SMB/SB Installation and Maintenance Manual 140-11000 • July 20038-18
Flow Control Division
Limitorque Actuation Systems
8.6 SB-4
a WARNING: See Section 4.1 and 4.2 on Safety Precautions and Safety Practices before proceeding with
disassembly.
a WARNING: Extreme caution should be used in the disassembly and reassembly of the spring compensator
assembly.
The SB-4 actuator is a basic SMB-4 actuator with the housing cover, drive sleeve, and locknut modified to provide spring compression
to the stem nut. The disassembly/assembly procedure for the SMB-4 is applicable (Sections 7.3.1, SMB-0, 1, 2, 3, 4, and 4T
Disassembly and Section 7.3.2, SMB-0, 1, 2, 3, 4, and 4T Reassembly), with the following procedures replacing Step 11 and stem
nut removal procedure.
8.6.1 SB-4 Disassembly/Stem Nut Removal
Piece numbers refer to Figure 8.6.
1. Remove the Spring Housing (piece #163).
2. Remove the Thrust Washer (piece #178).
3. Remove the Spring Cartridge Assembly including the Spring Cartridge (piece #173), Belleville Spring (piece #179), and Spring
Cartridge Cover (piece #180).
4. Remove the Bearing Cartridge (piece #168). Bearing Cone (piece #169) and Bearing Cup (piece #170) will come out with the
Bearing Cartridge.
5. Remove the Housing Cover Cartridge (piece #155).
6. Remove the Drive Sleeve (piece #11) in accordance with Step 12 of Section 7.3.1, SMB-0, 1, 2, 3, 4, and 4T Disassembly. If
only the Stem Nut (piece #20) is to be removed, see Step 7.
7. If the actuator is not on the valve, the Stem Nut (piece #20) is accessible. If the actuator is on the valve, bolt the Housing Cover
Cartridge (piece #155) to the Housing (piece #2) using two 1"-8 UNC x 2.5" long bolts.
a. Place the actuator in hand operation.
b. Rotate the Handwheel in the direction to effect a downward movement of the stem—usually the close direction. The Stem Nut
will climb up the stem until it clears its splines.
c. Rotate the Stem Nut off the stem.
8.6.2 SB-4 Reassembly/Stem Nut Installation
Piece numbers refer to Figure 8.6.
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.
b. 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 Bearing Cartridge (piece #168), the Bearing Cone (piece #169), and the Bearing Cup (piece #170). Ensure the
O-Ring (piece #175) and the Quad Ring (piece #176) are properly installed. Ensure the Bearing Cartridge engages the
splines on the top of the Stem Nut—the Bearing Cartridge will not rotate if engaged improperly.
3. Replace the Spring Cartridge (piece #173) as an assembly with Thrust Washer (piece #178) installed in the bottom and the
Belleville Spring (piece #179) arranged as shown in Figure 8.6. Also include the Spring Cartridge Cover (piece #180) and the
O-Ring (piece #181).
4. Replace the Thrust Washer (piece #178) on the top of the Spring Cartridge .
5. Replace the Spring Housing (piece #163) with a 1/32” gasket.
6. Remove the Cover Plate (piece #188). Realign deflection indicator.
7. Pull the Pointer and the Pointer Shaft outward and move to “O” deflection.
8. Push the Pointer and the Pointer Shaft back in and replace the Cover Plate (piece #188).
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