Affinity laws
Dynamic type pumps obey the affinity laws:
Capacity varies straight amongst impeller diameter as well as speed.
Head varies straight amongst the foursquare of impeller diameter as well as speed.
Horsepower varies straight amongst the cube of impellerdiameter as well as speed.
Horsepower
The handiest heart horsepower formula for a procedure engineer is:
HP = GPM(AP)/1715(Eff)
where:
HP = Pump horsepower
GPM = Gallons per minute
AP = Delivered pressure level (discharge minus suction), psi
Eff = Pump efficiency, fraction
Efficiency
An equation was developed past times the writer from the heart efficiency curves inwards the 8th edition of The GPSA Engineering Data Book.’ provided past times the M. W. Kellogg Co. The curves were works life to banking venture lucifer vendor information well. The equation admittedly appears bulky, but is tardily to use.
Eff. = eighty - 0.2855F + 3.78 x 103FG - 2.38 x 10-’FG2
+ 5.39 x 10-4F’ - 6.39 x 10-’F2G + four x 10-”F’G’
where :
Eff. = Pump pct efficiency
F = Developed head, ft
G = Flow, GPM
Ranges of applicability:
F = 50-3OOft
G = 100-1,000GPM
The equation gives results inside virtually 7%’ of the aforementioned heart curves. This way inside 7% of the plication valve, non 7% absolute, i.e.. if the plication valve is 50%, the equation volition last inside the arrive at fifty f 3.5%.
For flows inwards the arrive at 25-99GPM a crude oil efficiency tin last obtained past times using the equation for 100GPM as well as and then subtracting 0.35%/GPM times the departure betwixt 100GPM as well as the depression menstruation GPM. For flows at the bottom of the arrive at (25-30 GPM), this volition give results inside virtually 15% for the heart of the caput arrive at as well as 25% at the extremes. This is adequate for ballpark estimates at these depression flows. The horsepower at the 25- 30GPM degree is by as well as large below 10
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