section VIll etectrical generation R is highly desirable that a trained General Electric field representative conduct the dismant- ling, inspection, and reassembly procedures. ARMATURE CORE The armature core should be inspected during inspections, particularly for evidences of hot spots, damaged punchings, or evidence of movement of parts. Ifthe core is in need of painting, all sur- faces should be cleaned as recommended in the in- struction book, and the punchings should be sprayed with General Electric No, 7815 oil-resistant Glyptal enamel. The inside of the frame should be checked for evidences of oil which would indicate oil leakage from the shaft seals past the oil deflectors. ARMATURE WINDINGS, Inspect the ends of the armature windings for deposits of oil and evidences of corona discharge. If cleaning is necessary, it should be done as de- scribed under cleaning in the instruction book. After cleaning, inspect the windings and insulation care- fully, Inspect for evidence of excessive torques on the end windings due to synchronizing out of phase or short circuit. ‘These may show up as distortion of windings, broken or cracked varnish, broken or loose ties, broken or missing blocks, and any move- ment of the spacer between the inner and outer bars. ‘Significant damage should be reportedto the factory, If the end winding is in need of painting, it is recommended that General Electric enamel No. 7815, or equivalent, be applied by spraying, after the windings have been thoroughly cleaned and dried. Caution is necessary in the use of a spray because of the fire hazardinvolved, since practically all in- sulating varnishes are combustible and have a low flash point, and ignition is readily causedby a spark, flame, or excessive heat of any kind. To reduce this risk as much as possible, all metal parts, both of the spraying apparatus andthe machine tobe sprayed, should be grounded to a common ground, ROTOR ‘The rotor should be checked carefully for tight- ness of all parts and for any signs of cracks or other damage which might be caused by local over- heating, unbalanced load operation, or fatigue. Vis~ ually inspect rotor for cleanliness and indications of moisture, CLEANLINESS OF INSULATED WINDINGS To obtain the most satisfactory operation and life of insulated windings, they should be kept rea~ sonably clean from dirt, oil, metal dust, contamin- ators, etc. ‘This requires operation in clean air and the performance of complete inspection, clean- ing, and revarnishing at the required intervals. Under normal conditions, Class Binsulated wind- ings can be cleaned by blowing out with dry air, by brushing, by wiping with dry cloths, etc. For ex- tremely dirty conditions, it may be necessary to clean with a suitable liquid solvent having satistac- tory fire and toxic characteristics. ‘The solvent should dry reasonably fast, and should have proper solvent characteristics for grease and oil, but @ minimum ‘solvent effect on insulating varnishes. Moreover, it should not leave an oily residue on the windings which woutd preclude subsequent successful application and curing of insulating varnish. Such solvents can be applied by spraying, hosing, brush- ing, oF with cloths. ‘The solvent should be applied in such a manner as to obtain optimum cleaning without subjecting windings to cleaner for an undue length of time. After being cleaned by solvent, the winding should be thoroughly dried by air or heat circulation. The insulation polarization index should be used to deter- mine if the winding is sufficiently dry before the application of voltage. After several light solvent~cleaning operations, or following a severe cleaning or major overhaul, it is usually necessary to revarnish the windings. Be- fore revarnishing, the windings should be clean and dry, as determined by the polarization index. After varnishing, the machine should not be placed in op~ eration until the varnish has dried completely. Class B windings should be revarnished with ar air- drying varnish such as GE No, 1202, or equivalent. ‘Multiple coats should be applied, allowing for dry- {ing between each coat. All varnishes should be applied in accordance with the manufacturer's recommendations. ‘The time required for drying the windings after cleaning will vary according to conditions in the shop at the time, such as temperature, humidity, etc. Windings cleaned with this solvent should dry approximately two hours at room temperature, or approximately one hour if heated to 15 C above room temperature, or if subjected to forced air. vi-7