Polypropylene pipes and fittings: features, standards,

How to choose polypropylene pipes and fittings? In general, what they are and what standards are produced? How to use polypropylene for installation of home plumbing or heating systems?

In the article we will try to answer these questions.

General properties

What should you know about polypropylene?

• PN in the marking of pipes corresponds to the working pressure in atmospheres (kgf / cm2) at + 20 ° C.

Important: as the temperature rises, the maximum allowable pressure drops. So, for PN25 pipe at + 90С it is equal to 8-9 atmospheres. However, in normal operation of the central water supply and heating systems, the pressure in them does not exceed 6-7 kgf / cm2.

• The maximum working temperature for all types of polypropylene does not exceed 95С. According to the current SNiP, there should be no higher temperatures in the internal engineering networks of residential buildings; in practice, under certain conditions, exceeding this value is possible.
• Pipes and fittings made of polypropylene are connected by low-temperature welding. Adjacent surfaces are melted with a special nozzle for a soldering iron with a temperature of about 240 degrees and are combined; after cooling, the strength of the connection is not inferior to the whole area.

• The material is lightweight (polypropylene is the lightest of plastics, its density is only 0.91 g / cm2) and is exceptionally hard. The internal surface of the pipeline does not overgrow sediments and remains smooth even after decades of operation.
• The combined cost of polypropylene pipes and fittings makes them the cheapest solution on the market.. Polyethylene pipes themselves are even cheaper, but the higher price of fittings and the operating temperature limited to 40 degrees makes polyethylene uncompetitive.
• Production of polypropylene pipes and fittings has long been established in the territory of the Russian Federation. Products, in particular, are sold under the brands Sanpolimer and Potok.

Reinforcement

Specifications of manufacturers of polypropylene pipes and fittings always include, among other things, the presence of reinforcement and its type. What is reinforcement and why is it needed?

This is the name for the introduction of materials with high tensile strength into walls with a minimum coefficient of thermal expansion. Goals directly flow from properties — thus, elongation decreases upon heating and increases tensile strength.

Useful: long straight sections on the DHW and heating, however, are supplied with compensators - U-shaped or ring bends. The fastening of the pipes is made mobile, and when placed in the grooves at the end of each road the free space of 5 to 10 mm is always left.

Notice, fittings for polypropylene pipes are produced without reinforcement: high strength is achieved by a simple thickening of the walls, and elongation during heating is not decisive simply because of the small size of the fitting.

Reinforced pipes are mounted on hot water and heating.

On sale you can find products with two types of reinforcement.

Aluminum

Between the two layers of polypropylene glued a layer of aluminum foil with a thickness of no more than half a millimeter. Thus, at a fixed wall thickness, the working pressure increases from PN20 to PN25, and the elongation during heating approaches that of steel.

When welding, aluminum requires the mandatory removal from the area of ​​contact with the fitting. The fact is that under certain conditions, the metal in contact with water begins to break down, causing the pipe to separate and a sharp drop in its strength.

The reinforcing layer can be located strictly in the middle of the wall, and closer to the outer surface.

Instructions for preparing the end of the pipe for welding depends on its location:

• The outer layer is cleaned with a shaver - a nozzle of the appropriate diameter with knives located on the inner surface.

• The foil located in the middle is removed from the melting zone by means of a face-cutter, an instrument in which the knives are located at the pipe end.

Fiber

An alternative method of reinforcement is to form a layer in the middle of the wall, reinforced by the addition of chopped fiberglass - a fiber. Such products do not require stripping. Elongation during heating is reduced, but somewhat less than when using aluminum.

Standard

Main technical characteristics - dimensions of polypropylene pipes and fittings, tolerances, wall thickness, etc. - regulated by GOST R 52134 - 2003.

Curiously: the standard regulates the production of pressure pipes from all thermoplastics. In particular, plain and cross-linked polyethylene, PVC and polybutene are mentioned in its text.

 Pay attention to its key points.

• The minimum diameter specified in the standard is 10 millimeters, the maximum diameter is 1600.

• The minimum wall thickness is 1.3 millimeters, the maximum - 61 mm.
• The maximum deviation of the outer diameter depends on its value and must comply with the following table:

• Pipes of small (up to 180 mm) diameters can be supplied not only in straight sections, but also in coils or coils.

• Along with contact socket welding, the standard provides for the installation of polypropylene using electrofusion fittings (equipped with its own heating element).

Installation Tips

When welding polypropylene pipelines with your own hands, it is necessary to follow a few simple rules.

• At the end of the pipe intended for welding, the outer chamfer is removed.
• After melting, the parts are joined by translational motion, without rotation.
• After docking, the connection must remain fixed for at least a minute.

Conclusion

We hope that the information offered to the reader will be useful in the repair or construction (see also the article Fittings for polypropylene pipes: types and their technical description).

The video in this article will allow you to visually get acquainted with how polypropylene pipes and fittings are mounted. Successes!