Centrifugal pumps horsepower
Centrifugal pumps horsepower
(OP)
Hi everyone
How can I practically calculate centrifugal pumps horsepower and size the electric motor driver? including all mechanical losses of the pump and coupling and all other factors related to electric driver.
How can I practically calculate centrifugal pumps horsepower and size the electric motor driver? including all mechanical losses of the pump and coupling and all other factors related to electric driver.





RE: Centrifugal pumps horsepower
Eo pump efficiency including mechanical loss.
Sizing the electric motor with a safety factor of 125
RE: Centrifugal pumps horsepower
From Pump Handbook by Karassik et al. McGraw-Hill, Section 3.1, Power Pumps.
In USCS units:
bhp = (Q×Ptd)÷(1714×μ)
Q = delivered capacity (including gases and solids) in gpm
Ptd = developed (differential) pressure, psi
μ = mechanical efficiency.
http://www.mcnallyinstitute.com/12-html/12-11.html
online calculator:
http://www.pumpcalcs.com/calculators/view/73/
The rated horsepower of the motor necessary to produce the desired brake and water horsepower.
Motor HP = bhp/ Motor Efficiency
Where Motor efficiency is 85-90%
RE: Centrifugal pumps horsepower
Motor size should generally not be more than 10% higher than actually required, however the final value (maybe as high as 1.15) will depend on what you wind up with when you select what you actually need from the standard frame motor ratings.
85 to 90% efficiencies for a motor are pretty low these days. Motor efficiencies on new energy saver types built in the last 10 years can reach max values 92 to 95%.
What would you be doing, if you knew that you could not fail? Ans. Bonds and derivative brokering.
RE: Centrifugal pumps horsepower
Power
(hp) Minimum Nominal Efficiency
1 - 4 78.8
5 - 9 84.0
10 - 19 85.5
20 - 49 88.5
so go with 90%....
The NEMA Design B is what you will get unless you pay extra for a premium motor.
RE: Centrifugal pumps horsepower
Unless, of course, you WANT your motor to trip on overload if it runs out past the design point.
rmw
RE: Centrifugal pumps horsepower
If using metric units the motor size in kW is simply
Flow (L/s) x Head (metres)x SG (1 for water) / 102 / pump efficiency.
The motor size selection is an engineering consideration based on a number of considerations for which you need the system curve, the pump curve and the operating conditions of the overall system.
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.)