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Reinforcement of polypropylene pipes

Polypropylene pipes are products that have many advantages arising from manufacturing features. Among them:

1. Polypropylene pipelines are great for cold and hot water, but there are limitations for hot water - up to 95 degrees, for a short time this value can be exceeded. But this feature is rarely paid attention to, since the supply of hot water for apartment buildings is precisely this figure and is limited. Therefore, when discussing the disadvantages of polypropylene, mentioning this particular feature (withstand the temperature only up to a certain value), you can safely purchase them - boiling water at 100 degrees will not flow through the pipes anyway.
2. The coefficient of thermal expansion is quite large. Polypropylene makes it possible to compensate for expansion at high temperatures due to its flexibility, although there are situations where pipe displacement is extremely undesirable, especially when they are laid under a layer of plaster or screed.

To neutralize these features, the polypropylene water supply is reinforced. Expansions and high temperatures are not terrible for a reinforced water supply system, it does not expand, does not deform when it is suddenly heated to high temperatures.

Attention: you cannot rely only on the reinforcement in all cases. At a flow temperature of more than 100 degrees (with constant heating), there is a possibility that at the joints with the fittings the material will begin to soften, the water supply itself will simply not be able to withstand the pressure!

Reinforcement for polypropylene is used today in different ways:

1. Fiberglass mesh. This option is considered one of the best, the pipeline is five-layer: two layers of polypropylene and three layers of reinforcement. In this case, the middle layer is a kind of mixture of fiberglass and polymer.
2. Aluminum foil is the most commonly used reinforcement method, which is the use of an aluminum interlayer with a thickness of 1 to 5 mm. Such a layer can be located outside, inside or in the middle between the plastic layers. The foil is connected with glue, such a pipe can be solid or perforated.

Cleaning of the reinforced part in this case is necessary in order to remove the reinforcement layer from the place where the welding of individual sections of the water supply will take place.

Why do you need to clean the reinforced part?

The polypropylene layer can be cleaned in several ways:

Scheme of stripping reinforced pipes before reflow for connection.

1. External stripping. This method is used when the foil layer on the pipe is external. The reinforcing foil must be removed, since during welding the layers of plastic and aluminum are connected extremely poorly, that is, if the metal layer is not removed, the fastening of individual pipes will be very poor. Therefore, using a special tool, the outer layer of the pipe with foil is completely removed to the depth necessary for putting on the fitting and welding individual sections.
2. If the layer of reinforcement is inside the pipe, then a method is applied in which the foil inside the cavity is removed. Do you remove the foil here if the pipe melts when welding only from the outside? The fact is that aluminum should not come into contact with water at the attachment points, otherwise electrochemical processes begin inside the water supply system, and this will lead to the destruction of the entire reinforcement, that is, to pipe delamination, a decrease in the strength of the connection, leaks, and so on.

For fiberglass reinforcing polypropylene, cleaning is not required, since the mesh in this case is located inside the pipe, that is, when melted, it does not come into contact with the fittings in any way, it is also not afraid of water. Therefore, polypropylene pipes with a fiberglass layer are often preferred, despite its higher cost. In this case, the fastening is made more reliable, additional work is not needed before this. Such pipes are welded without stripping.

Pipe stripping tools

A variety of tools are used for stripping, this is a trimmer, manual strippers, special attachments for a drill, which works in automatic mode. Hand tools have removable or non-removable handles that allow you to work with them with great comfort, and special attachments are used with conventional drills without impact mode, they are inserted instead of the drill.

When working with a drill, you need to be more careful, since polypropylene is a very soft material, the stripping process should take place without damage.

To perform stripping and pipe connection, you need to prepare the following tools:

• a simple pencil for leveling;
• roulette;
• soldering iron for polypropylene pipelines;
• scissors for cutting;
• selected stripping tool.

Cleaning the outer and inner layers: we eliminate all unnecessary

In order to clean out the outer layer of the reinforcement, you can use a simple clutch with knives inside. The clutch is put on the end of the product, rotated, the cut is then smooth and very even, the operation itself takes only a few seconds.

The facing tool allows you to remove the middle layer, the blades are located at the inner end of the tool. The process is as follows: the facing tool is put on the end of the pipe, several turns are performed, after which you can start soldering.

