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Power Calculation of Hydraulic Rotators 3

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Startto

Mechanical
Joined
Dec 16, 2019
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EE
What is the formula to calculate Power(Kw) and Rpm of a hydraulic rotator (Vane model) from Torque 900 Nm, Displacement 330cm3, flow rate 14 L/min, volumetric efficiency is 0.9?
 
Rpm = flow rate/displacement per rev

Ted
 
@EngDesServices
Hello Friend,
Thank you so much for your kind reply.

But I see some faults in the formula when tested with my model.

When I tested the rotator with flow of 14l/min, RPM was 42.
So Power (KW)= (900*41)/9.548
= 3864.68 KW
= 5178.67 HP.
I think the constant should be 9554 instead of 9.548?
 
@hydtools
Hello friend,
Thank you so much.
As per your formula,
RPM = 14/0.33
= 42.42 RPM
Stays closer to the practical result of 41 rotations.


Do you have any Idea how to find power from the values provided in my question?
 
Startto,
The constant is 60/(2pi) = 9.9453

Ted
 
@hydtools,
Hello Friend,
I understand the concept behind 9.9453
But look the answer 3864.68 KW.
I am sure this power is not technically possible.
Please correct me if I am wrong
 
Startto,

What model pump are you looking at?
 
@cdill21
Hello,
Its a Vane motor
 
Hey Startto,

I edited my post to reflect Watts as opposed to kW, guess I wasn't paying enough attention the first time around. Sorry about that.

Power is simply the work done per unit of time or P = W/dt.

A watt is 1 joule per second which is equivalent to 1 NM/S.

So to get power in Watts, you are going to want to find out the amount of work performed in 1 second.

Using HydTools equation for RPM with your input values of 14L/min and 330mL displacement per rev and 0.9 volumetric efficiency gives roughly 38RPM.

To use RPM in the final equation, you need to convert it to angular velocity - which is where the 2*pi/60, or 9.549 in the formula comes from.

Putting it all together leads to: 900nm * 38RPM / 9.549 = 3,581.5 Watts or 3.58 kW or 4.8 hp.

Hope that helps.

Michael Hall, PE (TX) PMP - President
Engineering Design Services LLC
 
@EngDesServies,
Hii friend,
There is no need to be sorry, It happens.
But really thank you , yes it does helps.
 
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