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Join Date: Jun 2020
Posts: 14

Learning Pump Curves

07/03/2020 1:13 AM

Hi guys,

As I said before, I'm a brand new employee as a graduate mechanical engineer. I'm learning about equipments, specifically pumps. Could you help me how to deal with this curves? I've just installed this software and my goal is to plan pump overhaul according to pump prime. Thanks in advance.

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#1

Re: Learning pump curves

07/03/2020 9:01 AM

Let us begin the long question and answer process....

I don't know what your screenshot is... but I do know that it is not what is commonly referred to as a "pump curve"...... Wisely, you have made it small enough to ensure that no one can read it and people will ask many, many questions

I do not know what "my goal is to plan pump overhaul according to pump prime" means

Is there a problem with English word usage here ?

Why are there not pump vendor's manuals available to you describing normal maintenance ?

Let me guess... Your employer threw away all documentation and records when the plant was recently sold.

Have you googled: "centrifugal pump curves" and begun to read ?

There are many websites available for newbies who have never seen a pump before...

Tell us more about what you are trying to do ....

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#2

Re: Learning pump curves

07/03/2020 1:26 PM

What kind of pumps are you talking about?

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#3

Re: Learning pump curves

07/04/2020 4:20 AM
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#4

Re: Learning pump curves

07/04/2020 4:24 PM

In your Historian trends, it looks like you have the necessary instrumentation to evaluate pump performance, head pressure, density & flow. You need to know the speed of the impeller, and knowing the kw (or amps) consumption of the motor can be a help to see if the pump is delivering reasonable performance. Since you have varying process conditions, you have the information necessary to construct a performance curve, maybe 2 or 3 points. You can then compare actual performance with the manufacturer’s performance as published on the pump curve.

With enough data points, a thorough investigation of the suction piping to determine total head (usually no instruments there), you will have one indication of internal pump wear, impeller & casing. In addition, you need to assess packing or seal condition, bearings, coupling, lubrication, shaft wear & corrosion. A regular route of vibration readings, especially time stamped with actual pump operating conditions at the time, as captured on your PI system, will give you a wealth of diagnostic information with a not insignificant up front time investment, and relatively small periodic investment, if you set up some condition equations also in PI, calculated variables based on the instrument readings, and correlated with the pump curve.

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Active Contributor

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#5

Re: Learning pump curves

07/06/2020 8:05 AM

Sorry, my english is not very good.

the name of the software is "FactoryTalk Historian ProcessBook". we use it for equipment assessment.

As I know until now,most of pumps are centrifugal and we can determine their prime (the curves I said)by:

flow(from the flow transmitter),

the density (from the density transmitter),

the current,

and the discharge pressure (from the Pressure Indicator Transmitter).

the point is that I want to describe what happen to the pump according these datas.
For exemple, what's wrong if the density is too high and the pressure is low, etc...

in this way, I could plan frequency for primary maintenance (overhaul)for these pump

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#6
In reply to #5

Re: Learning pump curves

07/07/2020 12:29 AM

FactoryTalk Historian is a stripped down version of OSISoft PI, but I think you can still make computed tags, such as pump efficiency. Your density is what it is, the pump load will go up if the density is high. The load goes up as the flow goes up, also. Generally, as the pressure goes up, the load goes down, because the flow is restricted. That’s why you need to look at your pump curve, which shows you what a new pump will do under your conditions. If you have the model number of your motor, you can convert motor amperes to kW or horsepower by using a 2nd order polynomial regression of the no load, half load & full load amperes, and plug that into your pump efficiency PI equation. Cameron Hydraulics Handbook has a very good section on centrifugal pumps, look up Hydraulic Horsepower, look at that with one of your pump curves, and a P & I diagram of your pump circuit, so you understand what the instruments are showing you, and you will see better how to use your PI information.

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#7
In reply to #5

Re: Learning pump curves

07/09/2020 7:24 AM

<...what's wrong if the density is too high...> is that the process is operating outside its normal parameters. There will be other issues to settle at the facility well in advance of <...plan frequency for primary maintenance (overhaul)for these pump...>.

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