Flange adapter for connecting PE pipes. Connection of plastic pipes with metal Flange connection of polyethylene pipes

25.11.2019

When arranging modern systems sewerage, heating, water supply, polyethylene pipes are often connected with fittings. Also, when laying household communications, flanges are used to assemble tubular products from different materials.

Pipes made of polyethylene (PE) in last years are actively replacing traditional cast iron and steel products from the construction market. Plastic structures are superior to metal ones in a number of respects. Therefore, such a process has a completely logical explanation - everyone wants to have in their home reliable in operation and inexpensive in cost, heating, sewage, assembled without welding. When installing, you have to face one problem. It lies in the fact that many elements of household pipelines in apartments are made of metal products.

Connection of plastic and metal pipes

And here it is important to correctly connect PE pipes with steel (cast iron). This can be done in two ways: using flanges and using fittings. flange connection polyethylene (polypropylene) pipes with steel pipes are recommended for cases where systems of products with a cross section of more than 50 mm are being equipped. But pipelines with a diameter of up to 50 mm are best connected with fittings. They are special elements with a smooth socket for connecting PE pipes and a thread for metal pipes.

The flange is made in the form of a threaded part. It is most often used to connect metal and polyethylene water pipes, as well as gas communications without welding. Flanges for assembling household networks from different materials have not only a thread on one side, but also a mandatory seal. The latter is located at the second end of the described element. The seal guarantees a tight and truly durable connection, which, if necessary, can always be disassembled.

Flanged connection example

For laying communications, you can use:

metal cap flanges;
flanges for special bushings (they are called collars).

Experts advise home craftsmen to connect PE pipes using the second of these methods. In this case, the connection is obtained with the highest quality. Flanges for bushings are made of steel 20. Flanges for polyethylene pipes are designed for operating pressures up to 1.6 MPa. These details are made with a section from 20 to 1200 mm. Therefore, problems with the selection of suitable elements for creating detachable connections never arise. There are several subtleties of assembling communications using flanges. We present them below:

flanges based on cone-type bushings must be used when working with pipes with a cross section of more than 200 mm;
light PE pipe products with a diameter of 150–300 mm, as well as heavy ones with a cross section of less than 150 mm, are best connected using flanges with a straight collar;
to increase the strength characteristics of the connection of pipes made of different materials, straight-shaped bushings with a special conical transition can be used.

When choosing flanges for making detachable connections, pay special attention to the quality of the fasteners. They are not allowed to have burrs and sharp edges. Such defects can cause damage to PE pipes. The flange connection of polyethylene pipes with a cross section of more than 50 mm is made according to a simple scheme. You need to exactly cut the tubular product in the place where it will dock with another part of the communication. After that, you carefully pull the flange onto the pipe and put a rubber gasket on top.

Such a sealing element can go beyond the cut made by a maximum of 1 cm, no more. Then you push the flange onto the gasket and mate it (using bolts) with the counter flange. Bolts must be tightened very carefully. If you apply excessive force during this procedure, the polyethylene pipe may crack.

Individual elements of communications (heating, water supply) in an apartment or house are often connected with fittings. These elements are indispensable for connecting polyethylene tubular products to metal filters, meters, mixers, pipes and other details of a modern pipeline. Fittings are either external or internal threaded. Structurally, they, as noted above, are special adapters with a thread and a coupling.

Fittings for connecting pipes

When choosing fittings, consider the diameter metal pipe into which they will be cut.

Adapters are ideal when the pipeline has a lot of bends and turns. The assembly of the system (steel or cast iron pipes plus polyethylene) using fittings is performed as follows:

Unscrew the coupling of the metal tubular product. If the junction of PE and steel pipe falls on a different site, you will need to cut off the old metal product. And then you need to lubricate the cut edge with oil or grease and use a thread cutter to make a new thread for the fitting. The operation for a more or less experienced self-taught craftsman is simple.
Carefully wipe the thread on the pipe, wrap it with fum tape or ordinary tow. After that, apply silicone on top. Tape or tow is wound quite a bit. It is enough to perform a couple of turns. In this case, the edge of the wound material when clamping it must necessarily be directed along the thread.
With your hands (do not use a wrench or other tool), carefully screw the connecting fitting onto the thread. With strong pressure on the adapter, there is a high probability of cracking it.
Insert the PE pipe into the coupling at the second end of the fitting and solder it.
Treat the connection with a sealant.

Basically, everything. You have completed the connection of a polyethylene (or polypropylene) pipe with steel. Turn on the water (if a water supply system was made) and check the fitting attachment for leaks. If there is one, simply twist the adapter a little. The final work is the sealant treatment of the connection made. You can fully use the pipeline in 3-4 hours. During this time, the sealant will dry completely.

Flange connection of polyethylene pipes

1. Polyethylene pipe;
2. Sleeve for flange;
3. Loose flange;

The choice of shut-off, control and other valves installed on polyethylene pipelines is carried out in accordance with standards, specifications, catalogs, parameters of transported substances, taking into account the requirements of the project and operating conditions.

