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Instruction Manual
D103211X012
For all other NotchFlo DST valves, work the retaining ring (key 10) off the valve plug with a screwdriver. Carefully slide
the backup ring, seal ring, and anti‐extrusion rings (keys 9, 8, and 63) off the valve plug.
2. To replace the valve plug stem (key 6), drive out the pin (key 7), and unscrew the stem from the valve plug.
CAUTION
Never reuse an old stem with a new valve plug. Using an old stem with a new plug requires drilling a new pin hole in the
stem. This weakens the stem and may cause the stem to fail in service. If a new valve plug is required, always order a valve
plug, stem, and pin as an assembly. Specify the correct part number of each of the three parts, but state that the parts are
being ordered as an assembly.
A used valve plug may be reused with a new stem.
3. Thread the new stem into the valve plug and tighten it to the appropriate torque value given in table 8. Using the
valve plug pin hole as a guide, drill the pin hole through the stem. Refer to table 8 for drill sizes.
4. Drive in the pin to lock the assembly.
5. If it is necessary to lap the seating surfaces, complete the lapping seats procedure before installing the seal ring.
The Trim Replacement procedure provides seal ring installation instructions and valve reassembly instructions.
Lapping Seats
Key numbers referenced in this procedure are shown in figures 7 through 12, except where indicated.
With metal‐seat constructions, lapping seating surfaces of the valve plug and seat ring (keys 5 and 4) can improve
shutoff. (Deep nicks should be machined out rather than ground out.) Use a good quality lapping compound of a
mixture of 280 to 600‐grit. Apply the compound to the bottom of the valve plug.
Note
NotchFlo DST valves use spiral‐wound gaskets. These gaskets provide their seal by being crushed and therefore should never be
reused. This includes reusing a gasket after the lapping procedure has been performed.
An "old" gasket can be used to lap the seat, however the gasket must be replaced with a new gasket.
To preserve the effects of lapping, do not change either the position of the seat ring in the valve body cavity or the position of the
cage on the seat ring after lapping the seating surfaces. When the parts are removed for cleaning and replacement of the "old"
gaskets, return them to the original positions.
Use the following procedure to lap the seating surfaces.
1. Install the following parts according to the instructions presented in the trim replacement procedure: "old" seat
ring gasket(s) (key 12), seat ring (key 4), cage (key 2), "old" bonnet gasket(key 11), and (if applicable) the "old"
cage gaskets (key 65).
2. Proceed as appropriate:
For a NotchFlo DST balanced valve, install the valve plug and stem assembly (keys 5 and 6)‐‐without seal ring
(key 8)‐‐into the cage.
For a NotchFlo DST unbalanced valve, install the valve plug and stem assembly (keys 5 and 6) into the cage.
3. Install the bonnet (key 18) over the valve stem, and secure the bonnet with four of the hex nuts (key 14).
NotchFlo DST Valve
March 2011
13
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