River Pump Power Reduction 1

[itsmoked]

Have a river pump with a motor.

The motor is 440vAC, 60hz, 100hp, 134A , 3-phase. rated to output 2,045cubic/meter/min of water.

It's tripping its protection quickly and repeatedly.

It's also delivering 20% more water than expected, (2,454cubic/meter/min).

My take is that the twenty percent is pulling 20% more power hence the trips.
My advice is to restrict the outlet to reduce the mass-flow.

Now seeing the pictures finally, it shows the pump is an axial propeller type. Can I restrict the flow on this type and reduce the loading? Is a propeller a centrifugal pump?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[LittleInch]

You need to find and post the pump curve.

BTW I'm pretty sure you mean m3/hr, not m3/min.

Axial flow pumps normally reduce power as flow increases. So no, Axial pumps are completely different to centrifugals E.g.

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

 

[Artisi]

LI, is on the case, no way that pump can deliver 2,500,000 litre / min.
Is this a new installation?
Pump curve needed and accurate installation levels meeded.

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.)

 

[LittleInch]

Your flow and head at 70% efficiency gives me about 102hp.

But once you go out of the sweet spot, efficiency can fall off quite fast.

Your original "rated" flow doesn't mean much without the differential head figure. But given that the power increases with decreased flow, 100hp motor looks rather skimpy to say the least.

Adding a small head for discharge losses so a differential head of 8.5m with eff 65% gives me 115 hp shaft power.

Your motor is too small for the pump it is attached to is my verdict at the moment.

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

 

[miningman]

That is one serious size pump. Physically compared to a 58HP or 140HP Flyte submersible , something seems out of kilter if this unit is truly rated at 100HP

 

[LittleInch]

Errr and 134A at 440V phase to phase is nearly 100 kW, not 100 hp.

What's going on here Keith?

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

 

[itsmoked]

Hi LI. I'm trying to help a guy in the Philippians.

I'm passing you the info exactly has he's offered. I originally thought he had a centrifugal pump and the easy fix was to restrict it but then he sent me pictures and the sketch and that killed that assumption.

His electrician feels the new pump motor (from China) may be a mislabeled 50Hz motor. But, at the same time, the unit is apparently over pumping by a considerable amount which leads me to believe his protection is going off on the overload not some mythical wrong motor.

I've asked him for the curves but haven't heard back yet. We are dealing with some serious time zone issues so we'll see.

I've also asked more questions on the details of the trips and current measurements.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[EdStainless]

Well the 20% difference is what happens when you move from 50Hz to 60Hz.
But the load at the new speed is a real open question.
Sounds like it was mis-sized.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[electricpete]

In support of what LittleInch said, the BHP vs flow characteristics for an axial flow pump are generally monotonically decreasing over most of the operating range, which is opposite of radial flow pumps that most people are familiar with.

So the higher flow than expected doesn't explain the higher power draw than expected, it should be the opposite.

If you wanted to reduce power drawn by the motor most likely you have to decrease flow resistance. Example open a parallel recirc flowpath.

It's a little non-intuitive, but I have seen it myself by watching the slip (as indication of motor power) extracted from high resolution vibration spectrum in our power plant circ water pumps in different lineups (more pumps in parallel feeding same condensor = less flow per pump = higher power draw by motor = higher slip = lower speed).

I have a FAQ which attempts to discuss the subject faq237-1543
It gives generalities on how the curves vary. Actual pump curve is of course way better than generalities.

I put the word "centrifugal" in quotes because I find the terminology on whether people consider an axial flow rotodynamic pump to fall within the category of "centrifugal" varies among references and preferences (it has been a topic of debate on the forum in the past, I prefer not to debate it and just acknowledge that different people use that term differently).

These axial flow pumps tend to be high specific speed and low actual speed and probably larger diameter than a high-speed single stage radial flow pump of similar horsepower (maybe explains why someone thinks it looks too big to be 100hp).

Low speed motors tend to have higher exciting current which means higher no-load current as fraction of full load current.... at full load the power factor tends to be a little lower than higher speed motors but that is accounted for in FLA.

