Hydraulic Pump Power Requirement

[dawz]

Hi guys,

I have a water pump (A) with the rated power of 5kW.
Water pump (A) will be directly driven by a hydraulic motor (B) via a coupling.
From datasheet, hydraulic motor (B) runs at 13Nm and 371rpm at 15L/min.

If I use the power formula P = Tor. (Nm) x Rotation Speed (rpm) / 9549:

Power of Hydraulic Motor (B)
= 13 x 371 / 9549
= 0.505kW

Is the formula correct that my hydraulic motor (B) of 0.505kW is not able to drive the water pump (A) with the requirement of 5kW, even if my engine is close to 50HP?

 

[LittleInch]

Someones wrapped all the fixed numbers into one, but I used P = 2 Pi (rpm/60) x T(Nm) and also get 505W

15 l/m isn't very much. What pressure is the hydraulic supply?

Power of the driver is not relevant here if its only coupled to a very small hydraulic pump. For which you supply no data.

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

 

[dawz]

For the pressure, I have not run the system yet.
But seems your calculation tallies with mine. Probably pointless to test the system and get a larger pump (C) sorted out first..

The data that I have on hand:

Water Pump (A) <- Hydraulic Motor (B) <- Hydraulic Pump (C) <- Engine (D)

Hydraulic Pump (C) displacement rating:
P1: 20cc/r (used for travel motor)
P2: 20cc/r (used for travel motor)
P3: 6.4cc/r (the port that I plan to use to connect to hydraulic motor (B)) (Max pressure: 20.6MPa (2987.7 Psi))
P4: 2.7cc/r (UNUSED, blocked with a plug)

* port 3 has a very small gear pump. If this port's output is not enough, I might consider adding another pulley to engine crankshaft and install a bigger hydraulic pump.

* Hydraulic pump (C) Model: Nachi PVD-2B-40-6G3. This is directly connected to engine's flywheel.
* the number "6" from 6G3 = 6.4cc/r

Engine will run at 2300 rpm so in calculation it churns out 6.4 x 2300 = 14.72L/min.

Data for hydraulic motor (B):

 

[LittleInch]

Well at your pressure (20 MPa) from that table that is off the table, but will be a lot more than 13Nm which is based off 3 MPa ( the top row sets the pressure for the different columns no?

There seems to be a mismatch here between pressure from the pump and what the motor will handle. The fact that a lot of the notes are in Chinese doesn't help.

But that's a slow speed for a water pump. What sort of pump? PD or centrifugal?

Any water pump data or curves?

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

 

[btrueblood]

What LI said - what is the rpm at which the water pump power was specified?

 

[Doug Hunter]

I agree with LittleInch and Btrueblood. That's very slow for a water pump and the power rating was probably given for a higher speed. The power rating is one thing, but what does the application actually want? Water pumps are usually centrifugal for low pressure ( < 200 psi?) and PD for higher pressures. Also, hydraulic motors are usually designed for low speed and high torque. You can raise the speed by lowering the motor displacement relative to the pump displacement. Is there a reason to not go directly from the engine to the water pump?

 

[BEMPE16524]

few things you need to consider while attaching a hydraulic pump to the electric motor/ hydraulic motor:
1. operating pressure
2. shaft RPM
3. pump flow rate
4. shaft torque

you can get your pump detail from catalogue, remember your maximum pump displacement may be lower, normally 0.8 of Vgmax

after that you can calculate the required input power of the pump and compare it with the output power of your motor.

R.Efendy