Basic Fluid Power Formulas
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Variable
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Word Formula w/ Units
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Simplified Formula
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| Fluid Pressure - P |
(PSI) = Force (Pounds) / Area ( Sq. In.) |
P = F / A |
| Fluid Flow Rate - Q |
GPM= Flow (Gallons) / Unit Time (Minutes) |
Q = V / T |
| Fluid Power in Horsepower - HP |
Horsepower = Pressure (PSIG) × Flow (GPM)/ 1714 |
HP = PQ / 1714 |
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Actuator Formulas
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Variable
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Word Formula w/ Units
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Simplified Formula
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| Cylinder Area - A |
( Sq. In.) = π × Radius (inch)2 |
A = π × R2 |
| (Sq. In.) = π × Diameter (inch)2 / 4 |
A = π × D2 / 4 |
| Cylinder Force - F |
(Pounds) = Pressure (psi) × Area (sq. in.) |
F = P × A |
| Cylinder Speed - v |
(Feet / sec.) = (231 × Flow Rate (gpm)) / (12 × 60 × Area) |
v = (0.3208 × gpm) / A |
| Cylinder Volume Capacity - V |
Volume = π × Radius2 × Stroke (In.) / 231 |
V = π × R2 × L / 231
(L = length of stroke)
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| Cylinder Flow Rate - Q |
Volume = 12 × 60 × Velocity (Ft./Sec.) × Net Area(In.)2 / 231 |
Q = 3.11688 × v × A |
| Fluid Motor Torque - T |
Torque (in. lbs.) = Pressure (psi) × disp. (in.3 / rev.) / 6.2822 |
T = P × d / 6.2822
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| Torque = HP × 63025 / RPM |
T = HP × 63025 / n |
| Torque = Flow Rate (GPM) × Pressure × 36.77 / RPM |
T = 36.77 × Q × P / n |
| Fluid Motor Speed - n |
Speed (RPM) = (231 × GPM) / Disp. (in.)3 |
n = (231 × GPM) / d |
| Fluid Motor Horsepower - HP |
HP = Torque (in. lbs.) × rpm / 63025 |
HP = T × n / 63025 |
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Pump Formulas
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Variable
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Word Formula w/ Units
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Simplified Formula
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| Pump Output Flow - GPM |
GPM = (Speed (rpm) × disp. (cu. in.)) / 231 |
GPM = (n ×d) / 231 |
| Pump Input Horsepower - HP |
HP = GPM × Pressure (psi) / 1714 × Efficiency |
HP = (Q ×P) / 1714 × E |
| Pump Efficiency - E |
Overall Efficiency = Output HP / Input HP |
EOverall = HPOut / HPIn X 100 |
| Overall Efficiency = Volumetric Eff. × Mechanical Eff. |
EOverall = EffVol. × EffMech. |
| Pump Volumetric Efficiency - E |
Volumetric Efficiency = Actual Flow Rate Output (GPM) / Theoretical Flow Rate Output (GPM) × 100 |
EffVol. = QAct. / QTheo. X 100 |
| Pump Mechanical Efficiency - E |
Mechanical Efficiency = Theoretical Torque to Drive / Actual Torque to Drive × 100 |
EffMech = TTheo. / TAct. × 100 |
| Pump Displacement - CIPR |
Displacement (In.3 / rev.) = Flow Rate (GPM) × 231 / Pump RPM |
CIPR = GPM × 231 / RPM |
| Pump Torque - T |
Torque = Horsepower × 63025 / RPM |
T = 63025 × HP / RPM |
| Torque = Pressure (PSIG) × Pump Displacement (CIPR) / 2π |
T = P × CIPR / 6.28 |