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Centrifugal Pump Efficiency — Specific Speed

	
		

	Editor's Note: This is the second in a six-part series on centrifugal pump efficiency. For other articles in this series, click here.

Early centrifugal pump design was heavily influenced by turbine...	

	
           
        	













  



  

    





	
			
Centrifugal Pump Efficiency—What Is Efficiency?

	
		

	Editor's Note: This is the first in a six-part series on centrifugal pump efficiency. For other articles in this series, click here.In this multi-part series, we will investigate several aspects of...	

	
           
        	













  



  

    





	
	
Off-BEP Energy Cost
		
Off-BEP Energy Cost

	
		

	Keeping a close eye on pump efficiency can lead to energy savings.Last month, I discussed the Draw Down calculator and its role in determining the actual operating point of wastewater pumps. Like...	

	
           
        	













  



  

    





	
			
AC Motor Torque

	
		

	As a follow up on my AC Motors series, I thought it would be a good idea to provide a short overview of work, power and torque as it applies to the AC motor. I will provide a reference to a more in...	

	
           
        	













  



  

    





	
			
AC Motor Torque

	
		

	As a follow up on my AC Motors series, I thought it would be a good idea to provide a short overview of work, power and torque as it applies to the AC motor. I will provide a reference to a more in...	

	
           
        	













  



  

    





	
			
AC Motors Part 4: Frame Size, Enclosures & Nameplate Data

	
		

	The frame sizes (physical dimensions) of AC motors have changed substantially through the years. Originally, they were considerably larger than those in use today. This increased size was the result...	

	
           
        	













  



  

    





	
			
AC Motors Part 4: Frame Size, Enclosures & Nameplate Data

	
		

	The frame sizes (physical dimensions) of AC motors have changed substantially through the years. Originally, they were considerably larger than those in use today. This increased size was the result...	

	
           
        	













  



  

    





	
	
AC Motors Part 5: AC Motor Life
		
AC Motors Part 5: AC Motor Life

	
		

	One of the major impacts on motor life is common sense—or maybe the lack thereof!It always amazes me how many open drip proof (ODP) motors are used in agricultural irrigation applications where...	

	
           
        	













  



  

    





	
	
AC Power (Part Four): Transformers
		
AC Power (Part Four): Transformers

	
		

	Last of four partsLast month, we studied the properties and effects of resistive, inductive and capacitive loads in an AC circuit. This month, we will take self induction a step further and apply it...	

	
           
        	













  



  

    





	
	
AC Power (Part Three): AC Circuit Loads
		
AC Power (Part Three): AC Circuit Loads

	
		

	AC Circuit LoadsLast month we discussed the relationship between voltage and frequency and tried to make that somewhat complex three phase sine wave a bit more understandable. This month we will...	

	
           
        	













  



  

    





	
	
Calculating Energy Savings and Payback
		
Calculating Energy Savings and Payback

	
		

	Energy efficiency and reduced consumption are important issues in the pump and motor marketplace. Over the long term, electricity costs will continue to increase regardless of our actions. This will...	

	
           
        	













  



  

    





	
	
Calculating Pump Starts and Cycle Time
		
Calculating Pump Starts and Cycle Time

	
		

	Starting can have a significant effect on the life of the winding insulation of an AC motor. For this reason, motor manufacturers often limit the number of starts per hour and may also require a...	

	
           
        	













  



  

    





	
	
Calculating Radial Thrust
		
Calculating Radial Thrust

	
		

	The radial forces that form about the periphery of a single volute pump's impeller are proportional to total pump head, impeller diameter and vane width. They are seldom balanced, but they reach their...	

	
           
        	













  



  

    





	
			
Corrosion: A Natural Process

	
		

	About 900 years before Newton formulated his universal gravitational theory, the Greek philosopher Aristotle espoused something different. He believed that all things had a natural place in the...	

	
           
        	













  



  

    





	
			
Magnetic Couplings: An Investment that Can Provide Mulitple Returns

	
		

	A number of choices are available  when connecting pumps, fans and other rotating equipment to an electric motor. There are numerous mechanical and fluid coupling designs and, in some cases, a...	

	
           
        	













  



  

    





	
	
Net Positive Suction Head: NPSHR and NPSHA
		
Net Positive Suction Head: NPSHR and NPSHA

	
		
Addressing Net Positive Suction Head (NPSH) and its relationship to cavitation

	
           
        	













  



  

    





	
	
Variable Frequency Parallel Pump Analyzer
		
Variable Frequency Parallel Pump Analyzer

	
		

	There are several ways to control two identical, parallel pumps operating under variable frequency control in pumping applications. One method is to size a single drive to handle both pumps and vary...	

	
           
        	













  



  

    





	
	
Variable Speed Pump Analysis
		
Variable Speed Pump Analysis

	
		

	When selecting a pump for variable speed operation, a number of conditions must be evaluated. For example, will the performance curve allow the range of operation required by the application? Will the...	

	
           
        	













  



  

    





	
	
Wastewater Pump Draw Down Calculator
		
Wastewater Pump Draw Down Calculator

	
		

	Based on several of my previous Pumps & Systems articles, you probably know that I have major concerns about the off best efficiency point (BEP) operation of wastewater pumps. Last month, I...	

	
           
        	













  



  

    





	
			
Positive Displacement Pumps (Part Two): Rotary Pumps

	
		

	Rotary pumps are positive displacement pumps that use rotational, rather than reciprocating, motion during their pumping cycle. They can be designed to pump liquids, solids, gases or mixtures of all...	

	
           
        	













  



  

    





	
			
Preservation of Efficiency - Affinity Revisited

	
		

	My September tutorial took a look at the affinity laws and showed why each is able to predict changes in flow, head, and power when there is a change in pump speed or impeller diameter.One thing I did...	

	
           
        	













  



  

    





	
	
Centrifugal Force & Affinity- It's All About Velocity
		
Centrifugal Force & Affinity- It's All About Velocity

	
		

	Why do those three affinity laws do such a good job of predicting the performance of a centrifugal pump when its rotational speed or impeller diameter is changed? Well, it turns out that they are not...