Pump running in SF
Pump running in SF
(OP)
10hp down hole centrifugal pump.
New.
Set at about 70 feet.
Pressure measured and found at center of BEP.
Rated flow 90g/min.
Actual measured flow 85g/min.
230V 3ph.
Supply voltage 241V - all phases within 0.5V
Wire size from measured point to pump 6AWG.
Rated current 30A
Actual current 31A,31A,34A
Why?
New.
Set at about 70 feet.
Pressure measured and found at center of BEP.
Rated flow 90g/min.
Actual measured flow 85g/min.
230V 3ph.
Supply voltage 241V - all phases within 0.5V
Wire size from measured point to pump 6AWG.
Rated current 30A
Actual current 31A,31A,34A
Why?
Keith Cress
kcress - http://www.flaminsystems.com





RE: Pump running in SF
"I am sure it can be done. I've seen it on the internet." BigInch's favorite client.
http://www.youtube.com/watch?v=hpiIWMWWVco
"Being GREEN isn't easy." Kermit
http://virtualpipeline.spaces.live.com
RE: Pump running in SF
=====================================
(2B)+(2B)' ?
RE: Pump running in SF
=====================================
(2B)+(2B)' ?
RE: Pump running in SF
"I am sure it can be done. I've seen it on the internet." BigInch's favorite client.
http://www.youtube.com/watch?v=hpiIWMWWVco
"Being GREEN isn't easy." Kermit
http://virtualpipeline.spaces.live.com
RE: Pump running in SF
RE: Pump running in SF
Keith Cress
kcress - http://www.flaminsystems.com
RE: Pump running in SF
RE: Pump running in SF
Keith Cress
kcress - http://www.flaminsystems.com
RE: Pump running in SF
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If we learn from our mistakes I'm getting a great education!
RE: Pump running in SF
Did you check the direction of rotation? Debris?
RE: Pump running in SF
Could you post the pump performance curve and the system curve?
RE: Pump running in SF
For the particular question, I think most of the important questions have already been asked. The possibilities that occur to me are these:
Low voltage
Incorrect motor speed (50 Hz motor running in 60 Hz system)
Incorrect rotation
Incorrect pump (too many stages or wrong impeller pattern)
Alternate flow path.
Bad data.
I would suggest that you very carefully verify the data you are using for this analysis. The flow meter could be set up incorrectly or not calibrated. The pressure readings could be in error. The depth down to the pump could be different that you were told.
Johnny Pellin
RE: Pump running in SF
RE: Pump running in SF
Johnny Pellin
RE: Pump running in SF
"I am sure it can be done. I've seen it on the internet." BigInch's favorite client.
http://www.youtube.com/watch?v=hpiIWMWWVco
"Being GREEN isn't easy." Kermit
http://virtualpipeline.spaces.live.com
RE: Pump running in SF
Well I think a system curve could dispel some doubts and eliminate the need of assumptions.
RE: Pump running in SF
But, as I said, the system curve for my well application would also be unnecessary. If the header is pressure controlled to run between 95 and 105 psi, then I know all I need to know. I have almost never seen an application in my plant where a system curve is important except at original design or redesign. But, with vary rare exception, all of our streams are flow controlled. And, when I need to evaluate pump performance, it is done at discrete points in time where I only need to know the suction conditions, discharge conditions, product properties and flow rate. If I had a problem that might require evaluating a system curve, it would probably be a situation where the control valve reached 100% and the flow controller couldn't reach set-point. Then I would need a system curve (or at least a couple of points on a system curve) to determine if I can achieve the target flow rate best by making changes to the pump, control valve or system.
Johnny Pellin
RE: Pump running in SF
"I am sure it can be done. I've seen it on the internet." BigInch's favorite client.
http://www.youtube.com/watch?v=hpiIWMWWVco
"Being GREEN isn't easy." Kermit
http://virtualpipeline.spaces.live.com
RE: Pump running in SF
The pump is a Gould 95L10.
Here's the curves and everything else:
www.goulds.com/pdf/7313.pdf
More data with some corrections:
The voltage is 242~243V across all the phases.
The motor is a Hitachi.
It's FLA is 29A.
The motor is drawing 31A, 31A, 34.5A
All leads were rolled with no change.
Open delta. 12kV/240V - two transformers on the pole running ONLY this pump.
Correction: Pump set at 40 Feet with 30 feet of water above its intake.
Static pressure is about 105psi with pump off.
Gauge at well head reads 140psi.
