Bellows liner for water: what it is and what is it for

Even 20-25 years ago, in order to connect a washing machine, the work of welders was required to build a water supply system. Appearing later, flexible piping greatly facilitated the connection of various appliances and plumbing, but increased the risk of leaks. Today, the bellows liner that has appeared on the market allows all these problems to be solved at once.

The bellows connection is made in the form of a corrugated stainless steel hose for supplying or removing water. However, this type of liner is used to supply not only water, but also gas. Compared to rubber-metal hoses, the flexibility of the bellows hose is slightly lower, even though it is an extension corrugation. On the market, these products are presented in a variety of options that differ in color, price, size and service life. In recent years, they have almost supplanted metal pipes and are used for sinks, showers, cisterns, washing machines, water heaters, air conditioners, and more.

Each material and equipment has its own advantages and disadvantages. The strengths of the bellows line are:

• high quality stainless material of the product;
• the liner is not destroyed by water hammer;
• long service life due to the reliability of the structure;

• not afraid of a sharp drop in temperature;
• made of hygienically clean material and does not pose a threat to health;
• steel is not combustible;
• capable of supplying water with a temperature of up to 250 degrees Celsius.

Unfortunately, even such a versatile material has its drawbacks:

• the flow of water inside the corrugated metal creates a noticeable noise, especially when several water consumers are turned on;
• the bellows is not as flexible as a rubber or rubber-metal hose;
• high cost of eyeliner.

Increasing noise and vibration can be avoided by using larger diameter hoses or with plastic sleeves.

The eyeliner is made of steel with brand AISI304 in the form of corrugated pipes of various lengths with flared union nuts at the ends. The wall thickness of such a liner is 0.3 mm or more, depending on the manufacturer's documentation and production standards. During the production process, a steel pipe can be additionally processed by a vacuum-thermal method inside a furnace with a temperature of 1020 to 1100 degrees Celsius to give the metal such properties as flexibility. Hexagonal union nuts (fittings) with an internal half-inch thread are connected to the ends of the hose by flaring the edges without using welding. The presence of such nuts makes it possible to exclude twisting of the sleeve during installation. The pressure in the installed bellows is from 10 to 16 atmospheres and depends on the type and material of the gaskets used, which crimp the connection.

The corrugation is covered with an additional polymer material that protects the metal from corrosion and high temperatures, and also helps to avoid contact with structures that conduct current. Corrugations with stainless or brass nuts guarantee the absence of cracks and corrosion at the joints and a service life of up to 30-35 years. The liner is tested for microcracks using helium, and for the symmetry of the turns - using metallographic examination. The fitting may indicate the country of manufacture or a specific plant, the type of hose and even the date of its manufacture.The package may additionally include special gaskets for the connection and various documentation.

The dimensions of the bellows line can vary in a fairly wide range, ranging from very small hoses to meter pipes. The bellows is available in two types:

• with a fixed length (20 cm, 30 cm, 40 cm, 50 cm, 60 cm, 70 cm, and 80 cm);
• folding (for this type of liner, the range of values ​​is indicated from the minimum to the maximum 140-250 mm, 200-350 mm).

Flare nut connecting diameters can be 1⁄2, 3⁄4, 1 ", 11/4, 11/2 and 2" with allowable pressures ranging from 10 to 20 bar depending on which gasket is used. The corrugated pipe is flexible enough to maintain permeability even when fully bent, thereby ensuring smooth operation of the entire system. Hose end connections can be secured with a nut-nipple, nut-nut or nipple-nipple system.

The materials for the manufacture of the bellows line differ depending on what kind of substance will be carried through the pipe.

This eyeliner is made of stainless steel AISI 316to which nuts or nipples made of harder steel are welded AISI 304 or AISI 303... A copper, plastic, rubber or aluminum gasket is placed in the pipe joint. Some manufacturers make fittings or nuts using carbon steel. However, it is not recommended to use a liner with steel of different grades, since material corrosion occurs faster at the welding point. In some cases, the manufacturer may solder the fittings with tin or even glue them, which also reduces the strength and durability of the product.

This seamless corrugated tube is also made of steel, but coated with PVC in various colors. Such a shell protects the flexible hose from aggressive media, prevents gas leakage and serves as additional electrical insulation. If the liner has been processed by firing, it can be stretched in length up to two times.

