Compact C
NOV Mono Compact C — Transfer, marine, compact spaces.
Inspector Detail
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Common issues
- Stator elastomer wear or swelling from running dry or from fluid incompatibility
- Rotor wear reducing volumetric efficiency and self-priming ability
- Mechanical seal or packing gland leakage at the drive shaft
- Coupling/drive train misalignment causing vibration and premature bearing wear
- Loss of suction lift performance as stator interference wears down
- Overheating from prolonged dead-heading or closed-valve operation
Inspection checklist
- Check discharge flow/pressure against baseline to detect stator wear
- Inspect shaft seal or packing gland for leakage and adjust or replace as needed
- Confirm coupling alignment and guard condition
- Check for abnormal noise or vibration indicating rotor-stator contact wear
- Verify suction strainer is clear and suction lift is within the pump's rated range
- Check the elastomer compatibility record against the fluid actually being pumped
Service intervals
| Seal/packing gland check | per engine room rounds, minimum monthly |
| Coupling alignment check | annually or after any drive-train work |
| Stator/rotor condition assessment | typically 8,000-12,000 running hours or per manufacturer guidance - confirm against actual duty |
| Suction strainer cleaning | as needed per differential pressure, minimum quarterly |
Typical wear limits
| Discharge flow at rated speed/pressure vs commissioning baseline | rebuild is typically indicated once flow has fallen roughly 15-20% below baseline - confirm against manufacturer criteria rather than running to complete failure |
Ranges are typical for this design class. Always confirm against the manufacturer documentation for your serial number.
Critical spares
- Stator (elastomer, correct compound for the pumped fluid)
- Rotor
- Mechanical seal or packing set for the shaft
- Coupling element/insert
- Suction strainer element
Safety
- Never run dry, even briefly - dry running destroys the stator elastomer within minutes and can generate enough heat to be a burn or fire risk
- Isolate and lock out drive power before opening the pump casing or shaft seal
- Check elastomer chemical compatibility before pumping any fluid other than the original duty - an incompatible fluid can swell or degrade the stator rapidly
Class survey
Progressive cavity transfer pumps are not usually a dedicated class survey item unless part of a class-defined system (e.g. bilge or sludge transfer); class instead checks the system it serves - confirm the local requirement before treating this pump as a standalone survey point.
Components & Design
Component data being added…
Technical Data
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Common failures & inspection points
Monitor gland drip rate: 0-1 drop/minute acceptable; >1 drop/minute indicates excessive wear. Measure shaft radial deflection (should not exceed 0.003-0.005 inches). If eccentric wobble transfers to seal area, face contact is compromised.
Disassemble pump at 700-1000 hour intervals to measure rotor/stator internal clearances. Look for abrasion patterns on ridges and grooves of rotor. Check for fluid leakage from pump body. Replace stator if wear exceeds manufacturer tolerances; worn stator allows clearance increase and fluid escape.
Monthly: Check bearing temperature via infrared or bearing housing thermocouple. Quarterly: Monitor vibration signatures (velocity spectrum via FFT, API 610 standards). Bearing wear produces distinct rumble sound vs. cavitation (gravel sound). Replace grease every 4-5 months; ensure U-joints and connecting rod bearings are not stiff (transmits radial motion to seal).
Record baseline suction/discharge pressures at each operating point. Listen for cavitation (gravel-like noise). Check for ship pitching/rolling effects on tank levels. Verify suction strainers are clean, suction valve fully open, suction lift within design margin, and fluid temperature below boiling point. Maintain adequate NPSH margin (typically >2 metres for seawater systems).
For seawater service, verify all wetted parts are Bronze or Duplex Stainless Steel (cast iron fails via graphitic corrosion). Inspect mechanical seal faces and O-rings for salt crystallization. Monitor for unusual discoloration, pitting, or surface roughness. Verify grease seals are intact to prevent saltwater ingress into bearing cavities. Check impeller surface for corrosion initiation.
Type-general inspection and maintenance points for this equipment category — not model-specific.
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