KF, ISO and CF vacuum fittings
Vacuum hardware follows three flange families. KF (also called NW or QF) uses a centring ring and an elastomer O-ring held by a hinged clamp — fast, reusable, good to about 10⁻⁸ mbar, sizes DN10 to DN50. ISO-K and ISO-F handle the larger bores, DN63 upward, with claw clamps or bolt rings. CF (ConFlat) uses knife edges biting into a copper gasket, is bakeable to 450 °C and is the standard for ultra-high vacuum.
Specify the flange standard, the nominal size, the material and the finish. 304 stainless is fine for general duty; 316L resists chlorides and is the usual choice for chemistry; electropolished interiors matter where outgassing or particle counts do. Then pick the geometry — elbows, tees, crosses, reducers, adapters between standards, bellows for misalignment and vibration, viewports, feedthroughs and valves — and remember that every additional joint is another potential leak and another conductance loss.
We supply KF, ISO and CF fittings, clamps, centring rings, bellows, adapters and valves, in stainless and in custom sizes on drawing.
575 models listed, with specifications and quotation within 24 h.
FAQ
KF, ISO-K or CF — which flange standard should I use?
KF (quick-release, elastomer seal) for small bores and joints you open often, down to about 10⁻⁸ mbar. ISO-K or ISO-F for larger bores in the same pressure range. CF (knife-edge, copper gasket) when you need UHV below 10⁻⁹ mbar and bakeout — it is more expensive and single-use on the gasket.
Can I mix flange standards in one system?
Yes, with adapter flanges — KF-to-ISO and ISO-to-CF adapters are standard parts. What you should not do is put a CF joint downstream of an elastomer-sealed section and expect UHV: the system's base pressure is set by its worst joint and its worst material.
Do bellows and flexible hoses affect the vacuum?
They add conductance loss and surface area, so a long flexible line costs you pump-down time and base pressure. Formed metal bellows are far better than braided hose for vacuum work; polymer hose should be kept to rough vacuum only.
What material should fittings be for corrosive service?
304 stainless is the general-purpose choice; 316L is the standard where chlorides or acids are involved. Aluminium is used for weight and cost in clean high-vacuum work but not for aggressive chemistry. Tell us the gas and we will specify the material and the seal together.