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Selection of control valves – Regarding the valve body: 1. In applications with normal pressure differences, a top-guided one-way control valve with unbalanced fluid pressure is chosen; it is a single-seat control valve that is compact in size and simple in structure, yet capable of withstanding harsh operating conditions. Due to the use of an unbalanced spool, when combined with a compact multi-spring diaphragm actuator, its size is significantly reduced. Due to the absence of a fluid pressure balance mechanism, this series of control valves is particularly suitable for various fluids. 2. Double-seat control valves are used in high-pressure and high-pressure differential applications; however, sleeve single-seat control valves should be chosen when high requirements are placed on the leakage rate of the valve seat. 3. When the noise level generated by the control system at the control valve exceeds 85 decibels, a noise-reducing control valve should be used. 4. For applications with low pressure and a wide flow range, adjustable ball valves should be selected. 5. For valves that are subject to severe fluid erosion or operate in a flashing condition, indentation is generally adopted, with both the valve core and seat being welded with Stellite alloy. 6. For control valves that operate in strong acid or strong alkali environments, corrosion-resistant measures must be taken; for example, corrosion-resistant stainless steel can be used in the valve design, or the entire valve body can be lined with polytetrafluoroethylene to prevent corrosion. All valves and actuators are coated with sand-proof spray, and all bolts and nuts have anti-corrosive coatings to suit the conditions in Xinjiang. 7. The material and pressure rating of the valve body, internal components, and seals of the control valve shall meet the process conditions at the installation site as well as the requirements of the surrounding environment. The control valve is equipped with an on-site mechanical indicator that allows for the indication of the valve’s opening degree at the location where it is installed. 8. The piping joints of the control valve are supplied with matching flanges, nuts (120%), nuts (120%), and gaskets (200%). The material of the mating flanges must be exactly the same as that of the process pipeline to facilitate welding during on-site construction. 9. Markings and nameplates: Each valve is equipped with a stainless steel nameplate, which should be located in a position where it is easily visible. The nameplate must include the following information. 1) Name of the manufacturer 2) Valve tag number, manufacturing serial number, and model 3) Material, dimensions, and pressure rating of the valve body. The selection of control valves must be carried out using the original manufacturer’s software, based on parameters such as the medium, flow rate, pressure, temperature, viscosity, and process pipe diameter provided at the site; it must also meet all the requirements specified in the design. Regarding actuators: 1. The selection of actuators should take into account the climate and conditions in different regions. For areas in southern China, ordinary-type actuators can be used, while in the cold regions of the north, low-temperature actuators are necessary. For control valve actuators that operate in high-temperature environments for extended periods, high-temperature actuators should be chosen. The actuator used is of the low-temperature type; its mounting brackets are made of low-temperature resistant cast steel, while rubber components such as diaphragms and O-rings are also made from low-temperature resistant materials. The lubricant used is likewise a low-temperature resistant grease. 2. The actuating mechanisms currently used are mostly of the multi-spring type, which are characterized by light weight, small size, high performance, and large output force. The pneumatic actuator is matched to the type and size of the control valve selected ； For large-diameter control valves, a multi-spring diaphragm structure is selected. Regarding Attachment 1, the electrical valve positioner should receive an analog signal of 4–20 mADC, with a supply voltage of 24 VDC. Basic error ≤ ±0.1% ； Fine-tuning range for the insensitive zone: 0.3~10% ； Air consumption: