Cylinder Sizing Process

Selecting the right hydraulic cylinder involves determining bore, rod, and flow requirements from application parameters:

1. Determine required force from load and safety factor
2. Calculate minimum bore diameter from force and pressure
3. Select rod diameter based on bore and loading type
4. Calculate flow requirements from stroke and cycle time
5. Round up to next standard size

Bore Diameter Calculation

For push (extension) loads:

D_bore = sqrt(4 x F / (pi x P x eta))

For pull (retraction) loads, use annular area equation, or calculate as push load and verify pull capacity.

Rod Diameter Selection

Rod size depends on several factors:

• Standard ratios: Rod typically 50-70% of bore diameter
• Push loads: Consider buckling - longer strokes need larger rods
• Pull loads: Rod must have adequate tensile area
• Speed requirements: Larger rod = faster retraction for same flow

Flow and Power Requirements

Q = A x Stroke / Time

Power (kW) = P (bar) x Q (L/min) / 600

Power (HP) = P (psi) x Q (GPM) / 1714

Standard Bore/Rod Combinations

Cylinders are manufactured in standard sizes. After calculating the theoretical bore, round up to the next standard size:

• Metric (ISO): 25, 32, 40, 50, 63, 80, 100, 125, 160, 200, 250, 320 mm
• Imperial (NFPA): 1.5, 2, 2.5, 3, 3.5, 4, 5, 6, 7, 8, 10, 12 inches