One such federal mandate has a direct and perhaps relatively unknown impact on data center operators, a development that can undermine their disaster avoidance efforts if proper precautions are not taken.
In 2004, the U.S. Environmental Protection Agency (EPA) finalized the Clean Air 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. U.S. refineries have been churning out the reformulated diesel fuel – known as Ultra Low Sulfur Diesel Fuel (ULSD)– since June, and it is now required for diesel engine generators.
Although the EPA ULSD requirements for off-road engines do not go into effect until 2010, U.S. refineries have stopped manufacturing non-ULSD fuel as of June 1, 2007. 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.
Diesel-powered generators often serve as the last line of defense against a power failure at mission critical facilities such as data centers and hospitals. And while ULSD is less harmful to the environment, it can be very harmful to older generators responsible for keeping emergency systems up and running by causing issues such as fuel system leaks, clogged fuel injection systems and incompatibility with lubrication oil.
Most significantly, ULSD fuel contains less energy content, which means that generators may be less capable of adapting to rapid load changes. Translation: in isolated cases a generator that becomes used to operating at less than maximum capacity could prove unable to up its load capacity on short notice when called upon to backup a data center.
Challenges
While the ULSD switch is not going to render thousands of generators insufficient overnight, the transition does pose challenges for managers of mission-critical facilities that must oversee the operation and maintenance of their generator-sets. These challenges include:
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 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.
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 problems data center operators should remain aware of include:
- 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
While the worst-case scenario – an emergency systems failure – should drive all data center operators to remain vigilant and mindful of the shift to ULSD for diesel generator operators, following a set of best practices can minimize operational risk. These best practices should include:
Proper Monitoring
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 changeover to ULSD fuel.
Load Transmission
Consider how electrical loads are brought to the generator. If loads can be put on more gradually, engines will respond better than by doing a step load, for example (where sources of uninterruptible power supply (UPS) are suddenly transferred to a generator.
Consistent Testing
Adopt a regular schedule of fuel testing and reconditioning to detect and prevent fuel contamination. During your first year of using the new fuel, test it more regularly. All diesel fuel has some microbial growth in it. The change in fuel might cause some sediment and contamination to break loose and float in the tanks, affecting fuel performance.
Mind the Budget
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, and be sure to Review your budget for the extra cost of the new fuel, which will get less mileage per gallon, so to speak, as well as have a higher cost per gallon.
Communicate with Fuel Providers
Ask your fuel provider for information regarding their fuel dispensing practices and procedures for dealing with decreased conductivity. Plenty of data centers out there aren’t even aware of the new rule. Your fuel provider can be a good source of guidance on this front.
Conclusion
If you ask data center managers if they would prefer to spend their time on disaster prevention rather than disaster response, each to a man would choose the former. While the tendency may be to play the odds and assume this invisible threat will never materialize in their data center, the consequences of guessing wrong are monumental. By following this set of basic best practices, data center managers can better ensure the ULSD transition will not have a negative impact on business continuity and efficiency.
About The Author: Eric Gallant is senior account manager at Lee Technologies, a leading provider of mission-critical solutions that enable commercial enterprises and government agencies to mitigate risk to their physical infrastructure. He has been involved with issues related to power generation, power distribution and power quality for 15 years.
"Appeared in DRJ's Spring 2008 Issue"
