Vacuum Hardware Terminology
If you are involved in high vacuum technology, then you are probably very familiar with some or all of these terms: ANSI, CF, ISO, KF, LF, NW, QF ... they have become part of our vernacular; but what do they mean and how are they used?
Here are the most common terms and basic definitions:
ANSI = Stands for (American National Standards Institute).
These are 150 pound series flanges commonly made to fit
tubes ranging from 1.5” to 12” OD. One flange will contain a
machined o-ring groove and the other is smooth, and the seal
is made by compressing the two flanges together with bolts.
ANSI took over this standard from ASA (American Steamfitters
Association).
CF = Stands for "ConFlat" which is a trade-mark of Varian Vacuum
(now owned by Agilent). This is a flange system which
employs two knife-edged surfaces that press on a metal
gasket (usually copper) from opposing directions. Used
for ultra-high vacuum applications and also where the
flange temperature will exceed the rating of elastomeric seals.
DN: Same as KF.
KF: Originally stood for “Klein Flansche (Flange)”; but now is
usually thought of as “Kwik Flange” or “Klamp Flange.” This is
the most commonly used flange technique for vacuum
applications down to about 10-7 Torr for pipe sizes from
16mm to 50mm. An elastomeric o-ring is held in place by a
centering ring, which rests on a step machined into each
mating flange. A “Kwik” clamp then applies pressure
on the chamfer machined into the outside of each flange, and
the o-ring is compressed against the two flat inside surfaces of
the flange.
ISO: International Standards Organization). Most
common vacuum hardware is built to ISO standards
and thus different brands can be used
interchangeably. It is common to see references to
“ISO-KF” and “ISO-LF”, and sometimes you may see
an abbreviation to “ISO-40” or similar (which actually
means "KF-40" in this example).
JIS: Japanese Industrial Standard. A variation to the ISO
standard system.
LF: “Large Flange” system that employs a centering ring like the
KF system, except rather than Kwik/quick clamps, it employs
through bolts and a single claw clamp or double claw clamps
that grab onto a machined edge. Common sizes are 63mm to
250mm.
NW: Same meaning as KF.
QF: Quick Flange (same meaning as KF).
IES Technical Sales is a value added technical sales, distribution, and solutions provider serving the high technology vacuum, plasma/thin film, temperature, fluid handling and metrology markets.