Deep Well Pumps
These multi-stage centrifugal pumps are used in deep, small-diameter wells.
During the 1920’s, coupling a vertical motor to a deep well pump revolutionized the farming industry in California. Today, vertical lineshaft turbine pumps continue to serve a variety of industries. Typically seen as multi-stage centrifugal pumps, VTP systems lift water from deep, small-diameter wells and have a maximum operating depth of 400 feet.
Centrifugal pumps feature one moving part—an impeller or series of impellers attached to a shaft driven by a motor. A diffuser houses the impeller and captures liquid off the impeller. During operation, centrifugal force moves the liquid that enters the eye of the impeller. As the water leaves the eye of the impeller, the motion develops a low pressure area that—when combined with atmospheric pressure—causes more liquid to flow towards the inlet.
Since the impeller or impellers turn at high speeds, friction occurs between the impeller and the liquid, and the velocity of the liquid increases. The diffuser collects and converts the velocity to pressure through the use of specially designed, spiral casing that surrounds the impeller. Called a volute, the casing also called the bowl directs the flow to discharge either into the piping system or into another impeller stage that increases the pressure. Each combination of a bowl and impellers is one stage of the multi-stage pump.
Pumping more liquid or developing more pressure requires more energy. When determining the motor size for the pump, a number of factors become apparent. The head or pressure that a pump develops has a direct relationship with the diameter of the impeller, the number of impellers, the inlet opening size, and the amount of velocity developed from the speed of the shaft rotation. While adding stages provides higher pressures, increasing the bowl and impeller size result in larger volumes of flow. In turn, the exit width of the impeller determines the capacity of the pump.
Vertical lineshaft turbine pumps often have electric induction motors or a diesel engine rated at several hundred horsepower, and feature bowls and impellers with a maximum diameter of 55 inches. The pump bowls function as a volute case and submerge entirely into the liquid, and the impellers connect to the driver through a vertical shaft. VTPs work as process water intake pumps for industrial sectors such as mining, oil and gas, municipal, and power generation. They are also used for services such as cooling water, river water intake, industrial process pumps, cooling tower pumps, circulating pumps, fire services, and reclaimed water.
VTP pumps used for deep well applications remain relatively inexpensive and easy-to-maintain. However, deep well pumps decrease in effectiveness at increasing depths and as pumping lift increases. Depending on the need, deep well pumps offer many solutions. Check the depth of your prospective well to see if deep well pumps provide the answer you need. When selecting any type of pump and drive, always check the manufacturer’s specifications and the operating limits of the pump.
Impeller – a rotating set of vanes that cause fluid to rotate
Shroud – the front or back of the impeller
Closed-impeller – impeller with shroud in front and back
Semi-open impeller – impeller that has shroud only on the back
Open impeller – an impeller with no shrouds