A coupling is a connecting part with which a pipeline structure is mounted. Without connecting elements, the pipeline will be a straight section consisting of one pipe of a certain length. Modern pipeline structures are characterized by the presence of many parts that have different options for joining each other. They can also have different rotation angles, so during installation you cannot do without this type of part.
Using couplings of various types, pipelines from steel and other metal pipes are installed
What do couplings for metal pipes look like?
You can use different parts to connect metal pipes: there are many of them sold in the store. Thanks to couplings, the type of connection of pipeline elements can be any. At their core, the couplings we are talking about now are one of the types of fittings and perform the function of unification. These parts are attached to metal pipes using threads, which can be either inside or outside (there are options with threads on both sides).
A coupling is a hollow cylindrical part made of metal or other material (must be selected for a specific pipeline). Nowadays, polypropylene products for connecting plastic pipes are in great demand. Couplings can be either connecting or transitional. If this is a transitional part, then when installing it, for a better connection it is necessary to use materials such as FUM tape and flax thread.
Note! Transition couplings are installed when connecting pipes of different diameters.
The coupling can also be combined. It is necessary for connecting pipes made of different materials. Such couplings have a special thread, which allows you to easily connect, for example, metal pipes with plastic pipes, etc.
Read material on the topic: How to choose components for pipes
Pipeline assembly technology
To assemble the pipeline, you must perform the following sequence of actions:
- First, screw the coupling onto the pipe.
- Then the side with the short thread is screwed into the coupling (sometimes it is connected directly). The parts should be screwed all the way, then the connection will be reliable.
- A locknut is screwed onto the long side of the drive.
- Next comes the connecting fitting.
- Then the end of the drive is applied to the pipe and the coupling is screwed together so that it goes onto the pipe. The connection will be easier to complete if the axes of the parts coincide as much as possible.
- The fitting must then be secured with a locknut. To do this, it should be screwed to the coupling so that there is a distance of 2-3 cm between the parts. This space must be filled with strands of flax. They should be wound in the direction of rotation of the nut. Then the locknut should be tightened until it stops. This must be done to seal the connection and prevent water leakage through it. You should use a wrench to tighten the locknut because its edges are narrow.
Types of couplings for metal pipes
There are several types of couplings, each of which has its own special characteristics, and you can also find universal parts suitable for a wide variety of cases.
Here is the main classification of couplings:
- Threaded
- very actively used in the recent past, but now their scope is limited to steel pipes. They are quite difficult to install and, moreover, such couplings do not provide a very reliable connection.
- Compression
couplings for metal pipes are very similar to threaded parts. After installing them, the connection must be tightened with special nuts. To improve the tightness, rubber O-rings should be inserted into them.
- Press models
are often mistaken for crimp models. But there is a significant difference between them: installation of such couplings requires the use of special tools.
- Welded
couplings are used to connect polymer pipes.
- Electric welded couplings
are a type of welded coupling, but differ from them in the presence of a built-in heating coil. These parts are fixed to the pipes thanks to a special stop. After this, the heating element begins to work, heating the ends of the pipes to the melting point. After the temperature drops, the three elements (two pipes and a coupling) will turn into a single whole. This coupling can withstand a pressure of 10 bar for a gas pipeline and 16 bar for a water supply.
Couplings are usually used to connect metal pipes of different lengths and diameters. This is explained by the fact that these metal structures are produced in the form of small pieces.
The following types of couplings are distinguished:
- Angular
, with which you can change the direction of the pipeline. Such parts are quite common, since it is much more convenient to use them than to bend metal pipes.
- Direct or simple
. With the help of such couplings, you can very easily connect two metal pipes together. You cannot do without these parts when repairing a damaged section of a pipeline, as they allow you to quickly connect its elements to each other. Such couplings can also be used to join pipes made of different materials and having different diameters.
- Tee fittings
are needed to connect three pipes. When installing such a coupling, one of the pipes will be located at an angle of 90 degrees relative to the other two. These parts allow you to divert the pipeline to an angle of 45° or 90°. Using tees, you can connect pipes of any diameter.
- Cross fittings.
Here, perhaps, everything is clear by the name. They allow you to connect four pipes located in the same plane at an angle of 90° to each other. These couplings are easy to install and do not require the use of any special equipment. There are also crosses located in two planes, but they are found very rarely, as a rule, in manufacturing plants.
Read material on the topic: Types of pipe fittings: sizes and features
Sgony
Non-specialized information
The squeegee is also a connecting fitting, which is essentially a short tube. On one side, the part has a small thread for connecting to the fitting. At the other end there is a long thread on which the locknut and the entire coupling for connecting the pipes are placed.
It is necessary that the product has a sufficiently long thread, because if the parts do not fit in the area with the thread, it will be necessary to increase the distance between the connected ends of the pipe and the pipe, which will reduce the strength of the connection.
