Types of Centrifugal Pumps
Centrifugal pumps consist of impellers and volutes and turn electrical energy into mechanical energy. The impeller rotates producing centrifugal force that adds to the pressure of a fluid budging the liquids in the desired direction through a piping system. There are basically two types of centrifugal pumps; Single-stage radial flow centrifugal pumps and multistage centrifugal pumps.
Single-Stage Centrifugal Pumps
These pumps consist of one impeller and are used in production operations to offer pump low to moderate pump services total dynamic head of less than 700ft/min. The characteristic curve of the pump is shown below:
Graph showing single-stage centrifugal pump characteristics. Retrieved from http://www.globalspec.com/ImageRepository/LearnMore/20122/capacity24d5b861bd62d43958b3fdf32e180523e.gif
Multistage Centrifugal pumps
Multistage pumps have two or more impellers, each being a separate pump but al within the same casing installed on the same shaft. The pumps are used in moderate to high total dynamic head pumping services. Its characteristic curve is shown below:
Graph showing single-stage centrifugal pump characteristics. Retrieved from http://www.pianetaacquasrl.it/elettropompe/images/diagramma34acm.jpg
Centrifugal Pumps Clogging
Clogging on the discharge line of the pump causes high discharge pressure due to the increase in resistance to the flow of pumped fluids by the clogs. This leads to the pump operating at less than 10% off its best efficiency point (American Water Works Association). The high discharge pressure required to overcome the resistance causes the liquids to circulate at very high velocity inside the pump instead of out of the pump. This rapid liquid flow between the impeller and the housing causes a vacuum in the casing that leads to the formation of bubbles. Implosion of the bubbles results in intense shock waves that lead to rapid wear of the pump casing and impeller tip. This may also cause an overload in the pump’s motor.
Types of Pumps and their Applications
Air Operated Pumps
The pump use compressed air to operate its pumping movement and are designed to operate at most operating pressures and flows. The pumps can deliver high pressure, constant or pulsating flows. Air operated pumps are used in metal manufacturing and water cutting applications.
Piston Pumps
Piston pumps use one or more reciprocating pistons to pressurize and eject fluids usually powered by an electric motor through a crankshaft. The pumps are used as hydraulic pumps and employed to power heavy machinery and also in smaller applications like paint sprayers.
Submersible Pumps
The pumps are built to work with both motor and pump submerged in fluids to be pumped with the motor sealed to prevent liquids from seeping in and causing short-outs. The pumps are used in irrigation systems and oil production.
Slurry Pumps
Slurry pumps are designed with durable material to handle thick and solid filed slurries without wearing out quickly. The pumps are best suited for applications such as mining and mineral processing plant.
Static Head Measurement
Total static head is the total elevation that a pump must lift water when moving it from a lower point to a higher point. It can be found from measuring pump elevations and reservoirs using a pressure gauge when the pump is not running and finding their difference.
Velocity Head Measurement
This is the maximum force that a pumped fluid can exert when its velocity is changed. It can be found by dividing the square of the velocity by two times the gravitational constant (Casada). The velocity is calculated from the area of the pipe and the volumetric flow rate.
Hydraulic Grade Line
Hydraulic grade line is the level that water in an open vertical tube connected to a pipe would rise to when the pipe undergoes pressure.
Total Energy Line
This is the sum of the elevation in the center of a pipe, the pressure head and the velocity head.
Total Dynamic Head
This is the total elevation that a fluid needs to be pumped with various losses such as friction in the pipe accounted for.
Works cited
American Water Works Association. Basic Science Concepts and Applications. N.p.: American Water Works Association, 12 Jan. 2011. Web. 11 Feb. 2016.
Casada, Don. “Performance Optimization Tips: Field Measurements in Pumping Systems.” U.S. Department of Energy - Energy Efficiency and Renewable Energy (7 Sept. 2009): n.pag. Print.
Casada, Don. “Performance Optimization Tips: Field Measurements in Pumping Systems.” U.S. Department of Energy - Energy Efficiency and Renewable Energy (7 Sept. 2009): n.pag. Print
