valco fittings
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VICI AG International Sales: + 41–41–925–6200 Fax: + 41–41–925–6201
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Introduction
Precision Machining, Finishing, and Tolerances
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Figure 5
Valco/Cheminert high pressure
compression fitting
Figure 6
Poor quality
compression fitting
The machining methods used by
different manufacturers to finish the
detail of compression fittings vary in
several ways that affect performance,
as shown below. The fitting in
Figure 5
is the best choice for high
performance fittings, as the tube fits
squarely into the bottom of the detail.
This is the detail used in Valco and
Cheminert high pressure fittings.
Some fitting manufacturers omit a
critical finishing operation which
makes the bottom of the detail square,
leaving the shape of the typical
tapered drill bit instead. This results in
the fitting shown in
Figure 6
, which
introduces extra volume and mixing
potential. VICI uses proprietary tooling
specifically designed to produce the
same high precision detail in every
Valco and Cheminert fitting.
Although sometimes the tube
end may seal in the bottom of the
detail, the intent is for the seal to be
made at the ferrule. This leaves the
possibility of seepage up around the
tube and into the minute cavities
between the end of the ferrule and
the bottom of the ferrule seat. The
probability of this seepage increases
when there is an excessive variance
between the tubing OD and the
diameter of the counterbored pilot
in which it sits, and between the
ferrule OD and the ferrule ID at the
point where it “bites” or crimps the
tubing. The possibility is virtually
eliminated in VICI’s fittings, which
are manufactured with the precise
dimensions that chromatographic
applications demand. Use of VICI
precut tubing, which is manufactured
to quality standards in excess of most
commercial tubing, further assures the
best fitting connection.
CHROMalytic TECHnology Pty Ltd AUSTRALIAN Distributors e-mail:
Tel: 03 9762 2034
