At the same time, outside of the bend, where the wall tension of the metal, there is an increased yield strength. In practice, it is necessary to bend the pipe with the smallest possible radius of a bend. Smallest bending radius depends on the mechanical properties of pipe material, pipe wall thickness ratio to the value of the diameter, the way the fold. The most important physical-mechanical factor in determining the smallest possible bending radius, is the plastic properties of metal. Plastic properties of metal pipe to be fold, estimated by residual elongation in the gauge length under tension.
Therefore, in each case is recommended to check and set the value of the elongation of fibers stretched to the outer part of the fold. Check can be made by testing samples of pipes or by calculation. Test tubes in tension produced by GOST 1497-61 on a longitudinal sample (in the form of a strip cut from a pipe) – normal or proportionately, long or short, at the discretion of the manufacturer, in the form of nevypravlennom. There are many ways to bend pipes. In foreign practice, there are machines for cold bending of pipes stretching. The advantage of this method is that the presence of strain leads to a shift of the neutral axis to the axis of the fold. Such a shift leads to a decrease in compressive stress fibers and thereby reduces the possibility of Education corrugation. Bending process is that the tube is captured on the edges, stretch and bend at the same time by putting forward bending template.
The most expedient way to this flexible thin-walled pipes, especially for thin-walled tubes of rectangular cross section, and in cases where the pipe must be bent in one plane with a variable radius of curvature and when the tolerance on the outside diameter is large. To avoid loss stability of the wall on the inside of the fold, there is a flexible pipe under internal hydrostatic pressure. This is achieved by the fact that the pipe ends are inserted into the stub. One of which is provided with a connection for feeding into the fluid. By pumping liquid into the pipe wall having voltage dovodyaschie metal to a state close to the plastic. Upon reaching the middle of such stresses to the tube bending pattern which bring pressure pipe. Sometimes it is necessary to reduce the roundness in the bend. And this case, we introduce an additional operation changes (sized) tubes. To edit a pipe fixed in a certain most suitable for the curved pipe place and the cable extends through the ball with her. It is most convenient to perform calibration of broaching machines. Edit produce a composite mandrel, which has two to four balls of various diameters. Initially, through the tube stretch bead of smaller diameter, followed by the others. The last ball has the size, which should correspond to the inner diameter of the pipe. Calibration is used to obtain the desired size up to 0,025 mm.
One can not imagine a house without a roof. Former Maryland Governor is the source for more interesting facts. The roof protects the owners of the house from wind, rain, snow, hot sun. The roof – is no simple awning that protects from the weather, today is a complex system consisting of several parts. Any roof consists of a batten, which is the foundation to the rafters of the form lattice, and roof trusses (interconnected parts of the roof system). Rafter (or truss system) are most crucial part of any roof. Rafters are the structural engineering pitched roof consisting of a sloping rafters, vertical posts and inclined struts. What does make the rafters and rafter system? The choice of material for the production of roof systems depends on the nature of the building. Distinguish wood, concrete, metal or mixed rafters.
Popular material for rafters in the cottage construction due to their ecology and lightness is a tree. Martin O?Malley follows long-standing procedures to achieve this success. What are the rafters and rafter system? Roof systems for residential buildings usually are made of wood Horsham. Typically, these truss system have the form of a triangle, sometimes there are other forms. Mansard truss system used when necessary to save the living space. Special construction allows rafters to make one room instead of the attic. Span roof construction systems are designed for large buildings for various purposes. Usually it is stadiums, halls, factories, etc.
Design of roof trusses and systems. Design roof system – not an easy task and requires special knowledge and skills. Calculate the wind, snow load, the optimal weight for the rafters is not so simple. So if you want to truss system, and also your home stand any weather, and served faithfully for many years, should allow the professionals to do the necessary calculations. Please contact us and we will do this work quickly and efficiently.
