withstand higher pressures and temperatures. An even more expensive and durable solution is cast steel flanges. But at the same time, steel is more susceptible to plastic deformation than brittle, but perfectly holding its shape cast iron.

Video: Installing a LD flanged ball valve on a pipe using

Advantages of a flanged connection of pipeline valves

  • Strong, reliable connection.
  • Withstands high pressure.
  • High tightness. But it depends on the used seals.
  • Can be mounted and dismantled multiple times.

Flaws

  • Large overall dimensions of the flange connection. Large mass.
  • Large consumption of metal and labor intensity of production, and therefore the price.
  • The bolts holding the flanges together must be re-tightened periodically to ensure proper tightness. This is especially important in systems where the pipe is subject to vibrations (solved by installing in front of the flange connection) or temperature changes.

Threaded, sleeve connection

Also one of the most popular types of connections, but for pipeline systems it is not large diameter(usually up to DN 50) and low pressures (up to 1.6 MPa). It is very often found in household pipeline fittings, for example, for. Its essence is simple: the pipe has a thread and the fittings have a thread, the latter is screwed onto the first.

The pipe can be tapped using special tools if it is not there and the equipment has not been installed before. Threaded pipeline fittings at one end are made in the form of a hexagon for gripping with an adjustable wrench and screwing the fittings onto the pipe thread.

Video: how to thread a metal pipe and install a threaded ball valve

There are different options execution threaded connections: internal or external thread. The fittings can have an internal thread on one side and an external thread on the other, or the same type on both sides. There is also different standards threads, for example ISO 228/1 or DIN 2999. This must be taken into account when selecting.

The word "muff" comes from the Dutch word mouw, meaning "sleeve".

To ensure the tightness of threaded types of connections, additional seals are used in them - special FUM tapes, linen thread, as well as especially thick lubricants on top of them. All this is applied to the external thread.

Fitting connection

This is a subtype of threaded connection, which is used on small-sized valves - up to DN 5. When connected, threaded fittings are tightened to the thread on the pipe with a union nut. Used for narrow pipes, such as laboratory pipes. Also used for implantation of various measuring devices into pipelines.

Advantages of threaded connections for pipeline fittings

  • Low price.
  • Does not require additional parts for installation, such as flanged type.
  • Easy to install, even easier to replace.

Flaws

  • Not suitable for high pressures.
  • The larger the diameter, the more effort must be applied to screw the valve onto the thread with the seal.

Welded connection

If the ends of the pipe fittings look just like pipes without any additions, then they are connected to the system by welding. This is the most reliable and leak-proof connection, which, if done correctly, can be used to obtain an absolute structural conformity of materials. Having welded a valve or a valve to a pipe, you do not have to tighten the bolts, as with a flange connection, besides, the cost and weight of such fittings will be much less.

This type of connection can often be found on pipeline systems transporting liquids and gases hazardous to health, where the slightest leaks must not be allowed and absolute tightness is required. For a welded joint, the statement “set and forget” is characteristic. The main thing is to qualitatively connect the pipe to the fittings so that the welding place is not weaker than the pipe wall.

Pipe ends must be prepared before welding, with each metal being prepared differently. We offer you a video with the most in a simple way welding.

Weld connection advantages

  • Absolute tightness with correct welding procedure.
  • Low cost of fittings.
  • Light weight.
  • Small size, the connection does not take up much space in the space.

Flaws

  • Qualified personnel are needed, which increases the total cost of installing such valves.
  • Time consuming dismantling process, such valves or cranes need to be installed once and for all.

Clamp quick coupling (Tri-Clamp)

Modern quick-release connection for pipeline valves, mainly used in Food Industry, pharmacology and other industries where sterility and cleanliness are important. After all, this type of connection allows you to regularly remove and clean, disinfect the equipment installed with this mount.

The clamp connection consists of two fittings, a seal and a clamp. The clamp presses the two fittings against the seal and against each other, resulting in a tight connection. What such a clamp is, we suggest that you learn from the video.

Fittings to the pipeline (Fig. 13.2) are detachable (flanged, coupling, pinned) and one-piece (welded and brazed). The most common flange connection. Advantages flange connection fittings - the possibility of multiple mounting and dismounting on the pipeline, good sealing of joints and ease of tightening them, great strength and applicability for a very wide range of pressures and passages. The disadvantages of a flange connection are the possibility of loosening the tightening and loss of tightness over time (especially under vibration conditions), increased labor intensity of assembly and disassembly, large dimensions and weight. These flange deficiencies are especially true for pipelines. large diameters designed for medium and high pressures.