Drill bits make it possible to remove the inner and outer layers of pipe reinforcement. Instead of a bit, the attachments are put on the drill, carefully controlling the speed, a layer of foil is removed, after which the pipes can be welded. The choice of the nozzle should be in accordance with the types of reinforcement for the pipe.

Stripping a reinforced polypropylene product is necessary in order to remove a thin layer of polypropylene itself and the reinforcement to prepare pipelines for welding. In this case, the material is removed to a depth that is required to slide on the fitting. You can perform stripping using a special tool, the work itself does not take much time, you can use not only manual, but also automatic tools that facilitate the preparation of the pipeline.

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Two types of pipe cleaning: technology and tools

What types of pipes require stripping? What is it for? What tool is used for this? Finally, what is the correct way to clean the pipes in each specific case? In this article I will try to answer these questions.

Types of pipes

They need to be cleaned in one way or another:

• Black steel pipes... They are cleaned from rust and other contaminants for painting and before manual threading;

In the second case, rust is not simply removed from the ends of the pipe. An entry for a die or a die is formed on them - an external chamfer is removed at an angle of about 15 degrees to the longitudinal axis.

• Polypropylene pipes reinforced with aluminum foil.

Why is it needed

Steel

Cleaning before painting is designed to ensure maximum adhesion of the paint to the substrate. Painting over rust (especially stratal) guarantees the detachment of the decorative and anticorrosive coating in the shortest possible time. An alternative to cleaning is the use of rust converters - phosphating compounds that convert iron oxides into a strong and chemically resistant film, directly onto which paintwork materials can be applied.

Agree that painting a professional pipe in this state without stripping is not a good idea.

The threading lead-in allows the die or die cutter to cut the first threads with minimal clamping force. The larger the chamfer angle, the more you have to press the die against the pipe end. If there is no chamfer, the tool, even with the maximum clamping force, will not enter the pipe or will repeatedly break the first thread of the thread.

Polypropylene

Why do you need stripping for reinforced polypropylene pipes?

I'll start from afar.

Polypropylene has two problems with its performance in hot water and heating systems.

1. When heated, the tensile strength of the pipe decreases. If at +20 pipes PN 20 is able to withstand a hydraulic pressure of 20 kgf / cm2, then when heated to a maximum 95C for it, the permissible pressure decreases to 7 - 9 atmospheres. No wonder: polypropylene is a typical thermoplastic with all the ensuing consequences;
2. The polymer has a very high (even compared to other plastics) coefficient of linear expansion when heated. If the temperature of the pipe is raised by 50 degrees, each meter will lengthen by 6.5 millimeters.

Both problems are successfully solved reinforcement.

It can be done in two ways:

1. By mixing into the polymer melt fiber- chopped glass or basalt fiber. The middle reinforced pipe layer is fused with layers of pure polymer without reinforcement into a single whole during the extrusion process;
2. Bonding between two layers of polypropylene layer aluminum foil thickness of about 0.5 mm. The quality of an aluminum-reinforced pipe is highly dependent on the manufacturing technology used and used.

Typical working pressure of reinforced pipes is 25 atmospheres (as indicated by the designation "PN 25" in the marking). When heated, it decreases to 10 - 12 kgf / cm2. The elongation during heating also decreases markedly:

The steel pipe under the same conditions is lengthened by 0.5 - 0.55 mm.

For obvious reasons, pipes reinforced with foil are most in demand for hot water supply and heating. However, one unpleasant surprise awaits the happy buyer: aluminum forms galvanic vapors with copper and steel, which are often present in heating and hot water circuits.

The small thickness of the foil causes it to collapse due to electrochemical corrosion on contact with water in literally 2 to 3 seasons. As a result of its destruction, the pipe at the end, inside the socket fitting, begins to delaminate with a catastrophic drop in strength accompanying this process. A relatively weak water hammer or noticeable heating ends the career of such a pipeline ahead of schedule.

The obvious solution to this problem - remove the aluminum reinforcing layer from the welding area... Stripping of polypropylene pipes is the preparation of the pipe end for soldering with a fitting, which is reduced to cutting the foil from the pipe surface (with external reinforcement) or between two layers of polypropylene (with internal reinforcement).

Instruments

Steel

Steel pipes are prepared for painting using:

• Manual metal brush;

• Attachments of similar functionality for a drill or grinder.

