Newtonian and Non-Newtonian Fluids
How viscosity affects centrifugal pumpsThe Hydraulic Institute published a standard to account for the effects of viscosity of centrifugal pump performance. Effects of Liquid Viscosity on Rotodynamic...
Do Vibration Measurements Depend on Probe Placement and Probe Type?
Typically, vibration measurements are taken with a handheld accelerometer probe in four places:Pump outboard bearing housingPump inboard bearing housingMotor inboard bearing housingMotor outboard...
Editor's Note: While running a pump at its best efficiency point saves money, reduces downtime and improves performance, many plant managers are unaware of how their equipment is actually...
While running a pump at its best efficiency point saves money, reduces downtime and improves performance, many plant managers are unaware of how their equipment is actually performing. This series,...
One of the supposed advantages of centrifugal pumps when compared to positive displacement pumps is their ability to operate across a wide flow range. Because a centrifugal pump operates at the...
Lev Nelik answers a reader's question on thermodynamic sub-processes that are highly time dependent
In past “Pumping Prescriptions” columns this year, I have discussed the procedure of piping size selection when given the process flow requirement and how this affects the pump’s power...
Last year, “Reduce Thrust and Extend Bearing Life” (Pumps & Systems, December 2013) discussed the benefits and some potential pitfalls of adjusting the axial clearance of American National...
I received a lot of feedback on my column “How Much Energy Do Pipes Remove?” in the September issue of Pumps & Systems. This column described the use of two computer programs that evaluate the...
Who determines where pressure gauges are located in a pump system? How close to the pump should they be, and what happens if these rules are not followed? For a small pump system, the impact on the...
When the pump selection process starts, the required flow of the is often the only known variable for an application. For example, a system must move 2,000 gallons per minute (gpm) from a holding tank...
My last two columns (Pumps & Systems, April and May 2014) explained how pump suction behavior depends on how suction pressure is reduced. The original video, which showed two suction pressure tests,...
Pump System Design
Last of Two Parts
First of Two Parts Cavitation can severely damage pumps and is affected by pump design and system issues. What affects it most? Does the suction behavior from the discharge side (system) of a pump...
These days, the importance of a fresh water supply and safely-treated wastewater return to the river cannot be overemphasized. No matter how hard we try, we are still a long way from the most...
Positive displacement (PD) pumps do not function well if the discharge is blocked. Unlike centrifugal pumps, they have little tolerance for flow restriction. A piston pump will try to continue...
Part 1 (Pumps & Systems, August 2012) discussed an example in which neglecting corrections for velocity head and gauge elevation did not introduce significant errors in the calculations. Part 2...
How Important Is Accounting for Velocity Head and Gauge Elevation? (Part 1 of 2)
For a quick estimate of pump head in the field, the discharge pressure gauge is read. This number is multiplied by 2.31, and operators can get a rough value of the pump head. If the gauge reading is...
This article will discuss a case of how measuring vibration can help detect cavitation issues. It will also show how this can relate to a bigger problem at the plant. Sometimes a proposed change of...
There are many indications that end users should not use a valve for flow control—or at least not to extremes.
Recently, I received a call from a plant operator in Ohio. He said, “We have a big contract from a customer to supply multiple oil heating systems and have just completed the first unit. It is ready...
Summer Pump Quiz—Solutions
Last of Two Parts
This article was written in response to the following question from a reader: Could you explain how an ANSI pump impeller’s clearance setting (both an open-vane impeller with back pump-out vane...
Pump designers know that designing a complex pump is easier than designing a simple one. Having my own roots in design, I know how tempting it is to add another feature and a tweak to a pump design....
Resonant Frequencies
Last of Two Parts
Summer Pump Quiz—Cavitation
Let’s start with the basics: boiling is the vaporization of liquid. In a kitchen, water boils at high temperature—100 C (212 F). These temperatures are at atmospheric pressure, however.Liquid can...
Resonant Frequencies
From vertical pump rotors to bacteria, resonance has similar effects.
Thermal Stress Affects Pipe Forces on Pumps
Temperature changes can push pipe force beyond safe limitsTo view all of the articles in the Thermal Stress Affects Pipe Forces on Pump series, click here.Two major headaches for pump plant...
Shaft & Bearing Material Selection
How important is the hardfacing requirement below the sleeve bearings in the 416 stainless steel (ss) shaft of a vertical turbine pump used to move condensate? Consider an example with a condensate...