high Amps on newly replaced pump
high Amps on newly replaced pump
(OP)
hello,
I just had a non-seal centrifugal pump replaced with newer one as the old pump was obsolete after almost 20 years of service, its used in a high temperature application and the new pump is almost 100% exactly the same specs of the old pump, just the new model from the manufacturer with newer bearing monitor (digital), tested with ambient temp glycol instead of 205, however that is not the issue because if you calculate the head at the density at this temperature it will not still lead to this number in power and hence to current of 6 amps...
the pump sound is quite, nothing looks abnormal, however its drawing 6 Amps of current instead of its stated in datasheet of full load of 5.2 Amps, which causes the breaker to trip as the set point is 6.2 amps, I know that we can increase the set of the breaker but that is not the case, why would it take higher current?
direction of rotation is correct (shown in digital monitor panel of the pump), both radial and axial bearings indicates very well condition.
any clues?
pump info: suction 2 inch , discharge 1 1/2 inch
suction pressure = 0
discharge pressure 2.94 barg
rated BHP (KW) = 1.34
Max BHP (KW) = 1.79
pumping temp = 205 C
sp gravity @temp = 0.98
I just had a non-seal centrifugal pump replaced with newer one as the old pump was obsolete after almost 20 years of service, its used in a high temperature application and the new pump is almost 100% exactly the same specs of the old pump, just the new model from the manufacturer with newer bearing monitor (digital), tested with ambient temp glycol instead of 205, however that is not the issue because if you calculate the head at the density at this temperature it will not still lead to this number in power and hence to current of 6 amps...
the pump sound is quite, nothing looks abnormal, however its drawing 6 Amps of current instead of its stated in datasheet of full load of 5.2 Amps, which causes the breaker to trip as the set point is 6.2 amps, I know that we can increase the set of the breaker but that is not the case, why would it take higher current?
direction of rotation is correct (shown in digital monitor panel of the pump), both radial and axial bearings indicates very well condition.
any clues?
pump info: suction 2 inch , discharge 1 1/2 inch
suction pressure = 0
discharge pressure 2.94 barg
rated BHP (KW) = 1.34
Max BHP (KW) = 1.79
pumping temp = 205 C
sp gravity @temp = 0.98





RE: high Amps on newly replaced pump
Almost 100% - so what is not 100% - slightly higher flow, slightly less efficient?
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)
RE: high Amps on newly replaced pump
in fact its almost 100% because the new pump has got higher efficiency 41% compared to 34% of the old one.
RE: high Amps on newly replaced pump
RE: high Amps on newly replaced pump
thnx
RE: high Amps on newly replaced pump
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)
RE: high Amps on newly replaced pump
Please humour us and post the curves and copy of the test results for the pump (you stated it had been tested) and also test results for the motor (if available/).
What does 6 amps represent in shaft power?? Need to know running voltage at the motor and efficiency of the motor
Flowrate
Also are those values you quote measured or from the data sheet?
Options for excess amps include many of what you have apparently checked but also:
Your motor voltage measured across the terminal isn't what it says it should be - needs electrician to check when running
There is something extra rubbing on the pump shaft
This is a small pump and motor so often the variances in either pump or motor from the data sheet / brochure can be significant. As can be any small mechanical issue.
Await further info.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: high Amps on newly replaced pump
@Littleinch , as for running the motor solo, I have mentioned that its canned motor type, there is no chance for dis-coupling this, and there does not seem to be any indication of abnormality during operation, its quite, both radial and axial bearings are giving healthy lights, and for current it was checked by electricians and confirmed to read 6 instead of 5 or below. the rating of the motor is 1.7 KW.
the curves are attached as requested,
regards,
RE: high Amps on newly replaced pump
RE: high Amps on newly replaced pump
Can you verify the output of the old unit compared to the new unit in real terms -not hearsay or wishful thinking,
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)
RE: high Amps on newly replaced pump
SO what about the other things?
Have you actually measured flow?
Strikes me the new pump has a larger capacity so it may be that whereas the old pump might have been working at the end of its curve and the head dropped off, this new pump will maintain a higher head resulting in more flow and hence use more power?
Also you mention glycol - have you allowed for the difference in viscosity in the pump curves? might be very low, but you have only a fine margin here.
Also is that new pump curve just what the vendor supplied or was it actually tested?? before being installed? Can you alter discharge pressure / flow to do your own test and check the actual pump curve versus the one supplied by the vendor?
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: high Amps on newly replaced pump
Do you measure the actual flow?
RE: high Amps on newly replaced pump
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)
RE: high Amps on newly replaced pump
RE: high Amps on newly replaced pump
Come back with something that's actual and measured if you want answers.
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)
RE: high Amps on newly replaced pump
@Artisi : yes you are right and both datasheets agrees with you , old pump motor is 2.2KW (2200 watts) Synchronous speed is 3000 rpm , volts = 400 , phases = 3, hertz = 50 , full load amps 5.5 Amps,,,, for new pump motor is 1.7KW (1700 watts), full load amps = 5.2 Amps , speed volts phases hertz are the same, this data is from both pumps data sheets.
@Littleinch : the pumped fluid is the same since the old pump as this is an existing unit, however we are currently running the glycol @ 20 C instead of 200 C, although its a huge difference in temperature the impact on density is minimal when checking by pressure = density x G x head and applying on pump curve (testing result curve & rated curve which I uploaded earlier) you are not going to go higher than 5.2 Amps anyways, and so did the old pump.
