Introduction
When the display panel on your RWO Oily Water Separator shows a fault or alarm message, the clock starts ticking. Your vessel needs to resume bilge water discharge in compliance with MARPOL Annex I, keeping your 15 ppm bilge separator MARPOL compliant, and your team needs to know exactly what the message means, what caused it, and which part —if any — needs to be replaced.
This guide covers every fault and alarm message listed in the official RWO operating manual for the SKIT/S-DEBSPS 1.8, their likely causes, the recommended remedies, and the specific genuine RWO spare parts to order — from bilge water separator spare parts to control components.
All information in this guide is sourced directly from the RWO Operating Instructions for Oily Water Separator System SKIT/S-DEB SPS 1.8, 12th print run, Revision 24.02.2017. Page and section references are included throughout so you can verify each point against your own copy of the manual.
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Understanding the SKIT/S-DEB Control Display
The RWO SKIT/S-DEB is controlled by a PLC-based unit with a 2-line, 20-character backlit LCD display (§9.5, p.27).It shows system status, operating modes, warnings, and fault conditions in plain text — in English or German, depending on how it was configured at commissioning (§9.6d, p.31).
The display operates in two modes: normal operating mode (showing system state) and fault/alarm mode, where special alarm messages alternate with the status display (§9.6b, p.28). When an alarm is active, the Red LED (Failure) illuminates and the fault message appear cyclically on the display (§9.3b, p.26).
Normal Operating Mode — Display States
📖Manual ref: §9.6b, pp.28–29; Table 3 (Meaning of Indicators), p.19
Important: The OMD ALARM state is triggered by the Deckma Hamburg bilge alarm monitor (a 15ppm oil content monitor), not the OWS control unit itself. Both systems must be functioning correctly for MARPOL Annex I compliance (§4.4, p.15).
Complete Fault Reference Table
The table below is a complete reproduction of the RWO fault table (Table 5, §8.2, pp.23–25) with remedies and spare parts information added. Faults are grouped by system area for easier reference. Parts highlighted in green indicate a genuine spare part is recommended.
📖Manual ref: Source: RWO Operating Manual §8.2 Table 5, pp.23–25
Alarm Display Messages — What They Mean
In addition to the fault conditions above, the SKIT/S-DEB control unit displays a set of specific alarm messages on the LCD (§9.6b, p.29). These appear alternating with the normal status display when an alarm state is active. The Red (Failure) LED illuminates whenever any alarm is pending.
📖Manual ref: Source: RWO Operating Manual §9.6b, p.29
The Spare Parts Most Commonly Needed After a Fault
Based on the fault patterns in themanual, the following spare parts are most frequently required. Keeping a basicset of these on board can dramatically reduce vessel downtime.
📖Manual ref: Source: RWO Operating Manual Chapter 12 (Spare Parts), pp.38–44
1. Coalescer Filter (item 34) + Adsorber Elements (items 101, 103)
These are the two filtration consumables at the heart of the SKIT/S-DEB. The oily water separator coalescer filter handles first-stage oil-water separation; the RWO adsorber cartridge elements (activated carbon, 20" and 10") handle second-stage polishing. Both have a finite service life. Replace when OMD alarm persists after calibration, or when pressure difference across the coalescer exceeds 0.2bar (§6.1, p.22) or across the adsorber exceeds 2.8 bar.
Only genuine RWO coalescers should be used for RWO coalescer filter replacement. Non-genuine coalescers allow oil to pass through prematurely, activating the 15-ppm bilge alarm even with a recently replaced filter.
2. Sensor Electrode R1" (item 9)
The three-rod capacitance electrode (§9.7a, p.34) functions as the OWS sensor that measures the accumulated oil level in the separator. It must have the correct capacitance value to work with the PCB. Non-genuine electrodes — even those that look identical — often have different capacitance and will trigger an OIL-SENSOR FAILURE alarm. Annual cleaning and inspection is specified in §6.3 (p.22).
3. AEP Eccentric Spiral Pump Internals — Stator, Rotor, Stuffing Box Packing
The AEP pump (item 14) draws bilge fluid through the separator. Stator and rotor wear is normal over time; stuffing box packing can dry out after extended idle periods and cause insufficient suction. RWO supplies these in matched sets. Specify the correct AEP size (AEP1 through AEP6) when ordering. On restart after a long stand still, manually turn the pump shaft before starting (§5.1.7, p.17).
4. Solenoid Valves — 24V AC (items 23.3, 58.3)
The SKIT/S-DEB uses multiple RWO solenoid valves for marine OWS operation — controlling the oil discharge cycle (item 4), flushing water inlet (item 15), flushing water outlet (item 5), and adsorber bypass (item 58). Solenoid valve failures are a common cause of sequence faults and ‘piston valves do not operate’ faults. Note: the operating voltage is variable — always check and confirm voltage before ordering (§12.1, p.38).
5. Heating Element (item 10)
The heating element assists oil separation by warming bilge water in the separator to the 45°C setpoint. The spare parts list (Table 6a, p.38) specifies a 440V variant. Confirm your vessel's supply voltage before ordering. The thermal sensor set point and heater contactor (item 2K2) should also be checked before replacing the element.
6. PCB / Control Board (CPU-board, item PLC, Art. No. 5120101050)
The PCB controls oil detection, sequencing, and alarm outputs. Failures are less frequent than consumable items but affect multiple functions simultaneously. If electrode replacement does not resolve an oil detection fault, or if control voltage faults persist after fuse and wiring checks, RWO PCB board replacement is the next step. Article number from Table 7 (p.40): SPSPOL201675.
7. Transformer Fuse M6.3A (item 1F2, Art. No. 51311063M1)
A blown transformer fuse is one of the causes of 'No control voltage present'. This is a straight-forward replacement item. If the fuse blows again after replacement, identify the root cause before replacing again. Article number from Table 7 (p.40): 51311063M1.
Recommended Maintenance Spares — Based on RWO Manual Schedule
📖Manual ref: Source: RWO Operating Manual §6 Maintenance, p.22
The RWO manual specifies the following minimum inspection and maintenance schedule. N&P Maritime, your authorized RWO GmbH agent in Singapore, can supply a consolidated annual spares package.
Regular Inspections (§6.1, p.22)
• Check pressure difference across coalescer (max. 0.2 bar) — flush coalescer if exceeded; replace if flushing fails
• Check pressure difference across adsorber (max. 2.8 bar) — replace adsorber elements if exceeded
• Check stuffing box packing on pump — slight leakage (1–2 drops/min) is acceptable; re-tighten or replace if more
• Check suction vacuum at pump suction gauge — inspect stator and rotor if insufficient
Semi-Annual Inspections (§6.2, p.22)
• Check and replace zinc anode (item 41) if necessary
• Check gear motor oil level; top up if required
Annual Inspections (§6.3, p.22)
• Open inspection port —check for sludge deposits; clean if necessary
• Check inner coating —mend damaged spots
• Check seals and piston valves — replace damaged seals and components
• Check and clean sensor electrode (item 9) — replace if necessary
• Check heater element (item 10) function — replace if necessary
• Deckma OMD-24 calibration checks at each IOPP renewal — Deckma Hamburg measuring cells available from N&P Maritime Singapore.