It must be stated that this connecting element is much more often used for water pipes. For this reason, it lacks good anti-corrosion protection. The most common types of surges are:
| Nickel plated | They are much more often used in residential premises in order to give the pipeline a more aesthetic appearance. It goes without saying that the price of such fittings is higher than simple steel ones. |
| Galvanized | Used in areas where the system is exposed to atmospheric phenomena. |
| Steel | Much more often they are used for pipelines that are laid in the ground. They are painted to protect against corrosion. |
In accordance with GOST 6357-73, the dimensions of pipe bends can be as follows:
| Product length, mm | Inner diameter, mm | Length of long threaded section, mm | Length of small threaded section, mm |
| 150 | 50 | 65 | 17 |
| 130 | 32 | 55 | 13 |
| 110 | 15 | 40 | 9 |
In addition, there are some intermediate sizes. Naturally, connecting parts are selected in accordance with the diameter of the pipeline.
Connection Features
The instructions for assembling the pipeline are as follows:
- First of all, a coupling is screwed onto the pipe.
- After this, the product is screwed with the small side into the connecting fitting (in some cases, the squeegee is connected directly). The connection must be strong, so you need to tighten the parts until they stop.
- A lock nut must be screwed onto the long end of the part..
- Then, from the side of the long threaded section, you need to screw the connecting fitting until it stops.
- Then you need to bring the end of the drive to the pipe and unscrew the coupling so that it slowly begins to move onto the pipe . The more correctly the axes of the parts coincide, the easier it is to make the connection.
- Then the fitting is locked with a lock nut; to do this, the lock nut must be tightened to the coupling, leaving a distance of a couple of centimeters . The space that appears between the parts must be filled with strands of flax, which are wound in the direction of rotation of the nut. Then the locknut is tightened until it stops, as a result of which the connection will be sealed and water will not be able to leak through it.
Couplings for metal pipes made of steel
For installation of metal steel pipes, threaded and compression couplings are used. Let's look at them in more detail next.
Threaded
Threaded couplings are made of black or stainless steel; they can be used to connect not only metal, but also other types of pipes. Externally, they look like a thick-walled cylinder with a regular one-sided internal thread.
Metal pipes are connected to each other by screwing them onto the coupling on both sides. This installation method is quite reliable, but to increase the sealing of the connection point, insulating materials are additionally used.
Note! Steel couplings are susceptible to corrosion, so brass parts are often installed instead. Pipes are not made from this material, but couplings are very common. They are corrosion resistant, easy to install, versatile and inexpensive.
If the couplings have a threaded connection made of a steel alloy, then great forces can be applied during their installation. However, it is really difficult to disassemble this type of thread, since due to the water condensation that forms, the pipeline elements “stick” to each other. Thus, for connecting metal steel pipes, it is recommended to choose threaded couplings made of brass or cast iron alloy, as their performance characteristics are better.
A connection with a squeegee is used when the pipeline elements cannot rotate around their axis.
Compression couplings
To ensure a greater degree of sealing when installing compression couplings, a rubber ring and a special union nut are used. These couplings are similar to those used to connect metal-plastic pipes, but have significant differences in their functionality.
Compression couplings can be threaded either internally or externally. Thanks to these parts, it is possible to connect, for example, metal pipes with plastic ones (the diameters may be different). Such couplings are also suitable for installing pipes with other fitting elements: all kinds of valves, taps, etc.
Compression fittings have the following characteristics:
- With their help, easily removable connections are obtained. If necessary, such a coupling can be easily removed and replaced.
- Metal steel pipes are connected to each other using compression elements without threads.
- When installing a compression fitting, it is necessary to clean the metal pipe from paint or rust.
- This is not a very reliable way to connect metal pipes and requires the use of additional fixing materials. These parts are very often used as a temporary element when repairing pipelines.
Note! For temporary connections, as a rule, universal couplings are used, which have a thread on one side and a special element for compression joining on the other.
Read material on the topic: Pipe plug
Quick tips for connection and operation
- When using various fittings , it is advisable not to save much, since most often they are inexpensive and have a short service life.
- Be responsible when applying sealant to threaded connections, because most leaks occur precisely because of poor-quality winding.
- When starting the system for the first time , be sure to check all connections for leaks.
- Pipes connected in different ways must be painted to avoid rusting.
- When installing a water supply network , install a filter that will avoid contamination of the entire system.
- on the mounted elements as possible, do not place heavy things.
Couplings for metal pipes (cast iron)
To connect metal pipes made of cast iron, you can use one of the following two methods:
- Use a rubber seal during installation. This connection is very similar to joining plastic pipes. However, cast iron products are notoriously heavy, making installation difficult.
- Use couplings for metal pipes for embossing. This type of connection has been around for over a century. It is distinguished by the presence of two bells with opposite directions.
For the installation of sewers that remove wastewater and other substances, metal pipes made of gray cast iron, which are particularly durable, are used. If they are installed carefully and all requirements are met, the pipeline can last up to 50 years. Metal pipes made of cast iron can be either with or without sockets. The following types of couplings are suitable for connecting smooth elements:
- Sliding.
Their installation occurs in a hidden way. It is impossible to dismantle such couplings without disconnecting the main line.