Flow checked with two flow meters. 85~90gpm
An identical well a hundred yards away feeds the same main. They both ultimately feed a tank way up on a hill.
What say you now?
And thanks folks.
Keith Cress
kcress - http://www.flaminsystems.com
RE: Pump running in SF
[140 x 2.3] + 10 x 90 / 3960 / 0.72 = 10.5 HP
RE: Pump running in SF
Thanks for so nicely restating my point. The system curve is very important for designing a pumping system or a control system. After it is built, if the question is asked (as it was in this post) about the performance of the pump, I have no need to generate a system curve. I simply need to know the suction and discharge conditions, the product properties and the flow rate. And, you also quite nicely pointed out the relative importance of the system curve to a pipeline application (your expertise).
I make comments regarding my industry (oil refining). We almost never have a single pump that pumps different products at different times. We almost never have to consider the pressure up and over a hill. I have been analyzing pump performance in an oil refinery for almost 22 years. I am not being lazy or stupid. My industry is different than yours. The particular question that was stated was one of pump (and motor) performance, not system design. If the result of the first question was to say that the system was not correctly designed, then we could have a lively discussion about the way it might need to be redesigned. Instead, Artisi quite correctly stated the correct answer. The pump should be expected to require more than 10 HP at the published pump efficiency. The fact that the motor is drawing over full load amps is not particularly unusual or surprising given the data provided.
Johnny Pellin
RE: Pump running in SF
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(2B)+(2B)' ?
RE: Pump running in SF
RE: Pump running in SF
"I am sure it can be done. I've seen it on the internet." BigInch's favorite client.
http://www.youtube.com/watch?v=hpiIWMWWVco
"Being GREEN isn't easy." Kermit
http://virtualpipeline.spaces.live.com
RE: Pump running in SF
10.5hp would certainly fit the problem.. Yuck!
The chart:
This pump is below the curve. How does that square with the the 10.5hp?
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OK, You have a pump down the hole. Once you power it up you find the working pressure puts you below the curve a tad yet we're over working the motor.
If we throttle until we drop to 29A we seem to closing the valve down to about 20% of open - which is hideous.
Seems a waste to pull the whole string, return the motor and replace it with a 15hp which will be overkill.
What solution would you guys reach for here?
Keith Cress
kcress - http://www.flaminsystems.com
RE: Pump running in SF
RE: Pump running in SF
RE: Pump running in SF
Its doubtful that there is anyting wrong with the pump or the installation. Start looking at the motor. RPM is probably close, so its something in, ... or not in, the elect circuit.
"I am sure it can be done. I've seen it on the internet." BigInch's favorite client.
http://www.youtube.com/watch?v=hpiIWMWWVco
"Being GREEN isn't easy." Kermit
http://virtualpipeline.spaces.live.com
RE: Pump running in SF
RE: Pump running in SF
I don't see the problem, but true, I don't have the ampmeter.
"I am sure it can be done. I've seen it on the internet." BigInch's favorite client.
http://www.youtube.com/watch?v=hpiIWMWWVco
"Being GREEN isn't easy." Kermit
http://virtualpipeline.spaces.live.com
RE: Pump running in SF
If we throttle it don't we just trade higher head for lower flow? Which won't probably help.
What if we raise the pump so it has 10 feet less suction head?
Of course then we have 10ft less pumping head so the flow will rise..
Keith Cress
kcress - http://www.flaminsystems.com
RE: Pump running in SF
Steve
RE: Pump running in SF
The motor doesn't give damn about the current. It cares about temperature. If the fluid temperature is lower than that used when determining the rating then the chances are the windings are cooler than at rated conditions, and the motor will be ok. Might you be chasing a non-problem?
Anyway, if the motor is going to die because a 2% overload at rated conditions then it must be either Italian or Chinese.
----------------------------------
If we learn from our mistakes I'm getting a great education!
RE: Pump running in SF
"I am sure it can be done. I've seen it on the internet." BigInch's favorite client.
http://www.youtube.com/watch?v=hpiIWMWWVco
"Being GREEN isn't easy." Kermit
http://virtualpipeline.spaces.live.com
RE: Pump running in SF
In this industry if you want a pump that does not work in the service factor, you have to specifically order a n.o.l. pump. The good thing is that all the motor manf. know this and plan on it when they design a motor.
My other concern it the pump is below the curve. Was this a new pump?
RE: Pump running in SF
IMO this below the curve is a red herring thing. There is nothing particularly bad indicated by a difference of only 2% between a site installation calculation and a test bench curve, especially since I think that we still do not know the height of the water level over the pump.
