Speed Calculator — CentrivaLab

Cartridge & Rotor

Cartridge

Rotor

Any fixed-angle 25° rotor for 94–100 mL Oak Ridge tubes fits: choose "Other rotor" and enter its r_max from the rotor manual.

Initial feed volume V₀ (mL)

Permeate collected V_p (mL)

—

Feed density (kg/m³)

Water at 20 °C = 998. Dense feeds raise ΔP at the same speed: 0.5 M NaCl ≈ 1018, 1 M NaCl ≈ 1040, 1 M MgSO₄ ≈ 1115. The CP Calculator computes it from the solute.

r_m = — mm r_max = — mm r_s start = — mm r_s end = — mm

Operating point

set mean ΔP set rotor speed

Mean ΔP (bar)

Rotor speed (rpm)

Mean ΔP = ½(ΔP_start + ΔP_end) over the collection of V_p; with V_p = 0 it is the pressure at the initial fill.

⚠

Rotor speed

—rpm

—

ΔP start — bar
ΔP end — bar (—)
a_m at the membrane — × g
Rotor limit —

Speed table for these volumes and density

Mean ΔP (bar)	Rotor speed (rpm)	ΔP start (bar)	ΔP end (bar)	a_m (× g)

The ◀ row is your operating point. Red rows exceed the rotor's maximum speed. Speeds are rounded to 10 rpm; most centrifuges accept 10 or 100 rpm steps.

Model: ΔP = ½ρω²(r_m² − r_s²), with r_m = r_max − δ_m the membrane radius and r_s(V) = r_max − δ_s(V) the free-surface radius from the cartridge calibration (94/25: measured over 7.4–22.8 mL; 50/34: 11–13 mL). r_max is the rotor's maximum radius as given by the manufacturer. Over a run the speed is chosen for the arithmetic mean of ΔP at V₀ and at V₀ − V_p, which is within ~0.3 bar of the time-averaged pressure for V_p up to about half of V₀. Same constants as the specification pages and the CP Calculator.