Cat® marine engines that meet U.S. EPA Tier 4 Final emission standards do so through the use of Selective Catalytic Reduction (SCR) technology. Why did we choose SCR over other emissions-reduction technologies? Because it does the best job of meeting the requirements you told us matter most: Simple to operate and maintain. Proven to work efficiently and reliably. All without adding to your total cost of ownership. Here’s how:

Simple

Unlike engines with Exhaust Gas Recirculation (EGR), Cat Tier 4 Final marine engines aren’t complicated. SCR is an aftertreatment solution that breaks down emissions AFTER they’ve been generated. That means no alteration to core engine components and no increase in the injector, in cylinder pressure or in heat rejection. Emissions reduction happens in three easy steps:

1. The ECM determines the correct amount of Diesel Exhaust Fluid (DEF) to inject, based on closed loop feedback from the system.
2. The DEF is injected into the exhaust with the aide of compressed air, to help atomize and evenly disperse the fluid.
3. Water evaporates and the DEF is converted into ammonia, where it interacts with the SCR system (catalyst) to reduce the NOx into water vapor and nitrogen..

Maintenance is simple, with long life to overhaul, and installation flexes with your vessel design.

Proven

SCR’s not a new or untested technology. Patented in 1957, it’s been installed across multiple land-based applications over the past half century, including power plants, railway locomotives and cars. SCR was originally developed to control NOx emissions from stationary engines, but in recent decades, it’s been applied to mobile vehicles like freight-carrying trucks, buses, off-road construction equipment and diesel-engine passenger vehicles.

In the marine sector, SCR’s been at work for more than two decades. You’ll find marine engines with SCR systems successfully deployed on vessels ranging from ferries and cruise ships, to tugs and workboats, to tankers, container ships, icebreakers, cargo ships, naval vessels and more.

Fuel-efficient

Many people assume a decrease in emissions results in an increase in fuel consumption. But that’s not the case with our SCR solution. The relationship between engine-out NOx and fuel consumption is inversely proportional. In other words, the higher the engine-out NOX, the lower the fuel consumption. In fact, for some Tier 4 Final marine engine ratings, fuel consumption is up to 9% lower than equivalent Tier 2 / Tier 3 engine ratings. That more than offsets the cost of DEF in most cases — keeping your total cost of ownership low.