Air on, Air off
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What do 667 and 657 represent respectively? I keep getting it mixed up; please help me understand. Thank you
You mean the actuator, right? Where’s the picture?
The Fisher 657 and 667 series spring-loaded diaphragm actuators (Figure 1) adjust the pneumatic output signal from the controller or valve positioner applied to the actuator’s diaphragm by positioning the valve spool within the valve. The zero setting of the actuator depends on the pressure of the actuator spring. The range is set based on the spring stiffness of the actuator and the number of springs available. The Type 657 actuator is a direct-acting actuator ； The Type 667 actuator is a reaction-type actuator. These two types of actuators can provide reliable on/off or throttling operation for automatic control valves. Website for the Chinese instruction manual of Fisher model 657 and 667 spring-loaded diaphragm actuators: http://wwwdocumentation.emersonprocess.com/groups/public/documents/bulletins/d100087x012_chinese.pdf
Thank you for the information provided on the 3rd floor; it’s very useful.