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Connecting fittings for polyethylene pipes low pressure

HDPE (low pressure polyethylene pipes) are one of the most modern and popular products for pipeline construction. for various purposes. In turn, each of them has an inlet and outlet, and almost everyone has different shut-off valves and branches, respectively, for this, fittings for HDPE pipes are also needed.

Types of polyethylene pipes depending on the purpose.

There are a large number of them for HDPE pipes, which can be divided according to the principle of docking with the product. How to understand this diversity and how to choose one or another shut-off valves?

All types of HDPE pipe connections are divided into:

• by rigidity: rigid and non-rigid (elastic) connection;
• by detachability: detachable and one-piece connection;
• connection method.

During installation, fittings for HDPE pipes, including valves, can be connected to the pipeline in various ways.

Permanent connection

Welding is the main type of connection. Exist various ways product welding. Some of these methods are more common, some are less common.

Scheme of butt welding.

Welding methods:

1. Butt welding is the most common method, when the end of the product and fitting is melted with a special apparatus and they are pressed together, as a result of the melt, a monolithic seam is formed, which is similar in its properties to the pipe material. For this method, fittings and HDPE pipes must have the same diameter. Butt welding is very often used in the construction internal networks water supply and heat supply, while using "hand irons". If in the welding machine the products are fixed with particular accuracy relative to the docking point, then when performing work manually, it is necessary to pay Special attention relative position products, and best of all - before the seam hardens, fix them with any devices.
2. Nest welding - has the same principle, except that this method uses fittings for HDPE pipes with an inner diameter that is equal to the outer diameter of the product. If in the first method (butt welding) the soldering iron is made in the form of a disk, then in socket welding one side of the soldering iron is flat and equal to the diameter of the pipe, the other side has the form of a rod, the diameter of which is equal to the inner diameter of the fitting.
3. Edge (pressing) welding - is used mainly for welding the product with the entrances of wells, etc., where it is necessary to weld the pipe to a plane that is larger than its diameter. For this, special PE electrodes are used. This method is used only in a non-pressure system that does not require absolute tightness.
4. Electrofusion welding - the welding process consists in melting polyethylene, while fittings and HDPE pipes must also have the same diameter. However this method requires the use of special coupling. The coupling has a heating grid fused during production and two contacts. Each such coupling has a bar code. If using automatic welding machine, it independently reads the data and sets optimal parameters welding. Otherwise, these parameters must be set manually.

Scheme of electrofusion welding.

plug connection

Based on the fact that all welded fittings are one-piece connections, with their use no shut-off valves are installed and control devices. Since in the event of failure of these devices, with a permanent connection, their replacement requires considerable effort.

The next connection type is . They are used, as a rule, on external networks and the principle of their operation is the same. The compression fitting has a ring (split) and a tightening nut.

Flange connection - used, as a rule, for with large diameter, in places where shut-off and other valves are installed.

Nut, then we put the ring on the product, after which we tighten the nut. After it is tightened, this connection guarantees the impossibility of slipping of the ends of the product under tensile influences. In today's market, manufacturers offer both brass and compression type. As a rule, they are used when there is a threat of shock loads on this connection.

Based on manufacturer data, compression fittings are designed for pressure of the working medium up to 20 atmospheres, that is, they are suitable for use in pressure networks.

Flange connection - is used, as a rule, for joining pipes with a large diameter, in places where shut-off and other valves are installed, or when connecting a pipeline made of polyethylene with metal areas. At the same time, in polyethylene networks, cast HDPE flanges are usually used, and if it is necessary to switch to metal, brass fittings equipped with a plastic outlet, which is designed for welded joint with a polymer product.

Threaded connection - used external, which is cast on one of the ends of the pipe, and internal - on the other connection pipe or fitting. This connection is considered by experts not to be particularly reliable. Based on this, it is used for the installation of non-pressure liquid transportation systems or in the laying of cable communications.

Socket connection - based on fixing the end with a standard diameter of one product, inside the expansion at the end of another product or fitting. As a rule, this connection is used when installing a non-pressure drainage system (sewerage) or when laying a cable.

Types of fittings

For laying pipelines from, fittings are used in the following cases(by material and type):

Varieties of fittings for detachable connections of HDPE pipes

1. Equal bore coupling - made with the same diameter at both ends. It is used for joining individual pieces of pipe or with other elements with the same diameter size as the pipe.
2. Expansion sleeve - used to change the diameter of the pipeline or install an element with a larger / smaller size
3. Thread-plastic connection. When joining, for example, a polymer and metal fittings, a combined fitting is performed. An embedded element is mounted in a plastic sleeve with an external or internal thread, usually made of brass.
4. Flanges - used for mounting removable fittings or docking with pipes made of other materials. There are combined and PE. Flange couplings are their variety.
5. Branches. Of course, polyethylene is quite flexible material, but still it should not be allowed to bend too sharply. The use of bends allows the pipeline to significantly change direction. Bends are available as standard for 45°, 66° and 90° bends.
6. Crosses and tees - with the use of such fittings, the pipeline can be docked with necessary quantity other parts of the network. Branches can be both with the same and different diameters.
7. Plugs. This type of fitting allows you to perform the conservation of "deaf" HDPE pipes. Such a situation can be, for example, if it is necessary to decommission a certain section of the water supply, or they can be used in places where a new connection will be organized later, etc.

In general, and fittings for it allows you to create a combination that will make it possible to build a pipeline for any task and in any conditions. Along with a relatively low price and high operational properties HDPE products, it provides polymer material well-deserved high popularity, both among private consumers and installation organizations.