The stripping of a shaped tube can be partly automated. The simplest machine for cleaning pipes from rust is a chuck with a brush clamped in it, seated on the shaft of an electric motor, and a movable thrust roller with a locking mechanism that allows you to process pipes of any section. The pipe is slowly pulled through the machine by hand, turning 90 or 180 degrees between successive brush passes.

In the photo - the simplest machine for cleaning rust from a professional pipe.

How can you prepare the end of a pipe for threading?

• File for metal;

• Grinder with a cutting wheel for steel;

You will have to grind the pipe with the plane of the circle. Avoid using too much force: fragments of a broken circle often cause serious injury.

• Finally, in the absence of a more suitable tool, a pipe with a diameter of 15 - 25 mm can simply be slightly crumpled in a circle with a gas wrench or blows with a heavy hammer.

Polypropylene

A stripping tool for polypropylene pipes is most often called stripping. In stores with a more qualified commodity expert, you can find more accurate names:

• Shaver is a stripping for external reinforcement;
• The facing tool allows you to cut a foil layer glued into the middle of the wall between polymer layers of approximately the same thickness.

And this tool can be manual (with a notch on the outer surface or comfortable handles), made for installation in a drill or hammer drill chuck. Often, it is equipped with a pair of knives, which allows you to remove the outer chamfer from the end of the pipe.

The nozzle is a shaver chambered for a perforator.

The price of the tool is determined by the size, function and manufacturer. Here, for example, is the cost of Valtec's line of facers designed for installation in a hammer drill chuck.

Technology

I sincerely hope that the instructions for cleaning pipes from rust and chamfering are not required by the respected reader: this is a simple mechanical work, devoid of any subtleties.

Do-it-yourself stripping for polypropylene pipes is not much more difficult:

1. After examining the cut of the pipe, select the appropriate tool (shaver or trimmer);
2. Insert the pipe into its sleeve;
3. Do several full turns.

The trimmer knives remove the reinforcement to a depth of only about 2 mm. Pipe stripping takes 5 to 15 seconds.

Conclusion

We will consider our acquaintance with simple stripping technologies to be valid. Additional materials, as always, can be explored by watching the video in this article. I look forward to your additions and comments. Good luck, comrades!

July 22, 2016

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The pipe stripping procedure (in its classical sense) consists in removing a part of the outer layer of polypropylene and aluminum foil from the edge of the pipe so that the pipe and the fitting can be welded with socket-type thermal welding. Some "experts" believe that since pipes, reinforced in the middle, do not require stripping of the outer polypropylene layer, they do not have to be stripped from the end of the pipe either. However, it is not.

Process pipe stripping, especially of large diameters, is a rather laborious task. Many installers would gladly avoid the need to strip the aluminum before welding. And when a tempting and easy way to achieve this appeared, some installers, despite the recommendations of responsible manufacturing plants, and often without even knowing anything about them, began to mount systems without using a stripping (facing) tool.

Fig. 1.

Fig. 2. Facing tool for pipes reinforced with foil in the middle. View from above.

As the short empirical experience of installing and operating polypropylene pipes reinforced with aluminum in the middle without end stripping of the metal shows, there is nothing critical in the short term. Pipes without stripping are welded as standard, the system is pressurized, water is released, and everything seems to be fine.

Fig. 3. Installation of reinforced polypropylene pipes. There are two pipes in front of you. One of them (right) was stripped before being connected to the fitting (the foil was sealed, there will be no contact of aluminum with water), the other (left) was not stripped

But, as the thousand-year experience of human civilization shows, free cheese is only found in mousetraps. The main reason why most of the manufacturers responsible for the consumer advise using special end stripping is the transient electrochemical corrosion of the aluminum foil, leading to delamination of the combined pipe and its operational degradation.

Fig. 4. Installation of reinforced polypropylene pipes. Unsorted pipe. On the face of physical degradation and stratification. As a result - the presence of leaks and cracking over time

Polypropylene pipes with smooth inner surface, indeed, do not overgrow and are not subject to corrosion, however, in the case of pipes reinforced in the middle and reinforced "from the inside", they can not only overgrow (polypropylene swells inward, partially blocking the internal section), but also partially rot due to aluminum corrosion.

