Jump Starting Generator Maintenance

In order NOT to bore you with just another list of maintenance items to check and test, we felt it would better serve your interest and time if we pointed out some of the hidden reasons WHY maintenance should be performed on towable diesel generator sets — these are gen sets ranging from 25 kVA through 150 kVA. We will also mention some additional items of which you should be aware of in order to extend the service life of your generator.

Every manufacturer should have detailed information for its recommended general maintenance scheduling and procedures. Frequently, this procedure is broken down into a list of daily checks — 100-hour checks,
250-hour checks and 500-hour checks. These are all important and certainly should be followed and carefully documented if you want your warranty coverage to remain unquestionable.

Hopefully, the fact that you are reading this article
indicates that you take the maintenance of your equipment seriously enough to have implemented a computer system to help you schedule your intervals and track
your costs on a unit-by-unit basis. If you have not, you should immediately consider doing so, as the benefits in extended service life and “up-time” far outweigh the costs of hardware and software.

Power Plant Upkeep

Take into consideration the fact that most engine manufacturers recommend that oil and filters be changed every 150 hours on smaller generator units and every 250 hours on larger units. Based on a 24/7 application, that is every six or 10 days; therefore, the need for a good scheduling system is obvious.

Starting with the engine, let us emphasize that condensation happens. This is especially crucial to keep in mind when you are dealing with diesel generators. Realize diesel fuel contains some level of sulfur — even with today’s stricter standards. Sulfur plus condensation is the basis for sulfuric acid. There always will be some amount of diesel fuel “blow-by” that finds its way into your engine’s crankcase. If you do not change your oil as often as determined by the engine’s manufacturer, your bearings will suffer more damage from this acid than from actual wear.

When you “exercise” your diesel generator — hopefully, at least once per month to keep seals, rings and bearings lubricated — you should make sure you cycle it for at least half an hour (preferably introducing a load equal to half the expected load by using your load bank) to make sure you bring all components to their full operating temperature. This will help evaporate existing condensation in the top of the valve train, as well as in the exhaust system and in the generator-end.

Fuel Tank, Stator, Rotor, Breakers, Oh My!

Keep in mind that the fuel tank is also a great place for condensation to form. A full tank will develop far less condensation simply due to the lack of air space. Fortunately, condensation will make its way to the bottom of the tank and should be physically drained on a schedule that meets your weather conditions. Hot, humid days and cool nights can develop a lot of condensation both in the fuel tank and in the engine’s oil pan. Make sure the fuel in your tank is treated to avoid the formation of diesel fuel algae. For diesel units it is important to remember the oil in your engine will oxidize over time so it is necessary to change it based on hours used or time exposed, whichever occurs first.

Also, are you aware that moisture is one of the major causes of the eventual deterioration of your stator’s and rotor’s insulation? Unfortunately, this is generally overlooked, especially when a towable generator is rushed to the scene after a storm wipes out the local electricity.

No matter how well the cabinet is designed, towing the unit down the highway in the rain or snow can force (based on the speed of your travel) moisture into the components of the generator.

Alas, not everyone thinks to run the unit with the breakers off for at least half an hour (one hour is preferable) so the stator windings are dried before they have to produce power. In fixed diesel generator applications, there should be a heater system within the generator’s cabinet to reduce temperature fluctuations — thus reducing condensation — so the stator windings are dry when they are called upon to bring stand-by power to the critical application. In these applications, the diesel generator is expected to go from zero to full load within seconds. There is obviously no
drying time allowed.

Battling Dirt and Dust

Expanding the subject to dirt and dust, especially the kind that sticks or has a high iron content, keep in mind that moist dust can conduct electricity and reduce the efficiency of the generator. It can also act as an insulator and reduce the cooling capacity of the air being drawn through the generator and past the engine.

Heat is a major component in the eventual deterioration of the generator’s insulation too. This is why it is so important to research the amount of “rise in temperature” (above ambient) for the generator you choose to purchase. The lower the rise, the longer the service life you should expect. Always make sure you purchase from a high
quality manufacturer — this decision will save you money in the long run.

