The tendency of low-vapour-pressure oils, silicone fluids in particular, to wet metal and spread as a thin film along walls and baffles. Creep carries diffusion pump fluid up past cold caps and into chambers even when vapour backstreaming is under control. Anti-creep barriers, cold surfaces and choosing a fluid with a low creep tendency keep it in check.
Oil creep's brought diff pump fluid right up the baffle walls, it's on the gate valve seal now.
Also heard as
- creep
- oil migration
Related terms
Backstream
Of pump oil or vapour, to flow the wrong way, from the pump back toward the chamber.
Diffusion pump
High vacuum pump with no moving parts that drives gas toward the exhaust with downward jets of hot oil vapour.
Cold trap
Chilled surface in a pumping line that freezes out water and oil vapour before it reaches the chamber or the pump.