We do not have any flow device at this line, there is one orifice further but not sure about it if its restriction orifice or delta P for flow testing.
when we ran the pump, pump is quite, no any visible abnormality, and dismateling the pump is not an option its a new item and we have procedures over here, I am trying to get help as the vendor is faaaar away.
efficiency of old pump is 34% and 41% for the new pump ...
RE: high Amps on newly replaced pump
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)
RE: high Amps on newly replaced pump
Thanks for info
1) Your motor details don't make sense I'm afraid. 5.2 A only makes sense when looking at a single phase motor when power = V X amps ( and that's electric power, not shaft power). Are you sure it's a 3 phase motor?? Looks to me like someone is giving your single phase motor two phases from a 3 phase supply.
2) Even allowing for that, the new motor is less efficient. Old motor 400W/Amp, New motor 325 W/amp
3) I still think you're actually operating on the RHS of your curves. Because the old pump head dropped off quite rapidly this limited the max flow and max power. New pump head curve is longer and flatter so can flow more at a higher head hence more power. Allied to less efficient motor = more amps. Pump is quite happy because it's still operating inside its head curve, but motor is undersized.
You need to be able to measure flow to sort this out. Either that or somehow throttle a valve somewhere in the line to bring the power / current down.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: high Amps on newly replaced pump
RE: high Amps on newly replaced pump
The nameplate current may be different than the actual full-load current and should not be considered an accurate indication of motor load. Nameplate full-load current value applies only at the rated motor voltage. The root mean square current measurements should always be corrected for voltage.
Did you measure the amps on the old motor?
RE: high Amps on newly replaced pump
Again you should do a shut in head test to see if your impellor has been overcut
RE: high Amps on newly replaced pump
Why - its 1.7kW. My circular saw motor draws more power than that and it's single phase 240V.
I agree 400V sounds like 3 phase, but then the amps don't work so something isn't correct in the description. a picture of the name plate would probably solve a lot if wheel spinning....
With no flow measurement I don't think we'll ever know, but the pump is doing what it is supposed to do. The issue is with a system which allows more flow and an inefficient motor compared to what has gone before.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: high Amps on newly replaced pump
"With no flow measurement I don't think we'll ever know, but the pump is doing what it is supposed to do. The issue is with a system which allows more flow and an inefficient motor compared to what has gone before."
I think doing a simple shut in head test will help in determining if the pump curve that has been supplied is as what is shown. If the impeller is overcut then this will explain the increase in power consumption. BUT you have to reconcile the reported elecrical numbers by supplyimg the information everyone has asked for. Everything is so fuzzy right now
RE: high Amps on newly replaced pump
and good news is that I finally got it, OPS people insisted on testing it with cold glycol @ 20 , while I had density effect on head checked and checked with pump curve and found it minimal I did miss the viscosity effect, it might sound stupid from me but believe it or not I had many senior people with me and non even though about it, and not even the vendor helpdesk !!, visc @ 205 C is about 39 Cp while at 20 its about 0.8 Cp !!! that's a HUGE difference.
and when I came back to office and topic here it seems like Artisi had it right :) :)
the motor is now drawing about 5 Amps, and regarding the discussion above , its really 3 phase @Littleinch , but as you said its low HP pumps, but special type (canned motor), old pump used to draw about 5.2 Amps when operated too @ 205 C ..
Thank you all really
RE: high Amps on newly replaced pump
"Remember that for a 3 phase motor POWER (WATTS)= 1.73 * VOLTS * AMPS"
That calculation gives you the apparent power delivered to the motor.
You also need to know the power factor to calculate the active power input from the apparent power, and you additionally need to know the motor efficiency if you want to calculate the power output rather than input. IEC motors are rated based on output power at the shaft, so the relationship between voltage, current and power is a little more complicated than you wrote.
RE: high Amps on newly replaced pump
Hence I suspect you're still pumping more like 9 m3/hr instead of 6.8...
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: high Amps on newly replaced pump
RE: high Amps on newly replaced pump
You also need to ask them for the phase current next time - I still don't know what the amps you quote relate to...
See if you can get a clamp on flow meter or some other way of working out what the flow is.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: high Amps on newly replaced pump
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)
RE: high Amps on newly replaced pump
As I know you are aware, far too many people think of centrifugal units as simply "blocks" of flow - "I've bought a pump that says it does 6.8m3/hr so why is it doing 5 or 9? The pump is at fault". I would say 90% of posts that appear here saying the pump isn't working properly turn out to be a system or motor issue instead. If you don't match the pump to the system or provide some sort of flow control or measurement, it won't do what you think it's going to do.
Anyway somacast has the information so he can do what he likes.
It looks like the old pump was operating well beyond its duty point if it was also operating at 5 Amps so maybe that's actually what everyone wants....
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: high Amps on newly replaced pump
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)
RE: high Amps on newly replaced pump
they are about to about to raise the set current of tripping in the power breaker, justification is : when station is cold started current will jump high... ok go ahead, I am not the one to pay for repairs when the motor is roasted :)
thnx again :)
RE: high Amps on newly replaced pump
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)
RE: high Amps on newly replaced pump
Thanks again :)
RE: high Amps on newly replaced pump
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)
RE: high Amps on newly replaced pump
RE: high Amps on newly replaced pump
The manufacturer will be able to tell you the eddy currentl losses specific to the pump you have purchased.
Ash Fenn
www.cdrpumps.co.uk