Pressure polyethylene pipelines are connected to pipelines made of other materials using detachable steel flange connections.

The flange bushing at the base of the collar has a special structural extension designed for a more reliable connection of the collar. After all, it is on the shoulder of the sleeve that the main pressure occurs during the operation of the pipeline. Ordinary flanges supplied for steel pipes in accordance with GOST 12820.80 cannot be freely installed on the sleeve due to the narrow inner diameter. Therefore, for the flange connection of polyethylene pipes, free bored flanges are used in accordance with GOST 12822.80 with an increased inner diameter d1, which allows you to freely put it on a PE pipe.

Flange free

d - inner diameter of the flange according to GOST 12820.80;
d1 - free bored flange according to GOST 12822.80.

Connection types

Thus, to connect dissimilar pipes, apply:

NPSP is a one-piece connection in gas, sewer and water mains, for which a special-purpose adapter is used. The connection is essentially a welding of a polyethylene pipe with a steel one.
Compression couplings equipped with threaded threads - compression fitting. It is used in conjunction with ferrules and gaskets, which can be changed as they wear.
Flange transition.

What are flanges for connecting dissimilar pipes

The articulation of pipes made of dissimilar materials by means of flanges is optimal for the installation of a pipeline in which it is required to connect a metal pipe with HDPE or locking devices. For this purpose, a sleeve is used together with a clamping flange, which in turn is fixed with bolts. The shoulder (second name of the part) prevents the flange from slipping when the pressure in the pipe increases.

Bushings are of two types:

Segment, i.e. HDPE elements connected by butt welding.
Cast structures with no welds. The HDPE cast sleeve provides the flange with the necessary support and prevents the assembly from separating. It is also assumed that there is a second flange on the metal pipe.

The part is easy to mount and does not require special maintenance. A variety of standard sizes allows you to choose bushings of any size for any pipe diameter.

Flanges are also divided into two types:

Fixing, when the flange is put on a metal pipe, and a pipe made of HDPE is attached to the other end and the whole structure is fixed with a clamping ring and a seal.
Threaded - the flange has a thread on one side, onto which a HDPE pipe with a sealant is screwed.

Note! During installation, it is important to pay attention to the smoothness of the steel parts: any burrs or protrusions can damage the polyethylene.

NPSP

The design is most often used when replacing phased sections metal system on polyethylene, as well as for mounting stop valves.

For installation, thermistor welding is used, when the end of a polyethylene pipe is heated and melted to a state of a viscous mass with a special tool, and then connected to a steel pipe under pressure. Such a connection is used for the installation of high-pressure pipelines.

Regulatory documents regulate the technical characteristics of NPSP:

System pressure limits:

for gas pipelines PE 80 - 6.4 bar, PE 100 -10 bar
for water pressure systems PE 80 - 12.5 bar PE 100 - 16 bar

The length of the nozzles is regulated by GOST TU4859-02603321549-98 - for gas, and TU2248-001-86324344-2009 - for plumbing systems working under pressure.

Compression coupling

This is a collapsible modular design, the parts of which are easy to replace.

The body is made of polypropylene, equipped with a pipe stop and a trapezoid thread. A fixing sleeve with a sealing gasket, which ensures tightness, prevents the pipe from deforming and shrinking. The compression ring securely fixes the pipe in a fixed position.

Used mainly for plumbing systems.

Couplings come in different forms:

transitional,
connecting,
square,
plug,
tee,
withdrawal.

They can have both internal and external threads.

The diameter of the part varies from 16 to 110, and the value of the working pressure - from 10 to 16.

Methods for joining polyethylene pipes

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During a major or current repair the question often arises - how to connect a plastic pipe with a metal one, which is associated with the need to replace worn-out sections of communications of various lengths. A similar problem may also appear during the construction of private households - when connected to centralized engineering systems. Correct joining of pipes made of various materials, is not inferior in reliability to the connections of identical pipes, so it is important to find out in advance how to connect dissimilar sections.

Cases of connecting dissimilar pipes

Some of the cases where a connection is needed plastic pipes with metal, described above. In most cases, systems installed a certain time ago turn out to be metal. Currently, plastic is chosen not only because of its reasonable price and good specifications, but also because of the large selection of pipe and fitting sizes, making it easy to find components of any configuration for replacement.

An example of connecting a plastic pipe with an iron

Sometimes pipes made of various materials (metal and plastic) are used when installing the system from scratch. For example, when laying an outdoor section of water supply or sewerage of a private house, sometimes it is necessary to lay pipelines under a car entrance or parking lot. The dynamic load on the soil surface during the movement of vehicles will be transferred to communications located in the ground. It is recommended to install metal pipes in these areas, however, the use of metal for the installation of the entire system is not economically feasible and less practical.

Methods for connecting metal pipes with plastic

There are two ways to connect plastic pipes with metal pipes that are used for steel pipelines.

