The arrangement of utilities with the laying of a steel pipeline of various configurations cannot be performed without the use of connection parts.
Before proceeding with the calculation of the system and its assembly, it is necessary to understand what fittings for steel pipes the modern market offers and how are parts assembled, do you agree?
We have prepared a detailed review of pipe fittings for detachable connections, provided recommendations for the selection of elements, and also described the specifics of their application. Step-by-step installation instructions for a threaded fitting and crimp sleeve will help to assemble the pipeline without the involvement of specialists.
Options for execution of connection parts
The ends of the pipes of steel lines are connected in two ways: detachable and one-piece. The first involves the use of fittings, the second - the welding of parts.
The material for the manufacture of connecting elements is most often stainless steel or ferrous metal. From non-ferrous metals: brass or copper.
Image Gallery
Photo from
Despite the numerous developments of new materials for the communication device, pipelines from ferrous steel alloys with a painted outer surface still serve in country houses and city apartments
The use of steel pipes in some cases is preferred. For example, it is better to bring steel pipes to a wall-mounted boiler with a steel heat exchanger
For repair and modernization of pipelines made of steel pipes, it is better to use a similar material, because polymer and metal pipes have different thermal expansion
According to the standards, the internal wiring of all communications, especially those that were built for drinking water supply, must be made of galvanized pipes. However, they did not do this before, because it was too expensive, and now in wealthy houses they are made of stainless steel
According to construction requirements, all steel communication systems laid inside the house / apartment must be assembled from pipes with external and internal galvanization. From galvanized steel pipes collect the contours of gas and water supply, heating
Pipes of ferrous steel alloys are still used in the repair of heating systems connected to centralized networks. However, new pipelines are not collected from them.
In the case of connecting branches made of PVC, PP or metal-plastic pipes to steel pipes, fittings are used that compensate for the thermal expansion of polymers
The indisputable advantage of rolled steel pipelines is their strength. They are not afraid of mechanical influences, do not melt in a fire, do not burst when freezing
Old pipe made of painted black pipes
Wiring heating steel pipes
Connecting steel pipes to risers
Stainless steel pipe assembly
Galvanized pipes for water supply
Ferrous Steel Alloy Pipeline
Plastic Pipe Connector
The most durable of all types of pipelines
The connecting elements can be simply steel or coated with a chrome composition. Chrome products are more preferred in that they have higher anti-corrosion properties.
Using fittings makes it possible not only to connect pipe segments into a single system, but also to join elements of different diameters
Although experts do not advise using fittings from materials other than those used in the manufacture of pipes, but this is still allowed. So, brass fittings are great for joining copper pipes. Copper can safely connect pipes made of any type of material. Reliability of the connection will not be affected.
The main thing is to avoid a combination of joining of copper elements with bends of unalloyed galvanized steel. The interaction of these two metals instantly triggers corrosion processes that adversely affect the durability of the products.
Image Gallery
Photo from
Use of fittings in threaded connections
Weld elbow fitting
Pipe connection flange
Fittings for connecting pipes without welding
Fittings on the market in form and purpose are of several options:
- Couplings - elements installed in straight sections for joining pipes of equal diameter.
- Tees - structures with three exits that change the direction of the pipeline and create a branch from the main branch in one direction.
- Crosses - structures with four outputs divide the flow into several "beams", providing a branch from the main highway in perpendicular directions.
- Adapters - are intended for joining of elements having different diameters.
- Fittings - engage, if necessary, docking the rigid pipe with a flexible hose.
- Stubs - use, if necessary, tight sealing of the ends of the pipes.
To change the direction of the pipeline within the range of 45-90 °, both squares and verticals are installed.
To fit the ends of pipes of identical diameter, direct fittings are installed, and for joining the different-sized elements - transitional (for example, 1 ″ / 3/4 ″)
The size range of nominal bores produced by manufacturers of fittings is quite wide and varies from 8 to 125 mm.
The specifics of the use of pipe fittings:
- products D 16-63 mm use where the pressure does not reach 16 atmospheres;
- fittings D 75-125 mm used for pipelines, where the pressure is 10 atmospheres.
