A monitoring system failure during EGCS operation does not automatically mean a compliance breach. It does mean that the crew must take specific actions under MEPC.1/Circ.883/Rev.1 immediately and that the compliance position for the period of the failure depends entirely on what records exist and what actions were taken.
Getting this right under pressure requires the crew to know in advance what the procedure is, what records need to be made and when reporting to the flag and port state authorities becomes mandatory. This article explains the full procedure, the most common failure modes, what interim evidence to preserve and how to minimise the compliance risk during a monitoring system malfunction. For the broader context of the evidence records that a ship needs for ongoing scrubber compliance, see What Records Does a Ship Need to Prove Scrubber Washwater Compliance?.
| Key thing to remember MEPC.1/Circ.883/Rev.1 governs monitoring system failures for EGCS compliance. The four obligations are: record the malfunction immediately, preserve interim evidence during the failure period, repair as soon as practicable, and report to flag and port state if the failure lasts more than one hour. The compliance position for the malfunction period depends on how well these obligations are met and how complete the interim evidence record is. |
What Is MEPC.1/Circ.883/Rev.1 and Why Does It Matter?
MEPC.1/Circ.883/Rev.1 is an IMO circular that provides guidance on what ship operators must do when the washwater monitoring system of an exhaust gas cleaning system malfunctions. It applies to all vessels fitted with EGCS subject to MARPOL Annex VI washwater monitoring requirements, regardless of whether MEPC.259(68) or MEPC.340(77) is the applicable guideline.
The circular establishes four principal obligations when a monitoring failure occurs:
- Record the malfunction immediately in the EGCS Record Book
- Preserve interim compliance evidence for the period during which the monitor is not functioning
- Repair or replace the monitoring equipment as soon as practicable
- Report the malfunction to the flag state and port state Administration if it persists for more than one hour
These four obligations are not sequential — they run in parallel from the moment the fault is discovered. The record must be made immediately. Evidence must be preserved immediately. The assessment of whether reporting will be required begins immediately. Repair begins as soon as resources allow.
What Is the Step-by-Step Procedure When a Monitoring System Fails?
The table below sets out the complete response procedure in the order in which each action must be taken. This procedure should be incorporated into the vessel’s EGCS Standing Orders and crew training programme so that the officer of the watch knows what to do without having to consult a manual under pressure.
| Step | When | Action | What to do |
| 1 | Immediately on discovery | Record the malfunction in the EGCS Record Book | Date, time, nature of the fault, name of officer making the entry. Do not wait until the end of the watch or until the fault is repaired — the entry must be made immediately on discovery. |
| 2 | Immediately on discovery | Preserve interim compliance evidence | Retain voyage data recorder (VDR) data, vessel position logs, EGCS operational logs and any other data that documents what the EGCS was doing and where the vessel was during the malfunction period. This is the interim evidence that replaces the missing monitoring data. |
| 3 | Immediately on discovery | Assess whether discharge should continue | Consider whether the vessel can demonstrate compliance by other means during the malfunction period. If it cannot, stopping discharge is the safest compliance position. The decision will depend on the location of the vessel, the nature of the fault and the availability of other evidence. |
| 4 | Within 1 hour if fault persists | Report to flag state and port state Administrations | If the monitoring system fault cannot be rectified within one hour, report the malfunction to the flag state Administration and the port state Administration of the next port of call. The report must describe the nature of the fault, the time of discovery and the action being taken. |
| 5 | As soon as practicable | Repair or replace the monitoring equipment | Rectify the fault as quickly as the available spares, technical resources and operational constraints allow. Record the repair in the EGCS Record Book with the date, nature of the repair, components replaced and the name of the person or service agent carrying out the work. |
| 6 | On return to normal operation | Verify monitoring system is functioning correctly | Before resuming EGCS discharge following a repair, verify that the monitoring system is producing valid readings and that all data logging functions are operational. Record the verification in the EGCS Record Book. |
| 7 | Ongoing | Retain all records and correspondence | Retain all malfunction records, repair records, reports to flag and port state and any response received. Keep in the EGCS Record Book and the vessel’s correspondence file for the period specified by the flag Administration. |
| Step 4 is mandatory, not discretionary The reporting obligation in Step 4 is triggered automatically if the monitoring fault is not rectified within one hour. It is not a judgment call for the officer of the watch or the master. Failure to report a monitoring malfunction exceeding one hour to the flag state and port state Administration is itself a breach of MEPC.1/Circ.883/Rev.1, separate from the monitoring failure. This obligation should be prominently noted in the EGCS Standing Orders. |
Should Discharge Continue During a Monitoring System Failure?