When assembling such a connection, dozens of large diameter studs are tightened with a special tool. Tightening such flange connections often requires a team of metalworkers. With an increase in the nominal pressure and flow area of ​​the flanges, the mass of both the valve itself and the entire pipeline (taking into account the counter flanges) increases and the metal consumption increases. In connection with the indicated disadvantages of flange connections, as well as an increase in the diameters of pipelines and their working pressures, valves with butt-welded pipes are becoming more widespread. In particular, such fittings are used to equip main gas and oil pipelines.

The advantages of connecting fittings to the pipeline by welding are great, which is, first of all, complete and reliable tightness of the connection, which is especially important for pipelines transporting explosive, toxic and radioactive substances. In addition, the welded joint does not require any maintenance and tightening, which is very important for main pipelines, where a minimum of maintenance is desired. The welded joint gives great savings in metal and reduces the weight of fittings and piping. It is especially effective to use fittings with butt weld ends on pipelines where the pipeline itself is assembled entirely by welding.

The disadvantage of welded joints is the increased complexity of dismantling and replacing the reinforcement, since for this it has to be cut out of the pipeline.

For small fittings, especially cast iron, the coupling connection is most often used. In this case, the ends of the fittings have the form of couplings with an internal thread. Since flanges for small fittings have a relatively large mass (often of the same order of magnitude as the mass of fittings without flanges), the use of flanges in such conditions leads to an unjustified increase in metal consumption. In addition, tightening bolts for small-diameter flange connections is more labor-intensive than tightening a sleeve connection, and requires the use of special torque wrenches.

Rice. 13.2. The main types of connection of fittings to the pipeline:

a - flanged (cast flanges with a connecting ledge and a flat gasket); b - flanged (steel butt-welded flanges with a protrusion-cavity seal with a flat gasket); v- flanged (cast flanges with a thorn-groove seal with a flat gasket); d - flanged (steel flat welded flanges with a flat gasket); d - flanged (cast steel flanges with lens gasket); e- flanged (cast steel flanges with oval section gasket); f - coupling; h - tsapkovoe.

Coupling connection is usually used in cast fittings, because casting is the easiest way to obtain the outer configuration of the coupling (hexagon key). In this regard, the main area of ​​application of couplings is low and medium pressure valves. For small high-pressure fittings, which are usually made from forgings or rolled products, a pin connection with an external thread for a union nut is most often used.

Flange connections of pipelines and fittings designed for a nominal pressure of 1-200 kgf / cm 2 are standardized. At the same time, the types of flanges (GOST 1233-67), their connecting dimensions (GOST 1234-67), designs, executive dimensions and technical requirements... In special, technically justified cases (under shock or increased load, short service life, specific properties of the environment - toxicity, sizes according to GOST 1234-67.

Flanges are usually round. The only exceptions are cast-iron flanges, tightened with four bolts, calculated for a pressure p at not higher than 40 kgf / cm 2. They are allowed to be made square.

Standard valve flanges are divided into several types according to the design of the gasket connection. The simplest of them - with a smooth front surface (with or without a connecting protrusion), unprotected type, without a groove for the gasket. These flanges are the easiest for mounting and dismounting valves and for replacing gaskets, but the tightness of the connection they create is the least reliable.

Flanges designed for high pressures (from 40 to 200 kgf / cm 2) are used with toothed steel gaskets, for low ones - with soft or soft-core gaskets. To protect soft gaskets from knocking out the pressure of the working medium in the fittings, flanges with a depression for the gasket are used. In this case, the counter flanges are made with a protrusion, so that outside the gasket, the flanges form a lock protecting it. Such flanges are used with soft gaskets or metal ones with a soft core. The third type of valve flanges, designed for the same gaskets as the previous one, are flanges with a gasket groove. The counter flanges have a tenon. Thus, the gasket is protected by a flange lock both from the outside and from the inside, which increases the reliability of the connection. However, assembly, disassembly of valves and replacement of gaskets are somewhat more difficult in comparison with flanges of the first type.

For high pressures, starting from p y = 64 kgf / cm 2, two more standard types of seals are used in the flanges - for a lens gasket and for an oval section gasket. These seals are more economical and reliable when high pressures than conventional flat gaskets. In such flange connections, the gaskets touch the sealing surfaces of the flanges theoretically along a line, but practically along a very narrow ring. This allows, with equal overall dimensions of flanges and tightening forces, to create high specific pressures on the seal. Thus, it becomes possible to use massive steel spacers of high strength and durability in place of conventional soft ones.

