Editor's Note: This is the second article the year-long series, Understanding NPSH.  Definition of NPSHThe margin of pressure over vapor pressure, at the pump suction nozzle, is Net Positive...
Q. What are the best materials to use in pump construction to minimize part corrosion? A. Factors to consider in the selection of materials for wetted pump components include user's experience,...
Success Story of the Year 2009
The International Paper plant in Courtland, Ala., had experienced problems with a white water pump on a paper machine since the plant installed the pump in the late 1970s. The problem pump experienced...
Q.We have recently installed several double suction between bearing pumps and would like to verify that their vibration levels are within acceptable limits. How should this be done, and what is an...
An OEM and an end user had installed a number of large, double-suction pumps for a water pumping station project (Figure 1). Soon after, they began to suspect that the pumps were a significant...
Pumps & Systems, March 2007Q.What are the key requirements for good suction piping design for rotodynamic pumps?A.  Good suction piping design must eliminate air entrainment in the liquid,...
NPSH: A Characteristic of All Pumps
Note from Terry Henshaw:This is the first in a year‑long series of articles called Understanding NPSH. These articles were originally prepared as class notes for the all‑day seminar on NPSH...
Pumps & Systems, May 2008 While complete packaged gas and dry chemical feed systems have been in the water treatment industry for many years, liquid metering pump packaged systems are relatively...
PumpCalcs: Be the Pump Designer
I have seen, and I am sure you have too, countless examples of installed pumps that are poor hydraulic fits. These selection mistakes are called off-design pump selections, bad actors, misapplied...
Pumps & Systems, May 2007If pump cavitation is not detected and quickly eliminated, significant damage can occur to the impeller and other internal components. Since cavitation (the formation and...
Upgrades Maximize Efficiency of 82-Year-Old Refinery Pump
Thorough analysis, testing and upgrades renew the life of an old single-stage, double-suction, horizontal split case pump.
Due to high specific gravity, viscosity and particle size of mining materials, centrifugal pumps are continuously challenged in mining applications. New pump technology was created to efficiently move...
The Eleventh in a SeriesThe Injection of Air to Reduce Noise and DamageAs stated in an earlier article, most pumps are not suitable for handling any significant quantity of free gas. (They are just...
For the non-expert in pump technology, selecting the most appropriate pump technology for a specific application or process system can be challenging because many of today's pumps are so...
A power company in the Atlanta, Ga., area wanted to replace its older, coal-fired electric generating units with gas turbine, combined cycle technology to reduce nitrogen oxide (NOx), sulfur dioxide...
Acceleration Head
The Thirteenth in a SeriesIf a centrifugal pump is started with the discharge valve open too far and with a low discharge pressure, the liquid in the suction line may accelerate at a rate that causes...
Do Pumps Require Less NPSH on Hydrocarbons? Stepping NPSHR to Different Speeds
Do Pumps Require Less NPSH on Hydrocarbons?Yes.The extensive application of pumps to hydrocarbon services in the first half of the 20th century produced numerous observations that centrifugal pumps...
Suction Calculators
Last month I reviewed an Excel-based Radial Thrust Calculator and showed how it can predict the magnitude of unbalanced radial thrust when a centrifugal pump is operated to the left of BEP. This month...
Suction Specific Speed (Part Two)
Graph of Minimum Continuous FlowsIn 1982, Richard Dubner of Chevron developed a graph for use in establishing minimum continuous flow rates for centrifugal pumps (see Figure 1). It allows a lower flow...
A refinery's vertical pump passes the test, verifying its performance before installation.The rotating equipment engineers at BP's Whiting Refinery in Indiana approached the support team at a pump...
Packaged Pump Systems and Variable Flow Pressure Boosting
Packaged pump systems are gaining popularity due to their space saving design, simplified installation, single source responsibility and advanced control options with communication ability.Packaged...
April-Wise Pump Quiz: NPSH and Developed Head
In this installment of “Pumping Prescriptions,” I have a quiz for our readers. A typical pump system is shown in Figure 1. A centrifugal pump delivers 200 gallons per minute of water from an open...
How Poor Repairs on Boiler Feed Pumps Affect Performance and Reliability
Analyzing the poor repairs on a boiler feed pumps and how they affect the pump's performance and reliability.It is often said that a picture is worth a thousand words. This old adage could not have...
The Power of Wear Rings Part Two: Efficiency
With a 50 percent decrease in clearance, efficiency is increased by 2 to 4 percent.Part One of this series discussed how wear rings impact pump reliability by increasing rotor stability—reducing...
Hydraulic Pump FAQs April 2011
Q.  When monitoring power consumption by a pump, what measurement methods are normally used and for what purpose?A.  Monitoring the power consumed by a pump can give advanced indication of...
Will Running Pumps Slower Help NPSH Problems?
Pumps & Systems, January 2009If your immediate answer was yes, think again-you might be surprised. Sometimes running pumps faster can actually help avoid cavitation. How so? We need to first...
Performance Curves and NPSH Tests
Editor's Note: This is the fourth article the year-long series, Understanding NPSH. To read the previous article, click here. To read the next article, click here.NPSHR Shown as a Single...
Suction Specific Speed (Part Three): Using Suction Specific Speed to Establish Adequate NPSHA, net positive suction head, NPSH
Tenth in a SeriesA number of technical papers (1, 4, 7, 8) have shown that the maximum damage rate to centrifugal pumps, at least in water services, typically occurs when the NPSHA is in the range of...
Hydraulic Institute Pump FAQs January 2007
Q. I have been told that centrifugal pump impellers may still cavitate when operating with NPSH Available greater than NPSH Required. Is this true? If so, why do pump suppliers show NPSHR values when...