Catastrophes, acts of God, and other electrical utility related failures generally occur unexpectedly and with little warning. Facilities designed to function during these losses of electrical power from a utility typically rely on emergency generators to allow these facilities to continue to function. Failure of an emergency generator to start and provide reliable power can place the facility and occupant safety and lives at risk. Most emergency power failures can be prevented through scheduled maintenance (including weekly exercising) and monthly testing. Buildings with emergency power generators are dependent on their generators during a loss of utility power to provide the electricity needed to protect the building and occupant life and to support critical missions.
Scheduled maintenance and testing significantly decrease the risk of emergency generator failure. Common causes of a generator’s failure to start include the following:
Battery Failure – Battery failure is responsible for 80 percent of generators failing to start. The reasons include loose battery terminal connections, corrosion between battery terminals and connectors, and sulfation buildup within the battery where lead sulfates accumulate on battery plates.
Low Generator Fluids – Low coolant or oil levels will allow the generator to start but will cause shutdown of the generator due to internal safeties designed to protect the generator engine. Weekly or monthly tests where the generator is only run for fifteen to twenty minutes, which is the typical generator manufacturer’s recommendation, do not run long enough for this type of failure to occur. Scheduled maintenance should include checking fluid levels in the generator to help ensure generator performance in a time of need. The most obvious cause for a low coolant level is either an external or internal leak. Pay close attention to any visible puddles of coolant during weekly inspections of the unit(s). The color of the coolant varies by manufacturer and may look like red-dyed diesel fuel. Inspect the oil for any signs of color change or a milky texture and check hoses for “crusties”—the sign of coolant seeping and additives drying up at the connection.
Fuel Issues – Scheduled maintenance should include checking fuel levels, looking for fuel leaks, and testing diesel fuel quality. Diesel fuel in storage degrades faster at higher temperatures and in the presence of free water and contaminants. Under ideal conditions, diesel fuel can be stored between six and twelve months. To extend the life past twelve months, even under the best conditions, the fuel needs to be treated. Keeping water out of the tank is the most important factor in fuel quality maintenance. The most visible sign that something is wrong is when the fuel changes color. Normal, undyed diesel fuel is a beautiful, amber-green color. The same fuel once it has started to degrade will darken. This is because heavier components of the fuel blend are no longer dissolved in the fuel but are coming out of solution and floating freely in the fuel. These floating components have a darker color that turns the overall color of the fuel darker.
Empty Fuel Tank – Stuck fuel gauges and fuel gauges that read fuel levels incorrectly commonly result in an empty fuel tank. Manual checking of fuel levels against gauge indication as part of scheduled maintenance can prevent generator failure due to not enough fuel.
Control Setting Errors – Maintenance schedule checklists should include checking control settings. Many generators fail to start because of their controls being left at the wrong setting following maintenance or testing. If the proper resetting procedure is not followed, a control error could also occur after a fault shutdown.
Oil Leak – Oil leaks are caused by wet stacking, a condition where oil, fuel, and other liquids build up in a generator’s exhaust pipes due to carbonized fuel injection tips and faulty crankcase breathers that release too much oil as it vents. Most often, oil leaks are not in fact leaks but the result of “wet stacking” (or “engine slobber”) caused by excessive no-load run time. Diesel engine generators are designed to operate with a load—most effectively in the 70 to 80 percent range of rated output. When generators operate considerably below the rated output level, the engine can start to over-fuel or “wet stack” and damage the engine. Testing generators under load can help to reduce this issue.
Fuel Bleed Back – When fuel bleeds back into a generator’s fuel tank instead of going to the engine, air in the injection mechanism or faulty check valves could be the cause. In either case, the generator behaves as it were out of fuel.
CxGBS provides commissioning services for micro grids that include multiple sources of power from utilities, uninterruptible power supplies, and emergency generators associated with critical facilities including electrical utility companies, hospitals, and data centers. We can assist with the development of scheduled maintenance procedures to minimize the risk of system failure.
