# Hydraulic Calculator

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- Hydraulic Pump

& Motor Calculator - Cylinder

Calculator - Velocity & PSI Drop

Calculator - Thermal

Calculator - Accumulator

Calculator - Cylinder

Regeneration

## Pump Flow or Displacement

$$GPM(Flow) = \frac{RPM * DISPLACEMENT (Cu. In./Rev.)}{231}$$

## Pump Input Horsepower

$$HP(Power) = \frac{PSI(Pressure) * GPM(Flow))}{1714 * \text{% }Pump\text{ } Efficiency }$$

## Torque

$$Lb-in (Torque) =\frac{PSI (Pressure) * cu.in. / rev. (Displacement)}{2π} $$

## Torque

$$Lb-in (Torque) =\frac{HP(Power) *63025}{RPM} $$

## Cylinder Piston Area-Blind End (Extension)

$$in^2(Area) = in (Piston\text{ } Diameter) ^ 2 * (\frac{π}{4})$$

## Cylinder Piston Area-Rod End (Retraction)

$$in^2 (Area) = (in (Piston Diameter))^2 *(\frac{π}{4}) – (in(Rod Diam.))^2 *(\frac{π}{4})$$

## Cylinder Force

$$lbf. (Pounds\text{ }of\text{ }Force) = PSI (Pressure) * sq. in. (Area)$$

## Cylinder Flow Rate and Velocity

$$GPM (Flow) = \frac{in.^2 (Area) * in. (Stroke Travel) * 60 }{sec (Time) * 231}$$

## Cylinder Volume

$$Gal (Volume)=\frac{in.^2 (Piston Area) * in. (Stroke)}{231}$$

## Pressure Loss Per Foot of Pipe (Laminar Flow Only)

$$PSI/ft(Pressure Loss)=\frac{SSU(Viscosity\text{ at }Oper. Temp.) * GMP}{18300*(in(I.D. of Pipe))^4}$$

## Velocity of Oil Flow in a Pipe

$$ft/sec(Velocity)=\frac{GPM (Flow)*0.3208}{(in(I.D. of Pipe))^2*0.7854}$$

## Reservoir Cooling Capacity (Steel w/ Adequate Air Circulation)

*BTU/hr(Heat Loss) =2*sq. ft. (Surface Area of Reservoir) * (°F (Reservoir Wall Temp.)-°F (Air Temp.))*

## Heat in a Hydraulic System From Unused Flow / Pressure

*BTU/hr (Heat) = GPM (Flow)*1.485 *PSIG (Pressure Drop)*

## Heat in a Hydraulic System (Hydraulic Oil)

*BTU/hr (Heat Loss) = 210 * GPM (Flow) * (°F (Return Fluid Temp.) -°F (Pump Fluid Temp.))*

## Heat Required to Reach a Desired Temperature

$$kWh (Heat)=\frac{Lbs. of Hyd Oil*Specific Heat*(°F (End Temp.)-°F (Beg. Temp.))}{3413}$$

## Accumulator Make Up Oil Necessary to Stroke Cyl in “X” seconds

### Blind End

$$Oil Req. = \frac{3.14 * Cyl. Bore Dia.^2 * Stroke}{4}-\frac{GPM * 231 * Req. Stroke}{60}$$

### Rod End

$$Oil Req. = \frac{3.14*(Cyl. Bore Dia.^2-RodDia.^2)}{4}* Stroke-\frac{GPM * 231 * Req. Stroke}{60}$$

## Accumulator Sizing

$$StoredOil = \frac{0.95 * Pre\text{-}charge * Vol.Size}{Min. PSI} – \frac{0.95*Pre\text{-}charge*Vol.Size}{System PSI}$$

Note:

Due to heating and cooling of the nitrogen during operation, a 5% allowance has been added to the formula. Allow enough extra capacity for contingencies.

## Calculating Flow Rates in Regeneration Circuits

*DB* = Diameter Blind End

*DR* = Diamter of Rod End

*P* = Pump Flow

### Cylinder Speed

$$Cylinder Speed (in/sec) = \frac{P * 231}{60 * (\frac{DR^2}{4} * π)}$$

### Flow Out of Rod End of Cylinder

$$Flow Rod End (GPM) = \frac{DB^2-DR^2}{DR^2}*P$$

### Combined Flow (Regen. Flow + Pump Flow)

$$Combined Flow (GPM) = \frac{DB^2}{DR^2}*P$$

### Retraction Flow (Flow Out of Blind End)

$$Retract Flow (GPM) = \frac{DB^2}{DB^2-DR^2}*P$$

## Displacement

## Volume

## Distance

## Power

## Torque

## Force

## Viscosity (100° F)

## Velocity

## Heat/ Energy

## Temperature

## Disclaimer

While fluid power formulas are useful tools for specifying system components and capabilities; other factors such as mechanical efficiencies, fluid dynamics and material limitations must also be considered.

**Northpointe Industries** has taken great care to verify that the conversions and calculations on this page are correct. However, Northpointe Industries provides no warranties, nor does it assume any legal liability or responsibility for the accuracy, completeness or usefulness of any of the information supplied.

360-705-0918

sales@northpointeindustries.com

2918 Ferguson Street SW Suite C2

Tumwater, WA 98512