Exhaust Gas Recirculation - New technologies Tier III

Exhaust Gas Recirculation (EGR) in a Ship Engine Room

Exhaust Gas Recirculation (EGR) on Ships

How It Works and How We Maintain It – New Technologies

As a Chief Engineer who has worked on modern bulk carriers with Tier III WinGD engines, the EGR system, or Exhaust Gas Recirculation system, is one of the most important NOx reduction technologies found today in the engine room. It is also installed on MAN B&W marine engines.

Short technical information: The EGR system recirculates part of the exhaust gas back into the engine, reducing combustion temperature and NOx emissions.

On ships, this technology is critical for compliance with IMO Tier III emission requirements.

New technologies include:

ΠΩΣ ΛΕΙΤΟΥΡΓΕΙ ΤΟ ΚΑΖΑΝΙ (COMPOSITE BOILER) MIURA

Integration with dual-fuel engines, including LNG and methanol engines

Combination with the Miller cycle

Advanced cooling and water treatment systems, such as GEA solutions

Reduction of methane slip and improved engine efficiency by makers such as MAN, Kawasaki, and others

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How the EGR System Works

The system recirculates part of the exhaust gas, usually around 10–30%, back into the cylinder. This reduces the oxygen concentration and lowers the combustion temperature, which results in lower NOx emissions.

There are two main types of marine EGR systems:

• High Pressure EGR (HP-EGR)

• Low Pressure EGR (LP-EGR), which is a more modern and efficient arrangement

Main Components of the EGR System

• EGR Cooler for cooling the recirculated exhaust gas

• EGR Valve and EGR Blowers

• Scrubber or Cleaning Unit, mainly in low pressure systems

• Control valves and sensors for NOx, temperature, pressure, and flow monitoring

Maintenance by the Marine Engineer

1. Daily inspection for leaks, abnormal temperatures, and pressure deviations

2. Cleaning of the EGR Cooler from soot deposits and scale formation

3. Inspection and lubrication of EGR Blowers according to maker instructions

4. Replacement of filters and checking of sensors according to the PMS

5. Water treatment of the EGR circuit, including pH and conductivity control

The EGR system is a key technology for Tier III NOx compliance without the need to use SCR in all operating areas. In LP-EGR systems, the exhaust gas is cleaned with water through a scrubber before recirculation. This reduces corrosion, soot carryover, and deposit formation inside the system.

Practical Tip from a Chief Engineer

The EGR system requires disciplined maintenance. The biggest problems are soot accumulation, cooler fouling, water contamination, and corrosion. Carry out regular chemical cleaning when required and always check the pH of the EGR water circuit.

In case of high NOx alarms, do not immediately assume that the engine itself is the problem. First check the EGR valve position, EGR blower operation, differential pressure across the cooler, water quality, temperature sensors, pressure sensors, and NOx measuring equipment.

A poorly maintained EGR system can reduce engine performance, increase fuel consumption, create alarms, and lead to serious corrosion problems. Correct operation and maintenance are essential for safe and reliable Tier III engine performance.

📌 This article is useful for:

Marine Engineering students

Engine cadets and junior engineers

Marine engineers working on Tier III vessels

Chief Engineers and Second Engineers operating modern low-speed engines

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⚓ EGR is one of the most important technologies for cleaner shipping. Understand it, maintain it correctly, and master it on board.

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