Viktor Mikhailov Hoses small (10 to 200 mm) diameter are widely used in the creation of utilities since the mid 60-ies. Their share in the total number of pipelines is continuously growing - in Western Europe it is 80-90%, in Russia - about 30-35%. In the housing flexible ducts of small diameter are used to connect to the pipelines of medium and large-diameter wide variety of devices and systems: the end equipment (taps, faucets, air conditioners, washing machines, dishwashers, flushing cisterns, floor heating system, additional sections of radiators, gas water heaters, plates, etc.); water and gas fittings, pumps, ducts, glands supply systems; drains; measuring devices (thermometers, pressure gauges, meters and resource consumption, etc.), other equipment and communications. Currently, a special regulatory framework for flexible small-diameter pipelines do not exist. Therefore, when choosing, installing and operating such pipelines should be guided by the general requirements for piping systems, hot and cold water, sewerage, heating, gas and electricity, as well as the technical characteristics of the end devices and appliances. Cost-effectiveness of the use of flex depends on its complex technical and operational features. When choosing flex necessary to consider not only its cost but also the mechanical strength, resistance to low or high temperatures, reliability, complexity of installation, interaction with different chemical environments, toxic and bacteriological safety, aesthetics and other factors. Flexible tubing of small diameter are different: for the intended purpose: the presentation or removal, the working environment: hot and cold water, gas, steam, air, oil, fuel and other chemicals, operating conditions: pressure, pressure-free, high and low pressure, universal , heat-resistant, heat-and cold-resistant, etc., to cover: thermal protection, shock resistant, special chemicals and other internal and external protective coating; in design:-cast, welded, single-layer, dual layer or multi-layered, smooth, corrugated, reinforced, with the outer and internal (Cordoba) braided, shielded, etc., on the material: steel (ST), copper (M), Brass (A), metal or metal-polymer (MP), rubber (R), polyethylene (PE or HDPE), polypropylene (PP), polyvinylchloride (PVC), combined (Fig. 1), etc. Fig. 1. Device combination pipe 1 - the inner layer of cross-linked polyethylene, 2 - adhesive layers, connecting polyethylene and aluminum, 3 - aluminum layer 4 - the outer layer of PEX Flexible tubing of small diameter are available in two versions: flexible pipes (hoses) - pipe length from a few tens of centimeters to tens of meters attached to the end cap nuts or fittings (end fittings); pipe length from ten to several hundred meters. Flexible Hoses Flexible Hoses made of rubber, plastic, corrugated steel, etc. Sometimes they are provided with braided stainless steel or galvanized steel. As an assembly of elements used two free-set coupling nuts (HS), two fitting with male thread (SHSHNR), two female connector (SHSHVR) or combinations thereof: in one end of the nut, on the other - fitting with external or internal thread (GSHNR or GSHVR). Most hoses are used to connect terminal equipment (plumbing, appliances, heat, etc.) to the pipelines of medium and large diameter. Their main advantages are flexibility and easy installation, defects - non-adjustable length and a low mechanical strength. Fig. 2. Flexible hose Today industry produces special hoses to connect various devices: showers, taps, mixers, washing machines, dishwashers, electric floor heating systems, boilers, and columns, gas cookers, etc. The data sheet specifies a flexible tube devices, which You can connect with it, and substances with which it can work as well when selecting hose must be considered: the type and diameter of the fasteners and piping to connect the device, pressure and temperature of the environment with which it will operate, the temperature in the room where the hose will be installed ; the possibility of mechanical damage, the warranty period and service life of the product; other factors. When you purchase the hose to control the presence of his hygiene certificate data sheet (a product of domestic producers) or a certificate of conformity (product import manufacturers). When installing the hose should do the following: before installing the hose must be inspected for the presence of mechanical, thermal, chemical and other damage that may occur during storage or transport; connection must be carried out using pads. Their material and size are specified in technical requirements for this connection. On most flexible hoses such gaskets are installed by the manufacturer - when installing eyeliner their presence must be checked, for mounting the hose shall be subjected to considerable mechanical stress (twisting, stretching, fracture, etc.); bend radius hose should be 5-6 times higher than the outside diameter products (Fig. 3a, b); terminal fittings is not recommended to delay the effort more than a certain value (specified in the technical certificate hose) hose should not be placed in the preload, it should not be a few twists of a small diameter (Fig. 3c), the hose is not must be twisted (Fig. 3d) when used in combination hose fittings (at one end of nut, on the other - fitting) of the latter is always tightened nut. Fig. 3. Right and wrong connection eyeliner is usually an additional sealing liner is not necessary, but after installation it should be checked for leakage at operating pressures and temperatures. The test is recommended for 30 minutes. Causes of leakage could be: compression of a gasket in a cap nut, insufficient thickness of the strip in the nut, the mismatch of the diameter of the diameter of a landing strip slot. Visual inspection of the hose is recommended every six months. Proceedings of flexible pipes. Their advantages and disadvantages. Mounting methods. Today, domestic and foreign manufacturers are offering consumers a very large range of pipes from various materials. For the manufacture of flexible pipelines in Russia are most commonly used polymers or stainless steel. Compared with steel pipes made of polymers possess by several major advantages: high corrosion and chemical resistance and durability as a consequence. Many manufacturers of plastic pipes offer a guarantee on its products to 25 years. It is believed that with proper operation of such tubes can last 50 years or more. No corrosion products that reduce water quality and clog up the pipe. Less time-consuming washing. No need for a supplementary service and cathodic protection; roughness coefficient of the polymer tube on average 20 times lower than that of steel. This reduces the pressure loss due to friction and reduces the amount of energy required for pumping water through pipes or any other liquid, a small proportion - easy transportation and installation. Ability to supply pipes up to several hundred meters (coils), installation of plastic pipes less time-consuming and it may exercise specialists who are not highly qualified, high hygienic characteristics: negligible microbial fouling, polymer pipes do not alter the taste and smell of water, lack of noise any flow rate, high plasticity of the material reduces the probability of failure in the hydraulic tube shock or freezing, simplifies installation and reduces the use of fittings, low thermal conductivity - less heat loss on the outer surface of the pipe produces less condensation, esthetics, the possibility of staining pipe material in various colors . The main disadvantages of plastic pipes are: low in comparison with the steel strength, low resistance to pressure to rupture, loss of mechanical properties at high temperatures (restrictions on use in heating, hot water, etc.), high coefficient of thermal expansion - in some polymers at 20 times higher than that of steel; aging by ultraviolet radiation, high gas permeability of most polymers. In plumbing systems, utilities Russia polymer pipes are 80-90%, in engineering - up to 70%. More than 90% of these pipes are made of polyethylene, polyvinyl chloride or polypropylene. One of the most promising polymer is polybutene - pipes made of this material retain their properties at temperatures up to 120 ° C. Compound polyethylene pipe (PE) and fittings can be divided into one-piece and split. Permanent connection of plastic pipes made by butt welding. For this purpose a special device with electrofusion couplings or clutches with embedded heaters. Depending on the diameter of the pipe, such devices can be handheld or stationary. Sometimes they are equipped with special vise means for manual or hydraulic supply pipes, beveled edges, etc. The price of these devices can range from 3 to 100 thousand rubles or more. For releasable connection of plastic pipes used steel flanges. For the installation of pipes with a diameter of 50 mm or less is used collet connection with a crimp (compression) fittings that can withstand pressure up to 25 bar (2,5 MPa). They are widely used for connecting polyethylene pipes and joints of polyethylene pipes with pipes of other materials, such as replacing worn sections of steel pipe with polyethylene pipe. Sealed push-in connection is provided with rubber sealing rings. Currently, the Russian market are well represented not only polyethylene pipes, but also connective, distribution and other fittings used to create pipelines of any configuration: welded pipe bends, equal and neravnoprohodnye welded tees, crosses, reducers, flange bushings, etc . Disadvantages of polyethylene: a high coefficient of thermal expansion (up to 18 times higher than that