After reading everything written above, an inexperienced user or installer can exclaim in their hearts: “How confusing everything is! I will make a better system based on metal-plastic ”(approx. Common name for a pipe with a PEX / AL / PEX layer structure). However, there is no need to rush, everything is actually simple and clear. We take classic pipes with reinforcement closer to the outer edge of the pipe. Bearing in mind that almost any more or less large object has a perforator, we buy for relatively little money a special stripping nozzle for a perforator and without much effort, using the adjustable torque of the tool, we remove the outer layer of polypropylene together with aluminum. For those who do not have a perforator, but have to clean different standard sizes of pipes, we can recommend a new cleaning tool - hand shaver(stripping) into four main standard sizes of pipes (20, 25, 32, 40 mm).

Fig. 5. Installation of reinforced polypropylene pipes. Tools for stripping aluminum-reinforced polypropylene pipes. In the photo - a drill bit, a universal stripping tool for four sizes of pipes and a standard stripping tool for two sizes

The only pipes that for the most part have the properties of reinforced pipes and do not require stripping are the so-called fiberglass pipes. Such pipes have a three-layer structure with a middle layer of a compound (mixture), which contains a premix of glass fiber and polypropylene. That is, during the welding process, this layer from the end can also be welded, and even more so it will not enter into chemical reactions and corrode. Since all three layers of these pipes contain polypropylene and are basically the same type, these pipes are produced by the coextrusion method, i.e. the layers of the pipe are superimposed on each other at the same time. In this case, there is no need to pass any layer first through a water bath, and to use tie layers of adhesive.

Rice. 6. Glass fiber reinforced polypropylene pipes do not require stripping.

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Due to the operational parameters, aesthetic appearance and ease of assembly, polypropylene pipes are often used in the installation of utilities. Thanks to the reinforcement technology, the reliability and durability of pipes increases while maintaining all the technological characteristics of polypropylene, the pipes in terms of their qualities are not only comparable to metal ones, but also surpass them. ...

However, for the long-term and reliable operation of the pipeline system, proper processing and cleaning of the ends during connection are necessary.

Reinforced pipe is a product with three layers: two polypropylene and one reinforcing. Structural reinforcing shell ensures the retention of strength in the event of sudden temperature changes.

Such an indicator - as the coefficient of thermal elongation is 6% higher for pipes with aluminum reinforcement, which increases the durability and reliability of the pipeline, which uses reinforced pipes.

The presence of an aluminum layer in a polymer pipe allows maintaining high temperatures and prevents the rupture of communications in the system. Tempera leaps and bounds are compensated for by the flexibility of the reinforcing base. Reinforcement is carried out in two ways:

1. With fiberglass.
2. With aluminum foil.

Reinforced products are produced both with a solid sheet of aluminum foil and in the form of a mesh with perforations. The viscous polymer flows through the aluminum holes and creates a strong adhesion to the protective layer, increasing the reliability of pipe products even at increased high-temperature loads.

What is stripping required for?

If the fiberglass reinforcement does not require additional cleaning of the ends of the pipes, then during installation with aluminum it must be removed and cleaned.

During installation, molten aluminum does not give a hermetic connection with propylene, and it is required to exclude contact of metal with water at the joints of pipes and fittings, and to avoid corrosive processes.

Attention! The cleaning process removes the oxidized layer and various kinds of contamination from the surface of polypropylene pipes. This prepares the edge of the pipeline for making a reliable weld joint.

Stripping methods and technology

Before proceeding with the installation of reinforced pipes, you must first select a stripping tool. It can be both manual and mechanical devices.

Cleaning and reinforcing polypropylene pipes is not the most difficult task, but there are many nuances in them. This will be discussed in the article.

One of the advantages of polypropylene pipes is their long service life. They can be used many times longer than metal products. But the service life largely depends on the quality of the installation work carried out. It can be maximized if the reinforced polypropylene pipes were cleaned correctly.

It plays such an important role due to the fact that the presence of various irregularities and burrs will impede a reliable connection. Even during the planning of the installation of a polypropylene pipeline, it is worthwhile to delve into why this procedure is required. It is also worth understanding what tools exist for stripping polypropylene pipes (read: ""). Special attention should be paid to products with a reinforcing layer.

Features of reinforcement of polypropylene pipes

High performance properties of polypropylene pipes are achieved due to their coating with a protective layer. If we are talking about products intended for domestic use, then usually its thickness is not more than 0.1 mm.

