If a pump suction is not placed an acceptable distance from the surface of the liquid, the pump can experience vortexing. Similar to cavitation, with the loss of efficiency and damage that can occur to the pump, vortexing is the result of too much water relative to the pit/sump depth being drawn into the suction line. A depression forms on the surface of the water and is commonly seen as a whirling vortex.
Many have seen a whirling vortex form when a sink or bathtub drains. As the water level in the tub decreases, the ferocity of the whirlpool increases, with a column of air often visible all the way into the drain. A noticeable whirl on the surface of the body of liquid being pumped does not need to be perceptible to human eyes to cause damage, and in the worst cases, a column of air can lead straight into the suction pipe.
Vortexes form between the pump suction and intake tank fluid surface. This causes air to enter the pump suction, and the entrained air reduces pump capacity and efficiency. Excessive shaft deflection is also produced by the entrainment. The pump’s mechanical seals, bearings, piping, couplings and impeller can be damaged by the vortex condition.
Ideally, vortexing can be anticipated in the design phase and eliminated with the proper amount of suction for the water level. However, if a pump experiences vortexing, the issue can be reduced or stopped by changing the velocity of the water entering the pump. Reducing or eliminating vortexing can be accomplished through:
Increasing the size of the inlet piping or installing a flared suction line
Increasing the depth of the fluid source (or raising the pump to increase the distance between the bottom of the fluid source and the intake)
Reducing the pump flow rate
Operating at a different level to reduce head
Slowing the system Reducing the number of pumps running in the fluid source
Using diffuser screens or baffles
Alerting the fluids/solids ratio in the intake
Realigning the return line to reduce a waterfall effect in the liquid source
Floating large balls on the surface to dissuade vortex formation
A couple of weeks ago, Cornell had a request for some of Condensed Hydraulic Data Books from a P.E. in South Carolina. These slim, pocket-vest sized books have been offered by us for decades. The engineer who requested the books wrote:
“I have had the pleasure of using the Cornell Pump condensed hydraulic data book for hundreds of designs since1984. It’s my go-to source for all hydraulic calculations.
I’ve got a young engineer I’m bringing along and would love to have a copy to give him. Would it be possible to obtain a copy or two?”
We are certainly happy to oblige. The engineer even sent a picture of his copy of his much-referenced data book. (We sent him along a couple of new copies he can use as well…)
Cornell provides thousands of these diminutive books with C values, nomographs, and more for handy in-field calculations per year. Use our contact form to request one for yourself.
We also encourage you to use the mobile tool kit on your phone (Apple IOS and Android Play). The apps come in Imperial and metric versions, and allow calculations for TDH, NPSH, friction loss, and suggest Cornell pumps to meet specifications entered.
With these resources, you can make accurate system calculations on the fly!
In honor of those who gave their lives in service to our country, Cornell Pump Company will be closed for Memorial Day, May 25, 2020. We hope you have a wonderful holiday and we will be back on Tuesday, May 26th.
Often, pump maintenance and repairs are done out in the field with no access to shop tools. One of the most common maintenance tasks is replacing the shaft sleeve. Did you know there’s an easy way to remove the shaft sleeve, using only two hammers? This method works so well that it is often preferred over shaft sleeve pullers and other methods inside the Cornell shop!
Keeping one hammer steady on the shaft sleeve, strike the opposite side of the sleeve with the other hammer. Do this along the length of the sleeve, until the sleeve metal is stretched enough to be pulled off by hand. Watch the video to see how quickly and easily this method works!
Find more instructional videos for pump maintenance on the Cornell youtube channel.
Many may remember the eruption of Mt. St. Helens on May 18, 1980. Cornell Pump is located about 50 miles from the volcano as the crow flies, and the eruption was fiercely felt and imminently visible for our hometown. During that eruption, 57 people were tragically killed, the mountain blew more than 1,110 feet (335 m) off its top, and 3.9 billion cubic yards (3 billion meters cubed) of debris raced down the mountain into the surrounding landscape, choking off rivers and damming Spirit Lake, on the North flank of the mountain.
Those initial lahars (violent mudflows of earth, ice, snow, and water heated by the volcano) and subsequent smaller eruptions had created a dire situation by 1983. Debris had plugged the lake’s natural drainage and if the “earth dam” had been overrun it would have caused flooding and damage to the recovering towns below, with massive property damage and loss of life possible.
The Army Corp of Engineers called on Cornell to provide pumps that could be shipped very quickly, operate efficiently and reliability, and remove the massive amounts of water needed to reduce the breach risk. Cornell answered with 20 of our 10YB model pumps, removing more than 100,000 GPM—working within a month of the contract award.
See more Cornell accomplishments on our history timeline.
A Cyclone VT Series lineshaft turbine (25’ 6RB-75HP Open Lineshaft Turbine) is loaded onto a transport semi for delivery. Cornell offers both enclosed (oil-lubricated) and open (media-lubricated) lineshaft designs in 10 models, with numerous discharge heads combinations, and variable shaft lengths.
Based on our popular RB series of pumps, the Cyclone series is a single bowl short-set turbine ideal for applications in agricultural, municipal, and industrial markets. The Cyclone series meets or exceeds the efficiencies of other manufacturers in configurations offered. Learn more about the Cyclone Vertical Turbine series.
Last week, we looked at poor suction piping; but mistakes can be made on the discharge side as well! The problems in the graphic below are what Cornell has seen most commonly causing piping issues on the discharge side.
We encourage you to thoroughly look at your Operations & Maintenance manual (O&M) that came with your pump—where you can find tips like these, and much more.
Cornell has CD4MCu pumps in stock and ready to ship; 13 of our most popular models are available in this duplex stainless steel. CD4MCu provides enhanced strength and corrosion resistance compared to single phase stainless steel.
Last week, we talked about the importance of having your Operations and Maintenance (O&M) Manual handy for maintenance and repair on your pump—those are great times to reference your guide. Another great time though, is when the pump arrives!
The O&M manual will help familiarize you with the pump operation, and importantly should have a checklist of steps that you should follow to ensure the proper and safe operation of the pump. Below is graphic of a generic start-up checklist. These are good general procedures, but your O&M manual will have a list specific to your pump model—and it may be different than what is listed below, as in the case of refrigeration pumps. Refer to your O&M manual for your specific pump.
You should address each of these points to successfully start-up your pump! Be safe in your pump operations.
We hope you are enjoying out Tuesday Tips! Please drop us a line at email@example.com if you have any topics you’d like to see covered.