Conducting maintenance procedures at certain time intervals will improve engine generator set reliability and lengthen unit life.
The failure of an engine-generator set to start because of an improperly charged battery or faulty fuel pump is inexcusable. In many facilities, this failure can be an expensive experience. In a medical facility, it could result in loss of life.
Gen-set reliability hinges on proper maintenance. To verify this work is being done properly, you should develop a comprehensive performance and documentation plan. Since standby power and emergency generator sets typically run infrequently, the times for performing specific maintenance tasks are usually scheduled in daily, weekly, monthly, semiannual, and annual time frames, rather than in hours of operation.
Establish daily checks
Most of the maintenance work on a generator set is not complicated. Common sense and paying attention to the gen-set's visual indicators can avoid problems. On a daily basis, you should walk by the engine-generator set and verify that there are no coolant, fuel, or lubricating oil leaks. An oil or coolant leak often indicates a serious problem and should be addressed immediately. Fuel leaks can be dangerous and also need to be fixed promptly. We're not talking about arrangements to clean up the spill; we're saying you should correct the cause of the problem immediately.
The gen-set should be checked for proper operation of coolant and crank case oil heaters (when used). This is done by touching the engine block or engine oil pan (assuming that the gen-set has not been in operation for awhile); the block and oil pan should be warm to the touch. If they're not, then it's possible the auxiliary heating system is not operating. On a cold day, and on a relatively warm day of 70 [degrees] F, failed heaters can increase the starting time or cause the unit to be unable to pick up load.
Maintain proper site conditions
It's tempting to use the room where the engine-generator set is located for storage of just about anything. This is prohibited by NFPA 110, Art. 5.2-1, for critical applications. Take steps to make sure generator rooms are never used for storage because it's potentially dangerous. We've seen a situation where a gen-set was completely buried under cardboard boxes. At another site, the gen-set was surrounded by tables and chairs, and the facility's technician couldn't get to the unit to check its condition.
On a walk through the generator room, all loose items should be noted so they can be removed. And, after noting loose items, you should follow-up to make sure the items were removed. Even a loose rag used for checking the oil level of the engine can be blown into the radiator, causing overheating and possible failure. Make sure the generator room is not only free from loose items but also clean as well.
Finally, check that someone has not turned the gen-set or its battery charging system off. Most sets installed in emergency applications have a flashing light on the control panel to indicate the unit is switched OFF and will not automatically start. Battery charging circuits may or may not be automatically monitored or, if monitored, the monitor may not be working. Check to make sure the battery voltage is satisfactory. A simple procedure such as this may save you much grief later.
Importance of weekly checks
You should also perform a more comprehensive weekly check of the gen-set. This should include checking the oil level in the engine (and the governor, if it's a hydraulic type) and coolant level in the radiator. Check the air cleaner for obstructions and ventilation system for blockage. Also, drain the exhaust system condensation traps.
If the above conditions are satisfactory, you should start and run the gen-set under load. It's important that all sets, even those used in critical emergency applications, be tested under load. Ideally, the test should be run with the actual emergency load that would be served when a utility failure occurs. However, such testing will usually cause momentary power disruptions to these critical loads and is potentially dangerous if not planned in advance and well supervised. In spite of the potential problems, many authorities and relevant organizations, such as the Joint Commission on Hospital Accreditation, recommend this practice. If there is a problem with the emergency system, it's best to learn about it when utility power is available.
The time to arrange a procedure for testing the set under load is when the engine-generator installation is being planned. The ideal way to test an emergency or standby power system is by using the test/exercise controls normally resident in the transfer switch, which signals the generator set to start and then transfers all the emergency or standby loads over to the generator. Recognizing that this is often not done, investigate how best to carry out a load test without disturbing critical loads. Be sure the gen-set can operate all the emergency loads, and that it has enough load on it (at least half of its nameplate rating) to prevent engine problems caused by light load operation.
The engine should reach normal operating temperatures during the test/exercise period, This means the engine will need to be run for approximately 30 min at 50% of the full load applied. Regular exercise keeps engine parts lubricated, ensures a fresh fuel supply at the engine, prevents oxidation of electrical contacts, and provides more reliable engine starting.