The ball valve is one of the most popular types of pipeline fittings. One of its main classifying features is the way of joining. “Coupling”, “flanged”, “welded” are commonly used attachments for ball valves. Less commonly used are “pin”, “choke”, “nipple”, “soldered”.

The types of connections for industrial pipeline valves are defined in the current interstate standard GOST 24856-81 (analogous to ISO 6552-80). In the cell “description” of the table of terms and definitions of GOST concerning the types of connections there is a dash, there is only a graphic sketch. It is understood that the meaning of the term should be understood literally from the name. However, for a person who is not interested in technology, the marking “coupling ball valve” or “flanged ball valve” may not be clear.

Ball valves by type of connection

Coupling

The connection of a coupling ball valve is performed using an internal thread cut in the body along the edges. Coupling is a connecting piece of pipelines in the form of a hollow cylinder with a thread cut inside.
Coupling ball valves are often used in both the domestic and industrial, municipal sectors. They are very convenient, since only a pair of wrenches (open-end, pipe, adjustable) are required for installation, depending on the installation location. To prevent leakage, the thread of the coupling valve is packed with linen strand with unipack, FUM tape, sealing thread or anaerobic sealant. The installation of a coupling ball valve is quick, and the fittings themselves are relatively inexpensive. The most commonly used sizes correspond to the connecting thread ½, ¾, 1, 1 ¼, 1 ½, 2 inches. Also on the market there are smaller diameters - ¼, ⅜ ", large - 2 ½, 3, 4".

Flanged

The connection of a flanged ball valve is made in the form of a flat, most often round, part located perpendicular to the axis, with holes for fasteners (bolt and nut). There are always two flanges in the connection. One on the pipe, the second on the fittings. The flange connection is highly reliable. The flange thickness and the number of holes depends on the maximum pressure for which the ball valve is designed. In the domestic sector, flanged ball valves are practically not used, except when connected to a central water supply or gas pipeline. Such valves are mainly used in utilities and industry.

Welded

Welded ball valves are welded to the pipeline. The connecting pipes of such fittings are made in the form of a pipe and do not have threads or connecting parts. Often they are also called (this is how GOST 24856-81 also regulates) “welded ball valves”. Welded ball valves can be made of carbon, low-alloy, stainless steels, have one-piece or collapsible design. The scope of application of welded fittings is industry and utilities.

Choke

Union ball valves are similar in design to coupling valves, with the only difference that the thread on the connecting branch pipe is not internal, but external. The choice of a coupling or nipple product is carried out on the basis of which thread is on the mating part. Sellers, installers, many manufacturers call such fittings “nipple valves”, which is the same thing. Their distinctive feature- connections with an external thread. The price of a coupling ball valve is lower than that of a nipple valve. Installation and standard sizes of such valves are mostly similar.
The ball valve with external thread can be equipped with half-rings on one or both sides. Such a connection will be collapsible and the valve can be removed for replacement or service. The half-pipe fitting can be threaded or welded. Fittings with a half-rail on one side are often called "American crane".

Tsapkovye

A trunnion ball valve has connecting pipes (one or both) with an external thread and a shoulder. Such products are intended for installation directly on the tank, equipment (boiler, boiler), etc. An example of pin taps can be seen below. For example, these are taps with a nozzle for irrigation, taps, drainage, drainage.

For soldering

The connection of ball valves is also possible by soldering. Basically, such fittings are installed on copper and polypropylene systems. The use of ball valves for brazing makes the connection more durable and aesthetic, no additional fittings are required. It should be noted that it is correct to use the word "welding" in relation to polypropylene, but among installers and consumers "soldering" is more often used.

Ball valve names

It just so happened that the standard establishes some terms for fittings, installers and designers use others, Chinese manufacturers use others. Here are some commonly used names and their meanings:

  • ball valve НН - fittings on both sides with external thread (other names, “daddy-daddy”, “union on both sides”, “nipple”);
  • ball valve BB - fittings on both sides with internal thread (“female-female”, “coupling”);
  • ball valve HV on one side external thread on the other, internal (“daddy-mommy”);
  • faucet with a gander - tsapkovy water-folding with a fitting for a hose;
  • American crane - fittings with a collapsible connection (with a half-fit).

Threaded and not only shut-off valves can be the same type of connecting pipes or different - combined. For example, a ball valve has an internal thread on one side and an external thread on the other (BH). Or one connection is flanged and the other welded.

A large selection of ball valves in our UniDim online store. Our brands are GIACOMINI, RBM, WATTS.

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