A
WORD ABOUT O-RING CONNECTIONS
Pyrex neon manifolds, regardless of
manufacturer, typically incorporate several O-ring connections of some
type. These may be a glass tube with a threaded end and a cap that
screws onto the thread to compress the O-ring, or a ball and socket
arrangement with the O-ring compressed between the two components via
a pinch clamp, or what is commonly called a “KF flange”, which uses an
O-ring centered between two flat glass flanges, also compressed by a
pinch-type clamp.
There is a concern among some neon
technicians about the type and number of O-ring connections in a
manifold system. The general feeling is that the more connections
there are, the more the system will leak, or at least have more of a
potential for leaks with each increase in the number of connections.
However, a clean, properly installed O-ring connection of the types
mentioned will be vacuum tight and have been successfully helium leak
tested down to the 10-8 Torr range.
A case in point is the vacuum
system here at SVP Neon Equipment. Due to the various testing and
experiments, as well as general processing it is subjected to, our
manifold system has numerous O-ring connections not found on a typical
neon manifold system, as well as the typical ones. With a total of 37
O-ring seals exposed to the main vacuum chamber (not including the
ones between the main stopcocks and vacuum pumps) it has a
rate-of-rise (leak test) less than 0.1 (1/10th) micron per
minute.
If an O-ring connection leaks it is
because it is dirty, installed wrong, has a damaged component or a
combination of these.
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