Keeping your system clean can only further serve to get the maximum life from your investment. “Blow-by” from a worn engine, leaking rear main seal or a faulty PCV system will cause dust to stick to the internal components of your generator. Since generators rely on volumes of air being pulled through them by their internal fan to keep their temperature rise in check, they will also suck in leaked oil or oil fumes, giving dust the adhesion necessary to stick to the internal components and windings. Therefore, any engine problems mentioned above should be immediately addressed and corrected.

We would like to suggest that you develop a rigorous check-in policy for your generators when they are returned from rent. Most importantly, basic points of this check-in procedure should be immediately performed — and preferably quickly executed while the customer is still there. Later, your full testing procedures should include running the unit on a load bank and comparing results to your initially documented test results. Damage done to a rental unit, but not found until the “get-ready” procedure is
performed for the next rental, is money unnecessarily lost directly from your bottom line.

We also suggest that you set and lock the selector switch in the fixed position determined by the customer’s needs at the time of renting the unit. So much damage can be done to a unit should a customer change the position of the selector switch while the unit is generating, that you should take that possibility out of his or her hands. Maintain control of the situation by locking the switch with a padlock. Make sure you keep the key.

Cold weather requires that the fuel be properly treated to match your area’s expected low temperatures. If the fuel is not properly treated, the paraffin in the fuel will solidify and get trapped in all of the filters and screens. This will cause them to clog and the unit will not run until the
filters are changed, the screens cleaned and an additive is mixed into the fuel. This requires a major effort, and the cold temperatures make it a miserable job — so make sure that your fuel is treated before the temperature drops.

Generator Storage

Most manufacturers will also provide step-by-step procedures for long-term storage of your generator. In the rental industry, there could be periods during which rentals are slower than other periods – depending on your individual market. Keep in mind that long-term storage procedures were developed as a means to protect your investment.

The units can quickly be brought back to “ready” condition if a situation is about to make their availability necessary. If you choose not to use a long-term storage procedure (and the unit has not been rented for a long period), you may have to purchase replacement batteries, etc., at the least opportune moment.

Brushless generators, when stored for long periods, may lose their residual magnetism in the exciter circuit. This is easily resolved by disconnecting the AVR (automatic voltage regulator) and connecting two wires to a 12V source
(this procedure is generally described in the troubleshooting portion of your manual as it is an easy and accepted means of isolating the AVR). But, this is an often overlooked test of the generator-end’s condition. We recommend that you do this procedure as an initial test of your new generator. Measure the generator’s voltage output using this procedure and document the results as the generator’s baseline to use for comparison in future tests.

Trailer Maintenance

Your generator cannot perform if it cannot reach the jobsite. Maintenance of the trailer is often overlooked.

A new trailer requires thorough scrutiny within its first week of towing. Most trailer manufacturers recommend the wheel lug nuts be re-torqued several times during the first two hundred miles of towing. The spring shackle brackets and axle’s “U” bolts also need to be re-torqued within the first 200 miles of towing as all these components will “seat” themselves.

Another commonly overlooked maintenance item is the air pressure in the tires. Most trailer tires require a minimum of 50 psi — see the information on the side of your tires for details. The tires’ air pressure and the condition of the tread and sidewalls need to be checked prior to every rental. You should also grease the hubs and check the hub bearings’ free-play every 500 miles.

Speaking of often over-looked issues, confirming that the tow vehicle’s hitch is set at the correct height, keeping the trailer level while it’s being towed, is essential. Too high or too low will not only shift the weight to be heavier on one axle, but it will also change the angle at which the tires
hit the pavement causing them to wear prematurely. Needless to say, the tow vehicle must be within the right weight class to handle the unit. Keep in mind that by law, the fuel tanks must be empty while the unit is being towed, otherwise, all the requirements (including licensing and warning labels) of a fuel truck apply — resulting in what could be a hefty fine.

When you study the manufacturer’s maintenance schedule, keep in mind their recommendations are
set for “normal” applications. High ambient temperatures or dusty applications require that all of the
intervals be shortened. This is something to discuss and determine at the time of purchase so your warranty is well protected.

Good maintenance is always less expensive than a major repair and the documentation thereof as proof that it was done on schedule is your best ally during any warranty situation. Most importantly, good maintenance will extend the service life of your investment, increase its dependability and make it worth more at trade-in time.

Tom Grau is a product and R&D manager with MMD Equipment, Swedesboro, N.J.