ET Valve
Instruction Manual
Form 5081
June 2002
11
Figure 7. Typical Balanced TSO Trim
VALVE
PLUG
SEAL
PROTECTED
SOFT SEAT
A7096 / IL
plug. The PTFE material in the seal ring must be
permitted time to cold-flow during the stretching
procedure, so avoid jerking sharply on this ring.
Stretching the seal ring over the valve plug may
make it seem unduly loose when in the groove, but it
will contract to its original size after insertion into the
cage.
For the spring-loaded seal ring, the ring used on a
valve plug having a 136.5 mm (5-3/8 inch) or less
port diameter may be removed undamaged by first
working the retaining ring (key 27) off with a
screwdriver. Then carefully slide the metal backup
ring (key 29) and seal ring (key 28) off the valve plug
(key 2). The spring-loaded seal ring used on a valve
plug having a 178 mm (7-inch) or greater port
diameter must be carefully pried and/or cut from its
groove. Therefore, it cannot be reused.
A spring-loaded seal ring must be installed so that its
open side faces toward the valve stem, or toward the
seat of the plug depending on flow direction, as
shown in view A of figure 16 or 20. To install a
spring-loaded seal ring on a valve plug with a 136.5
mm (5-3/8 inch) or less port diameter, slide the seal
ring (key 28) onto the valve plug followed by the
metal backup ring (key 29). Then install the retaining
ring (key 27) by inserting one end in the groove and,
while turning the plug, press the ring into the groove.
Again, be careful not to scratch any surfaces of the
ring or plug.
To install the seal ring on a valve plug with 178 mm
(7-inch) or greater port diameter, lubricate it with a
general purpose silicone-base lubricant. Then gently
stretch the seal ring and work it over the top edge of
the valve plug. The PTFE material in the seal ring
must be permitted time to cold-flow during the
stretching procedure, so avoid jerking sharply on the
ring. Stretching the seal ring over the valve plug may
make it seem unduly loose when in the groove, but it
will contract to its original size after insertion into
the cage.
CAUTION
Never reuse an old stem or adaptor
with a new valve plug. Using an old
stem or adaptor with a new plug
requires drilling a new pin hole in the
stem (or adaptor, in case an
ENVIRO-SEAL bellows seal bonnet is
being used). This drilling weakens the
stem or adaptor and may cause failure
in service. However, a used valve plug
may be reused with a new stem or
adaptor, except with Cavitrol III trim.
Note
The valve plug and valve plug stem for
2-stage Cavitrol III trim are a matched
set and must be ordered together. If
the 2-stage Cavitrol III valve plug or
valve plug stem is damaged, replace
the entire assembly (key 2, figure 20).
Note
For plain bonnets and style 1
extension bonnets, the valve plug (key
2), valve stem (key 7), and pin (key 8)
are available completely assembled.
Refer to the Key 2, 7, and 8 Valve Plug
and Stem Assembly tables in the Parts
List.
2. To replace the valve stem (key 7), drive out the
pin (key 8). Unscrew the valve plug from the stem or
adaptor.