Threaded docking is used in cases where the diameter of the connected pipes does not exceed 40 mm.
Flanged connections are optimal for large diameters, since it is difficult to tighten the threads in such cases.

Features of threaded connections

To understand how to connect plastic pipe with a metal thread, you should study the fittings used for these purposes. They are adapters, on the one hand, on which there is a thread for connecting a metal pipeline and a smooth sleeve for soldering plastic pipes on the other. There are also models for connecting more dissimilar lines, as well as fittings for making turns and bends.

Polypropylene threaded fittings for transition from polypropylene to metal

The threaded connection of steel and plastic (polypropylene) pipes is carried out in a certain sequence.

The junction is being prepared from the side of the existing metal communications. If there was already a threaded connection in this place, it is untwisted. If the pipes were welded or the place of installation of the plastic insert is the middle of the whole steel pipe, the latter is cut, after which lubricant is applied to the edge and thread is made using a thread cutter.
The end of the threaded steel pipe is cleaned and a sealing material is applied to it: tow or fum-tape with silicone grease. In order to eliminate the possibility of leaks, it is important to properly seal - lay no more than 1-2 turns of winding with the direction along the thread.
The threaded edge of the fitting connects to the metal thread. In this case, you should not only not use special tools, but also do not over-tighten the connection manually. Excessive force may cause the fittings to crack. It will not be difficult to additionally tighten the thread if, after installation, a leak is detected during a test filling of the system.
After completion of work with the threaded part of the connection, a plastic pipe is fixed on the smooth coupling of the fitting by welding.

The fitting for polyethylene pipes (HDPE) at one end has a thread for connection with metal, and at the other end there is a compression retainer for the HDPE pipe - in contrast to polypropylene pipes no welding required

Making flange connections

The connection of a plastic pipe with a metal pipe without a thread is carried out using flanges. Its advantage is the ease of dismantling for repair or cleaning of communications.

The connecting elements for detachable connections of dissimilar pipelines are flanges various types.

Light structures with a diameter not exceeding 300 mm, as well as medium and heavy pipes up to 150 mm, are connected using free flanges, with a straight shoulder for support. Such modifications are the most common when installing communications in private households and high-rise apartments.
For pipes of any type with a diameter of up to 200 mm, loose flanges with a conical shoulder can be used.
A shaped flange and a steel ledge using a wedge type connection is a universal option.
Maximum strength can be achieved with a straight collar with a tapered transition.

Flange connection for HDPE pipes

As preparatory work before mounting the flange connection, it is important to carefully inspect the prepared flanges. They should not have burrs, which, when installed, can cause damage to the plastic part of the connection. In most cases, these burrs are relatively easy to remove.

The order of assembly of the assembly with flange connection is as follows:

Installation of a plastic pipe to a metal one using flanges

The steel pipe is cut off at the intended tie-in. At the same time, it is important to make the cut line evenly and accurately.
The flange is put on the pipe.
For the tightness of the connection, a rubber gasket is installed, the size of which must be such that it does not extend beyond the cut line by more than 10 mm.
The main elements of the assembly are connected - the flange put on the pipe is combined with the gasket and fastened to the second flange with bolts.

Tightening should be done by turning the threads of the fastener evenly around the entire circumference and avoiding excessive force.

If you are wondering what is better to make country water supply, then we recommend that you read our article "Plastic pipes for water supply in the country". Types and tips for installation.

For the installation of HDPE pipes, it is easiest to use fittings. We have another article about compression fittings for polyethylene pipes.

If you need to choose press tongs for the installation of metal-plastic pipes, then here you will find useful information.

Features of the connection of sewer pipes

When installing a sewer, a connection of a cast-iron pipe with a plastic one is often required, which is structurally different from the joints of steel and plastic pipes. For such connections, special components are required:

cuffs,
corrugations,
seals.

Transition sleeve cast iron-plastic

In most cases, picking up and purchasing components is not difficult. At the same time, and in those rare cases when it is not possible to find a suitable sealant, the problem can be solved with the help of improvised materials. A seal of the required size can be cut from microporous rubber, for example, from an old car mat. A long narrow tape is placed in the gap between the connected elements and sealed with a blunt wide screwdriver. Sealing is done without excessive force, so as not to damage the plastic. If a leak is detected during the test filling of the system, additional sealing of the connection can be made.

Sealing the connection by embossing or cement mortar not acceptable.

When chasing, the plastic plastic pipe is deformed, the joint will not be tight, and there is a high probability of leakage.
Cement mortar will not last long. Due to the large difference between the coefficients of thermal expansion of materials, the seam at each drain hot water will loosen. In the near future, the cemented joint of the plastic and cast iron sections of the pipeline will crack and cease to be airtight.

The connection of plastic pipes with copper is extremely rare, however, special fittings for such connections can also be found on sale. They have two smooth sleeves - one for soldering copper pipeline, the other - for connection with a plastic pipe.

