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. |
Observation – Rotor and valve body have deep scratches
| 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. Dirt and/or debris trapped between thrust washer and rotor | 5. Disassemble and then clean valve |
| 6. Seal rings are completely worn | 6. Replace seal rings (see maintenance manual) |
