Common issues
- Screw/rotor wear from dry running or from entrained solids in the pumped medium
- Mechanical seal leakage after long idle periods (seal faces drying out)
- Vibration from misalignment between pump and driver
- Loss of self-priming capability from worn timing gears or seal wear
- Overheating when run against a closed or throttled discharge valve
- Casing corrosion/erosion when handling media outside the pump's design chemical limits
Inspection checklist
- Check coupling alignment (laser or dial indicator) before and after any driver work
- Inspect mechanical seal for leakage or weeping
- Check timing gear backlash and gear case oil level
- Verify relief valve setting and function, if fitted for overpressure protection
- Check suction strainer for fouling or blockage
- Measure vibration and bearing temperature under load
- Check foundation bolts and pump base for looseness
- Confirm rotation direction and self-priming performance on start-up
Service intervals
| Gear case oil change (timing gears) | per the manufacturer's interval, typically 2,000-4,000 running hours or annually |
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| Mechanical seal inspection | annually, or immediately on any sign of leakage |
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| Coupling alignment check | annually or after driver/pump removal |
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| Suction strainer cleaning | weekly to monthly depending on service |
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| Bearing condition monitoring (vibration/temperature trend) | quarterly, overhaul on trend deviation |
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Typical wear limits
| Screw/rotor radial clearance | increases progressively from new-build clearance to a replacement threshold several times larger - confirm the exact figures in the pump's own manual, not a generic value |
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| Mechanical seal face condition | renew on visible scoring or once leakage exceeds a light weep - no single numeric limit applies; follow the seal maker's guidance |
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Ranges are typical for this design class. Always confirm against the manufacturer documentation for your serial number.
Critical spares
- Mechanical seal kit rated for the pumped medium
- Screw/rotor set (matched pair)
- Timing gears
- Bearing set
- Gasket/O-ring kit
- Coupling element
Safety
- This pump handles corrosive/abrasive liquids - use correct PPE when breaking the seal or opening the casing
- Never run against a closed discharge - self-priming twin-screw pumps can pressurise and overheat quickly
- Isolate and depressurise the pump before seal or casing work
- Verify any substitute seal/gasket material is chemically compatible with the pumped medium before fitting
Class survey
If this pump serves a class-relevant system, the surveyor will want overhaul records, seal renewal history, and evidence of capacity/pressure testing after any repair. Confirm the pump's actual service duty against the ship's piping diagrams before treating it as a Continuous Survey Machinery item.
Estimated lifetime: Rotors on twin-screw pumps in this class commonly reach on the order of 20,000-40,000 running hours before overhaul when kept within design limits (correct medium, no dry running); actual life depends heavily on the fluid handled and is not a fixed manufacturer-quoted figure.