"I am sure it can be done. I've seen it on the internet." BigInch's favorite client.
http://www.youtube.com/watch?v=hpiIWMWWVco
"Being GREEN isn't easy." Kermit
http://virtualpipeline.spaces.live.com
RE: Pump running in SF
Steve
RE: Pump running in SF
RE: Pump running in SF
"Close" counts in horseshoes, hand granades and ... pump curves.
"I am sure it can be done. I've seen it on the internet." BigInch's favorite client.
http://www.youtube.com/watch?v=hpiIWMWWVco
"Being GREEN isn't easy." Kermit
http://virtualpipeline.spaces.live.com
RE: Pump running in SF
RE: Pump running in SF
Yes! You have it. This is an agricultural site.
Yep.. This same pump was called a 90L10 when quoted and by the time it was ordered it had changed along with all the others in the series up 5 to a 95. Pure marketing BS.
So does the fact that we have to crank down the output valve to 1/5th open make sense to the throttling idea? I'm thinking it does because of the large head it's pumping against.
Keith Cress
kcress - http://www.flaminsystems.com
RE: Pump running in SF
----------------------------------
If we learn from our mistakes I'm getting a great education!
RE: Pump running in SF
You might replace the valve with globe or a plug valve with a better control pattern. Something that will give you a more linear response, or whatever response you're looking for. There is no worse control response than from a ball valve.
"I am sure it can be done. I've seen it on the internet." BigInch's favorite client.
http://www.youtube.com/watch?v=hpiIWMWWVco
"Being GREEN isn't easy." Kermit
http://virtualpipeline.spaces.live.com
RE: Pump running in SF
OR
Install the equivalent orifice in series with the valve, leaving the valve full open, so random twiddlers will think the valve is already in the optimum position, and can do no harm with their random twiddling.
On that last option, I have gone so far as to place such controlling orifices in places where no one would look for one, and in places where they're very difficult to reach if found.
Mike Halloran
Pembroke Pines, FL, USA
RE: Pump running in SF
This is starting to sound like the "Never ending story", but that's OK as it is of interest and keeping a few of us entertained.
I had a bit of spare time and have re-read all the posts and would like to summarise the application as I see it.
I will make a couple of assumptions
1. the flow is 90GPM
2. the discharge pressure taken at some point at ground level is 140PSI
3. the pump is set at 40ft with 30 ft of water over the inlet - making the water level 10 ft below grade.
4. pump efficiency is 72%
What is unknown
1. how accurate is the flow measurement.
2. how accurate is the pressure measurement.
3. how accurate is the power measurement.
4. what is the hydraulic loss from the pump discharge to the above ground pressure measuring point.
5. what is the standing water level during pump operation.
6. is the pump performing to the publish curve.
Using the assumed Q, H and efficiency the power at the pump duty point is;
[140 x 2.311] + 10 x 90 / 3960 / 0.72 = 10.528 HP
So what does this mean, well the pump is running somewhere on its curve at an unknown flow and total head consuming approx. 10.5hp which is above the nominal rating.
In my "neck of the woods" we don't have SF rating on electric motors however; it seems that operating above nominal is OK according to our North American colleagues. This being the case and as the motor is submerged and probably cooled sufficiently to operate in its SF it should, as pointed out by others, be OK to run.
Should you wish to reduce input power there is a couple of options, increase the head on the pump or pull the pump and reduce the impeller diameter on the final stage which will reduce the flow a little head a bit more and power at a greater ratio.
On the point of having a system resistance curve I agree with Johnny Pellin, there is no need to have this for an existing installation unless you are going to modify the system by changing the pipe work, operating conditions or changing pump speed or impeller diameter. If a pump is running smoothly, is free of cavitation, etc it is operating somewhere on its H/Q curve at a measurable flow, head and power input, it might not be where you want it to be or expect it to be – but it is somewhere on the H/Q curve.
But I guess the story will continue ---
RE: Pump running in SF
ScottyUK is right, all that matters is motor temperature. This is apparently a pump intended for pumping water from a well with the pump being cooled by the flowing water. Do you have any specifications regarding the water temperature range for which the pump & motor was designed for continuous operation? If the water temperature is near the upper limit, then the somewhat high current may be an issue. If the water temperature is well below the upper limit, the motor is probably running cool enough to not be a source of worry.
Artisi's listing of assumptions and unknowns is important. Nothing is known with enough precision to adequately deal with the level of precision that is of concern here.
