Table of Contents
D4 Valve
Valve Plug and Seat Ring
The Design D4 control valve is designed to allow
easy access to the valve plug and seat ring without
disturbing the packing. Refer to other sections of this
instruction manual if additional maintenance is
required.
Disassembly
1. Remove the loading pressure tubing and any
accessories that may hamper disassembly.
2. Break the hammer nut (key 6) loose with a
hammer. Continue turning the hammer nut by using
a hammer or a large adjustable wrench, tightened
around one ear of the hammer nut. If the bonnet is
stuck on the valve, continue to unscrew the hammer
nut. The hammer nut will contact the spring pins
(key 7) and will force the bonnet out of the valve.
Carefully lift the actuator, bonnet, and valve plug
assembly from the valve body.
The spring pins must always be in
place during valve operation. They
provide a safeguard against injury
when the unit is being disassembled.
3. Use a socket wrench to loosen the seat ring
(key 3).
4. Remove the seat ring (key 3) and seat ring
gasket (key 9) from the valve body.
5. Inspect parts for wear or damage that would
prevent proper operation of the valve body. Carefully
clean the seat ring gasket surfaces and seat ring
threads.
CAUTION
Be careful to avoid damaging the
seating surface on the valve plug or
seat ring as damage in these areas will
allow excessive leakage at shutoff.
Avoid damaging the highly polished
valve stem surface. A damaged valve
stem could cut the packing and allow
process fluid to leak to the
atmosphere.
6. For spring-to-close only: To remove the valve
plug (key 2), drive out the groove pin (key 4) and
unscrew the valve plug from the stem (key 47). If the
groove pin (key 4) is not exposed, verify that
6
Note
downward movement of the stem is not restricted by
instrument linkages attached to the stem (key 47).
Table 7. Torque for Seat Ring (Key 3)
VALVE SIZE
mm
Inches
25.4
1
50.8
2
If the valve plug cannot be easily unscrewed from
the stem, use a punch to keep the stem from turning
as the plug is removed.
7. For spring-to-open only: To remove the valve
plug (key 2), first remove the spring case assembly
(key 27). Remove the adjustment screw nut
(key 44), the upper spring seat (key 29), and the
spring (key 30). Push the adjustment stem (key 31)
fully downward until the diaphragm plate (key 40)
contacts the cap screws (key 38), exposing the
groove pin (key 4) in the plug. If the groove pin
(key 4) is not exposed, verify that downward
movement of the stem is not restricted by instrument
linkages attached to the stem (key 47). Drive out the
groove pin (key 4) and unscrew the valve plug from
the stem (key 47).
If the valve plug cannot be easily unscrewed from
the stem, use a punch to keep the stem from turning
as the plug is removed.
Assembly
1. Make sure the bonnet O-ring (key 8) is on the
bonnet and lubricated with lithium grease or
equivalent (key 49).
2. Install the plug (key 2) on the stem (key 47) and
insert a new groove pin (key 4).
3. Thoroughly clean the seat ring and bonnet
threads in the valve body (key 1). Also clean the
valve body seat ring gasket surfaces.
4. Apply anti-seize lubricant or equivalent (key 54)
to the threads of the seat ring (key 3), and its mating
threads in the valve body.
5. Apply anti-seize lubricant or equivalent (key 54)
to the seat ring gasket (key 9) and install into the
valve body.
6. Screw the seat ring into the valve body. Use a
socket wrench to tighten the seat ring to the torque
values shown in table 7. Remove all excess lubricant
after tightening.
7. Lubricate (key 54) the threads on the valve body
and hammer nut and the contact surfaces of the
bonnet and hammer nut flange. Install the bonnet
and actuator assembly with pinned valve plug onto
the valve body. Tighten the hammer nut using an
Instruction Manual
Form 5755
September 2005
RECOMMENDED TORQUE
NSm
LbfSft
407
300
698
515
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