Benefits of using HDPE pipes

It is easy to assemble water supply from HDPE pipes

Today, pipes made from low pressure polyethylene are in great demand. This is facilitated positive traits such products. Namely:

Long service life (more than 50 years).
Immunity to aggressive environments.
Corrosion to such pipes is not terrible.
It is possible to carry out laying in a trenchless way, which significantly reduces the cost of all work, but limits the period of use of such a water supply system.
The inside of the pipe is very smooth. This prevents the formation of deposits and growths, which eliminates the appearance of blockages.
The pipes are very light, which greatly facilitates and speeds up the laying of pipelines;
HDPE products are not afraid of temperature changes.
Pipes are highly flexible. The constructed pipeline easily tolerates soil movements. That is why such pipes are often used in earthquake-prone regions.

But there are also some disadvantages. So, HDPE pipes do not tolerate ultraviolet radiation. Also, such pipelines are not designed for pumping liquids with high temperatures, as a result of which they can be deformed.

Butt welding

Butt Welded HDPE Pipe

For butt welding of polyethylene pipes, special equipment is used. At the same time, it is very difficult to perform such work on your own, for this you need to have special qualifications. Butt welding of HDPE pipes is carried out in two ways:

using a mechanical welding machine;
using an electro-hydraulic welding unit.

The first method is used only when installing pipelines with low pressure. These include sewerage and wastewater disposal systems for industrial enterprises. Electrohydraulic equipment is capable of creating pipelines for any purpose. Connections made using this method are strong and durable. The pipelines themselves are able to withstand high pressure and any mechanical stress.

Welding of the swivel

Various HDPE parts can also be used for pipe welding. So, the industry produces bends, crosses, tees, transitions, etc. With their help, you can create a piping system of any configuration.

But, as mentioned above, welding requires the use of special equipment and sufficient experience. For these reasons, this method is rarely used in everyday life. More simple, but no less reliable way to connect HDPE pipes (and not only among themselves) is the use of fittings.

Use of fittings

The connection of HDPE pipes can be carried out using special fittings. Such designs are used when creating communications from pipes of small diameter (up to 50 mm). In this case, the following types of fittings can be used:

electrowelded;
compression;
reduction.

Electrofusion socket connection

The first option is a coupling with an electric heating element inside. When connected (after connecting to electricity), the fitting heats up and melts the polyethylene. The result is a strong and reliable connection, but at the same time non-separable.

To carry out work, it is necessary to first clean the pipe and fitting from dirt. Then they are set along one axis, while achieving immobility of the entire structure. After that, the connecting element is connected to a power source specially designed for this purpose. As a result of heating, the plastic begins to melt, hermetically connecting all the elements. You can learn more about working with such connecting elements by watching a video from the Internet.

Fitting

by the most the easy way to connect HDPE pipes is to use a compression fitting. Anyone can cope with this task, even without any skills. These fittings consist of:

polyethylene body;
sealing rings;
clamping rings (they protect the connection from mechanical damage);
bushings;
nut covers.

Before starting work, you need to disassemble the design of the connecting element. Then at the end of the pipe we mark the distance at which it should go into the fitting. Next, after wetting it in water, we put on the connecting element. The last step is to tighten the cap-nut (no need to apply excessive force). The result is a connection without the risk of leakage, moreover, collapsible.

In addition, at compression fittings there is another plus - this is the ability to make connections of different (by material) pipes. Very often, when repairing an apartment, it is required to connect communications to old metal pipes. With the help of compression fittings, making such a connection is very easy. The work process is the same as in the case of joining two polyethylene pipes.

Reducing fitting

Reducing fittings are used if it is necessary to connect two pipes of different diameters. The principle of using this connecting element is the same as that of the compression element.

Connecting polypropylene pipes to each other

Diffusion welding

Now the question of how to connect polypropylene pipes is a popular one. The most common method is diffusion welding. In order to securely fix them, fittings are used: couplings, corners, adapters.

Polypropylene pipes during the installation of a cold water supply system will definitely last up to fifty years. Approximately twenty-five years they will last during the installation of hot water supply. Please note that the service life depends on the inlet pressure and temperature.

Polypropylene products are very durable, able to cope with any changes in the system. High pressure and low temperature conditions can in no way affect the duration of their operation. High pressure and temperature, which are fixed at the same time, will reduce the life of the pipes by five to seven years. There are no extreme loads in domestic pipelines that can deform them, so there is no need to worry.

Device "Fuzioterm"

If you are interested in connecting with each other, pay your own attention to this device. Cold products made of polypropylene are connected, then the joint is processed with the Fusioterm device. If you need to weld 2 ends of the pipes, they are inserted into a special hole in the device, after preheating the device to two hundred and sixty degrees. Then they are pulled out and connected.

Socket soldering

If the radius is less than twenty millimeters, then they can be connected by manual welding. To connect to a metal part, a different method must be used. You will need a special soldering iron for socket soldering.

1. Cut off a piece of the product with special scissors. If reinforcement is present, process it, clean up the reinforcement layer in the cut area.

