Belt drive maintenance requires proper belt tension. If the belt is too loose or slack, the power of the prime mover is not transmitted efficiently. Belt slippage also results in excessive rubbing and wear of the belt on the sheaves. Sheaves worn or out of alignment can also contribute to excessive belt wear. Additionally, belt slippage can be caused by an accumulation of oil or grease on the sheaves. If the belt is too tight, on the other hand, the stress is transmitted to the bearings in the sheaves and along the shafts. This condition causes excessive bearing wear and misalignment.
A properly adjusted belt has a very slight bow in the slack side when running. When idle, the belt has an "alive" springiness when thumped with the hand. Lack of this springiness indicates too little tension. A belt that is too tight feels dead when thumped with the hand.
While the motor is in operation, you should visually inspect the belt drive periodically for any indication of improper tension or slippage. Also, be careful to keep the belt and sheaves clean and free of grease or oil at all times. At prescribed intervals, inspect the belt for fraying, for cracks, or other unusual wear. You should also inspect and check the alignment of the sheaves. Excessive belt rubbing on the sheaves is an indication of belt slippage. Sheaves that are out of alignment are normally a result of excessive belt tension.
Occasionally, it may be necessary to replace a worn and frayed belt. If the drive has multiple belts, ALL the belts must be replaced with a set of matched belts. The belts in a matched set are machine-checked to ensure equal size and tension.
In addition to the maintenance and inspections outlined above, the operator must test and inspect other items related to the motor, such as control switchboards, pilot lamps, alarms, and circuit breakers. Electrical connections and conductors must also be periodically inspected for proper insulation and security.
SAFETY. - Because of the danger in working with electric motors, all safety precautions should be observed. In operating electric motors and in performing operator maintenance on electric motors, remember that you are working on a device which carries a force of energy that is not only useful but also deadly.
CLEANLINESS. - Cleanliness of electric motor operation and maintenance is largely a matter of prevention, rather than inspection and correction. As an operator, you must develop clean housekeeping and maintenance habits. Dirt, dust, and other foreign objects that accumulate on and inside an electric motor can reduce ventilation and foul moving parts. When dirt and grit accumulate on windings, the cooling or ventilation of these electrical conductors is seriously reduced. During the inspection routines, prevent lubricants and lubricant fittings from getting contaminated. Dirt in lube oil, in many cases, settles to the lowest point in the system before doing any extensive damage; however, dirt or grit that gets into lubricating grease can remain suspended indefinitely and result in abrasion of bearings and moving surfaces.
The maintenance schedule usually requires periodic inspection and cleaning of the rotor and the stator windings. Low-pressure compressed air can be used to blow out the dirt and dust; however, in the stator, this method can sometimes result in dirt being driven deeper into the windings. Instead, you should use vacuum suction. In fact, vacuum suction is always the preferred method for removing dust and dirt from stator windings or from any other motor component when compressed air could force dirt and abrasive particles deeper into the mechanism. Accumulations of grease and oil can be removed with the proper type of petroleum solvent. In any case, consult local maintenance schedules and instructions for the specific and precise cleaning method.
An internal combustion engine is a machine that produces mechanical energy by burning fuel in a confined space (the engine cylinder). The term applies to both diesel and gasoline engines. is a machine that
The Utilitiesman should have a basic knowledge of the principles of diesel and gasoline operation, since the Utilitiesman has to operate and hold first-echelon maintenance of the engine used to drive various types of pumps and compressors.
Operation and Maintenance of Diesel Engines
Diesel engines change heat energy into mechanical energy. Heat is developed when a mixture of compressed fuel and air burns inside a cylinder. A complete description of the internal combustion engine and its principles of operation is in chapter 12 of Basic Machines, NAVEDTRA 12199.Continue Reading