All sizes of tubular metal products comply with current GOST 8996-75. According to this normative document, the production of couplings having an internal diameter of 150 mm is also allowed on an individual order.
If the pipe size is indicated in inches, then this indicates the value of the outer diameter. If in other units of measurement - millimeters, then this is an indicator of the internal section of the product.
An important point! Regardless of the design, when purchasing fittings, you should pay attention to the fact that both the outer and inner surfaces do not have any shells and foreign inclusions. The end planes of the connecting elements must be strictly at right angles to the axes of the passages.
The main types of fittings
Depending on the connection method with the metal pipe, there are several types of fittings: welded, crimped, threaded and flanged. Each of them has its own advantages and disadvantages.
Weld-on couplings
Welded fittings, referred to as segment fittings, are among the non-separable elements. They must not be dismantled or reused. Segment parts are used for pipelines operating at temperatures from -70 ° C to + 450 ° C with a working pressure of the system within 16 MPa.
The main difference between such products is that their ends have a smooth surface. The selection principle is based only on the identity of the characteristics and dimensions of the joined pipes and connecting elements.
The welded type of fittings in terms of size range is the most universal, since it has practically no restrictions in diameter
Fittings for welding are used when laying communications that are placed inside structures and do not require replacement of structural elements for a long period.
Due to the complexity of installation, welded fittings are used on pipelines of the oil and gas industry. To create tight joints, the installation is entrusted to qualified specialists working on special equipment.
Screw thread elements
Threaded fittings suitable for joining gas and water steel pipes are produced with a cylindrical screw thread. They are used in the assembly of highways, the temperature of the transported liquid of which does not exceed + 175 ° C. Typically, this type of connection is chosen for pipelines with a diameter of up to 50 mm.
The thread can be applied to both the inner and outer walls of the product; its length can be any and depends on the dimensions of the parts and materials to be joined
Stainless steel alloy threaded fittings are widely used in the construction, chemical, oil and gas industries. But they found the main application precisely in the arrangement of water supply networks and heating systems.
Among novice craftsmen and lay plumbers, a simple-to-use connection method, referred to as an “American”, is widely popular. It received its name in honor of the country in which it was patented. The main elements of such a connection are the body and the union nut.
To prevent self-loosening of the structure, another steel fitting is screwed on top of the main nut - a lock nut. She presses and fixes the details
One of the halves of the "American" is screwed onto the short thread of the first pipe, and the second onto the return pipe. Then, both halves are twisted using the union nut worn on the fitting. A high degree of sealing is achieved through a sealant. But to improve it, many masters still "in the old fashion" lay linen fibers.
Features of Crimp Couplings
Pipes can be reliably connected without welding and threading by installing crimp fittings. They are available with one or two o-rings made of flexible flexible materials. Mostly they are used when necessary, matching the elements of the pipeline having the same diameter.
Elements equipped with one ring are used in the arrangement of domestic water systems, with two - for strapping high-pressure pipes (+)
The design of crimp elements for steel pipelines practically does not differ from fittings for metal-plastic pipes or "brothers" of polymers.
It includes three main elements:
- housing;
- clamping ring and clamping nut
- sealing ring.
The principle of connecting pipe segments by means of crimp fittings is based on the fact that the o-ring and rubber gasket are tight against the surface by pressing the union nut. The crimp ring is tightened using a manual or automatic press.
When connecting pipes by installing crimp fittings, a deviation from the axis of up to three degrees is allowed.
Due to the tight fit of the elastic gasket pressed down by the clamping rings and the body of the crimp fitting, a tight connection is created
In terms of mechanical strength, the crimp method somewhat loses the same welded or threaded connection. To tear the pipe out of the unit, it is enough to make a little physical effort.
For this reason, crimp fittings are rarely used in the construction of pipelines designed to transport hot water.
The elastic O-ring included in the package of crimp fittings is designed for temperatures within 100 ° C. With prolonged exposure to hot temperature, rubber loses its properties. As a result, the tightness of the connection is broken.
