speed and time

hi,

I currently using a feed pump to drive water from one location to another.
I got a chart that show me the rpm of the motor and the output.

lets the say to run an output of 100ml of water in 1 min. My rpm required is 1000rpm. Can i say that if i run 1000rpm in 30s. My output will be 50ml. Is it linear also?

Depends on your pump output characteristics, check manufacturer chart.

If a positive displacement pump then it is definitely proportional to speed.

Centrifigul should be
BUT you must assume constant head - which may not be a valid assumption. You need the pump curve if centrifugal.

Dan Bentler

leitmotif said:

I
Centrifigul should be
BUT you must assume constant head - which may not be a valid assumption. You need the pump curve if centrifugal.

Click to expand...

As an ex nuke you should know that with centrifugal pumps, the operating point ( pressure and flow ) is determined by the intersection of the pump curve and the system curve. This will not be a linear function because the pressure drop as function of flow is not linear.

Peter

First the pump curve then the system curve. One step at a time.

Dan

actually i already do the experiment similar to the manufacture pump chart showing what rpm produce howm many ml per min.
My chart is definetely different. example...the chart show 1000rpm produce 100ml per min. but my experiment produce 1000rpm with 90ml per min. But i still ok...because my graph still linear and it show good consistent output.

There is variancee in every pump. So the manufacture chart is only a guide to tell you it is linear. I would still need to plot my on chrt for existing pump performance. am i right to say this.

So i also need to plot another chrt to show with this rpm. And with different time. What is my output. So i can have better expectation adjustment in future. am i right?

This verifies Peters statement that you have to derive a system curve.
With system in only ONE configuration. Run pump at varying speeds record discharge pressure and flow. Plot on curve and you have a system curve for that configuration. There are other factors you may have to include such as temperature and specific gravity if you run varying concentrations or different liquids.
Dan Bentler

thanks leti and all