Azbil VDD Series, User Manual

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Azbil Corporation
7
Chapter 4: Disassembly and Assembly
This chapter describes disassembly and assembly procedures for overhaul
inspection and for parts replacement due to modification of specifications, etc.
~CAUTION
(1) Before disassembling a control valve that is installed on the piping, be sure to
shut off the fluid in the piping, release the process pressure completely from the
valve, and wait until the valve cools off.
(2) Fluid may remain in the valve when it is removed from the piping. If the fluid
is corrosive, drain it out completely before disassembling the valve.
(3) Wear protective gloves and work in a well-ventilated place.
4.1 Detaching the Actuator from the Valve Body
(1) Apply air pressure to the actuator so that the pointer indicates about 10 to 20 %
above the fully closed position, and maintain that pressure.
(2) Loosen the hex bolts that hold the stem connector, remove the stem connector,
and detach the actuator stem from the valve stem.
(3) Loosen and remove the nuts that hold the yoke, and lift and remove the actuator
from the valve body.
4.2 Disassembly and Assembly of the Valve Body
Disassembly procedure
(1) Remove the hex nuts from the bonnet using a wrench.
(2) Remove the bonnet, spindle, and diaphragm unit from the valve body, paying
attention not to damage the O-ring inside the bonnet.
If the diaphragm sticks to the valve body and does not readily comes off,
gradually detach the diaphragm by slightly tilting the bonnet to the right and
left, and front and back. Never attempt to forcibly detach the diaphragm using a
sharp-edged object such as a screwdriver.
~CAUTION
The inner surfaces of certain models of control valves are lined with glass, hard
rubber, or other material which is not highly resistant to mechanical shock. Do not
apply any strong impact to the valve using a hammer, etc.
(3) The structure of the diaphragm differs according to its material and the valve
size as shown in Table 4-4. To detach the diaphragm from the compressor,
observe the instructions given below.
(a) Fit-in type: Pull out the diaphragm while twisting it.
(b) Screw-in type: Turn the diaphragm counterclockwise.
(c) Bayonet type: Turn the diaphragm 90° clockwise or counterclockwise and
then pull it out.