The throughput of a component divided by the pressure difference across it, C = Q/(p1 - p2), in L/s or m³/s. Conductances in parallel add, while in series their reciprocals add, so the smallest element dominates. In molecular flow it depends only on geometry and gas: for air at 20 °C a long round tube passes about 12.1·d³/l L/s with d and l in centimetres, so doubling the diameter gives eight times the conductance.
Turbo's 700 L/s but the conductance of that 2-inch nipple is maybe 150, so the chamber only sees about 125.
Also heard as
- C
Do not mix it up with
- Pumping speed: Both are quoted in L/s, but pumping speed belongs to a pump while conductance belongs to the plumbing between the pump and the chamber.
Related terms
Throughput
How much gas flows past a point each second, counted as pressure times volume, in units such as mbar·L/s.
Effective pumping speed
The pumping speed actually delivered at the chamber after losses in the connecting pipes and valves.
Molecular flow
Flow regime in which molecules bounce between the walls almost without meeting each other.
Pumping speed
Volume of gas a pump removes from its inlet per unit time, measured at the inlet pressure.