U.S. EPA Tier 4 Final Marine Engine Acronyms, Decoded

KEY TERMS AND WHAT THEY MEAN

 

SCR. EGR. DEF. DPF. DOC. If you can’t keep up with all the acronyms associated with Tier 4 Final marine engine solutions, don’t worry — you’re not alone. Use this handy guide to keep the terminology straight.

Acronym

Definition

NOX

Nitrogen oxides. Gases produced from the reaction of nitrogen and oxygen during the combustion of fuels, especially at high temperatures. NOX emissions are regulated by the U.S. Environmental Protection Agency and International Maritime Organization.

SCR

Selective Catalytic Reduction. A marine vessel emissions solution that reduces NOX in the exhaust stream by converting it to nitrogen gas and water vapor.

EGR

Exhaust Gas Recirculation. A marine vessel emissions solution that re-circulates a portion of exhaust gas back to the intake to reduce the oxygen content of combustion.

DEF

Diesel Exhaust Fluid. A carefully blended solution of high-purity urea and de-ionized water used in SCR solutions. It’s injected into the exhaust system, where it decomposes into ammonia, then selectively reduces NOX with the help of a catalyst.

NH3

Ammonia. A nitrogen compound used to selectively reduce NOX in an SCR system.

N2

Nitrogen gas. In an SCR system, NOX emissions are converted to N2 and water.

DPF

Diesel Particulate Filter. An aftertreatment device that removes diesel particulate matter (or soot) from the exhaust gas of a marine diesel engine. A DPF or DOC (see below) is typically required with EGR solutions to meet marine emissions standards.

DOC

Diesel Oxidation Catalyst. An aftertreatment device for marine diesel engines that converts carbon monoxide and hydrocarbons into carbon dioxide and water. A DOC or DPF (see above) is typically required with EGR solutions to meet marine emissions standards.