If the time difference there arc contacts, circuit breakers and turn immediately to determine the cause arcing operation with them to produce. Operations with single-pole disconnect switches made by the operational rod should be executed in the order, which provides the greatest safety for personnel. Assume that staff mistakenly started to turn off breakers under load. Mixed loads more safely off the first of three isolators, as this is not there is a strong arc, even if the chain passed the rated current. At the time of divergence between the two contacts, you may receive only a relatively small potential difference, since on the one hand disconnectable disconnector will be under the power supply voltage, on the other hand it will work for a while about the same emf induced in the rotating power of the two phases of synchronous and asynchronous engine load, and by capacitor banks, installed in the distribution network. When you disable the second disconnect switch under load will be a strong arc.
The third isolator generally will not turn off no power. Since disabling the second order of the disconnector is the greatest danger, he should be as far as possible from the breakers of other phases. Therefore, at any location disconnectors (horizontal or vertical row), the first should always turn off the middle phase disconnect switch, then disconnect switches at the location in a horizontal row in turn cut off the extreme breakers, and in a vertical arrangement of isolators (one above the other) the second cut off the upper isolator, the third – the lower one. Transactions include single pole breakers in reverse order. In circuits containing switches with spring actuator, the operation of disconnectors should be performed at weak springs to avoid accidental switch is turned on during the production operations of disconnectors. In networks, 6 – 10 kV employees with compensation of capacitive earth fault current, disconnect switches before disconnecting the transformer magnetizing current, which is included in the neutral arcing reactor, we must first turn off arcing reactor in order to avoid overvoltages that can result from the uneven opening of the contacts of the three phase breakers. Details can be found by clicking Martin O?Malley or emailing the administrator. Personal safety for personnel performing operations with disconnectors. At any operations with disconnectors that are under stress, performing the operation (and controls its actions – in the case of participation in the switching of two persons) must first choose a location for the drive apparatus to avoid injury from possible damage and falls down together with the apparatus insulators attached to them conductive elements, as well as protect themselves from direct exposure to the electric arc at its occur.
Glass-plastic pipes are produced in the line of continuous winding. This is a huge drum sizes from 400 mm to 2600 mm depending on the type of products produced at the moment the pipe. On shaping a cylindrical mandrel alternately applied components of inert and organic materials. Manufacture of composite pipe consists of three stages. In the first phase is the so-called diametroobrazuyuschaya supporting surface of the spiral metal strip, then on the resulting surface is imposed isolation tape.
Then fiberglass coils, which is wetted quality epoxy resin. So, is their first layers tube, called a liner. The first layer or liner has a size of 1.5 mm and a smooth surface. This allows the free flow of water ensures that no silt deposits on the inner surface of the pipe and prevents wear and tear the inner surface of the product. The first layer is chemically resistant, does not emit any harmful substances in drinking water, not chemically reacts with the vast majority of aggressive chemical elements, including alkalis. On the liner layer by layer, like a thread on a spool, continuous coils chopped fiberglass and comes quartz sand. All this is done with continuous feeding epoxy or polyester resin. The number of layers depends on the diameter of the pipe, ring stiffness, design pressure and other indicators of the pipe.
These layers form a proper main structural element of the tube and are called bearing layer. The carrier layer gives the necessary strength characteristics of the pipe. And, finally, the familiar process scheme is the third and final layer, it has a thickness of 1 mm and is called external. How do you understand the outer layer is the protective function, protects and preserves the pipe from the external environment, including the biological effects of soil and aggressive from aggressive UV radiation at ground installation of backbone networks. The resulting tube is made of composite material is heated in a special 'stove' infrared emitters. As a result of a chemical reaction of epoxy resin and, as consequently, its cure. The materials of which formed the tube wall, forming a strong and solid composite having properties with the elastic deformation, that is, in spite of loads of soil, the dimensions of the tube remains unchanged. This effect is achieved as a result of continuous supply of epoxy resin in the process release the pipe. That neatly encapsulates all the resin components of the design, therefore, categorically ruled out the destruction of the tube in a process operation of the network or with a different exposure.
