Exhaust Gas Systems for 

Marine Diesel Engine Installations


The exhaust gas is led from each turbo charger through insulated inlet pipes to the primary silencer designed as a single chamber reflection muffler. In this part of the system, the exhaust gas is at high temperature. Where the SCR option is included the SCR Reactor replaces the primary silencer.

Downstream from the primary silencer, in the primary injector, sea water is injected through several nozzles into the exhaust gas, and the exhaust gas is quenched to approximately 60°C.

The main silencer attenuates the acoustic noise and leads the cooled exhaust gas from the primary injector to the outlet pipes. A secondary injector is normally installed downstream of the main silencer for the final cooling stage and to scrub particles from the exhaust gas.

Residual water droplets that are not entrained in the exhaust gas through the main silencer are collected and the surplus water is drained and lead overboard by the exhaust piping. Downstream from the main silencer the exhaust gas is routed overboard through the outlet pipe either to the ships side or through a transom outlet, depending on the engine configuration.

Where the SCR option is selected by the client, the SCR Reactor acts as a primary silencer as well as facilitating the catalytic reaction and is incorporated in the exhaust line before the Main Silencer. With this option there will be

a reducing agent injection and mixing device included between the Engine manifold and the SCR Reactor.

Where the Waste Heat Boiler is selected it is integrated into the hot section of the line to maximize the benefit. The boiler has a cooling effect on the gas and therefore reduces the amount of heat to be extracted by the sea water injection process. 

A typical exhaust gas system delivered by Mecmar for a Diesel Engine Installation comprises the following main assemblies:

• Primary Silencer and Inlet Pipes
• Seawater Supply System and Pump
• Sea Water Injectors, Primary and Secondary

• Main Silencer
• Outlet Pipes
• Drainage System
• Flexible Bulkhead and Hull Penetrators
• Compensators
• Flexible Supporting Elements
• Temperature and Pressure Sensors
• Control and Monitoring System
• Reduction Agent Injection System (optional)

• SCR Unit (optional)
• Integrated SCR Control System (optional)
• Economiser or Waste Heat Boiler (optional)