Instruction Manual
D100398X012
ET Valve
November 2017
14
For the two‐piece seal ring, The ring cannot be reused because it is a closed ring which must be pried and/or cut from
the groove. Once the seal ring is removed, the elastomeric backup ring (key 29), which is also a closed ring, can be
pried from the groove.
CAUTION
To avoid damaging the seal ring, slowly and gently stretch it for the following procedure. Avoid jerking sharply on the ring.
To install a new two‐piece seal ring, apply a general purpose silicone‐base lubricant to both the backup ring and seal
ring (keys 29 and 28). Place the backup ring over the stem (key 7) and into the groove. Place the seal ring over the top
edge of the valve plug (key 2) so that it enters the groove on one side of the valve plug. Slowly and 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 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 (5.375 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 (5.375 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.
CAUTION
To avoid damaging the seal ring, slowly and gently stretch it for the following procedure. Avoid jerking sharply on the ring.
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).
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