2. Put on gloves, heat up the soldering iron and start soldering.

3. Do everything quickly so that the joint area does not deform.

Connection of polypropylene pipes with metal

The question remains how to connect polypropylene pipes (under conditions high pressure) with metal? There are 2 methods. You need to choose one of them, starting from the radius.

1. For products with a radius of up to 20 mm, threaded connections on the metal part of the system must be used. Fittings, on one side of which there is an ordinary coupling for mounting to plastic, and on the other, with the necessary thread, are sold everywhere. In order to seal steel threads, use flax with drying oil or modern sealing materials. This will ensure the durability of the connection.

2. For larger sizes, it is better to use flange connections. An iron thread with a radius of 300 mm cannot be screwed by hand, even if you are a strong man. So how then to combine a metal pipe and a polypropylene pipe if they are of large diameter? Use special adapters that can be purchased at the store.

Thread and flanges allow you to connect metal and polypropylene pipes without soldering, which is very convenient.

The right choice of polypropylene products

Difficult to choose from a wide range provided by many manufacturers. There are criteria that must be followed when purchasing.

1. Products must be in accordance with the characteristics of the plumbing / heating system.

2. In order to assemble the system with high quality, you need to purchase all the parts from one manufacturer. This approach will create a reliable and durable design.

3. When choosing, pay attention to the quality of pipelines, fittings. Evaluate the following:

smoothness of the inner / outer surface;
the presence of cracks, chips, bubbles, heterogeneous structure, foreign particles;
the correctness of the geometry;
same wall thickness.

4. Remember that polypropylene products are designed for operation at a temperature of at least minus twenty. Ask the store how to store them in the winter. Improper storage leads to product distortion.

5. If drinking water will flow through the water supply, ask the seller if the product meets the standards of sanitation and hygiene.

6. Buy only straight pipes, no bends. In stores, they are stored vertically, so they gradually bend, cease to be even. Be sure to pay attention to this.

7. Choose products from trusted manufacturers that have proven themselves and have all the necessary certificates. Trying to save money, you can buy a low-quality product that will not be able to serve you for the entire operational period. Therefore, it is better to pay more once than to spend money again and carry out complex repairs to the water supply / heating complex.

Connection methods

Polyethylene pipes low pressure can be connected in detachable and non-detachable ways. Below we describe each of these methods.

Plug connections

This type of connection is used on diameters up to 315 mm inclusive, but it is desirable to use on diameters not exceeding 110 mm. It is just as reliable as the one-piece methods.

Its advantages:

quick and easy installation;
cost-effectiveness - no special equipment is required; couplings and other fittings are not too expensive;
accessibility - can be used in cramped conditions, under water, for example.

Connectors (fittings, couplings) are mounted in the following order:

the ends are carefully cut perpendicular to the length of the pipe; cleaned of burrs;
chamfer is removed at the ends (using a special tool or a sharp knife);
a connecting element is mounted on the ends (it enters the adapter rather tightly);
then carefully tighten the nut on the fitting.

Coupling

This is the fastest and most equipment-free way to assemble pipelines. Can be easily applied at home.

Polyethylene couplings are of several types:

connecting - connect pipes of the same diameter;
reduction - used as a transition for different diameters;
compression - designed to connect PE pipes with various shut-off equipment, steel, propylene or PVC pipes.

Couplings are straight and angular. Types of couplings are shown in the table.

Fitting connection

Compression fittings are a type of connecting parts for water pipes.

Their installation is similar to the installation of couplings.

flange connection

It is used on main pipelines of large diameter (at least 40 mm) for the installation of gate valves, valves, regulators (for their subsequent removal for repair or replacement).

To fix the flanges, special couplings are welded to the ends of the pipeline, then the flanges are screwed onto them.

Permanent connections

Only possible method connections of large diameters.

Butt welding

Such welding is desirable to connect workpieces with a wall thickness of at least 5 mm.

The ends are cleaned, chamfered, inserted into a special heater, melted, then the workpieces are joined, pressed and held motionless until completely cooled.

Electrofusion welding

The two pipes to be connected are inserted into a special sleeve, inside which there is a heating element. Then voltage is applied to it from a special apparatus, the coupling and the workpieces are heated and welded. Highly convenient way welding. And very expensive. On large diameters, the cost of the coupling will far exceed the cost of the pipeline in your area.

When performing this type of welding, special attention should be paid to the preliminary cleaning of the ends and the immobility of the joint until it cools completely.

It is impossible to connect pipes with a pronounced ellipse - the quality of the seam will be unsatisfactory.

After welding, without fail, the welded assembly must be in a stationary state until it has completely cooled down.

Do not neglect cleaning the ends of the earth, dust, sand, chips and degreasing - these little things significantly affect the quality of the seam.

How to connect HDPE pipe with polypropylene

Polyethylene and polypropylene are not welded. Correctly connect them together only with the help of fittings. On the ends to be connected, one should weld or put on MRV (couplings with internal thread) from the appropriate material, screw a quick-disconnect threaded connection (“American”) onto one MRV, then connect two MRVs using a union nut.