Whether EGCS discharge should continue during a monitoring system failure is one of the most operationally sensitive questions crews face. MEPC.1/Circ.883/Rev.1 does not impose an automatic requirement to stop discharge when the monitor fails. However, the decision to continue discharge without a functioning monitor carries compliance risk that the crew and the operator must assess.
The factors that bear on this decision are:
Location of the vessel
If the vessel is in or approaching waters where discharge is subject to geographic restrictions — such as OSPAR internal waters, Singapore port waters, Fujairah or Chinese territorial waters — continuing discharge during a monitoring failure is extremely inadvisable. Without a functioning monitor, there is no parameter-based evidence that the discharge was compliant and no automated protection against exceeding the limits.
Availability of interim evidence
If the monitoring failure is a data logging or communication fault and the sensor itself is still producing valid readings, the crew may be able to preserve parameter data by alternative means — for example by recording sensor readings manually at frequent intervals. This does not satisfy the continuous recording requirement but provides interim evidence of parameter values during the fault period.
Duration of the fault
A brief fault of a few minutes that is promptly repaired and documented presents a much lower compliance risk than an extended failure of several hours. Where the fault cannot be resolved quickly, the case for stopping discharge and switching to compliant fuel strengthens as the duration extends.
Position relative to restricted waters
If the vessel is in open ocean and the voyage plan does not involve restricted waters within the foreseeable monitoring failure period, continuing discharge while actively working to resolve the fault may be a defensible position — provided the interim evidence record is maintained and the malfunction is reported as required.
| The safest compliance position during a monitoring failure The compliance risk during a monitoring failure is minimised by stopping EGCS discharge and switching to compliant fuel for the duration of the fault. This is the most conservative position and eliminates the parameter compliance risk entirely. Whether it is operationally practical depends on fuel availability, voyage economics and the expected duration of the repair. The decision should be made by the master in consultation with the company DPA and documented in the EGCS Record Book. |
What Interim Evidence Must Be Preserved During a Monitoring Failure?
When the monitoring system is not functioning, the vessel must preserve any alternative evidence of EGCS operational status during the failure period. Inspectors reviewing the period of the malfunction will look at everything available to reconstruct the picture of what the EGCS was doing and where the vessel was:
- Vessel position and track from AIS or the voyage data recorder confirming the vessel was not in geographically restricted waters during the failure period
- EGCS operational logs showing whether the EGCS was running, in which mode and at what load during the failure period
- Fuel consumption records showing whether the EGCS was in use or whether the vessel switched to compliant fuel during the failure
- Engine room log entries noting the monitoring system fault, the action taken and the vessel’s operational status
- Any parameter readings obtained by alternative means during the fault period, such as manual sensor readings or grab sample results
- Communications between the master, chief engineer and company DPA regarding the failure and the decision on whether to continue discharge
None of these interim sources individually replaces the continuous monitoring data record. Together they can provide an inspectable body of evidence that the vessel was not in a position of obvious non-compliance during the failure period and that appropriate action was taken.
What Are the Most Common Causes of Monitoring System Failure?
Understanding the most common failure modes helps technical superintendents and crew to carry out effective preventive maintenance and to diagnose faults quickly when they occur. The table below covers the six most common failure modes seen in EGCS washwater monitoring systems.
