Polyethylene tubes (PND) recently use more often metal for the device of various engineering systems. PND means low pressure polyethylene. Installation of pipes of this type can be performed without attracting qualified specialists. But, before proceeding with work, the main information about the pipes, about the technology of their gasket and compounds should be studied.

Scope of application and characteristics of PND pipes

In domestic conditions, PND pipes are used for the device of the following systems:

• sewage for wastewall and rainwater leads (free);
• gas pipeline;
• water pipes;
• channel for electrical cables and communication communications.

Wide use of polyethylene pipes is possible due to their unique characteristics.

1. Resistance to acid-containing and alkaline substances.
2. PND pipes cannot be damaged by corrosion.
3. Highly mechanical strength and elasticity.
4. Long service life (at least 50 years).
5. Easy installation and maintenance.
6. Resistance to pressure drops.
7. Light weight (heshes transportation).
8. Hold temperatures from - 50 to + 60 ° C.
9. Large selection of diameters: Manufacturers offer pipes from 20 to 1200 mm. The wall thickness varies in the range of 2 - 73 mm.
10. Due to the smoothness of the inner surface of the walls, the PND pipes do not worsen water quality and are not prone to clogging.
11. Low thermal conductivity.

Types of Fittings for PND pipes

Criteria for selecting PND pipes

1. The following conditions must be respected.
2. For cold water, pipes with a diameter of up to 60 mm are used, capable of withstanding pressure of at least 1 MPa. Wall thickness - not less than 2 mm.
3. For hot water, the pipes of the PE80 brand are chosen and above. Such a need is associated with a high water temperature in the system: the walls of the pipeline are deformed and melt at temperatures above 80 ° C. For pumping fluid, the temperature from + 80 to + 110 ° C is used PN20 and RT pipes.
4. The removal is performed using a pipe of a smaller diameter than the main one.

Important: non-pressure pipes can be used for systems that do not work under high pressure.

Mounting technology PND pipes

The compound methods used depend on the peculiarities of the site on which the installation of the system and the characteristics of the pipe itself is performed. When choosing attention to the following:

• diameter of stacked pipes;
• functional purpose of communications (for or without pressure fluids, for cable laying);
• the need to use connective reinforcement of various diameters or from various materials;
• convenience of assembly work;
• the possibility of applying welding equipment.

Given the listed factors, choose a way to connect.

1. Sectional. There are three conclusion options: flange, fuse-free and compression using fittings. All methods are characterized by ease of installation without the need to use special equipment, which is important for work in places with difficult access.
2. Low: Installation involves the use of butt or electrofusion welding. As a result, the compound is not inferior by strength characteristics of the pipe itself.

Important: Highlights of reliability and strength are the compounds of the welding method and flange. A threaded coupling for systems operating under conditions of increased loads is not recommended. Pouring compounds can be used only for installation of non-pressure pipelines.

Installation of PND pipes using compression fittings

The compound performed using compression fittings is most often carried out by fixing by split plastic rings, the inner side of which has notches. Tightness is achieved with rubber liners and sealing precipitated nuts.

In addition, the execution of detachable compounds is possible with cast iron, steel, brass and copper fittings. They may differ from each other constructively (there are threaded, welded and presses).

Distinguish the following types of compression fittings:

• coupling connecting straight line (used for single diameter pipes);
• transition (for connecting pipes from various materials or with different diameters);
• removal (for angular compounds from 45 to 120 °);
• tee and crosses (for connecting three or four pipes, respectively);
• transitional fitting (for attaching a flexible hose);
• the plug (deadlock) - for the ends of the pipes.

Phased Description of Mounting Technology:

1. The working circuit is prepared, which indicates the place of installation of valves and fittings.
2. The covers of the pipe covers and is temporarily fixed in the deployed form for several days. It is necessary in order to eliminate the striving of the pipe to curl.
3. The pipe is cut to the metal or pipe cutter on the segments of the required sizes. It should be striving to get a smooth edge. The alignment of the opening is performed by the calibrator.
4. Sanding paper eliminate burrs from the edges of the pipes, the knife form an outdoor chamfer.
5. Fitting sites are wetted by water, after which it connects with the pipe. It is necessary to make sure that the rubber seals are not deformed, and the end of the pipe entered the landing hole until it stops.
6. The clamping ring is supplied close to fitting, the nut is delayed manually.
7. Similarly joined the pipe on the other side of the fitting.

Tip: When installing temporarily disassembled systems (for example, for watering device in the country), rubber seals should be changed periodically. So you can avoid leaks.

Features of flange connections PND pipes

Flange pipe connections with water reinforcement

Connection using couplor flange couplings is used for pipes with a diameter of over 40 mm. Initially, the pipes are cut on the markup and weld the sleeves with sides. Metal flanges are installed on the sleeve.

The second option of how the compression of the pipes from metal and the PND is made, assumes the use of a compression flange for fixing the docking section. After that, an ordinary flange is attached, which, in turn, connects to the part on the steel pipe with screws.

The flange connection allows you to install valves, cranes, valves and other reinforcement and connect them with a pipe.

Connection of PND pipes welding

Welding equipment for household communications

Welding large diameter pipes

In places inconvenient to complete the installation and maintenance of the system, it is practiced to perform all-point connections. The greatest reliability is the welding with the help of electrical products. The process is heated fitting (using special equipment) after it landing on the ends of the pipes. Plastic is melted and a hermetic connection is formed.

Connection of pipes with welding electrical

Butter welding is performed in such a sequence of actions.

1. Plastic in the place of welding is cleaned by contamination.
2. Setting the welding device: The required parameters are installed (depend on the pipe parameters).
3. Pipes are fixed in special clamps and centered. The ends are treated (equalized by the calibrator, eliminate burrs).
4. Heaters warm up the ends of the pipes to the state of reflow.
5. Pipes are reduced and compressed to polyethylene pouring.
6. The connection is exempt from clamps.

Not a hermetic compound revealed during testing

Important: After the installation of the entire system, tests for tightness of the compounds. For this, the pipe is first filled with water at first, and then half an hour is pushing. The absence of leaks indicates a quality assembly.

Tips, how to avoid errors when connecting pipes PND

During installation, you must pay attention to the following points.

1. Pipe attachments need to be distributed along the length of the system in such a way as to minimize its deformation due to linear expansion. However, it is necessary to prevent pipe sagging. The optimal is the distance between the clamps, equal to 10 pipe diameters, in the case of vertical laying - 1-2 m.
2. The fastening of the pipe to the wall is performed with the observance of the gap - at least 4 mm.
3. Before laying into the pipe concrete, isolate a stock line from foamed polyethylene or rubber.
4. When installing the pipe should be fitted until it stops. So that the rubber seal does not damage, during the assembly it should be put on the pipe.
5. The tightening of the presser nut must be moderate, in order to avoid the destruction of the thread and shearing of the sealing pads.

In conclusion, we suggest familiarizing yourself with a visual benefit. To your attention - connecting pipe PND: video with specialist comments.