pump curves

[199292]

I am performing a field test of the pumps at our water treatment facility. While I know it is necessary for the pressure guage to be located between the throttling valve and the pump, is it necessary for the meter to be in the same area as the pressure gauge? The flow does not empty to atmosphere. It is under a constant head of the clarifier.
I ask this because when plant personnel performed a test years ago, they throttled the valve in the intake building where they read the pressure on the guage to get the head before the throttling valve but took the discharge rate by an existing magmeter in our pipe gallery at a point 1000 feet from the intake building (throttling valve point) at a difference of 25' in height. I think their results were skewed but I'm not sure.

 

[BobPE]

199292:

flow in your system will be conserved, it will not matter where you record it other that the possibility of interferences from your system on the meters efficiency or if there are flows out of the system prior to the meter.

BobPE

 

[25362]

Water is considered an incompressible fluid, and as such BobPE gave you a correct answer. Questions in addition to Bob's remarks:

1. Were the pressure readings on throttling equal at both
ocassions ?
2. What is the rangeability of the magmeter and its
accuracy at low flow rates ?
3. What difference did both flow rates show ?
4. "Noise" from air bubbles and/or solids in the water
stream may change the magmeter reading, especially after
some years, and it may need recalibration. See:

http://www.engineeringtoolbox.com/49_530.html

 

[checman]

199292, It can be very difficult to plot a pump on its performance curve. The site that you have your pressure gauge may be influenced by fluid velocity or turbulence. Many things can influence the flow characteristics of your system. The pump flange gasket that was in the flow or just wear in the pipe over time may effect this turbulence and the gauge reading. Depending on your pump curve small changes in discharge pressure can have a major effect on flow. The flow meter is also influenced by turbulence in the flow. The flow meter can be anywhere in the system that has a straight run that meets the meters installation requirement. As long as there is not a bypass or slip stream that discharges before the meter and it is calibrated for the installation its readings should be repeatable and accurate within a percentage of flow. The above is assuming you are pumping a liquid without entrained gases. Entrained gasses are compressible and will expand as system pressures drop due to pipe friction losses. If the bubbles do not mess with your meter they will add to the volume so either way they will effect your reading and its accuracy.

Regards checman

 

[lilliput1]

You should also use one pressure gauge that you can valve to measure either the suction or discharge. Otherwize you have to check the calibration of each.

 

[EdStainless]

When we did field testing we were only looking to hit a couple of known points. We then looked top see how far off of the original curve they were. When we went back latter (sometimes years) we expected to see the same deviation from the standard curve.
We were looking for degridation, not exact output.

= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.

http://www.trenttube.com/Trent/tech_form.htm

 

[pumpval]

Can someone help me to get the source of information on pump design (centrifugal), impeller and volute casing design starting from the fundamentals , website, books etc.

 

[pmover]

pumpval,

your question should be posted as a new thread. simple to accomplish . . .

good luck!
-pmover