Hidroteknik Calculators
Hydraulic Accumulator Sizing
The total volume of a bladder/piston accumulator is calculated from the usable oil volume and the working pressures using Boyle's law (isothermal).
⚙ Open the Hydraulic Calculator →Volume Formula
All pressures ABSOLUTE (bar abs = gauge + 1.013). Pre-charge p0 ≈ 0.9 × p1.
Units
| Quantity | Symbol | Unit |
|---|---|---|
| Total volume | V0 | L |
| Usable volume | ΔV | L |
| Min/Max pressure | p1, p2 | bar (absolute) |
| Pre-charge | p0 | bar (absolute) |
Worked Example
Given: ΔV = 2 L, min pressure 100 bar, max pressure 160 bar (gauge). Pre-charge p0 = 90 bar gauge.
1) Absolute: p0 = 91.0 · p1 = 101.0 · p2 = 161.0 bar
2) 1/p1 − 1/p2 = 0.00990 − 0.00621 = 0.003689
3) V0 = 2 / (91.0 × 0.003689) = ≈ 6.0 L
Frequently Asked Questions
What should the nitrogen pre-charge be?
Rule of thumb: pre-charge (p0) ≈ 90% of the minimum working pressure. Too low wastes most of the oil; too high empties the accumulator early.
Why use absolute pressure?
Boyle's law (p×V = constant) holds for absolute pressure. Add atmospheric pressure (≈1.013 bar) to the gauge value.
Isothermal or adiabatic?
For slow cycles the isothermal (constant temperature) assumption is adequate. Very fast cycles may need an adiabatic correction (exponent n≈1.4).