The main valve is considered a backup valve or fail-safe valve. The image below shows the main valve connected to zone 12 on a. This tutorial briefly discusses the differences between electric and pneumatic actuators, the relationship between direct acting and reverse acting terminology, and how this affects a valve's controlling influence. The importance of positioners is discussed with regard to what they do and why they. Control valves are the unseen workhorses of industrial systems, ensuring seamless flow regulation and safeguarding the efficiency of operations. From directing liquid flow to managing pressure, their role is indispensable. If there is a fire in Zone B (the secondary zone), Zone A and B's flow switches would activate. Control valves are part of a control loop that controls a process.
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