Selection of valves for superheated steam and heating steam, as well as manufacturers. Thank you all, fellow sailors

Introduction to the User Manual for Temperature and Pressure Reduction Devices (Part 1) Zigong Dongneng Power Station Valve Co., Ltd. (formerly Zigong Dongfang Power Station Valve Factory) is a specialized manufacturer in the design and production of temperature and pressure reduction devices. Consultation phone number: [0813-5105008] Purpose of Temperature and Pressure Reduction Devices: This device reduces the pressure and temperature of the incoming steam, using pressure and temperature reduction mechanisms, to bring it to the parameters required for use. It is a temperature and pressure reduction device widely used in industries such as electricity, petrochemicals, light industry, textile printing and dyeing, pharmaceuticals, and cogeneration. II. Instructions for ordering regarding the main technical parameters of the temperature and pressure reduction unit: Steam flow rate Q: t/h --- --- Inlet steam pressure P1: MPa; Inlet steam temperature T1: Outlet steam pressure P2: MPa; Outlet steam temperature T2: Pressure of the cooling water Pb: MPa; Temperature of the cooling water Tb: III. Brief description of the structure of the temperature and pressure reduction unit: This unit consists of a pressure reduction system, a temperature reduction system, safety protection mechanisms, steam pipelines, and a thermal control system. 　　　　1. Pressure reduction system: The pressure reduction of steam is achieved by a temperature and pressure reducing valve. The temperature and pressure reducing valve is connected to an electric (or pneumatic, the same below) actuator; when the steam pressure in the pipeline changes, the electric actuator activates, causing the valve disc to move up and down in order to adjust the pressure reduction ratio and keep the steam pressure in the pipeline within the specified range. 　　　　2. Temperature reduction system: It consists of an electric control valve, nozzles, mixing pipes, throttlers, and throttle valves. After passing through the electric control valve, the desuperheating water flows into the desuperheating and depressurization valve, where it is sprayed into the valve body through the orifices in the valve disc, allowing the water and steam to mix directly thereby achieving desuperheating of the steam. 　　　　When the pressure of the supplied attempering water exceeds the operating pressure by a significant margin, in order to ensure that the electric control valve and nozzle can still function properly, a throttle is installed on the feedwater pipe upstream of the electric control valve. This keeps the pressure of the attempering water as it enters the electric control valve within the specified range. 　　　　Electric control valves typically use a plunger type, with their valve stem connected to the electric actuator. When the steam temperature in the mixing pipeline changes, the temperature control system controls the electric actuator, which in turn moves the stem of the electric control valve, thereby adjusting the amount of water sprayed from the nozzle into the valve body and keeping the steam temperature in the pipeline within the specified range. 　　　　To prevent a sudden drop in the pressure of the cooling water in the feedwater pipe during operation, which could cause steam to flow back into the feedwater pipe through the nozzle, a check valve is installed on the cooling pipe near the nozzle. 　　　　3. Safety protection system: A spring safety valve (or main safety valve) is used to provide safety protection. When the steam pressure inside the pipe exceeds the permissible value, the safety valve automatically opens to release the steam. When the pressure returns to the specified value, the safety valve closes automatically. Maintain the secondary steam pressure within the allowable range to ensure the safe operation of equipment and pipelines. 　　　　4. Thermal control system: It enables control of electric temperature and pressure reducing valves as well as electric control valves, and is available in various modes such as automatic control, remote control, or on-site manual control. (Automatically selected when the user places an order) IV. Precautions for installing the temperature and pressure reduction device 　　　　1. Install them in sequence according to the numbers indicated in the overall layout diagram of the system. 　　　　2. A gate valve should be installed at the inlet of this device for opening and closing. 　　　　3. A fixed support must be installed below the safety valve of this device, and a sliding support should be provided at an appropriate position at each end of the device. Thermal compensation or natural compensation measures should be considered at the connections between the two ends of the device. A drain must be installed at the lowest point at an appropriate location on the steam outlet. 　　　　The aforementioned gate valves, supports, compensation measures, steam traps, etc. shall be resolved by the user based on the above circumstances. 　　　　4. The signal wires connecting the on-site instruments to the thermal control cabinet should be shielded wires with a single core of 1 mm2 or larger: three-core shielded wires are used for thermoresistors, two-core shielded wires for pressure transmitters, and four-core shielded wires for actuators (for integrated actuators that do not require feedback signals) or six-core shielded wires; the grounding resistance should be less than 4 ohms. The main power supply cable should be of 2.5 mm2 or larger, and all instruments that require grounding must be properly grounded. Refer to the on-site wiring diagram for details. 　　　　5. Install the inlet and outlet thermal resistors and pressure transmitters strictly in accordance with the installation diagrams and technical documents, ensuring they are not installed in the wrong order. We shall bear no responsibility for any damage resulting from installation errors. 　　　　6. When installing the various valves, attention must be paid to the flow direction of steam and desuperheated water. 　　　　7. After the installation of this device is complete, remove the valves from the pressure reduction system and the water supply system, and blow out the entire pipeline to remove debris such as welding slag and spatter from within it. Once it has been confirmed that there are no impurities left, reinstall the removed valves, and then conduct a hydrostatic test. The test pressure is 1.5 times the pressure applied to the workpiece. During the test, the safety valve must be removed and replaced with a sealing plate; thereafter, pressure is applied and held for 5 minutes, checking to ensure that there are no leaks at any of the connections. 　　　　