Evaluating Pump Efficiency

[Victordelahoya]

Evaluating Pump Design
There’s a pump with spec:
Q = 450 m3/h
H = 95 m
BEP = 83%
Hazen-William formula requires to determine the flow rate first to get head loss. The pump is 5 years old, so I think 400 m3/h (111 l/sec) is fair enough(?). After calculating head loss and head static, I get 70 m of total head. Now, how to determine the efficiency pump? Actually, it’s first time for me to see this curve.

When I see it, I am confused. Is this is right?

1) I plot a curve from static head (40 H, 0 Q) and total head (70 H, 111 Q), I named it head curve.
2) If you see the yellow bottom line, BEP 83% ended in 100 l/s, if you keep going to the right until the end of line it’s 125 l/s and efficiency 120% (?).
3) The head curve meet the 1800 rpm curve, the point is between BEP and the maximum efficiency (?), between 83% and 120%, so the pump efficiency is 93%.

Please use daily word to reply, because english is not my official language. Thank you.

 

[LittleInch]

For some reason, the efficiency curve has not been plotted. There should be an egg shaped curve, not a straight line.

The graph shows that the BEP- Best Efficiency Point for 1800rpm is 100 l/s. This means the efficiency either side will be less than this maximum (83%). What it is you can't say as the efficiency is not shown on the pump curve.

That's why you're confused. Efficiency is not plotted.

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

 

[Artisi]

You can calculate your own efficiency from the Q, H, and Power curve shown on the pump curve.

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]

E=QxH/102/kW

You might have a problem in a much you are going to operate right of BEP at higher than 111 l/s - - NPSHr looks ok so maybe no problem.


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.)

 

[1gibson]

Yep, calculate it. Do a few points if you want a curve, plot different curves for each speed.

Calculate the "water horsepower" using the head and flow. Then compare this to the power per the pump curve. If water hp is 80 and the curves says 100, then the pump is 80% efficient at that point.

If you want to represent it graphically on the same curve, write the efficiency scale on the right side of the chart, use whatever grid lines you want.