The Technology Explained

The Technology Explained


The beauty of our Selective Catalytic Reduction (SCR) system is that it’s not complicated. It doesn’t affect engine efficiency and durability like other emissions-reduction solutions. There’s no alteration to core engine components and no increase in the injector, in cylinder pressure or in heat rejection. Maintenance is simple, with long life to overhaul, and installation flexes with your vessel design. Best of all, our marine engine Tier 4 Final solution improves fuel efficiency, lowering your costs. Here’s how it works in three simple steps:

  1. The dosing cabinet mixes the right dosage of compressed air (1A) and Diesel Exhaust Fluid (1B).
  2. That mixture is transferred to the SCR module (2A) where it’s injected into the exhaust stream (2B).
  3. Water evaporates and Diesel Exhaust Fluid is converted into ammonia. The ammonia comes in contact with the SCR catalyst to reduce NOx. The final output is carbon dioxide, nitrogen, water and oxygen.

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Selective Catalytic Reduction (SCR) Explained
Go inside a working tug engine room to see our Selective Catalytic Reduction (SCR) aftertreatment installed.

Airless VS. Air Assisted Dosing

Caterpillar' robust development and validation processes have been employed to fully optimize our Marine SCR solutions to provide the appropriate DEF injection system for each engine platform.

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From Sketch to Shipyard

Our marine engine Tier 4 Final solution started as a sketch on a napkin. Today it’s a real-world solution reducing marine vessel emissions across industries.

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A Simple Solution, Delivering Results

SCR is a simple, reliable and proven way to meet marine emissions regulations while reducing total fluid consumption and costs. Here’s how it works.

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Tier 4 Acronyms Decoded

Struggling to remember the meanings behind all those marine engine Tier 4 Final acronyms? This handy guide will help you keep things straight.

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