Valve assembly is the final stage in the production process. Valve assembly is based on the premise of the delineation of the technology, the valve of the zero, components together, making it a product of the process. Machine is the most basic unit of valve assembly, a number of parts form the valve parts (such as valve cover, valve parts, etc.). The assembly process of a number of component parts is called part assembly. The assembly process of a number of parts and components constituting a valve is referred to as a total assembly. Assembly work has a great impact on product quality, even if the design is accurate, the parts are qualified, if improper assembly, the valve also failed to meet the requirements, or even produce seal leakage. Therefore, special attention should be paid to the use of reasonable assembly methods to ensure the quality of the finished valve. In the production process in the form of documents designated assembly process known as the assembly process. Common valve assembly methods Valves commonly used assembly methods can be three, that is, a complete exchange method, repair method and matching method. (1) Complete exchange method: When the valve is completely interchangeable, each part of the valve can be assembled without any trimming and choice. The assembled product can meet the specified technical requirements. At this point, the valve parts to be fully processed in accordance with the design requirements to meet the requirements of dimensional accuracy with the position tolerance. The advantages of the full exchange method are: simple assembly work, economy, low skill level of workers, high production efficiency of assembly process, easy organization of assembly line and specialization of production. However, in absolute terms, to take full exchange of assembly, the machining accuracy of the parts higher. Practical for globe valves, check valves, ball valves and other construction of the absolute simplicity of the valve and the small diameter of the valve. (2) Matching method: The valve adopts matching method to assemble. The whole machine can be processed according to economic precision. When assembling, the size of one adjustment and compensation function is matched to meet the specified assembly accuracy. The principle of matchmaking is the same as matchmaking, but different ways of changing the size of the compensation loop. The former is to use the method of selection of accessories to change the compensation ring size, the latter is the method of dressing parts to change the compensation ring size. For example: the control valve model wedge gate valve wedge and the top of the regulator gasket, the valve opening between the two gaskets, etc., is in the assembly accuracy of the size of the chain in the choice of special parts as compensation, through Adjust the thickness of the gasket to achieve the required assembly accuracy. In order to ensure that in different situations can be compensated with a fixed compensation, it is necessary to create a different thickness of the gasket in advance, sleeve compensator hydraulic control valve model for assembly. (3) repair law: repair the valve assembly method, the parts can be processed according to economic precision, the assembly of a regulation, make up for the size of the effect of repair, in order to achieve the required assembly goals. Such as the wedge gate valve and valve body, because the exchange requirements of the processing cost is too high, the majority of manufacturers are using repair process. That is, when the size of the last grinding gate sealing surface is controlled, the opening size of the sealing surface of the valve should be matched with the open size of the valve sealing surface to achieve the ultimate sealing requirement. Although this method has added a plate with the process, but greatly simplifies the front of the dimensional accuracy of the process requirements, with the skilled operation of the panel process, in general, does not affect the production efficiency. Valve assembly process valves are used individually fixed site assembly, valve zero, assembly and assembly of the assembly is carried out in the assembly shop, all the necessary parts and components shipped to the assembly work site. Usually the assembly and assembly of the total assembly by how many workers at the same time, so that not only shorten the assembly cycle, but also facilitate the application of special assembly tools, the technical level of workers is also relatively low. Some foreign manufacturers or high-tech grade valves are also equipped with hanging lines or assembly turntable mode. (1) Preparations before assembly: The valve parts must be machined to remove burrs and weld residue remaining before assembly, to clean and cut fillers and gaskets. (2) the cleaning of valve parts: as a fluid pipeline control valve installed, the lumen must be clean. In particular, nuclear power, medicine, food industry valves, in order to protect the purity of the media and to avoid media infection, the valve cavity cleanliness requirements more stringent. Responding to the valve parts before assembly cleaning, the parts of the debris on the chip, the residual smooth oil, coolant and burrs, welding slag and other dirt to clean. Valve cleaning is usually used to add alkali water or hot water spray (kerosene can also be used to clean) or in the ultrasonic cleaning machine. After the parts are polished and polished, the final cleaning is required. In the final cleaning, the surface of the sealing surface is usually cleaned with gasoline and then air-dried with compressed air and wiped clean with a cloth. (3) filler and gasket preparation: graphite packing due to the presence of corrosion resistance, good sealing and friction coefficient of small advantages, are widely used. Fillers and gaskets are used to prevent media from leaking through the valve stem and bonnet and flange mating surfaces. These parts must be prepared before the valve assembly with the collar ready. (4) valve assembly: the valve is usually based on the valve body parts in accordance with the order and manner of assembly process. Before assembly, zero parts review, to avoid deburring and cleaning parts into the assembly. During the assembly process, the parts should be handled gently to avoid bumping and scratch the finished name. Valve parts (such as stems, bearings, etc.) should be painted with industrial butter. The valve cover and the valve flange with bolts, the bolt, the response said, intertwined, repeatedly, tightened on average, otherwise the valve body, valve cover joint surface due to uneven circumferential force and flow control valve leakage. Handle used when fastening should not be too long, to prevent the preload is too large and affect the bolt strength. Valves that require severe pretensioning should be torque-shielded and screw-tightened to the required torque. After the assembly is completed, the control mechanism should be rotated so as to check whether the activities of the valve opening and closing parts are maneuvering or not. Valve valve cover, brackets and other parts of the device is in line with the drawing direction, after all the review of the valve can only be tested.
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