icm16

ICM January-February 2017

Mark K, Smith Advanced Fuel Solutions mark@yourfuelsolution.com Recommended practices for fuel filter life in diesel trucks Shortened fuel filter life in diesel trucks has been an issue since lower sulfur diesel fuels became available in 2006, according to the Technology & Maintenance Council (TMC) recommended practices RP–367. Although fuel filter life expectancy can be compromised by any number of factors, one cause stands out from the rest and affects Tier 3 and Tier 4 engines with high pressure fuel injection systems (HPFI). TMC reports: “One cause of dark fuel is due to newer high-pressure common rail fuel systems that thermally degrade fuel, which results in carbonaceous materials developing in the fuel. Common rail fuel systems put more heat stress on fuel which can promote by-products coming out of suspension and covering the filter media.” (Source: TMC RP 367-4). As an industry, we expected that 15 ppm ultra-low sulfur diesel (ULSD) fuel would cause issues with lubricity, generate fewer British thermal units (BTUs), affect gasket material compatibility and increase the potential for microbial activity. What we did not anticipate was the thermal instability of ULSD when exposed to new engine technology, specifically high pressure common rail (HPCR) injection systems. These HPCR systems were designed to meet strict government exhaust particulate standards and fuel economy requirements. This is where fuel meets technology. The HPCR system exposes diesel fuel to extreme heat (600°F or higher) at the combustion cylinder and high pressure (up to 35,000 psi) at the injectors, which combine to elicit punishing effects on the ULSD. Unburned heated fuel containing carbonaceous material is returned to the saddle tank, where it comingles with existing ambient temperature fuel, causing fuel oxidation, accelerated darkening, decomposition and sediment. This process is repeated over and over as the vehicle operates and the filters catch the hydrogen-rich carbonaceous material, leading to shortened fuel filter preventative maintenance intervals (PMIs) and premature filter failure. A partially blocked filter will result in sluggish performance, while a completely blocked filter will lead to vehicle down-time due to fuel starvation. Fuel filters are not the only components affected by HPCR technology. The punishing effects of HPCR on ULSD also affect the exhaust system. A diesel engine operating at normal highway speeds will burn off most of the exhaust particulate. The diesel particulate filter (DPF) uses exhaust heat created under normal operating conditions (1,000 to 1,200°F) to oxidize the trapped particulate matter into nitrogen gas and carbon dioxide. This by-product is then expelled through the exhaust pipe into the air we breathe. This process is called filter cleaning and part of a passive regeneration (or “regen”) of the DPF. When a vehicle experiences high idle time or stop-andgo traffic, however, the exhaust gas temperature (EGT) can fall below the 1,000 to 1,200°F required to effectively burn off the excess soot. For this reason, original equipment manufacturer (OEM) companies have installed exhaust sensors that detect back pressure in the system and the engine central processing unit (CPU) automatically initiates an “active regen.” At this point, diesel fuel is injected by the doser valve, or seventh injector, and ignited in the exhaust system downstream of the DPF in order to raise the exhaust gas temperature (EGT) and burn off soot in the DPF. When a vehicle stops to make deliveries or is in heavy traffic, the “active regen” will discontinue and start again from the beginning, or may require a “parked active regen,” which requires the vehicle to sit stationary for 45 to 55 minutes for the truck to clear the DPF. Active regens, whether driving or parked, consume additional fuel, increasing operation costs, reducing fuel economics and promoting nonproductive drive time. Excess soot in the exhaust system resulting from consistently low EGTs can also overwhelm exhaust sensors, the exhaust gas recirculation valve (EGR) and the doser valve, causing them to malfunction and require costly downtime and repairs. So what can a fleet manager do to improve the performance and reliability of its diesel operated vehicles? Just as diesel OEMs have met new U.S. Environmental Protection Agency emissions and mileage standards with improved technology, progressive additive companies have developed contemporary, fuel-based technologies to correct the unexpected thermal instability of today’s ULSD. Advanced anti-foulant and detergent additive solutions are designed to return fuel filter PMI schedules to normal, recoup lost fuel efficiency, keep DPF regens to a minimum, reduce downtime and repair costs and, ultimately, maintain customer satisfaction. Call Mark at 978-494-2494 or email mark@yourfuelsolution. com for more information. ICM 16 ICM/January/February 2017


ICM January-February 2017
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