Built at HHI-EMD?s works in Ulsan, South Korea, the six-cylinder, Wärtsilä X72 diesel engine employs a compact, pre-turbocharger selective catalytic reduction (SCR) system. The system is supplied by HHI-EMD and has demonstrated its ability to reduce the engine?s NOx emissions below the required limitations of IMO Tier III for vessels operating in ECAs, the companies said. Likewise at the shop test, the Wärtsilä X72 engine demonstrated its compliance with the NOx limits of IMO Tier II without exhaust aftertreatment. Commenting on its pre-turbocharger SCR system, HHI-EMD noted that locating the SCR catalyst in the hotter exhaust gases before the turbocharger turbine was designed to reliably achieve the temperature level required for the NOx-reducing reaction of the exhaust gases with the urea reducing agent. In addition to WinGD Korea and HHI-EMD staff, the test was witnessed by representatives of the classification societies ABS Korea, KR, the shipyard Hyundai Samho Heavy Industries, and SeaQuest Marine Project Management. Following the test, the 15,080-kW-rated engine (74.7 rpm) was delivered to HSHI (Hyundai Samho Heavy Industry) in Samho-Eup, Yeongam-Gun, South Korea, where it will be installed on a 159,000dwt crude oil products tanker.