of steel), a rapidly aging by ultraviolet radiation, oxygen permeability, loss of mechanical properties at temperatures above 40-60 ° C. Therefore, in hot water and heating systems use pipes made of the so-called cross-linked polyethylene. This material can operate at temperatures up to 95 ° C and has high durability. The structure and composition of the polypropylenes are divided into homopolymers, block copolymers, and Random Copolymers. In the production of pipes most commonly used Random copolymers - they differ in improved mechanical properties and are resistant to high temperatures. They are obtained by adding ethylene in the polypropylene molecular chain. Maximum operating temperature of pipes and fittings from Random copolymers is 75 ° C or more. Therefore, PPR pipes are widely used for the installation of hot and cold water. They are assembled by the contact thermal welding, by means of fittings or flanges. Deficiencies of polypropylene: a high linear expansion coefficient (10-15 times higher than that of steel), a rapidly aging by ultraviolet radiation, permeability, loss of mechanical properties at temperatures above 75 ° C. Hoses and pipes from polyvinyl chloride (PVC) used for the installation of sewerage and drainage systems, water systems, water treatment, etc. They are mounted in the socket, sealing compounds used rubber sealing elements. PVC pipes of small diameter can be bonded together using a special glue - technology "cold welding". Disadvantages of PVC: high coefficient of linear expansion (several times higher than that of steel), and combustion emits toxic substances at low temperatures increases the fragility of the material, PVC pipe can operate at temperatures over 80 ° C. Steel pipes have high strength, low rate of thermal expansion, resistant to pressure to rupture, high temperatures and UV radiation, impermeability to gases. They are supplied segments relatively short length, so the installation of pipelines extended to account for connecting more than plastic pipe. Thus, one kilometer pipe diameter of 110 m accounted for 84 or more joints. In addition, steel pipe not plastic, and where the polymer tube can simply bend the direction of the steel pipe would have to change with the appropriate fittings, that is, two additional compounds. Steel pipe should be used only where the use of plastic pipes is impossible or ineffective - in systems with high pressure, high temperature working fluid, at sites where pipes may be exposed to prolonged static loads, high temperatures or ultraviolet radiation, etc. Connect steel pipe with flanged and threaded connections or welding. Labor and cost of installation of steel pipes is almost always higher than the pipes of the polymer - this is connected with a large proportion of steel, high strength, hardness and the need to use expensive equipment. Copper tubes have high consumer and service properties and their easy to install, but copper is fairly expensive material. So while in our country such pipes are not widespread. In addition, Russia has few specialists who can work with copper pipes. For the installation of copper are most commonly used high-and low-temperature solder or press-fitting. Brazing is carried out using capillary fittings and solder of copper alloy with silver and phosphorus. For copper and brass tubes you must use a special flux. The soldering is carried out at temperatures from 450 to 750 ° C. Heating of copper up to 800 ° C leads to a significant deterioration of its mechanical properties. Connection with the use of brazing high durability, they are recommended for use where the connection is under the terminations. Soldering is recommended for installation of pipelines, which operating temperature will not exceed 110 ° C. As the solder used an alloy of tin and silver, the temperature of the burner - 200-250 ° C. If circumstances do not allow to use an open flame, soldering can be carried out using hot air or electrical contact devices. Compound copper pipe press fitting is not very reliable, so it is recommended where you can not use open flames and has the ability to visually monitor the tightness. Also for copper pipe fittings used SELF that can disassemble and assemble a few times. The compound of copper and steel by the so-called welding-soldering - as the solder used bronze. Composite (or combined) pipes are made from several different materials: polymers, steel, copper, aluminum, etc., combine their advantages. Such as pipe PEX-Al-PEX (crosslinked polyethylene-aluminum-crosslinked polyethylene) have high technical and operational features cross-linked polyethylene and are impermeable to oxygen. Composite pipe may have from two to five or more layers, their technical characteristics are varied and deserve a separate article
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