Frequently Asked Questions |
| Symptom |
Possible Cause |
Corrective Action |
|
1.) Drive motor running, but shaft between speed reducer and packing gland not turning (SHEARED KEY)
|
- Obstruction in element/backwash arm
- Stop collar not set (VWS-7 to H/VDWS-314)
- High differential pressure
- Packing gland too tight
- Improper tube sheet to seal plate clearance
|
- Remove obstruction
- Set stop collar after setting tubesheet to seal plate gap
- See Symptom 4
- Loosen, replace packing if necessary
- Set clearance to 1 /8², using spacer and stop collar
|
|
2.) Continuous or frequent backwash (differential pressure normal)
|
- Excessive incoming solids
- Faulty or improperly set DP switch
- Optional backwash initiation timer (TR) set too low
- Control panel selector switch in 'HAND'
|
- Reduce solids loading
- Adjust to 4 PSI, replace if necessary
- Adjust setting
- Return to 'AUTO' position
|
|
3.) Strainer not backwashing (differential pressure high)
|
- No power to control panel
- Faulty signal wiring from DP switch
- Faulty or improperly set DP switch
- Control panel selector switch in 'OFF'
- Faulty backwash duration timer(TDR)
- Blown fuse in strainer control panel
- Instrument tubing to DP switchplugged
- Valves to DP switch closed
- Motor overloads tripped
|
- Restore service
- Check wiring
- Check set point, replace if necessary
- Return to 'AUTO' position
- Replace timer
- Determine cause of fuse failure, replace
- Remove tubing and clean
- Open Valves
- Reset overloads
|
|
4.) Continuous or frequent backwash (differential pressure high)
|
- Plugged elements
- Inadequate backwash duration
- Inadequate backwash frequency
- Excessive flow rate through strainer
- Sheared key (see Symptom 1)
- Inadequate backwash pressure
- Excessive incoming solids loading
- Backwash valve closed during backwash (See Symptom 6)
- Excessive back pressure downstream of backwash valve
- Distributor barrel/seal plate worn (Contact surface less than 3 /16² tk.)
|
- Manually backwash strainer, clean elements by hand if condition persists
- Set backwash duration timer (TDR) to 2-3 minutes
- Decrease backwash interval timer
- Decrease flow rate
- Increase strainer operating pressure to 25 PSIG minimum
- Backwash continuously, reduce incoming solids if possible
- Reduce back pressure
- Replace distributor barrel/seal plate
|
|
5.) Drive motor overload tripped
|
- Starter overload heaters improperly sized
- Low voltage supply to motor
- Packing gland too tight
- Speed reducer damaged
- Motor damaged
- No clearance between seal plate and tubesheet
|
- Install proper size overload heaters
- Restore proper voltage
- Loosen packing gland
- Repair/replace speed reducer
- Replace motor
- Set clearance at 1 /8² gap between seal plate and tubesheet when seal plate is fully recessed.
|
|
6.) Backwash valve closed during backwash
|
- Actuator improperly wired
- Valve actuator damaged
- Faulty backwash duration timer (TDR)
- Valve actuator cams loose (electric valve) or cam(s) displaced
- Valve stem stuck or clutch disengaged (electric valve)
|
- Check electrical drawings, re-wire, check wire continuity
- Replace actuator
- Replace timer
- Adjust and tighten cams
- Clean and lubricate stem, push and twist stem to engage clutch
|
|
7.) Water leak at weep holes on drive shaft (VWS-7 to H/VWS-40)
|
- Worn drive shaft gasket or gasket missing
- Loose drive shaft hex and jam nut
- Loose drive shaft stud
- Drive shaft coupling halves not engaged
|
- Replace drive shaft gasket
- Tighten hex nut and jam nut
- Loosen hex and jam nuts, tighten stud, re-tighten hex and jam nuts
- Loosen hex and jam nuts, tighten stud, engage coupling, re-tighten hex and jam nuts
|
|
8.) Water leak at packing
|
- Loose packing gland
- Worn packing
- Worn drive shaft
|
- Tighten packing gland
- Replace packing & split ring gaskets
- Replace drive shaft (Consider use of ceramic-coated drive shaft if problem is persistent)
|
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9.) Excessive backwash flow rate
|
|
- Contact factory regarding throttling backwash flow
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