How to join a polyethylene and steel pipe

Such docking is carried out similarly to the joining of HDPE and polypropylene. Steel pipeline, as a rule, ends with a thread. You can use the drive instead of the “American woman” - but this option has already become obsolete.

On large highways, a valve or valve is usually mounted at such joints - in this case, a flange connection can be used.

We hope that our article has helped the reader understand the intricacies of connecting low-pressure polyethylene pipes with their own hands. Share useful information with friends and acquaintances on social networks, invite friends and subscribe to our newsletter yourself - and you will always be fully equipped to start any home repairs.

When installing water and gas pipelines, there is a constant need to connect pipes made of different materials. To connect pipes made of polyethylene (HDPE, PE) with steel pipes, special polyethylene-steel adapters (NSPS), threaded compression couplings or a bushing for flange connection are used.

Types of connection of PE pipes with steel.

1. One-piece connection polyethylene-steel (NSPS)

One-piece connection polyethylene-steel (NSPS) or adapter PE-steel it is used in the construction of gas pipelines, water pipelines, pressure sewerage to make the transition from a steel pipe to a polyethylene HDPE or vice versa. They are used when installing pipeline fittings or tie-in into an existing steel pipeline. The steel-PE transition does not require maintenance, it can be placed directly in the ground without wells on straight sections of the pipeline.
The polyethylene-steel transition is a joint obtained by welding a steel pipe with a polyethylene pipe. The length of the nozzles is regulated by the technical specifications for gas pipelines TU 4859-026-03321549-98, for pressure pipelines according to TU 2248-001-86324344-2009. The maximum working pressure for gas pipelines from PE80 is 0.64 MPa, PE100 is 1.0 MPa. The maximum working pressure for pressure water pipelines is PE80 1.25 MPa, from PE100 1.6 MPa.
In the manufacture of a permanent polyethylene-steel connection, a HDPE polyethylene pipe is used GOST R 50838-95 for gas pipelines and GOST 18599-2001 for water pipelines. And steel water pipe according to GOST 10705-80, GOST 10704-91, GOST 8731-74, GOST 8732-78. NSPS is a connection that is made by welding a steel pipe with polyethylene. The length of the product is regulated by the specifications for pressure pipelines and gas pipelines. Pressure for gas pipelines PE 80 - 0.64 MPa, PE 100 - 1 MPa; for pressure pipelines PE 80 - 1.25 MPa, PE 100 - 1.6 MPa.

Most often, NSPS are used for connecting metal locking devices to a polyethylene pipeline, gradual replacement of sections of a steel pipeline with polyethylene, a tie-in branch made of polyethylene. The principle of the NSPS part is a strong and tight connection of a pipe or a steel part with a polyethylene pipe of the same diameter.

The permanent connection to the end of the pipe is made by means of thermistor welding, which requires special equipment. The end of the polyethylene pipe is heated to a viscous-ductile state and connected under pressure to the steel end. Polyethylene couplings are used to strengthen the connection, but you can do without them. It allows the use of such a connection in high-pressure pipelines.

NSPS allow:

Use them as stubs;
Use metal shut-off valves on HDPE polyethylene pipelines
To produce on their basis gas inlets of various diameters
Drain from polyethylene into an existing steel pipe
Apply welding on steel pipelines with steel pipes according to regulatory documents.
Installation of metal shut-off valves in HDPE polyethylene pipelines
Sequential replacement of sections of steel pipelines with polyethylene ones with permanent joints until the complete replacement of the existing steel pipeline with polyethylene
Insertion of branches from HDPE polyethylene pipes with one-piece connections into an existing steel pipeline
Welding with steel pipes in accordance with the current regulatory documentation for steel pipelines with permanent connections.

2. Threaded compression sleeves

Compression polyethylene HDPE fittings. This type of connecting hardware is called compression tube fittings. They are attached to the system using gasket material and crimping rings. No additional equipment is needed to use this type. In addition, when developing the gasket material, you can replace the old gasket with a new one. That is, HDPE fittings of this type can be used repeatedly, especially in hydraulic systems.

Compression products are mainly used for hydraulic water supply systems. They can be built into such a system, even if not fully assembled. This makes it possible to widely vary their application in water supply systems. Compression fittings are of the following types:

transitional couplings of different diameters;
couplings, including those with internal and external threads;
tee without thread and adapter with thread;
square;
withdrawal;
plug.

They come in both internal and external threads. Like other fittings, these come in a variety of shapes. They are: coupling, triple, cross, plugs, flanges, bends.

They are made in different diameters: from 16 to 110 mm. Working pressure, depending on the diameter, can vary from 10 to 16 atmospheres.

All components of the structure are modular and can be disassembled. It has good advantage, since in the future such pipes will be easy to replace, and the connection can be reused.

Application of polyethylene HDPE fittings

Most often, these fittings are used to connect pipes in places where a change in the direction of the pipeline is expected, as well as the presence of branches or transitions to pipes of a different material. They are used both for technical and drinking water supply, in irrigation systems or as cable channels. Thanks to the material, these fittings allow you to make a complete tightness of the pipe joint.

