The following are the various types of engines which are mostly used to operate pumps: 1. Electric Motors 2. Gasoline Engines 3. Steam Engines 4. Diesel Engines.
Type # 1. Electric Motors:
These can be used only at such places where electric current is available with ease. But now-a-days as mostly everywhere electric power is easily available; water works use electric motors to operate the pumps. Cities also obtain electric power at cheaper rates, because they can use it at off-peak periods, thereby improving the load factor of the power plant.
Motor drive is very convenient for simple and durable centrifugal pumps. While choosing electric motor for water pumping, its cost, simplicity in construction and operation, ruggedness, power factor, starting torque and desirability for varying speed should also be considered.
Type # 2. Gasoline Engines:
The operational cost of these engines is so high that these are uneconomical, therefore, these can be used only in emergency service when other power fails. The pumps can be directly connected to the gasoline engines. The gasoline engine employed should have at least 25% excess power to allow for wear of valves.
Type # 3. Steam Engines:
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Now a days electricity has largely replaced steam engines used for water supply pumps, steam engine is suitable at such places where fuel is very cheap. These engines are most reliable.
Type # 4. Diesel Engines:
The initial cost of these engines is very high, they are difficult to start and their speed is low. These engines required separate electric storage batteries and compressed air for starting. There are large number of moving parts in diesel engine therefore only experienced operator can operate it.
The maintenance cost of these engines is less, but due to above difficulties, these are not commonly used in water pumps. They can be used as stand by units for emergency periods.