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Common Calculations FAQs

Calculating force, speed, pressure, power, and efficiency in hydraulic applications.

How do you calculate actuator speed?

Actuator speed is determined by flow rate and cross-sectional area:

Speed = Flow rate ÷ Area

Flow rate is the volume of fluid delivered (in L/min or GPM).

Area is the cross-sectional area of the actuator piston: π × (diameter ÷ 2)².

How do you calculate cylinder force?

Cylinder force can be calculated using:

Force = Pressure × Area

Pressure is the system pressure (in psi or bar).

Area is the cross-sectional area of the cylinder bore (in square inches or square centimeters).

Area = π × (bore diameter ÷ 2)².

How do you calculate pressure drop across a valve?

Pressure drop can be calculated using the valve flow coefficient (Cv):

Pressure Drop (ΔP) = (Flow Rate)² ÷ (Cv² × Fluid Density)

Flow Rate is the fluid flow (in GPM or L/min).

Cv is the valve flow coefficient.

Fluid Density is the density of the hydraulic fluid.

How do you size an accumulator?

Accumulator sizing considers required flow, pressure, and pre-charge:

Accumulator Volume = Flow Rate × Time ÷ Pressure

This determines how much fluid must be stored to maintain system pressure.

How to convert psi to bar?

Use the conversion factor: 1 bar = 14.5 psi.

To convert psi to bar, divide psi by 14.5.

Example: 200 psi ÷ 14.5 = 13.79 bar.

What is pre-charge pressure in an accumulator?

Pre-charge pressure is the initial gas pressure in the accumulator before fluid enters.

It helps maintain system pressure as the accumulator discharges.

Typically set to 70–80% of system operating pressure.

What is specific gravity of hydraulic fluid?

Specific gravity is the ratio of hydraulic fluid density to water.

A value of 1 means equal density.

Less than 1 means the fluid floats; greater than 1 means it sinks.

What is torque in a hydraulic motor?

Torque is the rotational force produced based on system pressure and motor displacement:

Torque = Pressure × Displacement ÷ 2π

Pressure is the operating system pressure.

Displacement is the volume displaced per revolution (in cubic inches or cubic centimeters).

What unit is hydraulic power measured in?

Hydraulic power is measured in horsepower (HP) or kilowatts (kW).

Hydraulic horsepower can be calculated using:

HP = (Pressure (psi) × Flow rate (GPM)) ÷ 1714.

What’s the relationship between pump speed and flow?

Flow rate is directly proportional to pump speed.

If pump speed doubles, flow rate doubles (assuming constant displacement).

This is important when adjusting flow or selecting a pump for varying speeds.