- Repair roll-up.
These couplings include two main parts with a rubber or plastic gasket. In addition, these parts have special clamps and connectors for connection. They are often installed on those sections of metal pipes that have to be frequently repaired.
- Plastic.
These couplings for connecting metal pipes can be used more than once, which distinguishes them from others.
Installation with threaded connection
How to connect iron pipes without welding will be discussed further, but in this article you can learn how to properly weld galvanized pipe products. To make docking, this method is very common.
The threaded connection can be located in places on the highway where conditions allow for constant monitoring of the joint. At the same time, it should be possible to carry out repair work if necessary.
Most often, threads are rolled using special equipment, but such work can be done independently.
It is performed in the following sequence:
- Cut off a piece of the workpiece, which provides the required allowance for the threaded part.
The pipe is secured to the die holder. A piece of metal workpiece is secured in a vice so that it does not rotate.- The die must be carefully attached to the end of the metal pipe. In this case, it is important not to make even a slight distortion, otherwise the thread will come out crooked and it will not be possible to connect the sections.
- For ease of operation, it is recommended to lubricate the workpieces with machine oil.
- When the die stops turning, it is recommended to perform one rotation in the opposite direction. This will remove the cut chips, which become an obstacle to moving forward.
- In a section that runs close to the wall, it is not always possible to make a full turn when cutting threads. In such situations, it is recommended to use a die holder with a ratcheting mechanism.
- To make a threaded connection reliable, you need to use a seal. For these purposes, plumbing winding will be used.
- Before tightening a threaded joint, it is worth checking the products for the presence of burrs and remaining chips. And the twisting itself must be done with a certain force.
Couplings for copper pipes
Couplings designed for installation of copper pipes are characterized by the highest reliability and durability. They belong to a higher class and, as a result, are more expensive. Couplings for copper pipes are of the following types:
- threaded;
- compression;
- capillary;
- press fittings.
It is necessary to take into account the fact that when installing copper pipes, the couplings must also be made of copper. This is a must. Compliance with this simple rule will ensure long-term and trouble-free operation of the pipeline. Couplings made from other materials can be used only if copper is not available when creating temporary pipelines.
The use of couplings when installing both metal and other types of pipes is the most common way to connect them. These parts are presented on the market in a wide range: they may have different fastening methods, shapes, and features of use. This way you can always choose the most suitable couplings for your pipes.
When purchasing, do not forget to take into account the material from which the pipes are made, as well as their diameter, wall thickness, temperature of the transported medium, length and shape of the future structure. Let's draw a small conclusion: if you take into account all the listed points, you will probably be able to purchase exactly those parts that will last a long time and will not create problems during operation.
Read material on the topic: Angles for pipes: overview of the range
Peculiarities
The elements of engineering systems under consideration have various features that can be noted as advantages or disadvantages.
Connectors called “pipe couplings” have the following positive qualities:
- a light weight;
- quick and easy installation;
- low price;
- many varieties;
- Possibility of application in many areas;
- mechanical resistance.
Some types of couplings have certain disadvantages. For example, elements wear out quickly, become deformed, and not all of them are able to absorb vibrations.
To choose the appropriate options from those on the market, you need to take into account the scope of application of the products, as well as the material used to make the parts:
- Couplings can be rigid. These are the ones that are made of metal. The main scope of application of such couplings is various highways that have certain properties.
- Couplings can be spiral-shaped. Such products are usually aluminum. The main feature of the products is easy bending. The accessory has a special structure, thanks to which the specified function is ensured.
- Couplings can be polyurethane. Inserts made of this material are usually placed between two metal parts. Such a coupling is a shock-absorbing element that absorbs a significant portion of vibrations.
- Couplings are made of membrane types. The main feature of these products is that these elements are prefabricated. They are often used to connect parts located in different planes. The accessory is considered not only multifunctional, but also quite durable.
The pipeline network, which transports water under a certain pressure, consists of connections between individual sections of metal pipes. The water supply throughout its entire length, especially at the junctions of the pipes, must be dense, durable and impermeable to any temperature changes. The connection of steel pipes occurs by welding, threaded connections and flanges .
Flange connections are mainly used for large diameter pipes. In individual houses, apartments and gardens, pipes are connected using the threaded method, using connecting elements (fittings). The threaded connection allows, if necessary, to repair and replace individual pipeline segments without dismantling the complete system. It is accessible to anyone, while work related to welding requires appropriate qualifications and special equipment.
To join pipes without welding into a single system, steel fittings and connecting parts made of ductile cast iron are used. Cast iron connecting parts are used for water pipelines that pass hot steam or water no higher than 175 degrees - at a pressure in pipes of up to 1.6 MPa, the diameter of which is no more than 40 millimeters, and at a pressure of up to 1 MPa - in structures with a diameter of 50 mm or more up to 100 millimeters.
Steel fittings are used for products of all diameters with pressure up to 1.6 MPa. The cast iron connecting elements have thickened collars at the ends for maximum strength. Steel fittings do not have such collars.
