The conventional water production process of waterworks is inseparable from the use of valves from the raw water intake, sedimentation tank flocculation and sedimentation, filtering in the filter tank until the final output of water supply from the pump room. Water supply system is the water treatment plant to the treated water through the municipal water distribution network to various water points, this process sometimes requires secondary pressurization. But in different parts of the valve selection requirements are very different. The main difference lies in the caliber of the valve, the type of valve and the control method of the valve. The pipeline is pressure conveying pipeline, the most used are gate valve, globe valve, ball valve, butterfly valve, check valve, soft connection, etc. The painting and internal treatment of each valve must meet the requirements of drinking water sanitation permit.

    1, determine the process requirements, that is, to determine the pressure and flow within the site pipeline. According to the caliber of the pipeline, site working conditions, select the type of valve, combined with the first step of the process parameters, select the valve, and also according to the installation location of the valve, decide whether to add an extension tube.

    2, according to the form of transmission to select the transmission mechanism, the butterfly valve of the water plant is mostly multi-turn rotation mechanism, the gate valve is a straight stroke transmission mechanism. Determine the control mode, for the gas control system is the cylinder and supporting transmission mechanism selection, for the electric control system is the electric actuator selection. For the selection of electric actuator that is based on the full travel time required by the valve, the torque of the valve and other parameters, to determine the speed ratio and output torque of the transmission mechanism, the type of interface, to determine the speed and power of the motor, etc.

    3, consider the level of protection of the actuator, communication methods, whether to choose silicon controlled and other configurations. With the improvement of the level of automation, the water plant requirements for the valve is getting higher and higher, more and more, but no matter how it changes, the conventional selection on roughly within the scope of this paper. The main valves are mentioned in this paper, of course, water plants and exhaust valves, solenoid valves, etc., here will not be introduced in detail.

    4、When the diameter of the pipe is not greater than 50 mm, it is appropriate to use globe valves, gate valves and butterfly valves.
    5、It is appropriate to use regulating valves and globe valves when the flow and water pressure need to be adjusted.
    6、The parts requiring small resistance to water flow (such as the pump suction pipe), it is appropriate to use gate valves.
    7、The water flow should be two-way flow on the pipe section should use gate valves and butterfly valves, not globe valves.
    8、The parts with small installation space should use butterfly valves and ball valves.
    9, in the frequent opening and closing of the pipe section, it is appropriate to use the shut-off valve.
    10, the larger diameter of the water pump discharge pipe should be used on the multifunctional valve.