Introduction With the progress of science and technology, the control valve used to control the flow of fluid in the production process automation has been widely used in various industries. For thermal and chemical control systems, as the final control of the quality of the process medium and safety indicators for the production of valves, in the stable production, optimal control, maintenance and overhaul cost control play a decisive role. In the control valve applications, calculation and selection is the premise, installation and commissioning is the key, use and maintenance is the purpose. Control valve if improper installation, or debugging is not good, it will not play a regulatory role, or even become a system cumbersome. 1, the installation of regulating valve 1.1 The basic principles of installation The installation of regulating valve should follow the relevant national standards, in strict accordance with the provisions of the design drawings and design documents. For example, construction and installation engineering quality inspection evaluation standards, industrial automation instrumentation construction and acceptance norms, electrical equipment installation construction and acceptance norms; installation of equipment, auxiliary equipment and main materials should comply with the relevant provisions of the existing national standards. 1.2 Pre-installation inspection Check valves and accessories from the factory to the installation prior to transport by the random vibration caused by the transport and handling impact, as well as in the transport and storage process, the environment temperature and humidity changes , These may cause the performance of regulating valve and accessory to change. Therefore, it is necessary to test some of the performance before installation. Control valve installation before the test include the following: appearance, static characteristics, leakage, no-load full travel time, compressive strength, insulation, air tightness and tightness, of which the first five items for the seizure. Of course, there are certain requirements for the place of inspection. For example: the ambient temperature is required at 10 ~ 35 ℃; air relative humidity is not more than 75%; the venue has enough space, and the light is sufficient or lighting conditions; around can not have strong vibration and strong magnetic field interference; Requirements and so on. 1.3 Installation Notes Regulating valve installation, we must ensure safety, ensure the use of performance, ease of operation and maintenance, saving installation costs. Here are four points to talk about the installation of the need to pay attention to the specific issues. 1.3.1 to ensure safety 1) to prevent leakage The installation process does not allow the control valve leak. In use, if the filler culvert, flange gasket and other parts of the formation of cracks or pores may leak. If the operating conditions of the fluid medium are harsh, such as high temperature, high pressure, corrosive fluid, then the damage will be aggravated, the risk of leakage even greater. There are many ways to prevent leakage. During the installation process, the choice of packing, the choice of sealing method, the selection of the valve with good sealing performance and so on are all factors that must be considered. 2) Installation of any design and installation of drain valve, when cut off are inevitably accumulate high-pressure fluid, if the accumulation of fluid potential energy is very large, should be installed in the valve on both sides of the release valve, so that in the After the system is cut off, the energy of the residual high-pressure fluid in the regulating valve can be released, the safety of personnel is protected, the maintenance of the regulating valve is favorable, and the discharge valve capable of limiting the flow can also be considered. 3) Safe Pipeline Before installing the control valve, all the fittings and pipelines should be purged cleanly. The sand, scale and iron filings in the pipeline may damage the inner surface of the control valve, especially the strict sealing surface. When the system pressure fluctuations, it is recommended to install buffer facilities in the pipeline. If the fluid being discharged is a noxious gas or liquid, the line used to discharge the fluid must be connected to a safe location or to a safe, special container to protect personnel from harm and to the environment. 1.3.2 to ensure the performance of When installing control valve, try to ensure that its performance is not affected. This effect destroys the various factors considered when selecting the valve. 