In-depth discussion of the control valve procurement and selection of a number of issues

Correct choice of control valve and process pipe end connection form (ring connection / convex connection / clip type). When equipped with a flange, a gasket is required between the valve supplier and the mating flange supplied by the valve supplier and the required flange material, pressure rating and flanged pipe designation shall be indicated in the contract technical attachment. Clamp-type control valve itself, if there is a single flange, flange connection hole of the carrier thread should be metric, if the load on the thread for the English system, the valve supplier should be required to provide connection bolts. If the control valve is equipped with a solenoid valve, it is recommended that the technical parameters of the solenoid valve part in the technical annex of the contract indicate the manufacturer, brand, voltage level, explosion-proof type, material requirements and the travel time of the control valve on and off, The specific model of the solenoid valve shall be specified by the valve supplier according to the final calculation or factory test. However, it shall be indicated whether the supplier is allowed to use the solenoid valve as the pilot valve in the control circuit. In order to shorten the control valve travel time when the actuator of the control valve requires air volume, using the solenoid valve as a pilot valve in combination with a large-capacity pneumatic actuator reduces costs but also increases the number of accessories as the gas The increase in road links means an increase in the number of points of failure. Therefore, when discussing technical attachments, it should be determined whether to permit the use of the pneumatic control scheme. It is recommended that both the diaphragm actuator and the piston actuator be equipped with an air filter pressure reducer that will allow the actuator to be driven by the source of pressure. Prior to delivery, the control valve equipped with accessories should be connected in the factory complete, and tested to meet the technical requirements of the contract accessories. Control valve supplier should be based on the application of the valve, the connection pipe is to determine the pipe, PVC sheath or stainless steel pipe, according to the valve travel time requirements to determine the diameter of the gas pipe connection. General control valve gas pipe connection pipe diameter should not be less than 8 × 1mm, because too small will cause the control valve response speed is too slow, of course, if the control valve switch travel time allowed, you can also use the pipe diameter of 6 × 1mm gas connection pipe. The size of the control valve should be as close as possible to the design document and, if necessary, be communicated to the process piping, equipment and related professional engineers (if no change is allowed, the relevant professional should discuss the decision to change) The corresponding design changes. Should pay attention to the corrosion of the valve. If the purchased control valve cavitation, flash, cavitation, erosion and other issues, should pay attention to whether the appropriate treatment, whether to avoid these problems or minimize the possibility of these phenomena. Valve body, valve core, cage, seat ring material should be made of hard steel or alloy steel, or nitriding treatment or surface coating (such as Galilei too Levin). Control valves should be absolutely avoided cavitation under various application conditions. There must be a confirmation of the dimensions of the valve and the location of the accessories such as the positioner in the technical annex of the contract to determine whether there is any conflict between the installation space for the control valve and the available space for the attachment and the installation location on the drawing. If there is a conflict, we should first confirm whether to change the control valve actuator mounting position or valve attachment installation location and orientation. If the valve position can not be changed, should inform the process, piping, equipment, electrical and other professionals to modify the appropriate layout and design to move. The contractor shall be required to provide the material analysis report of the key components of the control valve, the control valve leakage test report, the pressure test report, the formation of the test report or certificate of conformity, the gas connection diagram, the pressure control procedures and methods Test control valve leakage test procedures, methods, in order to check, review. The bidder shall require the bidder to provide the selection of the control valve sample (the specific model code in the sample, the acronym should be described in detail), the application performance. Technical contract should be required to provide the contractual parties to the valve body and its accessories routine maintenance manuals, accessories, agents and distributors of the contact address, fax, telephone number.

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