Flexible bellows connection allows replacing a section of the pipeline where installation of rigid structures is impossible. It is used to connect faucets and various plumbing equipment (for example, a washing machine, toilet bowl and bathtub). The bellows is used to supply gas to heating systems, gas stoves and water heaters. With the help of such a connection, you can connect various climatic equipment and automatic fire extinguishing systems or compressors. Bellows are often used in large industrial plants to supply steam, oil products, chemical solutions and even bulk substances.

When working with flexible types of liner, certain guidelines must be followed. Do not allow a bend radius smaller than allowed in the documentation. Bending at the ends closer than the distance specified in the documentation is unacceptable. Avoid kinking, re-bending, and over-stretching hosesas this can lead to tears and cracks. One of the most important recommendations is not to overtighten the nuts when tightening, so as not to damage the gaskets and not to strip the threads. Damaged liners are not repaired, but completely replaced with new ones.

Today, bellows liners can be purchased from both domestic and foreign manufacturers. One of the main Russian manufacturers is the company "Monolith"who registered the trademark "Monoflex"... The quality of the products of this company is guaranteed by foreign technologies used in the production process. Also, the products under the brands have proven themselves. "Aquatekhnika" and Flexiline.

Also, a budget version of the bellows is offered by the company Zurflex from Belarus.At a reasonable price, the quality of this brand's products can be compared with large European manufacturers, for example, a German company Witzenmann. The traditional quality and reliability of the products of this company, located in Germany, is presented not only in bellows wiring, but also in other types of various plumbing equipment.

One of the leading suppliers of water wiring at the moment is a Turkish company Ayvaz, the equipment of which has practically no competitors in terms of technical parameters. Their wiring is reliable, durable and has a well thought-out design that excludes unnecessary elements. Italian companies are the undisputed leader in the flexible gas conduit market Emiflex and Idrosapiens... Bellows hoses of these companies in Russia are certified by Rostest and Gosgortekhnadzor. The service life of such liners is up to 15 years and more.

Often on the market, under the logos of world brands, you can buy a fake from China. However, there are two categories of Chinese equipment:

• products manufactured in China by the official order of European companies;
• pirated wiring.

In the first case, the customer-digging moves production to China to reduce costs due to the cheapness of labor and materials. In the second case, the quality of the products leaves much to be desired, which can lead to leakage of water and gas. Also, one should not exclude the presence of various hazardous chemical and even radioactive compounds in the product. The price, unfortunately, is not a guarantee of the quality of the product, therefore it is necessary to carefully study all products and request photocopies of the necessary certificates.

In order to choose a high-quality bellows liner, many parameters should be taken into account:

• The hose must be suitable for temperature and pressure. If any type can be used for the dishwasher, then for the boiler only a special hose marked for hot water. With what water (hot or cold) the eyeliner is used, the color designation on the pipe or fittings will show: blue exclusively for cold water, red or two-color for cold and hot water.
• The bellows is selected in such a way that its inlet fittings are threaded directly with the connected machines and equipment, without various adapters. To do this, we produce liners with fittings and unions of various sizes.

• You should buy a product with more flexibility, which can be determined in a simple way by holding the pipe horizontally and comparing the angle of inclination.
• Fittings and union nuts should only be made of stainless steel or brass and are of sufficient thickness. Hardware made of cheap aluminum indicates a fake and low quality of the product. The corrugation itself must also be made exclusively of stainless steel. It is quite easy to distinguish it from aluminum, since aluminum is very light in weight.
• If the hose is to be used for drinking water supply, it must be checked for a strong chemical odor. If the smell is present, then the product contains materials that can harm human health.
• All other things being equal, the choice should be stopped on the products of well-known European manufacturers, upon sale of which copies of the necessary certificates are provided. You should not purchase eyeliner with defects visible to the naked eye: damaged fittings or nuts, deformed gaskets, poor-quality corrugation. Products made of galvanized steel inevitably rust within 1-2 years after installation, therefore, they are also not recommended for purchase.

• It is best to choose the length of the hoses with a significant margin, since it is not recommended to stretch the bellows too much: this will reduce its service life. A high-quality product must necessarily be sold complete with a technical data sheet and a warranty card for a period of at least one year.
• Although the bellows liner is considered the most reliable and durable, manufacturers recommend conducting an inspection at least once every six months for preventive purposes and immediately replacing elements on which any defects are found.

For more information on bellows water liner, see the next video.