The use of compression fittings for connecting pipes

Also, their ease of installation allows you to install parts of small diameters without outside help and special equipment. These parts are stored in dark rooms, away from direct sunlight.

This part consists of 5 collapsible parts. To fix the crimp, there is a nut cover, which has external grooves for easy tightening and internal thread. It is made from polyethylene copolymer.

Crimp ring - a detail that allows you to prevent any movement of the pipe, including spontaneous unscrewing.

Structure of compression fittings

The sleeve fixes the gasket in a stable position, limits its compression and deformation of the pipe. Made from polypropylene copolymer.

The sealing gasket is made of rubber. Provides good tightness, even in case of pipe bending.

The body itself is made of polypropylene copolymer, has a special pipe stop and trapezoidal thread.

3. HDPE bushing for flange

Polyethylene sleeveunder the flange is used for connecting a PE pipe to a steel pipe through a flange connection, as well as fasteners to control or shutoff valves.

Among the bushings made of HDPE, there are 2 groups:

Segment bushings HDPE — Such bushings are butt-welded elements made of HDPE, partially or completely consisting of HDPE pipe.

Cast HDPE fittings - differ from segmental ones in that they are made by injection molding and do not have welds. Fittings of large diameters are sometimes produced by casting with subsequent machining.

The principle of using this fitting is to provide a stop for the flange, which is put on the sleeve and excludes the possibility of separation of the assembly during its operation. A bushing is used for the flange at the transition points of the polyethylene pipeline on the valve or a steel pipe, if it has a counter flange.

The HDPE flange bushing is used in conjunction with a clamping flange, which must have a wider internal diameter than a conventional standard flange. The need for boring the inner part of the flange lies in the presence of a reinforcing expansion of the polyethylene part of the sleeve at the base of the shoulder, which prevents the flange from fitting snugly to the clamping part.

After installing the sleeve on the pipe, using a steel flange and bolts with nuts, the pipe is attached to the valve, and the shoulder on the sleeve does not allow the flange to come off when the pipeline is operated at operating and maximum pressures.

Using HDPE bushings

Installation of bushings is quite simple, because everything modern elements connecting fittings strive for ease of use. This saves time and money at the time of piping, and also allows you to achieve long-term operation of the system without problems. The benefits of mounting different types of system elements using bushings are as follows:

complete tightness of the joints and the absence of risks of sudden breakage;
the system does not require maintenance, any problems can be quickly corrected;
installation of HDPE pipeline elements is quick and very simple;
a wide range of bushing diameters can be found at the supplier.

When organizing a pipeline for a liquid or vaporous working medium, you can rely on the quality and reliability of molded plastic bushings under the flange at the joints. These elements will help to organize a reliable and durable pipeline system.

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When laying a pipeline from polyethylene pipes, a flange for PE pipes is used to solve problems related to connecting them to each other or to reinforcing elements. What is flanged fittings, as well as the installation features of such a connection are discussed in this article.

Flange - as an element of pipeline fittings

Product Features

Structurally, the fixing flange for PE pipes is a flat ring, or rather a disk, in which holes are located at the same distance. These holes are used to fix the connection with bolts (studs). Flanges are installed together with collar or sleeve.

The sleeve for the PE flange directly in front of the shoulder has a special expansion for reinforcement, due to which the flange does not seal tightly against the flange. To solve this problem, bored flanges are used. Such products differ from standard products in that they have an enlarged (bored) inner diameter to the required size so that the flange fits snugly on the sleeve. All other parameters, such as the number of bolt holes, their diameter, center distance are fully consistent with the standard, flat, steel flange.

Flange application

Steel flanges are used to connect polyethylene pipes:

pressure and non-pressure lines;
systems designed to remove atmospheric precipitation;
storm sewer;
technical (industrial) pipelines, etc.

Thanks to the flanges, it is possible to create a reliable, detachable connection of tubular products with various gate valves, taps (valves) and other pipeline fittings. If necessary, such a connection can be quickly disassembled for repair or cleaning of pipeline products.

Flange types

Geometric standard dimensions, as well as manufacturing technology of these products fully comply with the requirements of state standards. To establish a connection different pipes with fittings and devices, the industry produces a wide range of products. All flanges for polyethylene pipes are characterized by:

inner diameter;
external dimensions;
diameter of holes for bolts;
weight;
working pressure.

Depending on the tasks performed, the following types of flanges are distinguished:

With special welded bushings.
Cap metal.
Free type, based on shoulders, which can be straight and conical.

For connection polyethylene pipelines, laid with medium and heavy PE pipes with a diameter of not more than 150.0 mm, as well as light pipes, but with a large diameter (up to 300.0 mm) the best option there will be loose flanges that rest on a straight shoulder. Flanges of a free type, but supported by conical collars, are used for pipes with a diameter of 200.0 mm and more.

