Azbil VDC - Specification of Control Valves; Construction; Valve Body Section; Actuator

General Azbil Corporation
1-2 VDC, VAC, VST, VAA - Diaphragm Control Valve
1-1 : Specication of Control Valves
The basic model number, valve size, pressure rating and other related specications
of the control valve is indicated on its nameplate. (See Figure 1.) Please conrm that
the process ow condensations the specications match before installation.
Figure 1-1 Nameplate
1-2 : Construction
Control Valves consist of two major sections - valve body and diaphragm actuator.
Di󰀨erent combinations of valve body and actuators, type of connections, types of
materials and other specications result in a control valve that optimally suits the
requirements of process ow control.
1-3 : Valve Body Section
The valve body section consists of a bonnet, a valve plug, a cage or a seat ring, and
other trim parts. The bonnet is assembled to the valve body with stud bolts, nuts and
with gasket, to provide a pressure - tight valve body section. The valve plug in the
valve body is moved up and down by the actuator through the valve stem, thereby
varying the opening formed between the plug and cage or seat ring to control the
amount of ow. (See Figures 1-2 through 1-5.)
1-4 : Actuator
The actuator is a spring - loaded diaphragm motor. It converts a pneumatic input
signal into a mechanical positioning force with its spring and diaphragm, in order
to drive and hold the valve plug at a position corresponding to the pneumatic input
signal. (See Figure. 1-6, 1-7.)
~Note “Air- O-Motor” is Azbil Corporation's trade name for its diaphragm motors
(Models VA1 to 5).