853722 20 Mercury NUT

The high voltage that is produced by an operating generator set can cause severe injury or death. Before performing any maintenance or repairs, ensure that the generator will not start.Place the engine control switch in the "OFF" position. Attach "DO NOT OPERATE" tags to all starting controls. Disconnect the batteries or disable the starting system. Lock out all switchgear and automatic transfer switches that are associated with the generator.
Refer to Safety Section, "Generator Isolating for Maintenance" for information regarding the procedure to isolate the generator safely.Correct maintenance of electrical equipment requires periodic visual examination of the generator and periodic visual examination of the windings. Proper maintenance of electrical equipment also requires appropriate electrical checks and appropriate thermal checks. Insulation material should be examined for cracks. The insulation material should be examined for accumulations of dirt and dust. If there is an insulation resistance value that is below normal, a conductive path may be present. This conductive path may be made of one of the following materials:
Carbon
Salt
Metal dust
Dirt that is saturated with moistureThese contaminants will develop a conductive path which may produce shorts. Cleaning is advisable if heavy accumulations of dirt can be seen or if heavy accumulations of dust can be seen. If excess dirt is the cause of a restriction in the ventilation, cleaning is also advisable. Restricted ventilation will cause excessive heating.
To avoid the possibility of deterioration to the generator windings, do not clean the generator unless there is visual, electrical, or thermal evidence that dirt is present.
If harmful dirt accumulations are present, various cleaning techniques are available. The cleaning procedure that is used may be determined by one of the items on the following list:
The extent of the cleaning procedure that is being attempted
The type of enclosure of the generator
The voltage rating of the generator
The type of dirt that is being removedCleaning (Assembled Generators)
Do not use water to clean the generator.
Do not use trichloroethane, perchlorethylene, or trichloroethane or any other alkaline products to clean the generator.
Cleaning may be required at the point of installation. At this point, complete disassembly of the generator may not be necessary or feasible. In this case, a vacuum cleaner should be used to pick up the following items: dry dirt, dust and carbon. This will prevent the spreading of these contaminants.A small non-conductive tube should be connected to the vacuum cleaner. This will allow the vacuum cleaner to clean the surfaces that are not exposed. After most of the dust has been removed, a small brush may be attached to the vacuum hose in order to loosen dirt that is more firmly attached to the surface.After the initial cleaning with a vacuum, compressed air may be used to remove the remaining dust and dirt. Compressed air that is used for cleaning should be free of moisture and free of oil. Air pressure should be a maximum of 210 kPa (30 psi) in order to prevent mechanical damage to the insulation. If the above cleaning procedures are not effective, consult a Cat dealer.Cleaning (Disassembled Generators)
Do not use water to clean the generator.
Do not use trichloroethane, perchlorethylene, or trichloroethane or any other alkaline products to clean the generator.
An initial insulation resistance check should be made on the generator in order to confirm electrical integrity. A minimum reading of one Megohm would be expected with severely contaminated generators. A zero Megohm reading may indicate an insulation breakdown. An insulation breakdown requires more than cleaning. An insulation breakdown requires repair.Use the following for cleaning the stator, the rotor, the exciter, and the diode bridge:
Unleaded Gasoline
Toluene
Benzene
CiclohexareAvoid permitting the solvent to run into the slots. Apply the solvent with a brush. Use a sponge on the windings frequently in order to remove the debris. Dry the winding with a dry cloth. Allow the solvent to evaporate before reassembling the generator.Allow the generator to dry at room temperature. Check the insulation resistance. The insulation resistance should now be normal. If the insulation resistance is not normal, repeat the procedure.Note: For more information on drying methods, refer to Special Instructions, SEHS9124, "Cleaning and Drying of Electric Set Generators".