When we talk about the efficiency of a machine, we simply mean how well it can convert one type of energy to another. If a machine receives one unit of energy and produces one-half unit in the same units of measurement, its efficiency is 50%.
A common example of such a machine is the heat engine, which uses heat energy to generate mechanical energy. Although, the machine is a necessary part of our daily lives, its efficiency in converting energy is much lower than we might expect.
Here, we will understand about pump motor efficiencies in wastewater treatment plants.
What is Pump Motor Efficiency in Wastewater Treatment Plants?
Much of the work in the pump industry is done with two extremely simple, but efficient machines: the centrifugal pump and the AC induction motor.
The centrifugal pump converts mechanical energy into hydraulic energy (flow, velocity, and pressure), while the alternating current (AC) motor converts electrical energy into mechanical energy.
Many medium and larger centrifugal pumps have efficiencies ranging from 75 to 93 percent, and even smaller ones typically have efficiencies ranging from 50 to 70 percent. Large AC motors, on the other hand, approach 97 percent efficiency, and any motor with ten horsepower or more can be designed to exceed 90 percent efficiency.
Types of efficiencies in wastewater pumps
There are three types of efficiencies to consider with a typical submersible wastewater pump: pump end, motor, and wire-to-water.
Wire-to-water efficiency, also known as combined or total efficiency, takes into account both the pump end efficiency and the motor efficiency, to generate a single number for the entire pump and motor system. This includes losses attributed to bearings, mechanical seals, and power cables.
Wire-to-water can also include controls and variable frequency drives (VFDs), emphasizing the importance of overall system efficiency. Because, the pump and motor both have efficiency curves, the wire-to-water efficiency should be described as a curve plotted against flow.
What factors should be considered when choosing a pump for a wastewater treatment process?
Some pumping characteristics that are important for various processes include:
· ability to work with viscosities ranging from high to low and variable
· pumping of solids
· repeatability of self-priming flow
The following factors are considered during the pump selection process:
· The fluid properties of the process application
· Batch or continuous operation
· The operating envelope system curves for the system hydraulics
· Pump and control selection to meet the process application and operating envelope
· Material selection for dependable operation
How is Pump Efficiency achieved?
A centrifugal pump's overall efficiency is the sum of three individual efficiencies: mechanical, volumetric, and hydraulic.
1. Mechanical efficiency includes bearing frame, stuffing box, and mechanical seal losses.
2. Volumetric efficiency includes leakage losses through wear rings, balancing holes, and vane clearances in semi-open impellers.
3. Hydraulic efficiency takes into account liquid friction as well as other losses, in the volute and impeller.
If you have any questions about wastewater treatment pumps and the calculation of pump motor efficiency in WWTPs, please contact the Netsol Water team right away. Our team is an expert in water treatment and can help you tailor a solution to your specific requirements.
We collaborate with our clients to design a customized wastewater treatment solution that meets your specific requirements, as well as an on-going service plan to completely maintain your system.