Alfa Laval S936-HFO-Clarifier
Alfa Laval S936-HFO-Clarifier high-speed disc-stack centrifugal separator for fuel/lube oil treatment, large vessels, optimised for heavy fuel oil clarification. Fuel oil capacity 37400 l/h, lube oil capacity 29920 l/h. Bowl diameter 610 mm, motor power 37.0 kW. Part of the S-series — the current generation marine separators with ALCAP control.
Inspector Detail
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Common issues
- Bowl vibration from sludge buildup imbalance if the discharge interval is set too long for the fuel quality being processed
- Seal ring or O-ring leakage in the bowl after extended running between overhauls
- Wrong gravity disc selection for the fuel/water density in use, reducing separation efficiency
- Sliding bowl bottom sticking, preventing a clean discharge cycle
- Frequent or erratic discharge cycling caused by poor fuel pre-heating rather than a separator fault
- Bearing wear or noise developing gradually and only caught by vibration monitoring
- Water/interface detection malfunction on the control unit
Inspection checklist
- Check bowl vibration levels during running
- Check discharge/overflow water for oil carryover, indicating poor separation
- Verify feed temperature and viscosity are within the design range for this unit
- Inspect seal rings and O-rings for condition at scheduled bowl disassembly
- Inspect the disc stack for scale or sludge deposits at overhaul
- Check gearbox oil level and condition
- Check bowl spindle/bearing play against the manufacturer's limit at overhaul
- Verify safety interlocks on the bowl casing function correctly before restart
Service intervals
| Bowl disassembly, cleaning, and seal inspection | per running hours and sludge loading, commonly in the range of 500-2000 hours depending on fuel quality - confirm against Alfa Laval's own PM schedule for this model |
| O-ring/seal kit replacement | at each major bowl overhaul, per manufacturer interval |
| Gear oil change | per Alfa Laval's stated interval for this unit |
| Bearing inspection/replacement | per Alfa Laval's stated running-hour interval |
Typical wear limits
| Bowl vibration | running vibration above the manufacturer's stated trip threshold indicates imbalance or wear and should stop the separator rather than be run through - confirm the exact threshold against Alfa Laval's own limit for this model |
Ranges are typical for this design class. Always confirm against the manufacturer documentation for your serial number.
Critical spares
- Bowl seal ring/O-ring kit
- Gravity disc set (assorted sizes for different fuel/water densities)
- Bowl spindle bearings
- Sliding bowl bottom seal
- Gear oil of the specified grade
Safety
- High rotational speed of the bowl carries significant stored energy - never disturb a running or coasting-down bowl
- Hot HFO handling at the feed and discharge
- Pressurised operating water supply used for the discharge mechanism
- Entrapment/crush risk during bowl disassembly and reassembly
- Hot surfaces at the sludge tank and associated piping
Class survey
Fuel oil purifiers are commonly a Continuous Survey Machinery item where fitted; class wants planned maintenance records for bowl overhauls and bearing condition, and evidence that discharge water quality is monitored where the arrangement requires it.
Components & Design
Component data being added…
Technical Data
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Common failures & inspection points
Paring disc, top disc, mud ports check for dull spots/wash-out; erosion depth >0.2 mm (bowl/cap) or >0.5 mm (other) = replacement.
Leaks at cover/bolted joints/mud outlet; gasket rings (EPDM) change every 6000–8000 h, original parts only.
Check vibration/noise; bearings change in pairs every 12000–16000 h, lubricate correctly; do not increase throughput during vibration.
Belts every 3000 h (tension per manufacturer), cracks/wear; coupling check for axial play (>0.5 mm = fault), corrosion.
Monitor current consumption nominal/actual; clean bowl during shutdown; check pre-filtration + lubrication; limit sludge volume.
Type-general inspection and maintenance points for this equipment category — not model-specific.
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