D22
NOV Mono D22 — Industrial, wastewater, marine.
Inspector Detail
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Common issues
- Stator wear or swelling from chemical incompatibility with the pumped fluid, reducing capacity
- Rotor wear reducing pump efficiency and increasing slip
- Mechanical seal or packing leakage
- Dry-running damage to the stator elastomer if the pump is started without adequate fluid present
- Coupling or universal joint wear on the drive shaft
- Excessive discharge pressure from downstream blockage causing overload trips
- Bearing wear in the gearbox or drive end
Inspection checklist
- Check pump capacity and discharge pressure against baseline performance
- Inspect the mechanical seal or packing gland for leakage
- Check stator condition, where accessible, for swelling, tearing or chemical attack
- Inspect the rotor for wear and coating condition
- Check the drive coupling and universal joints for play and wear
- Verify dry-run protection, if fitted, operates correctly
- Check motor and gearbox bearing temperature and vibration
- Inspect the suction strainer for blockage
- Check alignment between the pump and driver
- Verify the relief valve, if fitted in the discharge line, is set correctly and operable
Service intervals
| Mechanical seal or packing inspection | every 2,000-4,000 hours or per observed leakage |
| Stator and rotor condition check | annually or per performance drop-off |
| Gearbox oil change | per maker's schedule, typically annually |
| Coupling and universal joint inspection | annually |
| Suction strainer cleaning | per operating condition, at least monthly |
Critical spares
- Stator, elastomer grade matched to the pumped fluid compatibility
- Rotor
- Mechanical seal or packing set
- Universal joint or coupling kit
- Gearbox oil
- Suction strainer element
Safety
- Pumps handling wastewater or chemical residues require appropriate PPE and isolation before seal or stator work
- Stored pressure in discharge piping - depressurise before disconnecting
- Rotating drive shaft and coupling guards must be in place before running
- Confirm the pump is isolated and drained before opening for stator or rotor replacement, particularly on chemical or wastewater duty
Class survey
Where this pump serves a class-relevant system such as sewage treatment discharge, surveys typically check that discharge performance and any required treatment process indicators remain within approved limits, alongside standard machinery maintenance record review.
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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