Exhaust gas economiser outlet temperature rise on passage
A 4,500 TEU container ship is on passage. At 1400 the exhaust gas economiser outlet temperature reads 208 °C against a normal 162 °C and has risen 46 °C in 40 minutes; the EGE inlet is steady at 340 °C. Boiler water level is normal, the circulating pump is running and steam pressure is steady. The alarm log shows repeated high EGE outlet temperature alarms since 1300. Funnel exhaust looks light grey. The EGE is fitted with a steam smothering connection and a water washing line; the soot blowers were last used at 0800. The chief engineer is on deck supervising ballast operations and the bridge has called to ask whether speed can be increased. You are the duty engineer.
1. What is your diagnosis and what are your immediate actions?
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Diagnosis: a soot fire in the EGE. The signature is a rapid outlet temperature rise with a steady inlet, repeated alarms and normal boiler water level/steam pressure. A tube leak would normally show falling water level, abnormal feed demand or steam-pressure disturbance; a simple fouling case would not rise 46 °C in 40 minutes.
Immediate actions:
- Tell the bridge that speed must not be increased and that you may need a load reduction; explain why.
- Inform the chief engineer and ask him to return to the ECR.
- Keep the boiler circulating pump running. This is the single most important action: it removes heat from the tubes and prevents overheating and rupture.
- Stop soot blowing; do not start it to “clear” the fire.
- Do not open inspection doors - air ingress feeds the fire.
- If an EGE gas-side bypass is fitted, line it up and isolate the EGE; if not, reduce main engine load gradually to lower exhaust gas temperature.
- Line up steam smothering and be ready to use it.
- Monitor water level, steam pressure and outlet temperature continuously.
2. Why are water washing and soot blowing the wrong response, and what is the correct extinguishing method?
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Water washing is wrong because injecting water into a hot EGE can cause thermal shock and tube rupture, and water on hot soot/oil can produce a steam explosion or spread burning material. It also adds oxygen via steam generation and can lead to a serious boiler/water-side casualty.
Soot blowing is wrong because it supplies air (oxygen) and disturbs the deposit, which can spread the fire and raise the temperature further. It is a fouling-removal tool, not a firefighting tool.
The correct method is to starve the fire of oxygen and heat: isolate the gas side if a bypass is fitted, reduce exhaust gas temperature by reducing load, keep the water side circulating, and use the fitted steam smothering connection. Steam displaces oxygen and cools the space without thermal shock. If steam smothering is not fitted or not effective, the fallback is to stop the main engine and allow controlled cooling while maintaining circulation, keeping the casing cool and monitoring for distortion.
Throughout, watch for tube rupture: falling boiler water level, abnormal feedwater demand, water hammer or a sudden change in outlet temperature. If rupture occurs, isolate the EGE water side and shut down the boiler as required.
3. What monitoring tells you the situation is deteriorating, and what criteria would make you stop the main engine?
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Deterioration indicators:
- EGE outlet temperature continuing to rise despite load reduction, or approaching the builder’s casing/tube limit (often around 250–300 °C, but use the manual).
- Boiler water level falling or feedwater demand climbing - a tube leak.
- Steam pressure falling or rising abnormally, or water hammer in the EGE.
- Casing discolouration, smoke or sparks at joints, or abnormal noise.
- Circulating pump trip or loss of water-side flow.
Criteria to stop the main engine: the outlet temperature keeps rising after load reduction and isolation, or water level cannot be maintained, or there is evidence of tube rupture, or the EGE structure is overheating. Stopping the engine removes the heat source and protects the boiler and casing. Before stopping, inform the bridge and chief engineer, agree the manoeuvre, and ensure circulation continues after the engine stops. Record the timeline, temperatures, actions and notifications; report to the company and class if there is damage.