Views: 220 Author: Site Editor Publish Time: 2021-10-10 Origin: Site
The filter shall be equipped with triple offset butterfly valves for water inlet, water outlet, backwash water inlet, backwash air inlet, and backwash water discharge. Besides, the switch type pneumatic valve shall be adopted. When constant head and constant velocity filtration design is adopted, the outlet valve should be liquid level control type and the regulating wafer type butterfly valve should be preferred.
Actuated butterfly valve is generally composed of valve body, pneumatic actuator, and accessories, while switch type and pneumatic butterfly valves are realized by matching different accessories. Switch pneumatic valve is generally equipped with solenoid valve, limit switch, and filter pressure reducing valve. The regulating valve must be equipped with positioner to realize the regulating function, which can also be equipped with solenoid valve, limit switch, and filter pressure reducing valve. The following is the specific explanation of several attachments:
1. Limit Switch
The limit switch can feed back whether the on-site valves (such as motorized butterfly valve) are opened or closed in place to the control room.
The full name of solenoid valve is electromagnetic directional valve, whose function is to realize the opening and closing of the valve through power on and power off. Double acting actuator is equipped with 2-position 5-way solenoid valve, while single acting actuator is equipped with 2-position 3-way solenoid valve. Similarly, the solenoid valve can be divided into single control and double control. If the double offset butterfly valve needs to remain open at all times, it needs to be continuously energized, which can cause heating and reduce service life. Dual electric control has coils at both ends, which only requires one of the coils to be energized. Since it only needs to be powered on at the moment of the switch, and the other coil can remain closed for the rest of the time, the dual electric control can prolong the service life.
Filter pressure reducing valve can be used to filter air moisture impurities and reduce pressure, which can extend the service life of cylinder and high-performance butterfly valves. There are many types of filter pressure reducing valve, including separate filter, separate pressure reducing valve, filter-pressure reducing integration valve, and filter-pressure reducing-oil mist device integration valve, which can also be called single-connection, two-connection, and three-connection.
The electric valve positioner and the butterfly control valve form a closed-loop automatic control loop. After 4-20mA signal is input into the valve positioner in the automation system, the double eccentric butterfly valve adjusts the opening of the valve through air intake, so as to realize the proportional and accurate adjustment of process parameters such as medium flow, pressure, temperature, and liquid level in the pipeline, which is the best device to adjust the flow and cut off the fluid.
Single acting cylinder and double acting cylinder need to be selected according to the site conditions. When the air source fails, you should choose the single acting cylinder if the flanged butterfly valve must be in the open or closed position, which has a spring inside. For example, the valve can be kept closed when there is no ventilation, which is also known as the air open valve. The air supply will compress the internal spring and the spring will return to drive the valve stem when the air supply is interrupted. Single acting cylinder has less gas than double acting cylinder, but its torsion or thrust is smaller than double acting cylinder. In the case of sufficient air supply on site, most people will choose double acting cylinder because single acting cylinder is relatively expensive.
