remove the old grease and lubricatethe bearings with new grease. To do this. disassemble the bearing housings and clean the inside of the housings and housing plates or caps and the bearings with a suitable solvent. When you have thoroughly cleansed them of old grease. reassemble all parts except the outer plates or caps. Apply new grease, either by hand or from a tube, over and between the balls. The amount of grease you should use varies with the type and frame size of the particular motor. You should consult the instruction sheet that accompanied the motor for this information.

You should add enough grease to fill the bearing housing one-third to one-half full. Do not use more than the amount specified. After reassembling the motor, you should refill any V-grooves that are found in the housing lip with grease (preferably a fibrous. high-temperature-sealing grease) that will act as an additional protective seal against the entrance of dirt or foreign particles.

Roller Bearings

The technique for greasing motors equipped with roller bearings is quite similar to that used for ball bearings. However, you should follow specific instructions for the individual design because more frequent greasing or slight changes in technique may sometimes be necessary.

Sleeve Bearings

With the motor stopped, you periodically should check the oil level in the sleeve-bearing housings. If the motor is equipped with an oil-filler gauge, the gauge should be approximately three-quarters full at all times.

If the oil is dirty. drain it off by removing the drain plug, which is usually located in the bottom or side of the bearing housing. Then flush the bearing with clean oil until the outcoming oil is clean.

Fractional-Horsepower Motors

In fractional-horsepower motors, there may be no means of checking the oil level, as all the oil may be held in the waste packing. In such cases, a good general rule for normal motor service is to add 30 to 70 drops of oil at the end of the first year and to reoil at the end of each subsequent 1,000 hours of motor operation.

Most fractional-horsepower motors built today require lubrication once a year. Small fan and agitator motors often require more frequent lubrication with 3-month intervals between oilings.

MOTOR STORAGE

Motors should be stored in a dry, clean place until ready for installation. Heat should be supplied, especially for larger high-voltage machines, to protect them against alternate freezing and thawing. This advice is equally applicable to spare coils.

Motors that have been in transit in a moist atmosphere or have been idle for an extended period without heat to prevent the accumulation of moisture should be dried out thoroughly before being placed in service. Machines also may become wet by accident. or they may sweat as a result of a difference between their temperature and that of the surrounding air. This condition is harmful particularly in the case of large or important motors, and should be prevented, by keeping them slightly warm at all times.

You can pass current at a low voltage through the windings, use electric heaters, or even use steam pipes for protective purposes. During extended idle periods, you can stretch tarpaulins over the motor and place a small heater inside to maintain the proper temperature.

If a motor should become wet from any cause, you should dry it out thoroughly before operating it again. The most effective method is to pass current through the windings, using a voltage low enough to be safe for the winding in its moist condition.

You can apply heat externally by placing heating units around or in the machine and cover the machine with canvas or some other covering, and then leave a vent at the top to permit the escape of moisture. You can use small fans to help circulation. You should not allow the temperature of the windings to exceed 100°C for Class A insulated motors.

PERIODIC INSPECTION

A systematic and periodic inspection of motors is necessary to ensure best operation. Of course, some machines are installed where conditions are ideal; and dust, dirt, and moisture are not present to an appreciable degree. Most motors, however, are located where some sort of dirt accumulates in the windings, lowering the insulation resistance and cutting down creepage distance. Dusts are highly abrasive and actually cut the insulation while being carried by ventilating air. Fine cast-iron dust quickly penetrates most insulating materials; hence, you can see why motors should be cleaned periodically. If conditions are extremely severe, open motors might require a certain amount of cleaning each day. For less severe conditions. weekly inspection and partial cleaning are