1) Control valve, the downstream cut-off valve and the bypass valve installation, the downstream cut-off valve and the control valve between the straight pipe length should take into account the resistance of the pipeline and the impact on fluid flow. Long straight pipe length is conducive to the stability of the fluid after the shut-off valve, the fluid flow can be smooth and reduce the impact of turbulence and reduce noise; straight pipe length is short, the fluid is not stabilized after the shut-off valve into the control valve so that the noise increase However, the short length of the straight pipe helps to reduce the pipeline resistance, increase the pressure drop across the control valve, and reduce the distortion of the flow characteristics, which is in favor of the stable operation of the control system. Therefore, the pros and cons should be weighed and taken into consideration. According to experience, usually the upstream side should have 10D ~ 20D straight pipe section, the downstream side of 3D ~ 5D straight pipe section (D for the pipe diameter), if necessary, should be set rectifier device. When the control valve is disassembled and repaired, the bypass valve can be used to operate the production process. When the controlled flow is too large, with the control valve can not be properly adjusted, as a contingency measure, but also can be used as a bypass valve control valve parallel connection program, the process control. To reduce costs, large-caliber control valve installed handwheel actuators can be replaced by the bypass valve to operate. The installation of bypass valve should be easy to operate, it together with the control valve and upstream and downstream shut-off valve to form a control valve group. Therefore, the installation of regulating valve should be shut-off valve and bypass valve supporting consideration, and at the same time to complete the construction and installation. The nominal diameter of the bypass valve is the same as the nominal diameter of the pipe, and the withstand voltage level is also consistent with the withstand voltage of the process. 2) Relief Valve, Vent Valve, Drain Valve Installation To facilitate the disassembly of the control valve, pressure relief before and after the valve must be released before disassembly. The relief valve should be installed between the control valve and the upstream and downstream shut-off valves . The vent valve and blowdown valve are used to discharge non-condensable gas and condensate entrained in the fluid. If the charged fluid is gas or steam during installation, the blowdown valve should be installed at the lowest point of the control valve group to facilitate condensate discharge. The controlled fluid is liquid, in order to facilitate non-condensable gas emissions, vent valve should be installed in the highest point of the control valve group. 3) control valve and pipe connections Regulating valve and pipe connections are threaded connection, flange connection and welding connections and so on. Threaded connection for the installation of small-diameter control valve, must be installed at the same time removable removable connectors; flange connection with normal flange and clamp connections, pipe connection flange nominal diameter should be adjusted The same diameter of the valve, pressure rating and pressure regulating valve should be the same level, flange and pipe axis perpendicularity allowable deviation of l °; try to avoid the use of welding connections. When connecting the control valve, new projections shall not be formed inside the connecting pipe. For example, gaskets, welding seams, etc. shall not protrude in the pipe. At the same time, it should be noted that the flow of fluid in the regulating valve should be consistent with the direction of the arrow marked on the valve body, under special circumstances may not be subject to this restriction. 4) Installation of Actuator Normally, the actuator is directly connected with the valve body of the regulating valve. However, when the hydraulic actuator, long-stroke actuator, etc. are separated from the regulating valve body, pay attention to the connecting rod of the actuator and the mechanism Movable parts should be flexible, no loose or stuck and torsion phenomenon; connecting rod length is appropriate to ensure that the entire trip range of action stable, flexible and reliable; hand wheel actuator has side and top two installed, the installation should be left with the operating space , Handwheel operation should be flexible, there is no stuck or reversed phenomenon, handwheel direction of rotation and valve opening of the relationship between the label, limit device should be adjusted to play a protective role; hydraulic actuator should be lower than the controller installation, If it must be higher than the controller installation, the height difference should not exceed 1.0m, and the exhaust pipe should be installed in the exhaust manifold, close to the controller installed automatic shut-off valve. 5) The installation of valve positioner Valve positioner valve position detection device and the valve stem or valve shaft directly connected, therefore, the installation should ensure that the feedback signal to correctly and timely reflect the valve position signal and changes. Normally, the valve positioner is supplied with the regulator and the connection between the two is done by the manufacturer. When the production process control valve positioner needs to be added, valve positioner valve position detection device should ensure that the action is correct, reliable and flexible, mechanical feedback lever fulcrum gap should be as small as possible, the valve positioner signal lines should be connected properly, the gas source Pipeline and output lines, the input line should be marked; valve positioner valve position signal should be conducive to the operation and maintenance personnel observation.
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