| Failure mode | Typical cause | How it presents | Resolution approach |
| Optical sensor fouling | Fouling of the optical measurement cell or light source by biological material, oil film or scaling in the washwater sample | Progressive drift in readings, decreasing signal quality, readings that become erratic or implausible | Clean the measurement cell according to the manufacturer’s maintenance schedule. Increase cleaning frequency if fouling is recurrent. Check sample conditioning for particles that should have been removed upstream. |
| Sensor replacement interval exceeded | The measurement sensor has not been replaced within the service interval specified by the manufacturer | Gradual loss of measurement accuracy; readings that diverge from grab sample reference values | Replace the sensor at the specified interval. Retain the replacement record in the EGCS Record Book. |
| Sample conditioning failure | Failure of pressure regulation, flow control, filtration or temperature control in the sample conditioning system | Readings outside the expected operating range; unstable or erratic readings caused by gas bubbles, high solids or incorrect sample pressure | Check sample conditioning components individually. Replace failed components. Confirm sample conditions at the analyser inlet are within the specified operating range before resuming monitoring. |
| Data logging or communication fault | Failure of the data logging system or the communication link between the monitoring unit and the vessel control system or EGCS Record Book system | Gaps in the continuous data record; alarm events not being logged; readings not transmitted to the control system | Diagnose the data logging system. Restore data recording. Ensure that any gap in the data record is documented in the EGCS Record Book with an explanation. |
| Power supply fault | Loss of power to the monitoring system caused by electrical failure, blown fuse or power supply unit failure | Complete loss of monitoring; monitor display blank; no data recorded | Check power supply circuit. Replace fuse or power supply unit as applicable. Restore power and verify that monitoring resumes correctly. |
| Software or firmware fault | Monitoring system software error causing incorrect readings, system freeze or loss of function | Incorrect readings that do not correlate with grab samples; system unresponsive; erratic display | Restart the monitoring system. If the fault persists, contact the manufacturer for software support. Document the fault and recovery action in the EGCS Record Book. |
The most frequent cause of monitoring performance issues in service is optical sensor fouling, which can often be addressed by increasing cleaning frequency without a full system shutdown. Sensor replacement interval exceedance is the most common cause of calibration drift and is entirely preventable through proactive maintenance scheduling.
How Does Monitoring System Failure Affect the Compliance Record Under MEPC.340(77)?
Under MEPC.340(77), the EGCS Record Book must contain a record of every monitoring system malfunction. The absence of a malfunction entry when a fault is subsequently identified from other records — such as a gap in the continuous monitoring data log — is itself a compliance weakness. For a full explanation of what MEPC.340(77) requires for EGCS records, see What Is MEPC.340(77) and How Does It Differ From MEPC.259(68)?.
A monitoring system failure that is correctly handled under MEPC.1/Circ.883/Rev.1 creates a documented event in the EGCS Record Book that port state control inspectors can review. An inspector who finds:
- An immediate and accurate malfunction entry with date, time and nature of the fault
- Evidence that the reporting obligation was met where required
- A repair entry with date and details of the work carried out
- Interim evidence that the vessel was not in a non-compliant position during the failure
will typically treat the failure as a managed compliance event rather than a compliance breach. An inspector who finds a gap in the monitoring data record with no corresponding EGCS Record Book entry, no interim evidence and no report to flag and port state will draw a very different conclusion.
What Spares Should Be Carried Onboard to Minimise Monitoring System Downtime?
The speed with which a monitoring system fault can be resolved depends directly on the availability of spare parts onboard. For a vessel trading without easy access to port facilities, a monitoring system fault that requires a part to be flown in from the manufacturer can result in days of downtime. The table below sets out the key spare items that should be held onboard.
| Spare item | Why it matters | Recommended onboard holding |
| Measurement sensor or optical cell | The primary measurement component — the item most commonly requiring replacement during service life. Availability onboard allows in-service replacement without requiring a service call. | At all times — replace immediately on installation of the onboard spare |
| Sample conditioning filter elements | Consumable filtration media in the sample conditioning system. Fouling frequency depends on washwater composition. | Minimum 3 to 6 months supply onboard based on the manufacturer’s recommended replacement interval |
| Pump and valve O-rings and seals | Consumable sealing components in sample pumps, valves and flow control equipment | Minimum 12 months supply based on service history |
| Fuses and power supply components | Electrical protection and power supply components. Failure can cause complete monitoring system shutdown. | Minimum quantities as specified in the monitoring system O&M manual |
| Reagents for reference calibration | Where the monitoring system requires periodic calibration against a reference standard, reagents must be available onboard | As specified by the manufacturer for the calibration interval |
Rivertrace provides spares packages and planned maintenance agreements for the SMART ESM designed to minimise monitoring system downtime and ensure that the key consumable and replacement components are available onboard. For marine vessel operators seeking to review their SMART ESM spares holding, contact the Rivertrace service team.
How Should Crews Be Trained to Respond to a Monitoring System Failure?
The effectiveness of the malfunction response depends on whether the crew know the procedure before the fault occurs, not after. The MEPC.1/Circ.883/Rev.1 obligations — record, preserve, repair, report — need to be embedded in the vessel’s EGCS Standing Orders and the crew’s operational training.