Although crimp fittings are among the collapsible systems, but in the event of failure of one of the structural elements, the entire unit has to be replaced.
Flange Fittings Design
The flange connection is not inferior in strength and durability. For this reason, it is successfully used in the installation of systems that transport aggressive media under high pressure.
In household communications - water supply and heating systems - it is used quite rarely. This is due to the fact that the thickness of the pipeline increased due to the large diameter of the flange becomes inconvenient in terms of installation and unattractive in terms of aesthetics.
Flanges are prefabricated structures, the main element of which are metal washers with protrusions, grooves and corresponding cavities on the surface
The fittings kit includes:
- paired discs;
- nuts with bolts for tightening the planes;
- gasket made of rubber, graphite or paronite.
The number and size of bolt holes of flange connections is determined by the manufacturer in accordance with GOST. The fastening of the fittings to the pipe is most often carried out by welding or by means of a thread applied to the inner surface of the flange.
If you compare these types, the most common are crimp and threaded fittings. The secret of this popularity lies in the ability to create airtight joints, as well as re-dismantle the products in order to reuse them.
In addition, the installation of such removable elements is easier and faster than in welded joints.
Mounting technology for threaded fitting
Installing a steel fitting on a pipe is no big deal. For example, consider the installation technology of a threaded type coupling.
A set of tools required for work:
- pipe cutter for steel pipes;
- gas and adjustable wrenches;
- manual screwdriver equipped with a holder;
- sealing material.
To increase the tightness of the threaded connection of pipelines intended for transporting cold and hot water, flax strand impregnated with minium or FUM tape is used.
For trunk with a coolant whose temperature is above 100 ° C, a linen strand impregnated with graphite, interwoven with an asbestos cord, is used as a sealant.
Image Gallery
Photo from
Assortment of fittings for steel pipes
Metric thread on steel pipe
Threading at the facility
Elbows for linear connection of pipeline elements
Threading dies and taps
Set of plumbing for threading
Threaded seal
Tightening the connector with the sliding key
The installation process includes a number of basic steps:
- The pipe is clamped in a clip. The ends are pretreated with drying oil, a thread is cut.
- Sealing material is wound in a thin layer along the thread.
- At the end of the first pipe, pre-treated with drying oil or oil paint, screw the sleeve until it is jammed on the run.
- Dock the end of the second pipe, wrapped in the same way, twisting the second branch of the coupling to jam on the run.
The clutch is first twisted by hand, and then reinforced with a pipe wrench. The result is a connection in which the ends of the pipes screwed into the sleeve meet but do not abut against each other.
After completion of the repair work, it remains only to check the quality of the connections. To do this, open the tap and fill the system. If leaks are detected at the connection, tighten the locknuts. If the efforts did not give the desired result, it is better to reinstall the connection.
Subtleties of installing a crimp coupling
In a situation where the thread on the pipe has rotted, and it is not practical to cut it, the installation of a crimp coupling will be a universal solution.
Installing a crimp coupling is a win-win option in a situation where you need to connect pipes or connect equipment without using threads
To correctly install the crimp fitting, installation is performed in the following order:
- The pipe section to be joined is cleaned of burrs, processing both the outer surface of the product and the inner one.
- The end of the pipe is inserted into the fitting body, positioning it so that the central part of the coupling strictly matches the joint.
- A crimp ring is pulled onto the pipe.
- A crimp nut is put on the resulting segment. Moving along the thread, the nut will press the crimp ring into the pipe, creating a tight connection.
Do not use excessive force when tightening the nut. Otherwise, the nut will transfer the connection or simply burst.
Installation procedure using a threaded sleeve:
Threadless Docking Technology:
We have described the basic methods for joining steel pipes by installing fittings. The best option should be chosen based on the conditions of a particular situation.
Do you have personal experience in assembling steel piping using fittings? Want to share your knowledge or ask questions about the topic? Please leave comments and participate in discussions - the feedback form is located below.