Equipment World Digital Magazine
Issue link: http://read.dmtmag.com/i/846046
EquipmentWorld.com | July 2017 37 the same thing and like- wise tends to enlarge the footprint of the engine. Tier 4 Final engines added an additional layer of emissions technology, the selec- tive catalytic reduction system, or SCR. In an SCR system, the exhaust stream is injected with a mist of diesel exhaust fluid (DEF) and water and then run through a catalyst. This transforms the nitrogen oxides (a harmful pollutant) in the exhaust into harm- less water and nitrogen but requires storage tanks for the DEF, dosing hardware and related plumbing. "From a practical standpoint, the primary problem is simply hav- Untitled-50 1 4/18/17 9:54 AM High-cost, high-value machines with dura- ble frames, like this wheeled tractor scraper, make good candidates for repower.