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SV DIRECTIONAL CONTROL VALVE: TROUBLESHOOTING

Observation – Internal leakage

Causes Solution
1. Damage (scratches, chips, etc.) to seal ring 1. Replace seal rings (see maintenance manual)
2. Damage (scratches, galling, etc.) to rotor 2. Replace rotor (see maintenance manual)
3. Wear on seal ring sealing surface resulting in material loss after millions of cycles 3. Replace seal rings (see maintenance manual)
4. Wave springs under seal rings failed 4. Replace wave springs (see maintenance manual)
5. Rotor has lost alignment with seal rings because of worn out shaft pins or detent disc 5. Replace shaft or detent disc (see maintenance manual)
6. Seal ring elastomers (O-ring and/or back-up ring) are worn out or damaged 6. Replace elastomers (see maintenance manual)

Observation – Valve is locking up or exceedingly difficult to shift

Causes Solution
1. Inadequate return circuitry/piping results in back pressure and inadequate drain 1. Ensure pipe diameter in return line matches the valve (e.g. minimum 1” pipe ID for SV-100, 1” valve)
2. Restrictions in return circuitry (excessive bends, check valves, etc.) 2. Remove restrictions
3. Case drain not installed with “All Blocked” (rotor) valve 3. Install case drain piping from valve to tank
4. Valve installed incorrectly with pressure connected to the return port 4. Install valve correctly
5. Damaged or bent detent disc rubbing on housing 5.  Replace detent disc (see maintenance manual)
6. Dirt and/or debris trapped between thrust washer and rotor 6. Disassemble and then clean valve
7. Worn or missing shaft pin(s) causes rotor to rub on housing 7. Replace shaft (see maintenance manual)
8. Seal rings are completely worn 8. Replace seal rings (see maintenance manual)
9. Galling between rotor and seal ring 9. Replace seal rings and rotor (see maintenance manual)
10. Worn or damaged thrust washers are causing ball bearings to not roll properly or bind in race 10. Replace thrust washers and ball bearings
11. Inlet pressure exceeds valve rating 11. Adjust upstream pressure as appropriate

Observation – Leakage around shaft

Causes Solution
1. Shaft O-ring is worn out 1. Replace O-ring (see maintenance manual)
2. Shaft hole in housing is wallowed out (enlarged) as a result of heavy use or excessive actuator load 2. Replace housing. Inspect shaft for wear/damage and replace if necessary. Reduce actuator load.

Observation – External leakage between housing and body

Causes Solution
1. Body O-ring is installed incorrectly 1. Correctly replace body O-ring (see maintenance manual)
2. Valve bolts are loose 2. Replace body O-ring and tighten bolts as specified in the maintenance instructions
3. Excessive back pressure in housing caused by inadequate return circuitry or downstream restrictions 3. Check return port pressure and correct circuitry if it exceeds maximum rating for valve. Replace body O-ring.
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