Why Your Centrifugal Pump is Drawing Too Much Power

Author: Jesse Sage | September 27, 2016 | Category: Pumps

Today's pumps account for no less than 10% of the world's electricity consumption. Two thirds of all pumps in operation today use up to 60% too much energy. (Grundfos Energy) Your pump might be one of them. 

If you've got a suspicion that a pump is drawing too much power, consult your IOM first, then check against this list of other possibilities.

Pump Sized Too Large or Small for Application

Possibly due to process changes in your facility, the pump may be oversized or undersized for the application.  This will cause the pump to run in a less efficient point in its operating range, causing the pump to use more horsepower.
Recommendation: Resize the pump to a more efficient size for your application. 

Incorrect Rotation

If your pump is rotating in the opposite direction, your pump is using much more energy than if your pump was rotating the proper direction.  This is due to the pump running less efficiently since most impellers are not designed to run in the opposite of its intended direction.

Recommendation: Ensure the power to the drive unit is correctly installed for the proper rotation of the pump.

Packing gland not properly adjusted

Many times, the packing gland on a pump is over tightened so the packing "doesn't leak".  The nature of packing requires the packing to leak to keep the seal area properly lubricated.  Another impact of having the packing gland too tight is that the packing is over compressed on the pump shaft, causing a drag on the shaft that requires more power to overcome.

Recommendation: Use pump and packing manufacturer's installation manual to ensure the packing is properly installed (i.e. "packing should have x drops per amount of time to properly lubricate the packing"). This will ensure the packing has the correct compression and does not require excess energy.

Specific Gravity Higher Than Specified 

This may again be a change in process conditions rather than the original pump sizing, but it still causes the specific gravity of the pumped fluid to change.  The pump will require more horsepower to pump a higher specific gravity fluid due to the fluid being heavier.

Recommendation:  Much of this is process dependent, so there is not a simple answer to solve this particular situation.  Possibly resizing the pump into one that is more efficient may help to reduce horsepower, but if the pump currently installed is already the most efficient for the application, the horsepower requirement may not be able to be changed.  lf so, a different pumping technology may need to be used (centrifugal vs. positive displacement).

Viscosity higher than specified

Similar to the specific gravity situation, in the pumped fluid viscosity is thicker than what was specified, it will also take more energy to meet the application needs due to the fluids resistance to flow.

Recommendation: Similar to the specific gravity situation, this may require the pump to be resized to run efficiently in the application.  Also, a different pumping technology may need to be used.  Check out our post on "The Effects of Viscosity on Systems and Pump Selection" to learn more.  

Internal Clearances Not Set Properly

The internal clearances of a pump are critical to a pump operating effectively and efficiently.  If the pump clearances are too open, the pump will lose efficiency due to not moving the fluid through the pump as intended (i.e. centrifugal pump creating recirculation back to the suction side of the pump.)

If the pump clearances are too tight, the pumps internal components may rub against one another, causing drag on the components that requires extra energy to overcome.  This rubbing may also cause damage to the internal components of the pump, also causing the pump to become less efficient and possibly requiring new parts or an entirely new pump to be purchased.

Recommendation:  Follow the manufacturer's IOM manual to properly set the clearances of the pump. 

A little too much power draw from one or two pumps might not seem worth the time, but considering some chemical plants have more pumps than employees, it's easy to see how the energy savings can quickly add up. 

Got a pump that's drawing too much power? Ask us about it! We gladly provide technical assistance to businesses and municipalities in Wisconsin and upper Michigan.

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Jesse Sage

Jesse Sage

Jesse Sage head of the Application Engineering Team at Crane Engineering. Jesse has a degree in Paper Science, with extensive knowledge in pulp and paper applications, as well as general industry.

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