valco fittings
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tech tip
Filtering capability can be added to a union by inserting a screen or frit into it before making
up the fittings. However, when a fitting detail has a screen or frit in it, the pilot depth is
reduced, so that the ferrule makes up closer to the tube end than it otherwise would. If
that tube is used in any other Valco fitting, it will introduce unswept volume. Our filter
design takes this into account, allowing our fittings to remain truly interchangeable.
Filters . . . . pages 50-52
Frits and screens . . . 53
Unions
tubing made up in a union
Tubing made up with a frit
lengths of
pilots are
different
without frit
with frit
frit
Unions join two pieces of tubing of the
same OD. Select the union with the
bore that matches the ID of the tubing.
If the IDs are different, choose the
union with a bore which matches the
smaller tube bore. Standard material
is 300 series stainless steel.
Internal
unions have female
threads and a fitting detail for zero
volume fittings. The nuts have male
(external) threads.
External
unions have male threads,
requiring a nut with internal threads.
External/internal
unions have male
threads on one end and female
threads on the other, for connecting
a standard zero dead volume fitting
to an existing tube which already
has an external nut made up on it.
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.
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.
0.25 mm = .010"
0.50 mm = .020"
0.75 mm = .030"
1.0 mm = .040"
1.5 mm = .060"
2.0 mm = .080"
4.6 mm = .180"
6.0 mm = .236"
6.4 mm = .253"
7.0 mm = .275"
10.0 mm = .400"
27.0 mm = 1.08"
1/32" = 0.8 mm
1/16" = 1.6 mm
1/8" = 3.2 mm
1/4" = 6.4 mm
3/8" = 9.5 mm
1/2" = 12.7 mm
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Tel: 03 9762 2034
