Motor Power Monitor for Small Horsepower Centrifugal Pump Deadhead Protection 1

[PWEVO]

We are thinking about using power monitor to protect some small centrifugal pumps (from 3HP to 10HP, 3-phase, 480V) from deadhead in a chemical plant. But we were told that it won't be reliable and accurate for small pump application. We are not sure if newer instrument products are available for this application now. Here are my questions:
(1) Do you have real experience of successfully using power monitors on similar small pump deadhead protection?
(2) If you do, can you please recommend the power monitors (brand and model) that you used in your cases?
(3) Do you have other suggestions or concerns for doing this way?

Thank you in advance for your helps.

 

[Compositepro]

Use a pressure or flow switch to detect deadhead. Deadheading a centrifugal reduces its power consumption compared to higher flows.

 

[PWEVO]

Switch is not a favorite device in our plant because it can fail without being noticed.

By the way, I just heard that Eaton C441 or C445 may work for small (3-10HP) pumps - measuring the motor power and protect the pump from deadhead... Has anybody successfully used it for similar application?

 

[EmmanuelTop]

Everything can fail - including the electrical current meter, not only the switch. Depending on how important this measurement (instrument) is, it can always be SIL-rated to improve reliability.

If you don't like pressure and flow switches, you can always look deeper into the process downstream and see if there are any variables (i.e. % opening of a certain valve downstream) that are affected rapidly if the pump gets dead-headed, and use those variables for detection of dead-head conditions.

Dejan IVANOVIC
Process Engineer, MSChE

 

[LittleInch]

I can't see how power monitor can affect this action unless you have a very accurate monitor and accurate power curve because power is normally lower than at full flow.

Other thing you might be able to use are differential pressure across the pump or some sort of basic flow meter which should register flow when running so you can see when it fails

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[controlnovice]

We've used power monitors from Load Controls for loss of suction or empty pipe detection. May work for you on deadhead situations as well. On the smaller HP motors, you can make more than one wrap/loop through the CTs to double or triple the current seen by the device as well. This may produce a larger deviation to detect deadhead.

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[PersonalProfile]

http://www.eng-tips.com/viewthread.cfm?qid=383174

Regards,
Lyle