Service Tips: Tier 4-Final engine maintenance
Prevent wet stacking with proper sizing.
By Enrique T. Guzman
While diesel engines have always been efficient and reliable, they have also had a history of emitting high levels of pollutants. For that reason, federal emissions standards for non-road diesel engines have been becoming increasingly stringent over the past two decades.
Clean diesel technology, a system made up of cleaner diesel fuel, advanced engine technology and exhaust aftertreatment, is now the standard for all new non-road engines.
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Tips for optimizing generator performance 1. Know your power needs. 2. Perform regular maintenance. 3. Consider ambient temperatures. 4. Use artificial load/wet stacking avoidance devices. |
Tier 4 emissions standards are the latest regulations established by the U.S. Environmental Protection Agency (EPA), requiring particulate matter (PM) and nitrogen oxide (NOx) emissions be reduced by about 90 percent over Tier 3-complaint engines.
The regulations have affected the performance and maintenance requirements of diesel engines. Some users report these engines have less tolerance for light loads, leading to wet stacking. It was a problem with pre-Tier 4 engines, but users operating a Tier 4 engine have seen more cases.
Wet stacking issues
Wet stacking becomes an when diesel engines do not work hard enough to create the temperatures needed to activate the technologies and components needed to reduce the PM and NOx required by the EPA, such as diesel oxidation catalysts (DOC), selective catalytic reduction (SCR) and components like diesel particulate filters (DPF). Wet stacking is an annoying and real issue, with significant cost implications.
Complete fuel burn needed
For any modern engine to operate efficiently, it needs to have the ideal air-to-fuel mixture and sustains an ideal running temperature for complete fuel burn. If a diesel engine is not required to deliver at least 30 percent of its rated horsepower, it may have difficulty attaining an optimal operating temperature. It happens when a diesel generator is improperly sized or oversized for the job.
When that happens, unburned diesel fuel builds up on the exhaust side of the engine, which fouls fuel injectors and builds carbon on valves and turbocharger.
Engines that experience wet stacking require considerably more maintenance for periodic artificial load-banking, cleaning and repair. Load-banking forces the generator to operate a full load to burn off the accumulated build-up. A full load creates the heat needed to burn off build up. Proper loading can prevent wet stacking issues.
The John Deere diesel engines used in Generac Mobile’s Final Tier 4 mobile generators are designed to resist wet stacking. John Deere’s latest diesel engines feature an exhaust temperature management (ETM) system that monitors and regulates engine exhaust temperatures and provide supplemental heat as needed.
Generac engineers performed a test with its MDG175 mobile generator equipped with a John Deere diesel engine. Those tests showed John Deere’s ETM is quite effective at regulating engine exhaust temperature, keeping it at above the 536 F temperature, regardless of load.
With right-sizing the generator to the job and using engine technology that burns off excess engine fluids, wet stacking problems and additional maintenance and downtime can be avoided.
Enrique T. Guzman is engineering manager at Generac.
This story was originally published in the March-April 2019 issue of Pro Contractor Rentals magazine. ©Urbain Communications LLC. All rights reserved.
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