SMB/SB Installation and Maintenance Manual 140-11000 • July 20038-12
Flow Control Division
Limitorque Actuation Systems
8.4.2 SB-2 Reassembly/Stem Nut Installation
Piece numbers refer to Figure 8.4.
1. Replace the Stem Nut (piece #20).
a. If the actuator is not on the valve, the Stem Nut will drop in the Drive Sleeve (piece #11) until it bottoms out on the shoulder
of the Drive Sleeve. Ensure splines are engaged.
c. If the actuator is mounted on the valve, thread the Stem Nut (piece #20) down the stem until the splines hit. Put the actuator in
manual operation. Rotate the Handwheel in the direction to move the stem upward—usually the open direction. The Stem Nut
will lower as the Handwheel turns, until it bottoms out on the shoulder in the Drive Sleeve and the stem starts to move up.
2. Replace the Thrust Sleeve (piece #168) and the Bearing Cup and Cone (piece #169 and #170). Ensure the Quad Ring (piece
#194) and the O-Ring (piece #176) are properly installed. Ensure the Thrust Sleeve engages the splines on the top of the Stem
Nut—the Thrust Sleeve will not rotate if engaged improperly.
3. Clean the Housing (piece #2), flange, and mounting flange of the Spring Housing (piece #163).
4. Install the Spring Housing without any gasket. Measure the gap between the Spring Housing (piece #163) and the Housing
(piece #2).
5. Remove the Spring Housing (piece #163). Install a gasket between the Housing and the Spring Housing. The gasket thickness
should be the same as the gap measured in Step 4, plus an allowance for the compressibility of the gasket material used. If an
exact gasket thickness can not be obtained, use the next higher thickness gasket available.
6. Install Spring Housing (piece #163).
7. Replace Spring Cartridge (piece #173) as an assembly. Install O-Ring (piece #197) in Spring Cartridge Cap.
8. Install Spring Housing Cover (piece #161) using a gasket of sufficient thickness, including allowance for compressibility, to fill
any gap between the Spring Housing Cover and the Spring Housing.
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