A test in which the chamber is valved off from its pumps and the pressure rise is logged over time; the gas inflow is Q = V·Δp/Δt. A real leak gives a straight line that keeps climbing, while outgassing or a virtual leak gives a curve that bends over as surfaces saturate or the trapped pocket empties. Vacuum furnace specifications typically cap it at a figure such as 10 microns per hour.
Rate of rise on furnace 4 is 25 microns an hour and dead linear, that's a real leak, not wet walls.
Plot rate-of-rise data on linear axes, not a log scale; a straight line on linear axes is the signature of a real leak.
Also heard as
- ROR
- leak-up rate
- leak-back test
- pressure rise test
Related terms
Virtual leak
Gas trapped in a hidden pocket inside the vacuum that bleeds out slowly and behaves like a small real leak.
Outgassing
Slow release of gas from the surfaces and bulk of materials inside a vacuum system.
Leak rate
Quantity of gas entering a vacuum system through a leak per unit time, usually in mbar·L/s.
Base pressure
The lowest pressure a particular chamber reaches after pumping for a set time with no process gas flowing.
Micron
Shop name for a millitorr, one thousandth of a Torr, used in US furnace shops, labs and refrigeration work.