VALVE GP-RELIEF 1913952 - Caterpillar

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Personal injury or death can result from improper troubleshooting and repair procedures.The following troubleshooting and repair procedures should only be performed by qualified personnel familiar with this equipment.
Refer to this Operation and Maintenance Manual, "Generator Isolating for Maintenance" for information regarding the procedure to isolate the generator in a safe manner.Refer to Special Instruction, SEHS9124, "Cleaning and Drying of the Generator" for further necessary information.Of the following methods for drying the generator, the use of external heat is preferred.
External heat
Internal heat
Combination of external and internal heat
Circulating currentExternal heat is the most preferable method. Insulation drying time can vary from a few hours to several days. The drying time depends on the moisture content and the process for drying that is used.Note: Drying sometimes does not produce the required results. The use of a qualified rebuild shop may be necessary for dipping and drying the generator.
Illustration 1 g02175752
Typical curves of the resistance in the insulation that is drying
(1) Curve of the temperature in the windings
(2) Heat turned off.
(3) Drying time in hours
(4) Temperature in degrees celsius
(5) Curve of insulation resistance during drying process
(6) Insulation resistance in megohmsNote: When new insulation or damp insulation is being dried, the resistance will probably fall rapidly. The rapid fall in resistance is the result of the temperature being raised to a value for drying. After reaching a minimum for a given temperature, the resistance will again rise as moisture is driven out of the insulation. The actual values will vary with each situation. Refer to Illustration 2.If the windings or insulation is wet during the resistance measurement, use a 5 megohm resistor for protection in series with red positive lead. This procedure limits the voltage across the circuit under the test. Use this method until drying is well in progress and the resistance has reached an acceptable level.Check the windings after every 4 hours when either external or internal heat is used to dry the generator. Check the windings every hour when circulating current is used to dry the generator. Refer to Special Instruction, SEHS9124, "Cleaning and Drying of the Generator" for more information.Drying is complete when the tests show no increase in resistance and the resistance is above the minimum. Record these readings and compare these readings. Keep these records for future reference.
Illustration 2 g01696934
Curve of insulation resistance for windings in good condition
(1) Resistance after 30 seconds
(2) Resistance