Instruction Manual
D100392X012
EH Valves NPS 8 through 14
July 2014
13
1. With the valve plug (key 3) removed per the Trim Removal procedure, proceed as appropriate:
For the EHD valve, the piston rings (key 8) are each in two sections; remove the sections from the grooves in the valve
plug.
For all EHT valves, work the retaining ring (key 10) off the valve plug with a screwdriver. Carefully slide the backup ring
and seal ring (keys 9 and 8) off the valve plug. Additionally, for the EHT valve with Whisper Trim Level D cage, remove
the two sections of the piston ring (key 30, figure 14).
2. Toreplacethevalveplugstem(key4),driveoutthepin(key5)andunscrewthestemfromthevalveplug(key3).
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 until the stem wedges tightly at the end of the thread. Using the valve plug
pin hole as a guide, drill the pin hole through the stem. Use a 1/4 inch drill for 31.8 mm (1-1/4 inch) stems and a 3/8
inch drill for 50.8 mm (2-inch) stems.
4. Drive in the pin to lock the assembly.
5. If seat lapping is necessary, complete the Lapping Seats procedure before installing the EHD piston rings or the EHT
seal ring. Piston ring and seal ring installation instructions and valve body-to-bonnet reassembly instructions are
presented in the Trim Replacement procedure.
Lapping Seats
Key numbers referenced in this procedure are shown in figure 12 for the EHD valve and in figure 14 for the EHT valve.
A certain amount of leakage should be expected with metal-to-metal seating in any valve. If the leakage becomes
excessive, however, the condition of the seating surfaces of the valve plug (key 3) and seat ring (key 6) can be
improved by lapping. (Deep nicks should be machined out rather than ground out.) Use a good quality lapping
compound with a mixture that contains 280 to 600 grit. Apply the compound to the bottom of the valve plug.
Use the following procedure to lap the seating surfaces.
1. For all designs, install the seat ring gasket or O-ring (key 12), seat ring (key 6), seat ring cap screws (key 7), lower
cage gasket (key 12), cage (key 2), and upper cage gasket (key 12) into the valve body per the instructions in the
Trim Replacement procedure.
2. Install the assembled valve plug and stem (keys 3 and 4)--without piston rings or seal ring (key 8)-- into the cage.
3. For all seating surfaces, install the bonnet (key 1, figure 11) over the valve stem and secure the bonnet with four of
the hex nuts (key 14).
4. Attach a handle, such as a piece of strap iron secured by stem locknuts, to the valve plug stem. Rotate the handle
alternately in each direction to lap the seats.
Note
In order 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. If possible, clean the parts without disturbing their positions. If the
parts must be removed for cleaning, return them to the original positions.
(24 pages)
Manymanuals.com
Manymanuals.de
Manymanuals.fr
Manymanuals.it
Manymanuals.pl
Manymanuals.cz
Manymanuals.es
Manymanuals-pt.com
Comments to this Manuals