Forgotten Maintenance: Backup Generator Fuel

March 29, 2012 3 Comments »

For mission-critical data centers, downtime can be a tremendous expense, and even for less critical data centers and IT facilities, downtime can reduce productivity and sales and cause extensive hassles as personnel scramble to restore operations instead of focusing on normal business operations. A critical part of preventing downtime is implementing adequate backup systems, including backup power sources, such as uninterruptible power supplies and diesel generators. But just having these systems is not enough; they (like the rest of the data center) must be maintained to ensure proper operation when they’re needed.


For diesel backup generators, maintaining the physical machinery is important, but that’s not all. The diesel fuel can become contaminated over time, and using degraded fuel (or even simply leaving it in the generator when not in use) can damage the equipment over time. Ultimately, this can mean that backup generators may not function properly (or at all) when needed. And a utility outage is not when you want to find out about the ill effects of a lack of fuel maintenance.

Bill Miller, regional account manager for Algae-x International, notes, “Fuel for data center generators needs maintenance to ensure optimal quality fuel to the generator at all times. The number one cause of a generator failure is a clogged filter, which is a direct result of fuel degradation that forms tank sediments.” In addition, “The formation of acid in the tank will eat at the guts of the injector pumps as well as the injector tips. The pumps will fail and the injector will no longer aspirate the fuel properly meaning the spray pattern changes allowing for hot and cold spots in the head. A warped head will be a huge headache.” Part of proper maintenance involves checking for water and, if present, removing it from the fuel. One of the threats of water is that it can harbor microbes, which create sediment that can pose a threat to filtration systems. These microbes can and do exist in fuel tank water bottoms. Addition of biocides can also aid in preventing this source of sediment.

But the threat to filtration and other systems in backup generators is not limited to microbial activity: part of the threat comes from the fuel itself. According to Miller, “Biocide dosing can be effective if microbial activity is present, however with or without use of biocides, the fuel will still form sediments as a result of refining processes such as catalytic cracking.” Furthermore, “the vast majority of tank sludge (up to 95%) forms from the fuel itself as the fuel ages. Fuel will break down, form solids and create diesel sludge all on its own, so microbial activity is a minor issue regarding fuel breakdown sediments. This material is what we need to remove when present, and prevent from accumulating by implementing a ‘fuel maintenance’ program.” According to Exxon (“Diesel FAQ”), “If you keep it clean, cool and dry, diesel fuel can be stored 6 months to 1 year without significant quality degradation. Storage for longer periods can be accomplished through use of periodic filtrations and addition of fuel stabilizers and biocides.”

Part of fuel maintenance is inspection of the fuel around the time of delivery. This includes inspecting the tank for water before the fuel is delivered and then inspecting the fuel several days after delivery. “Most commonly, the water is delivered with the fuel. This is the reason for waiting two days after the fuel delivery so the water if any can separate and fall to the tank bottom. The data center is paying for fuel not water,” said Miller. In addition, other steps can be taken to ensure that the fuel, along with the generator, is ready when power failures strike. Miller suggests establishing a tank maintenance schedule “where someone sticks the tank to check for water, pulls a fuel sample from the tank bottom for a lab to test and report and adds a full spectrum catalyst (not biocide) to the fuel every six months and when fresh fuel is added.” And, of course, proper documentation of maintenance procedures and problems is critical to the entire process.

Damage to generator equipment owing to bad fuel is not the only concern. Given the rising cost of diesel fuel, the cost in diesel alone is enough to make regular maintenance important. The longer you can make your fuel last, the less your overall costs will be over time. As in most areas of data center operations, a little time and money put into maintenance can yield much larger returns in the long term, owing to better-performing equipment, less downtime and fewer major equipment repairs and replacements.

About Jeff Clark

Jeff Clark is editor for the Data Center Journal. He holds a bachelor’s degree in physics from the University of Richmond, as well as master’s and doctorate degrees in electrical engineering from Virginia Tech. An author and aspiring renaissance man, his interests range from quantum mechanics and processor technology to drawing and philosophy.

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