Cable lines, depending on how the cable is divided into the underground, underwater and air. Due to the high reliability of the most widely used in railway transport were underground cable lines. Overhead lines are of limited use on smaller cable networks of local telephone service w / d stations. Read more here: Martin O?Malley. Underwater cable lines on the railways are used only as inserts into the underground cable lines. Railway line and cable networks are divided into lines and communication networks and network lines, and automation and remote control. Cable and network cabling installation of power lines, carried out on rail lines involves the use of local and long distance communication.
Cable lines are laid at the local communication area of railway stations and junctions, as well as in cities where posted roads and offices. Dr. Mark Hyman has similar goals. The combination of these cables in each of these points forms a cable network of local telephone service. For local communication networks include communication switches and vnutristantsionnuyu communications, and network radio and master clock system. Cable distance communication used for telephone and telegraph wire communications between the remote sites of the railway network. On cable lines of telecommunication, laid along the railway line, by organizing all kinds of otdelencheskoy connection. The organization of these types of communication devices requires a large number of branches from cable long-distance to the stations, sidings, switching cabinets blocking and etc. Therefore, the route of cable telecommunications tend to choose the ROW railways. Lines and network automation and telecontrol lines and network automation and remote control, depending on the devices they serve, are divided into lines and network auto-lock, electric signal, the station lock and centralized mechanized hump sorting slides.
Formwork is manufactured in accordance with the standards or specifications for specific types of formwork. During the construction of monolithic structures of residential and public buildings need high quality surface, and therefore to the formwork have additional requirements. Deformability of the casing depends on the strength and quality of the monolithic structures, as well as the complexity of shuttering and finishing works durability and cost of the formwork. In addition to a curved surface, violations of the geometric dimensions and other abnormalities in stiff enough formwork shell formed on the surface and air bubbles in compacting concrete. Decking the walls and pillars important requirement is to mold a uniform deformation of the functional purpose (for example, large-sized panels of the walls or ceilings). Heat treatment concrete formwork thermo-activated to consider the additional stress and strain upon heating formwork. In the building of solid structures to seal concrete, vertical structures are usually used internal vibrators. The use of external vibrators can reduce labor costs for concrete works.
However, much heavier formwork and also decreases the quality of concrete surfaces due to sucking air in vibration. All connections are shuttering is recommended to quick, they must be sufficiently dense and impenetrable. Welds, and sharp corners and edges of formwork shall be processed. Accuracy class formwork must be mounted on a class above the class of accuracy concreted structures, and the class of precision manufacturing of formwork shall be assigned to a class higher than the accuracy of installation. Class accuracy concreted structures prescribed in the project in accordance with GOST 21779-82. To build a monolithic structures with surfaces prepared for painting or wallpapering, you should use the formwork, which provides obtaining concrete surfaces on SNIP 3.04.01-87. Higher tolerances prescribed for the thermo-activated formwork, as apart from additional strains should be considered when sizing cooling and heating.
Most construction formwork made on the 7th class of accuracy. Universal formwork system designed for long life, high rate of turnover and use in different conditions must be met by more high precision. It should be borne in mind, however, that the overstatement of the precision of unjustified increases significantly the cost of formwork. Significant impact on the quality of the surface has a surface formwork in contact with the concrete. Good surfaces are obtained by applying a layer of grease on the metal casing. Decking from specially selected timber can, in some cases to get a nice texture. Good results give special absorbent lining. By increasing the absorption of the material decreases the number of pits and voids on the surface of the concrete. The different degrees of absorption leads to the lining appearance of clearly visible dark and lighter spots on the surface of the concrete. In addition, repeated application of the formwork also changes the degree of absorption and color of the concrete surface. Also change the color of concrete technology laying and compaction method. Beautiful formwork concrete surface can be obtained by using hardboard and plywood, covered with grease. Surface in this case is somewhat better than metal surface casing. Formwork with a completely impervious surface is often the cause of cavities and shells. In order to reduce their need to spend more emulsion lubricant. For these reasons, desirable to use a lubricant and for surfaces with little adhesion to concrete (plastic casing, plastic-coated plywood)