What is a Centrifugal Pump?
A centrifugal pump increases the speed of a liquid in a pipe system by using a rotating impeller. An impeller is built inside the pump itself and is responsible for moving the liquid into the pump. This type of pump is most commonly used in relation to a liquid pipe system and can be found in a manufacturing environment, water treatment or food processing plant. The centrifugal pump was first documented in 1475 in the writings of Francesco di Giorgio Martini. Modern pumps were developed in the late 1600's by Denis Papin.
The force behind the pump is created through the use of the rotational kinetic energy from an electric motor. As the pump impeller rotates, it creates energy that allows the liquid to be drawn toward the center of the impeller, and then forces it out again. This pressure causes an increased pressure further downstream in the pipe, forcing the liquid to flow. An impeller is just like a propeller, but without the blades.
In order to slow down the flow of a liquid, resistance must be created. When the centrifugal pump casing catches the liquid and controls the flow, it slows down the kinetic energy and converts it into pressure energy. It is important to remember that the pressure is a measurement of the flows resistance and is not create by the pump.
On occasion, the discharge of the centrifugal pump is pointed straight up. In these circumstances, the liquid is pumped up, but only to a predetermined height. This height is called the shut off head and is limited by the diameter of the pump's impeller and the rotational speed of the pump itself.
There are seven different types of pump heads in a centrifugal pump: total static, total dynamic, static suction, static lift, static discharge, dynamic suction and dynamic lift. The head of the pump is measured in imperial or metric measurements and can be found in a wide range of hardware stores. All fluids will be pumped at the same height, as long as the shaft of the centrifugal pump is putting out the same level of effort.
The only adjustment required when changing the liquid in the pump is the amount of power required. To determine if more or less power is required, check the specific gravity for the fluid. The higher the rating, the more power you will need to generate to obtain the same amount of height.
Why don't centrifugal pumps require a relief valve like positive displacement pumps have?
@bluespirit - It depends on what you want to do with the water and how far up you need to push the water (So it just keeps getting more difficult to decide, huh)!
Here are some pointers:
If you're lifting less than 25 feet, from the pond, a centrifugal pump is best.
The next question is do you need to run an irrigation system with this water? If you do you will want a centrifugal irrigation pump.
If you're just moving water from point A to point B, you will need a small centrifugal pump.
If you need to pump more than 25 feet from the pond your only option is the vertical centrifugal pump.
I'm going to guess you may be moving water from point A to point B and wanted to let you know small centrifugal pump options include small disposable engine powered pumps from 200-300 dollars or PTO powered pumps from 2000-3000 dollars.
I am trying to decide what type of pump I need to pump out my pond, but am overwhelmed with the multitudes of choices. Even if I narrowed it down to needing a centrifugal type pump there is still a small centrifugal pump, vertical centrifugal pumps, and centrifugal irrigation pumps!
I'm simple pump-whelmed!
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