The U.S. Environmental Protection Agency (EPA) has finalized the Clean Non-road Diesel Rule, mandating a reformulation of diesel fuel in order to reduce the fuel's sulfur content from the unregulated level of >3000ppm to a level of <15ppm. The reduction in sulfur content for land-based engines was accomplished in two steps. First, the sulfur content was capped at 500ppm starting in June 2007. Second, the sulfur cap will be reduced to <15ppm by June 2010. Although the EPA ULSD requirements for off-road engines do not go into effect for three years, U.S. refineries have stopped manufacturing non ULSD fuel as of last June 1. The result of the manufacture of only ULSD means that data centers and other mission critical facilities with diesel generators have either already received shipments of ULSD or will be receiving this fuel in the very near future.
To help managers of mission critical facilities understand how this change in generator fuel may affect the operation of their generator sets, Lee Technologies offers these important observations and recommendations:
Reduced Energy Content
The refinement process that reduces the sulfur content of diesel fuel also reduces the aromatics content of the fuel resulting in a reduction of the volumetric energy content (BTU/gallon) of the fuel. The expected reduction in energy content is 1.2 percent or more. This lower fuel energy content can reduce the instantaneous output rating of the generator and can have the following effects on operation:• The generator may be less able to respond to sudden changes in load.
• In some cases, where the generator routinely operates near its rated capacity, the generator may be rendered inoperable.
• The generator may take longer to come up to speed and voltage when starting.
• The generator will consume more fuel to provide the same output. As a result, operation duration before replenishment will be reduced.
Reduced Lubricity and Increased Fuel Particulate
Sulfur content in diesel fuel contributes to the fuel's ability to lubricate and protect various parts of the engine's fuel injection system from wear. In addition, the refinement process that reduces sulfur content also removes other naturally occurring lubricity agents. In order to offset this loss of lubricity, refiners utilize fuel additives that were previously not needed. Because of these additives, lubricity is not a problem for ULSD. However, the additives can become unstable in storage, which can result in increased particulates in the fuel. These particulates can contribute to clogged or fouled fuel filters and fuel injection systems.Fuel System Leaks
A side effect of the reduction in fuel aromatics is an increased incidence of fuel system leaks. These leaks generally occur at system points where O-rings are used to seal joints with most leaks occurring at the fuel pumps and injectors. Long service/high temperature Nitrile Rubber (Buna N) seals appear to be most prone to leaks.Incompatibility with Lubricating Oil
Lubricating oil contains additive packages that neutralize combustion products to prevent engine corrosion. With a reduced amount of sulfur, there is more un-reacted additive in the lube oil, which may result in formation of deposits when some of the oil is burned. These deposits can build up behind the piston rings and result in cylinder-liner scuffing.Additional Potential Problems and Considerations:
• Increased incidence of microbial growth due to increased concentration of n-alkalines (linear molecules).
• Copper and zinc engine components are incompatible with ULSD because they are oxidative catalysts that will accelerate the formation of sediments, gels, and soaps.
• Changes in tank and pump labeling requirements. Diesel fuel storage tanks are required to be labeled with the type of fuel that they contain. This may require a change for some facilities.
• The introduction of ULSD fuel to older systems may loosen deposits in fuel tanks.
• Because ULSD has a lower conductivity than high sulfur diesel, this fuel is more likely to accumulate an electrical charge. As a result, there is an increased risk of a static discharge accident.
Recommendations
In general, the operational effects of the shift to ULSD for diesel generator operators are expected to be minimal. While the potential problems and considerations listed above are real and should be carefully considered by stakeholders, the overall impact of these issues will not be dramatic. Lee Technologies recommends the following best practices:• As part of a good maintenance program, owners and operators of generator sets are encouraged to monitor their diesel-powered generators closely for potential fuel system leaks or premature fuel filter plugging during the change-over to ULSD fuel.
• Adopt a regular schedule of fuel testing and reconditioning to detect and prevent fuel contamination.
• ULSD will be more expensive than previous formulations of diesel fuel and fuel efficiency will go down. As a result, diesel budget and regular delivery schedules may need to be adjusted.
• Ask your fuel provider for information regarding their fuel dispensing practices and procedures for dealing with decreased conductivity.
• Update signage on fuel storage tanks and pumps.
More information is available on this important topic from these references:
• US Environmental Protection Agency "Clean Air Nonroad Diesel Summary"
• American Society for Testing and Materials (ASTM) D975, Appendix X2.7.2
• Nuclear Regulatory Commission (NRC) Information Notice 2006-22
• Clean Diesel Fuel Alliance Information Center
• Chevron Products Company Publication "Heavy Iron: Reliability 2007 Volume 1"
The Effect of Ultra-Low Sulfur Diesel on Off-Highway, Diesel-Powered Equipment"
• Chevron Products Company Publication "Technical Bulletin: Fuel Leaks from Seals of Vehicles Using Ultra Low Sulfur Diesel"
• National Fire Protection Agency (NFPA) 77 "Recommended Practice on Static Electricity"
• Association of Equipment Manufacturers (AEM) "New Diesel Fuels: They Are in Your Future for Non-road Equipment"
About Lee Technologies
Founded in 1983, Lee Technologies protects technology infrastructure from disaster for some of the world's most demanding government agencies, Fortune 1000 companies, and IT-dependent firms of all sizes. By ensuring that their mission-critical technology resources are always available 24/7/365, Lee Technologies empowers its customers with infrastructure peace-of-mind, enabling them to focus on accomplishing their core business objectives. Lee Technologies' services and solutions enable clients to power, protect, monitor, and maintain the physical infrastructure on which mission-critical facilities depend. From risk analysis, infrastructure assessments, design and construction management, integration and commissioning to monitoring, facility staffing and maintenance, Lee Technologies offers its customers a single source for eliminating downtime in their facilities.Lee Technologies has its headquarters in the Washington, DC, metroplex where it operates a state-of-the-art National Operations Center, and has offices in Atlanta, Houston, Seattle, San Francisco and Los Angeles.
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