Hydraulic Pump Sizing -- Multiple Cylinders

   / Hydraulic Pump Sizing -- Multiple Cylinders #1  

fishguy10

New member
Joined
Nov 22, 2012
Messages
3
Location
John Day, OR
Tractor
Kubota m7950, NH TC40DA
I recently purchased a used Thorson hydraulic cattle chute that uses three hydraulic cylinders, spool, a Vickers vane pump of either 3 or 8 gpm (it's overstamped with both numbers and FluidDyne can't help) and what appears to be a GE 10hp electric motor without a rating plate or any identifying numbers. The capacitors on the motor burned up (probably a bad relay) and I'm having difficulty replacing them due to a lack of identifying marks. Since the motor is bad, I cannot test the flow rate of the pump.

Rather than chase ghost parts, I'm thinking about replacing/updating the pump and electric motor and cannot find advise on how to size a hydraulic pump based on the size/desired cycle times of the hydraulic cylinders. I've searched google and this site and while there are a number of posts that come close to answering this question, I was not able to find anything directly responsive.

Q: Is it possible to calculate the hydraulic pump requirements given that at least two of the cylinders are typically in operation concurrently and, if so, how is that done?

Thanks,
Shaun
John Day, OR
 
   / Hydraulic Pump Sizing -- Multiple Cylinders #2  
Shaun,
To figure flow rate required for cylinders you will need to know two variables.

One is cylinder size / bore and rod diameter
Velocity - Desired extend or retract rate

formula is Q = VA
Q = flow in cubic inches per minute
V = velocity in inches per second
A = area square inches

To convert GPM Gallons per Minute into cubic inches per second multiply by 3.85 this is derived from 231 cubic inches per gallon by 60 (seconds in a minute)

Example: 2 inch bore cylinder want to extend at rate of 4 inches per second
A = 3.14 times 4 = 12.56 Cubic inches per second flow required which equals 3.26 GPM

Depending on style or model of the Vickers vane pump there could be number stamped the vane rotor housing. This is the flow rate at 1,200 RPM.
 
   / Hydraulic Pump Sizing -- Multiple Cylinders #3  
Here is a simple all in one solution. I get them in 12 volt for dump trailers and 120 volt for our shop lifts. Screenshot_20201003-104208.jpg
 
   / Hydraulic Pump Sizing -- Multiple Cylinders
  • Thread Starter
#4  
Thank you for the reply....I'm familiar with the calculation. What I'm unsure of is whether you simply add together the flow rate for two cylinders that will be operating at the same time.

Using your example, would the required flow rate be 6.52 GPM if two similarly sized cylinders were operated at the same time?
 
   / Hydraulic Pump Sizing -- Multiple Cylinders #5  
Yes you add all of the flow requirements together to obtain the maximum flow required from the pump
 
   / Hydraulic Pump Sizing -- Multiple Cylinders #6  
Only if the valving allows multiple functions to work simultaneously. Separate open center valves plumbed in series may not. Individual valve flow ratings must also be considered and those ratings should not be exceeded.
 
 
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