This isn't a multi-thousand horsepower boiler feed pump where the performance curves have been established by very accurate (and expensive) test bed operation of this specific pump. If this pump's performance is within 10% of the generic curves, that is about all you can expect for accuracy. Unless your instruments have been very accurately tested for their specific calibration, each is likely to be accurate to only about 4% of full scale.
If I was dealing with such a problem and was really concerned about cooking the motor, I would find some way to monitor the temperature differential across the pump and motor by attaching thermocouples in the water flow close to the pump suction and very close after the motor. I would make sure to connect them for differential indication since this would minimize instrument error problems. The potential combined instrument errors associated with simply getting two individual temperture indications can easily approach or even exceed differential temperature range that would be of interest. I would monitor the inlet water temperature with a separate primary element (RTD, thermistor, or thermocouple). Since the discharge pipe is apparently passing through a considerable depth of surrounding water, the water temperature measured above ground may not reflect the discharge water temperature leaving the pump & motor accurately enough to be meaningful. The temperature rise across the pump & motor provides a good indication of net efficiency for the combined pump & motor when combined with accurately measured flow and head.
I've seen "seriously overloaded" motors (125 - 130% of rated load) work well for years when provided with enough extra cooling.
Valuable advice from a professor many years ago: First, design for graceful failure. Everything we build will eventually fail, so we must strive to avoid injuries or secondary damage when that failure occurs. Only then can practicality and economics be properly considered.
RE: Pump running in SF
RE: Pump running in SF
The puzzle remains.
The pump was pulled. The motor changed from a Hitachi to a Franklen. No obvious change in the current. Same imbalance even.
The flow was restricted until FLA was achieved. That was when the 95gal/min pump was throttled clear down to 48gal/min.
Keith Cress
kcress - http://www.flaminsystems.com
RE: Pump running in SF
Since changing the motor left the phase imbalance, my normal response would be to get one or more EE colleagues involved in dealing with the magical characteristics of 3-phase power. I will be the first to state my near-total ignorance of the mysteries of 3-phase power, but from encountering some messy problems in the past, my expectation is that the apparent phase imbalance may be the result of some power factor problem being induced by something other than this motor. Something else nearby (electrically) is probably introducing the problem that you are seeing at the subject motor. There may even be some goofy harmonics in play.
In situations like these, I can't help recalling a professor's remark many years ago that "the most dependable electric motor is a Detroit Diesel 6-71 with an air starter and a large fuel tank." No poly-phase power issues involved!
Valuable advice from a professor many years ago: First, design for graceful failure. Everything we build will eventually fail, so we must strive to avoid injuries or secondary damage when that failure occurs. Only then can practicality and economics be properly considered.
RE: Pump running in SF
RE: Pump running in SF
I see your curve is rated 3450 rpm (3600 nominal) which is a pretty good amount of slip to begin with. Get it into the SF and I can see losing another 10-20 rpm, which will show up on the pump curve as below rated.
RE: Pump running in SF
You have changed motors and still have the same result, if you don't want to or can't run into the SF then change the pump duty or change the pump.
Long winded discussions and wishful thinking will never reduce the power input for this application as it seems fairly obvious that the flow / head/ efficiency equals more than 10HP as has already been shown.
RE: Pump running in SF
"I am sure it can be done. I've seen it on the internet." BigInch's favorite client.
http://www.youtube.com/watch?v=hpiIWMWWVco
"Being GREEN isn't easy." Kermit
http://virtualpipeline.spaces.live.com
RE: Pump running in SF
Forgive me for weighing in here, I read this post to see if I might learn something or be reminded of something I've forgotten from years ago. It seems like there needs to be a benevolent buttinsky in this conversation. Perhaps one person's choice of words doesn't sink in with someone else (a problem I have all the time).
Your last comment was "the puzzle remains". No, it doesn't.
You had posted: "It's FLA is 29A. The motor is drawing 31A, 31A, 34.5A" Others have posted that the required HP for the flow conditions you give is 10.5~. Your motor's 29A FLA is for operating at 10HP. It is actually putting out 10.5~HP so it's using more than 29A to do so.
"What's up with that?" you might ask. You've already pointed out the marketing BS from the mfg, and others have spelled out the BS in the downhole water pump industry regarding their stated performance. You're apparently able to get the flow output you need, and if, as someone else stated, the motor is not running hot, don't worry about it, it's close enough. I've forgotten what little I once knew about electric motor intricacies, but they often operate slightly above their rated HP. Temperature is the hard limit, melt the insulation and you're done.