Flange connection installation procedure

Due to the simplicity and speed of installation, this type of connection is very common when laying pipelines made of polyethylene. To obtain a flange connection with welded bushings, it is necessary:

Cut the pipe at the place of the planned docking. Ensure that the cut is perfectly even.
Weld a flange adapter for PE pipes (special sleeve) onto the end of the pipe.
Install the flange itself on the welded sleeve using a threaded connection.

Flanges should always be carefully inspected prior to installation for burrs and sharp edges that can easily damage tubing and fittings.

On another section of the pipe or other element of pipeline fittings, install a counter flange in the same way.
After docking, the flanges are fastened together using bolted joints.

To use a free-type slip-on metal flange, you must:

In both cases, it is very important last step Tighten the flange bolts evenly in a cross pattern. The force must comply with the technical documentation.

Thus, a steel flange for PE pipes is a reliable and durable element of pipeline fittings, with which you can mount a tight, detachable connection of parts (assemblies) of a polyethylene pipeline.

Recently, very often, when installing various water supply and heating systems, it is required to connect plastic pipes with metal ones. To solve the problem of installing pipes from various materials, you can choose one of the options proposed in our article - a threaded or flanged connection.

Connection types

There are two types of connections:

Threaded connection. To connect polyethylene pipes with metal pipes of small diameter (up to 40 mm), it is best to use special fittings that have a thread for a metal pipe and a smooth sleeve for a plastic one.

Pro tip:

To securely seal the threaded connection of the metal part of the structure, use oiled flax fiber, as when assembling ordinary steel pipes.

Flange connection. For large diameter pipes, various types of flanges are used, since it is difficult to imagine a thread on a large diameter pipe, for example, 600 mm, that can be screwed in by hand.

We will consider a threaded connection using the example of polypropylene pipes, and a flanged connection - polyethylene, however, it is worth noting that each type of connection is suitable for both types of pipes.

The technology of connecting plastic pipes with metal

Using Threaded Fittings

For the installation of polypropylene pipes with metal parts (pipes, mixers, meters, filters, etc.), fittings with a thread of the required diameter on one side and with a coupling for soldering a plastic pipe on the other are used. The thread on such fittings can be both internal and external.

Connection of steel and polypropylene pipes using fittings:

Unscrew the steel pipe coupling where it is supposed to be connected to a plastic pipe, or cut off a part of the old metal pipe, grease the edge with grease or oil and cut a new thread with a thread cutter.
Wipe the thread, wind the tow (or fum-tape), grease with silicone. Make no more than one or two turns so that the edge of the tape when clamping is directed along the thread.
Screw on the press fitting without using a wrench to avoid cracking. If necessary (when water flows after turning it on), tighten the fitting.

With the help of polypropylene fittings of various configurations, it is very convenient to make various kinds of bends and turns in the mounted pipeline system. It is also possible to change the configuration of the fitting by heating it with a building hair dryer, but not more than 140 degrees. It should be remembered that polypropylene ignites when heated above 350 degrees, and you should not allow it to overheat.

Polypropylene pipes have the properties to expand and contract when different temperatures. Therefore, when using them for heating or for supplying hot water, mounting pipes in the wall under a layer of plaster, you should leave a gap in the strobes of at least 1 cm using tubular insulation, especially around the contours, tees.

Use of flanges

A fairly commonly used detachable type of polyethylene pipe connection is a flange connection. For its implementation, flange bushings are used, welded to the ends of the pipes, or cap flanges made of metal.

Installation of plastic pipes using flanges is used:

for connecting polyethylene pipes with steel constituent parts systems: pipes, pumps, valves;
for the opportunity quick disassembly pipeline in case of need for cleaning or repair;
when connecting pipes of large diameter.

Free type flanges based on collars are most applicable for plastic pipes. To connect steel and polyethylene pipes,

free steel flanges of such dimensions are selected that correspond to the dimensions of the metal parts of the pipeline being installed.

Pro tip:

Pay special attention to the absence of sharp elements and burrs on the metal flanges, which can damage the polyethylene pipe.

Some features of flange connections:

for medium and heavy polyethylene pipes with a diameter of up to 150 mm and for light pipes with a diameter of up to 300 mm, the most suitable option- the use of free flanges based on a straight collar;
a straight collar with a tapered transition is used to increase the strength of the connection;
free type flanges based on conical collars are used to connect pipes with a diameter of more than 200 mm;
the wedge connection, which has a figured flange and a steel ledge, can be used for pipes of any diameter.

Work procedure:

Cut the pipe at the connection. Make sure the cut is even.
Put a free-type metal flange on the pipe.
Put on the rubber pad. Do not allow it to overlap beyond the pipe cut by more than 10 mm.
Push the flange onto the gasket, bolt it to the counter flange.

Pro tip:

Tighten the bolts evenly to no more torque than the specifications for the flanges and accessories.

As you can see from the instructions, both methods are quite simple to perform. The only condition for their performance is to carefully follow the description - then your pipeline will be of high quality and reliable.