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Differences between NW / KF / QF and CF / ISO

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A selection of vacuum flanges and fittings are available in all the standard type vacuum component systems, including NW (also known as KF or QF), ISO, ConFlat (CF, metal seal) and Weldable. We offers a complete line of accessories needed in rough, high vacuum and UHV systems including vacuum traps, electrical feedthroughs, vacuum valves and optical vacuum viewports. The standard material of construction is 304 SS, but 316L SS is available.


NW flange systems are quick connect systems with quick clamp and centering rings providing the connection. Sizes of 10mm to 50mm ID are available. NW fittings are good for all vacuum systems up to high vacuum. ISO flanges are similar to NW except they are larger in diameter, starting at 63mm and going to 500mm. ISO fittings are good choices for up to high vacuum. CF (or, metal seal) flange systems use a knife-edge seal with softer OFHC copper gaskets to form the leak tight vacuum seal that can be heated for bake-out to 450°C. CF flanges and fittings are great for UHV systems and/or systems that must be heated.


NW / KF / QF

NW Vacuum flanges and fittings use quick release latches, and are great from rough to high vacuum applications. The  utility of these fittings comes from their quickness and easy use. NW flanges and fittings are sometimes referred to as KF, or QF. KF is a more popular name in Europe coming from Klein Flansche. QF, standing for Quick Flange, is descriptive of the flange system type.

ConFlat (CF)

ConFlat Vacuum Fittings are used in high vacuum and ultra-high (UHV) applications. CF vacuum hardware is preferred due to its low outgassing and superior vacuum sealing capability. Their seals are generally operated with the principle of a knife edge seal that can seal the system from atmosphere. Out CF fittings are constructed with 304 stainless steel, though other materials can be manufactured by request. These seals are capable of withstanding bakeout temperatures of 400°C to minimize out-gassing.


ISO Flanges are similar to NW flanges, but on a larger scale. ISO flanges use a centering ring with an elastomer material, held together with bolts or claw-type clamps. There are two main versions of ISO fittings: ISO-F and ISO-K. Bolted clamps are generally referred to as ISO-F while clamped are noted as ISO-K. ISO-F is more common on industrial connection when the quick release of the clamp is not a major priority.

We are pleased to offer a full line of vacuum valves. Types of vacuum valving include gate valves (pneumatic or manual- piton or metal seal bonnet), poppet valves or ball valves. All fitting types are provided including weldable tube end flanges on the roughing valves.

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