Benefits of Reinforced Pipes:

1. Reducing exposure to high temperatures on the product... An ordinary polypropylene pipe is designed for operation in conditions where the temperature does not exceed 95 degrees. Usually this is sufficient for the installation of heating systems or domestic water supply systems. However, in certain situations, for example, emergency, the temperature of the transported liquid may exceed the maximum permissible value. Such a mode of operation leads to the fact that sections of the pipeline are deformed or completely fail. Reinforcement allows you to reduce the impact of high temperatures on the product, preventing system ruptures.
2. Increased resistance to temperature extremes... One of the main disadvantages of conventional polypropylene pipes is their exposure to temperature extremes. The result is their sharp expansion and contraction. The product does not tolerate such deformations, gradually losing its original properties. Over time, the pipes will simply fail. To avoid such a situation, they are additionally reinforced.

However, the reinforcement has one significant drawback. It somewhat complicates the welding of polypropylene joints. For this reason, a pipe stripping is required first. The procedure is extremely simple: remove the upper thin layer of aluminum from the product. If this is not done, the quality of the welding will decrease, which will lead to a decrease in the service life of the entire pipeline.

It is important to do the job carefully, understanding the general principle. To better understand everything, study the technological process, as well as prepare the necessary tools. Detailed information on these issues will be presented later in the article.

Cleaning of polypropylene pipes

There are several methods of stripping, each of which is designed for a specific reinforcing layer.

Outer layer... If the reinforcement is applied as the top layer of a polypropylene pipe, then it will become an obstacle when connecting the structure to the fitting. Then the pipe section entering it melts during installation. If you delay stripping, then the molten aluminum will not be able to bond with the molten polymer. In this case, nothing will ensure the tightness of the connection. It will be violated immediately after starting the system.

The inner layer... Despite the fact that the aluminum located between the polypropylene layers is not used for welding, it still needs high-quality stripping. It is necessary in order to prevent the interaction of aluminum and water. If a potential jump occurs in the pipeline, then there is a risk of electrochemical processes. They can completely destroy the aluminum layer.

Prompt! The reinforcing layer of aluminum can be applied in one piece or with holes. If there is a choice, then the second option is much more preferable. The perforated aluminum layer has good adhesion and does not require any glue. In addition, the stripping of perforated aluminum pipe is much faster.

Glass fiber reinforcement... In this option, do-it-yourself stripping for polypropylene pipes is not required. A thin fiberglass wall is placed between the polypropylene layers. It does not come into contact with the fitting, nor is it affected by the liquid. One of the advantages of this method is that a reliable fastening of the pipes is achieved without additional work. But this leads to one drawback - on such products, sharp temperature drops have a greater effect than on options with aluminum reinforcement.

Stripping tools

There are hand and mechanical stripping tools for polypropylene pipes. Hand tools are great for doing homework. If a more voluminous task is ahead, then mechanical tools will already be required.

Types of stripping tools:

1. Stripping for the outer layer... To remove the outer layer of aluminum, special couplings are used, in the middle of which there are blades. Such devices have handles (removable and non-removable), which greatly simplify the workflow.
2. Trimmers... In such a tool, the blades are located on the inner end of the sleeve, and not on the outside. The facing tool is threaded into the pipe, then several full turns must be done. This allows for a perfect cut. Then you can proceed to welding products. Such pipe stripping tools are also used for other types, not just polypropylene. Even those without a reinforcing layer are suitable.
3. Shaver... This is a special drill bit used to clean both the inner and outer layers of the pipe. There are shavers designed for different types of reinforcement. They vary in diameter.

An important nuance! It is worth understanding the difference between stripping pipes before welding and cleaning metal products. These are two different types of work. Different equipment is used for each of them. In addition, they have different technological processes, which should also be taken into account.

Also, for stripping polymer pipes, you will need: a tape measure, the necessary stripping tool, a construction pencil for marking, a soldering iron, as well as scissors, a pipe cutter or a hacksaw. These are popular tools and can be found in almost every home.

To obtain a perfect cut on the pipe, high alloy steel tools should be used. It is preferable to choose two-sided solutions. Such a tool is effective when working with products of different diameters.

Stripping polypropylene pipes is not particularly difficult. One person can cope with the task, no special knowledge is needed for this. Also, no expensive tools are required. Simple machines will do just fine. Even with their help, it will be possible to carry out the cleaning quite efficiently and accurately. It is enough just to prepare everything in advance, having carefully studied the technological process of this task.