As the generator set is running, check for proper operation of the ventilation system dampers, unusual noises in the engine, smoke in the engine exhaust, leaks in the exhaust system, etc. Be sure the engine fuel system is working properly and the day tank (if used) is being refilled properly. As the engine is running, record the values shown on all the generator set meters, as well as the ambient temperature in the generator room and outdoors. Finish the job by completing the test report documents that show what you did and how the equipment worked for that test period.
You might opt for fitting the engine, generator set with a data gathering panel, with connections to the automatic transfer switch(es) and to a monitoring system for the starting battery. This can be networked to a computer and will automatically log the test data to provide comprehensive reports. An important advantage of such systems is they can show trends on how the generator set is operating, which could be useful for planning replacement of key components. These systems greatly simplify report gathering for health care facilities and other applications that demand regular comprehensive operating reports. Contact your generator set vendor for more information.
Features of monthly checks
In your monthly check of the gen-set, you should perform a closer inspection of engine conditions. Because this inspection is more thorough, you must recognize that the set may start at any time (unless it is disabled). This can cause severe injury or death. OSHA requires that the gen-set be locked out. This usually involves taking steps to prevent the engine from starting by placing the control switch in the STOP position, disconnecting a battery cable, and tagging prior to servicing the unit. Note that NEC Sec. 700 5(b) requires a portable or temporary power source (usually another generator temporally installed) be provided whenever an emergency generator is out of service for major maintenance or repair. When maintenance of the unit has been completed, return the generator set to automatic operation.
Check the specific gravity of the engine coolant with a hydrometer. Note any unusual conditions, such as rust foaming. Examine condition of hoses and clamps, making sure there are no leaks and they are tight and properly fitted. Also check the battery condition with a battery hydrometer (if the battery is not sealed). The specific gravity should be 1.260.
Check all battery terminals for clean and tight connections, as loose or corroded connections create resistance that can hinder starting. If the connections are loose, clean and reconnect the battery cables. Always disconnect both ends of the grounding battery cable. When reconnecting this cable, first connect one end to the battery, and then connect the other end to the grounding point. Thus, any arcing will be away from the battery and unlikely to ignite explosive battery gases, which can cause severe personal injury. Do not smoke while servicing batteries.
Finally, all tools used for servicing the gen-set should be in their proper location.
Procedures for conducting semiannual maintenance
Many gen-sets customarily receive what might be termed "an in-depth maintenance review" in the spring and fall each year, before the more stressful operating periods of summer and winter. At these times, the gen-set and associated control equipment should be physically cleaned and checked for proper operating condition.
All control and supervisory equipment should be checked for proper operation. This includes inspecting the governor linkage to be sure it's clean and moves freely. You also should check the operation of all alarm and status lamps and replace any lamps having failed elements. Actually, a good idea is to replace all such lamps and verify that the new ones light.
If qualified electricians are available, they should visually check the condition of the automatic transfer equipment and distribution switchboards. This inspection should reveal any indication of arcing or burned contacts, loose connections, etc.
At this time, the engine and governor oil and filters should be changed (even if the engine operation hours don't warrant the change). The coolant filters, if used, and the engine air filters should be checked and replaced if necessary. Drain sediment from the day tank(s) and change the fuel filters. Check the fuel supply and return lines for leaking or loose fittings.
During the semiannual maintenance review, you should perform a full-power failure test. During this test, power to the automatic transfer switch(es) is physically interrupted so that the emergency/standby power system has to respond to a true power failure. This procedure not only tests the ability of the gen-set to start and assume all available load, but it also checks the operation of automatic transfer switches, related switchgear and controls, circuits, and all other components of the emergency or standby power system. This type of testing will result in a loss of power to critical loads of about 10 sec in duration. Careful planning and coordination with all concerned personnel is important here. The test should be carried out by qualified technician(s) with close supervision to help assure no problems will result.
Semiannual inspections may be more than your in-house staff maintenance personnel are able to handle. Rather than not conducting such a full-maintenance review, it's possible to get service contracts from gen-set suppliers to perform this work.
Performing the annual maintenance inspection
Recommended annual maintenance procedures are only a bit more detailed than the semiannual work. The components involved are the engine, alternator, and distribution equipment, including automatic transfer switches.
All procedures should be followed as called for in the weekly, monthly, and semiannual maintenance inspection/testing. The engine exhaust manifold and turbocharger cap screws should be tightened per manufacturer's recommended practice. All engine hardware should be tightened. The engine itself should be cleaned. The fan hub, drive pulley, and water pump should be checked, and the cooling system should be cleaned. Vibration isolators should be checked and readjusted if necessary. When performing such examinations, you must exercise extreme care to avoid injury and follow OSHA guidelines.
