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ZXDAOrder Code:ZXDAZSHP Price: 126$ Weight: 15 Kg Model Set: ZSHP-50K Control valves need actuators to operate. 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 are required for many applications. (Water system , steam system) *The major constituent parts of globe valves are: The body. The bonnet. The valve seat and valve plug, or trim. The valve spindle (which connects to the actuator). The sealing arrangement between the valve stem and the bonnet. *Diaphragm actuators have compressed air applied to a flexible membrane called the diaphragm. These types of actuators are single acting, in that air is only supplied to one side of the diaphragm, and they can be either direct acting (spring-to-retract) or reverse acting (spring-to-extend). *Positioners (ABB Siemens,CHx1000).To ensure that the full valve differential pressure can be accepted, it is important to adjust the positioner zero setting so that no air pressure opposes the spring force when the valve is seating.