Instruction Manual
D100425X012
YD and YS Valves
July 2017
12
CAUTION
Never use an old stem with a new valve plug. The use of an old stem requires drilling a new pin hole through 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.
7. The internal parts of the bonnet can now be disassembled, if necessary. For packing replacement, refer to the
section entitled Packing Replacement on page 6.
8.
Standard YD Only—
It is recommended that the cage seal (key 19), seal ring (key 20A), and backup ring (key 20B) be
replaced upon assembly. These can be removed by prying them out of the upper cage grooves with a screwdriver or
a soft‐tipped instrument. If a screwdriver is used, take care not to scratch the surfaces of the cage.
9. The remaining trim parts can now be lifted out of the valve. Under severe service conditions, some of these parts
might have become stuck to the valve. In this case, it might be necessary to use a seat ring puller to remove these
parts. Because there is a slight clearance around the outer circumference of the lower cage (key 4) and seat ring
(key 8), it might be possible to remove these by tapping them loose, if interior room permits.
Assembly
YD (Standard)
1. Use new gaskets, seals, and shim (keys 9, 11, 14, 19, 20A, 20B, and 22) on assembly and wipe all sealing surfaces
with a clean cloth.
2.
For NPS 8 YD,
install the bottom flange adaptor (key 24) and gasket (key 9).
3. Install the seat ring gasket (key 14) and place the seat ring (key 8) on top of the gasket.
4. Install the lower cage (key 4) into the valve, being certain that it fits down over the raised portion of the seat ring.
The narrow portion of the cage windows should point downward.
5. Slip the O‐ring cage seal (key 19) over the bottom of the upper cage (key 3A) and into the cage groove.
Figure 8. Typical Bolting Pattern
A0274‐1
6. Press the backup ring (key 20B) and the seal ring (key 20A), respectively, into the inner groove of the upper cage. It
might be necessary to bend one side of each of these in slightly to accomplish this. Take care not to distort the rings
when doing this.
7. If a new stem (key 5) is to be used, screw the stem into the valve plug (key 2) until it wedges tight at the end of the
valve stem thread.