As with previously scheduled maintenance that calls for the gen-set to be disabled for a short period of time, annual maintenance also has this requirement. If the gen-set is serving emergency loads, NEC Sec. 700 5(b) is in effect, thus requiring a portable or temporary power source. Obviously, you should make arrangements to perform this maintenance as fast as possible so the generator set(s) are available again to pick up load as needed. However, after the maintenance, adequate testing should be carried out.
Electrical load and control wiring connections between the gen-set(s) and transfer switches should be retightened. Alternator bearings should be greased (if they are not sealed), and the alternator insulation resistance should be checked/recorded.
Switchgear and transfer equipment should be checked for excessive wear and high operating temperature. This equipment should be shut down and cleaned according to manufacturer's instructions.
Gen-sets that operate at less than a third of rated capacity should be connected to a resistive load bank and operated for at least 1 hr at close to their standby rating. This may require temporary connection of auxiliary loads so the gen-set can be fully loaded. Operating a gen-set under a light-load condition can cause excessive lube oil consumption and, in diesel engines, incomplete combustion. When this occurs, the unburned engine fuel is deposited on the engine injectors and/or the exhaust system, resulting in poor engine performance and even a fire hazard.
Performing inspections with the gen-set running
At various times here, we've recommended the system operator or maintenance technician check the generator set while it's running. This is not a job for just anyone. Be sure the person doing this work knows how to do it safely, what is involved when the gen-set is operating an emergency load during testing, and what to look for to prevent problems with the equipment.
Be sure the maintenance technician has reviewed all operation manuals, particularly any safety warnings. Generator set suppliers often can provide training sessions for operating people to help them understand their equipment better. The operator should know how to start and stop the equipment and how to accomplish an emergency system shutdown.
Remember, gen-sets and their rooms are noisy, and the equipment has hot surfaces and rotating belts, fans, etc., that can cause injury. Hearing protection will probably be necessary in the generator room when the set is operating. No loose clothing should be worn around gen-sets.
What to inspect when the set is running
Exhaust system. Inspect the entire exhaust system visually and audibly, including the exhaust manifold, muffler, exhaust pipe. Check for leaks visually, by smell, and also by listening for unusual sounds at all connections, welds, gaskets, and joints. Make sure exhaust pipes are not excessively heating the surrounding areas. If any leaks are detected, shut down the gen-set and correct the leaks. Warn personnel performing the tests that inhalation of exhaust gases can result in serious personal injury or death. Deadly exhaust gas must be piped outside and away from windows, doors, or other inlets to the building.
Mechanical system. With the set running, listen for any unusual noises that may indicate mechanical problems and frequently check the oil pressure. Investigate anything that indicates possible mechanical problems. When the generator set is not running (but remembering, you may have to take steps to prevent it from starting automatically and carry out all associated precautions), check for loose belts and fittings, leaking gaskets and hoses, or any signs of mechanical damage. If any problems are found, correct them immediately.
Fuel system. Inspect the fuel supply lines, return lines, filters, and fittings for leaks. Check any flexible sections for cuts, cracks, and abrasions, and make sure they are not rubbing against anything that could cause breakage. If any leaks are detected, correct them immediately. Warn your testing personnel that fuel ignition can cause a fire or explosion, resulting in serious personal injury or death, and/or serious equipment damage. Do not permit any flame, cigarette, or other igniter near the fuel system.
Electrical system. While the gen-set is running, you should check for proper operating voltage and frequency. Most sets are provided with permanently mounted meters for this purpose. If your set doesn't have such meters, then getting this data will usually require using a qualified electrical technician. When viewing meter outputs, you should note not only that the unit is operating at proper voltage and frequency, but also that voltage balance on all phases is correct. The current output of each phase should be noted and permanently recorded. You also should verify all indicating lamps in the system function properly for each of the operating modes.
A properly trained operator can make minor voltage and frequency adjustments, but should probably leave other electrical adjustments on the generator set alone. Indiscriminate adjustment of other controls on the gen-set can cause improper operation or nuisance shutdown of the equipment.
Richard Demot is Technical Service Manager, and Gary L. Olson is Technical Counsel, Onan Corp., Minneapolis, Minn.