Have they checked if the current is balanced?

Is the voltage matched to the motor? (I'm not familiar with 440 volt as either a distribution or utilization voltage).

Have they checked the motor terminations are correct?


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(2B)+(2B)' ?

 

[itsmoked]

Thank you everyone for your great input!

Here's more info I've received:

The hunt for curves continues.

This pump's factory rating on its plate is:
440vac
100hp
60hz
3-phase
134a
2,043m3/h @ 9m

The pump goes up to 172 amperes and even climbs to trip.

It should probably be around 120A or there-abouts.

Pete; I did not think to ask about voltage or current balance.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[HTURKAK]

The sketch gives some information..The height between Water level and hump is 27 ft. But apparently, the discharge point level is lower than hump level.

Will you provide more details ; what ia the level of discharge point and River water level and pump suction point ?

I suspect that, the pump inlet is not submerged enough to avoid vortice formation and outlet point substantially lower than hump level, the siphon effect tripping the pump.

 

[Artisi]

itsmoked: using raw numbers of 570 litres/sec @ 9 metre head assuming 80% pump eff. gives 63 kW or ~ 85 hp. so within motor rating.
However, it is more than possible the 9m head is the performance across the turbine and NOT from the bell-mouth inlet to the discharge flange outlet - from my 10+ years of experience as an application / sales engineer on axial flow pumps ranging from 4"diamerter to 48" diamster, the units we manufactured were tested for turbine performance only, for field performance the losses for the inlet, discharge head, column and line-shaft had to be added for a correct hydraulic selection.
Without a performance curve we are guessing so it's very possible the motor size is marginal or even undersized.


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.)

 

[LittleInch]

Keith,

It all hinges on the pump curve. You can get some pumps where the efficiency drop off as you move off the duty point has more effect than the reduction in head and hence the power line becomes more of a wavy line with a high spot after 2000m3/hr before falling away again. Can you get make and model no?

I don't know how they are measuring flow exactly ( some sort of total volume pumped total over time?), but in THIS PARTICULAR INSTANCE, it may well be that 2000m3/hr is the sweet spot for the pump and hence some sort of additional flow restriction to bring it back to 2000m3/hr will work.

Can they give it a go? If it's tripping now then it won't make it worse, but might just work.

Probably easiest to fit a restriction plate at the end and then gradually decrease the hole size until the required flow is achieved.

Or increase the length of the discharge pipe by 2m to get a higher point before discharge to get your 27 feet to be say 30 ft or 31 ft.

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

 

[itsmoked]

And

So, why is it over-amping?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Artisi]

Keith: at the moment we have a bunch of numbers - but no application data / numbers.
The inlet water level to the discharge point needs to be measured. Ideally the flowrate, but might be a problem with the pump overloading.
The flow and head stamped on the name plate really doesn't tell us what's going on.

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.)

 

[Artisi]

Keith, note that some flows and head the 100 hp (74 kW) is marginal)

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.)

 

[Strong]

Pump must be a special version of this:

http://www.tjaote.biz/products/showproduct.php?id=44

Note that flow rate is specified as cubic meters per Hour!
Pump was designed(?) and made in China where power is 220 V at 50 Hz, and power in Philippines is 60 Hz, so what could possibly go wrong with pump-motor performance?

Walt

 

[itsmoked]

Still scratching my head on this. Note the performance data above?

That is a 60Hz induction motor speed for a 6-pole motor.

While spinning a 50Hz axial with 60Hz gets you 20% more flow as the problem seems to be, I'm flummoxed by the data above stating 89hp.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[LittleInch]

The data is not consistent and doesn't match reality.

However when I stuck in 380V instead of 440 it started to get close. 380 wan mentioned in a few places as being the 3 phase supply in the Philippines...

Or the efficiency is not as good due to fouling of the blades or things wrapped around the shaft out that the data you have is for a different pump.

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

 

[Compositepro]

As for the OP flow numbers, keep in mind that in many countries the meaning of commas vs decimal points in numbers is the reverse of what we mean in the US or UK.