8. Special warning! If there is dirt such as weld slag inside the pipeline, it will block the orifices in the valve body, preventing the temperature and pressure reducing valve from functioning properly; in severe cases, it can cause the valve disc to get stuck, damaging the valve and the electric actuator. V. Operation of the temperature and pressure reduction device 1. Preparatory work before operation: 1.1 It is necessary to check whether the connections between the flanges on the pipes, as well as between the flanges and accessories, are in good condition, whether the valves operate properly, and whether the safety valves function correctly ； Check that all instruments are in good condition and confirm that their circuits are connected. 　　 1.2 Close the gate valve at the steam inlet and the stop valve at the desuperheating water inlet. Operate the electric actuator manually to verify that the travel of the pressure reducing valve and the feedwater control valve, as well as their positions when fully open and fully closed, match the travel of the electric actuator. Then determine whether the valve and electric actuator can be put into normal operation. 　　　　1.3 Before operation, this device, as well as the pipes and accessories leading to the user, must be preheated. The preheating procedure is as follows: slightly open the pressure relief valve (about 5% of its full stroke), close the stop valve at the inlet of the desuperheating water, and then slowly open the gate valve at the inlet to introduce new steam for preheating. During preheating, the steam pressure should be between 0.02 and 0.05 Mpa, with a preheating time of >60 minutes. 2. Trial operation: After the preheating is complete, open the stop valve at the feedwater cooling water inlet, and gradually open the gate valve at the steam inlet. Increase the pressure at a rate of 0.1–0.15 Mpa per minute. Meanwhile, operate the pressure reducing valve and the electric control valve manually to bring the steam pressure and temperature to the required levels. During the pressurization process, when the pressure reaches 50% of the rated pressure, manually activate the safety valve. Check whether the safety valve opens and closes smoothly; once confirmed, set its opening pressure according to the regulations. Open the drain valve to discharge the condensate water. Through adjustments, the steam parameters must reach the specified values before it can be put into use. 　　　　Pressure reduction adjustment: Manually adjust the valve position to around 20% (to prevent the pressure relief valve from reacting too slowly and causing the safety valve to activate). Slowly open the inlet gate valve, paying attention to the readings on the secondary pressure regulator. When the secondary pressure approaches the target value, switch the secondary pressure regulator to automatic mode so that the system enters automatic regulation mode. Continue to slowly open the gate valve while monitoring the system’s pressure regulation capability, until all parameters meet the required levels. Debugging completed. Temperature reduction tuning: Manually adjust the feedwater control valve position using the secondary temperature regulator to 10%~20%. Once the temperature of the secondary steam approaches the target value, start the water pump and switch the secondary temperature regulator to automatic mode, thereby putting the system into automatic control. Observe the system’s temperature regulation capability until all parameters meet the required levels. Debugging completed. 3. Precautions during operation: The cooling water used must be pure and softened water, free of any solid impurities to prevent clogging of the nozzles. 4. Shutdown: Before shutting down, the steam supply department and the steam source department should be notified first; then, the temperature and pressure reducing valves as well as the electric control valves should be gradually closed to reduce the pressure and temperature until the valves are fully closed. After the thermostatic pressure reducing valve and electric control valve are fully closed, close the gate valve at the steam inlet and the stop valve on the condensate water pipeline, and open the trap to discharge the condensed water. VI. Inspection and automatic control of temperature and pressure reduction devices 1. Check according to the on-site wiring diagram whether the wiring of various on-site sensors (pressure transmitters, thermal resistors, flow sensors), actuators, water pumps, and control cabinets is correct. 2. Check whether the inlet and outlet thermal resistors and pressure transmitters are installed in the wrong order; the pressure transmitter with a higher range corresponds to the inlet, while one with a lower range corresponds to the outlet. 3. Before powering on the water pump, it must be filled with water to remove all air, in order to prevent the mechanical seal of the pump from being damaged due to operation without water. 4. After confirming that the water pump is filled with water, power on the feed water pump and check whether it rotates in the correct direction. If it reverses, turn off the water pump and swap any two phases of the power supply. Turn off the water pump after the inspection is complete. 5. Check whether the instrument settings are correct; turn on the power to the instruments and verify that the upper and lower limits of the instruments on all panels match the range of the sensors in the field. Also, ensure that the setpoint values for the PID instruments are appropriate, and that the direction of action of the PID instruments is correct – the instrument should be set to reverse action when the pressure control valve is installed in the correct orientation, and to forward action when it is installed in the reverse orientation. The temperature control valve is set to positive action. For specific operating procedures, please refer to the instrument’s instruction manual). 6. Press the “ENT” key on the PID instrument to switch it to manual mode, manually adjust the valve, and check whether the valve can operate across its full range of motion properly. To check whether the instrument components in the control loop are functioning properly. Note: Press the “ENT” key for 2 seconds and then release it to switch from automatic to manual mode (displaying “HXX”) or from manual to automatic mode (displaying the target value). For the remaining settings, please refer to the instruction manual. Compiled by Zigong Dongneng Power Station Valve Co., Ltd

It depends on whether you need a control valve or a globe valve; generally, those available in China are sufficient for such purposes