valco fittings
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VICI AG International Sales: + 41–41–925–6200 Fax: + 41–41–925–6201
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Reducing Unions
Reducing unions join two tubes of
different outside diameters. Standard
material is 300 series stainless.
Internal reducing unions have
female threads and a fitting detail
for zero volume fittings. The nuts
have male (external) threads.
External reducing unions have male
threads, requiring a nut with internal
threads.
External/internal and internal/
external reducing unions have
male threads on one end and
female threads on the other. We
recommend the use of external/
internal fittings when connecting
to an existing external nut.
Internal fittings are almost always the
best with tubing of 1/8" OD or smaller.
They make a stronger connection and
offer the lower volume necessary for
high performance instrumentation.
Also, because 1/16" external fittings
have very thin, easily distorted walls,
they are not as durable as 1/16"
internal fittings. In sizes larger than
1/8", external fittings are generally
easier to make up because of less
thread friction.
Bulkhead
versions can be mounted
through an instrument panel or on a
bracket. The fitting body is undercut
so that it bites into the panel when the
mounting nut is tightened, eliminating
the need for a lock washer. An O-ring
can be installed between the body and
the panel to allow operation in purged
environments. Typically the mounting
nut goes inside the instrument, so
that the long threaded portion will be
out of sight. In the external/internal
bulkhead unions, the mounting nut
is on the side with the Valco internal
fitting.
deadvolume
“Dead volume”is created in obvious
situations such as the one shown.
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1/16" Tee
(ZT1)
unswept volume
Even in connections which are by most definitions
“zero dead volume”, unswept volume may be created
where large ID transitions occur. The amount of mixing
depends on the amount of mismatch in the IDs.
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1/8" to 1/16" Reducing union
(ZRU21)
CHROMalytic TECHnology Pty Ltd AUSTRALIAN Distributors e-mail:
Tel: 03 9762 2034