Effective training and preparation for a monitoring system failure includes:
- EGCS Standing Orders that include a specific section on monitoring system malfunction response, setting out the four MEPC.1/Circ.883/Rev.1 obligations in plain, actionable language
- Contact information for the flag state Administration and the port state Administration of the next port of call, available to the officer of the watch without having to search for it during a fault
- A standard EGCS Record Book entry template for monitoring system malfunctions, so that the officer making the entry covers all required information in the correct format
- Familiarity with the monitoring system’s self-diagnostic functions and fault codes, so that the nature of the fault can be accurately described in the malfunction entry
- Training in the interim evidence preservation actions, so that VDR data, position logs and operational logs are secured promptly on discovery of the fault
- Drill or tabletop exercise covering the monitoring failure scenario, including the reporting obligation trigger and the decision on whether to continue discharge
| False alarms during startup are a separate issue from genuine failures Monitoring systems that generate false high-parameter alarms during EGCS startup, load changes or mode transitions can lead crews to develop alarm fatigue and to dismiss alarms without investigation. This is a distinct operational problem from a genuine monitoring system failure and must be addressed through maintenance and calibration review rather than by treating all alarms as nuisance events. A monitoring system that generates false alarms is not functioning correctly and the underlying cause should be investigated and documented in the EGCS Record Book. |
Frequently Asked Questions
What should a ship do if the scrubber washwater monitoring instrument fails?
Under MEPC.1/Circ.883/Rev.1, the crew must immediately record the malfunction in the EGCS Record Book with the date, time and nature of the fault. They must preserve interim compliance evidence including position logs, VDR data and EGCS operational logs. The monitoring equipment must be repaired as soon as practicable. If the fault persists for more than one hour, the malfunction must be reported to the flag state Administration and the port state Administration of the next port of call.
Can EGCS discharge continue if the washwater monitor fails?
MEPC.1/Circ.883/Rev.1 does not impose an automatic requirement to stop discharge when the monitor fails. However, continuing discharge without a functioning monitor carries significant compliance risk, particularly in or near geographically restricted waters. The safest compliance position is to stop discharge and switch to compliant fuel for the duration of the fault. The decision should be made by the master in consultation with the company DPA and documented in the EGCS Record Book.
When must a scrubber monitoring system failure be reported to authorities?
Under MEPC.1/Circ.883/Rev.1, a monitoring system malfunction that cannot be rectified within one hour must be reported to the flag state Administration and the port state Administration of the next port of call. This is a mandatory obligation, not a discretionary decision. The report must describe the nature of the fault, the time of discovery and the action being taken.
What interim evidence should be preserved during a monitoring failure?
The crew should immediately secure vessel position and track data from AIS or the VDR, EGCS operational logs, fuel consumption records, engine room log entries covering the fault period and any parameter readings obtained by alternative means such as manual sensor readings or grab sample results. Communications between the master, chief engineer and company DPA regarding the failure and the operational decision taken should also be retained. This interim evidence collectively supports the compliance position for the failure period.
What are the most common causes of scrubber washwater monitoring system failure?
The most common causes are optical sensor fouling from biological material or oil film in the sample, exceedance of the sensor replacement interval causing calibration drift, sample conditioning failures affecting pressure or flow to the analyser, data logging or communication faults causing gaps in the continuous record, power supply failures causing complete loss of monitoring, and software faults causing incorrect readings or system freeze.
What spares should be held onboard for the washwater monitoring system?
The key spares to hold onboard are the measurement sensor or optical cell for in-service replacement without a service call, sample conditioning filter elements in sufficient quantity for at least three to six months of operation, pump and valve O-rings and seals, fuses and power supply components, and reagents for reference calibration where required by the monitoring system. Quantities should be based on the manufacturer’s maintenance schedule and the vessel’s typical time between port calls.
Does MEPC.340(77) require monitoring system failures to be recorded in the EGCS Record Book?
Yes. Under MEPC.340(77), the EGCS Record Book must contain maintenance and servicing records for the monitoring system including malfunction events, the action taken and the repair completed. An absent or incomplete malfunction entry is a compliance finding during a port state control inspection, separate from any question about the monitoring data itself.
| Related content → What Records Does a Ship Need to Prove Scrubber Washwater Compliance? → What Is MEPC.340(77) and How Does It Differ From MEPC.259(68)? |