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Introduction
PrecisionMachining,Finishing,andTolerances
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Figure5
Valco/Cheminerthighpressure
compressionfitting
Figure6
Poorquality
compressionfitting
Themachiningmethodsusedby
differentmanufacturers tofinish the
detail of compressionfittingsvary in
severalways that affectperformance,
as shownbelow. Thefitting in
Figure5
is thebest choice forhigh
performancefittings,as the tubefits
squarely into thebottomof thedetail.
This is thedetail used inValcoand
Cheminerthighpressurefittings.
Somefittingmanufacturersomit a
critical finishingoperationwhich
makes thebottomof thedetail square,
leaving the shapeof the typical
tapereddrill bit instead. This results in
thefitting shown in
Figure6
,which
introducesextravolumeandmixing
potential. VICI usesproprietary tooling
specificallydesigned toproduce the
samehighprecisiondetail inevery
ValcoandCheminertfitting.
Although sometimes the tube
endmay seal in thebottomof the
detail, the intent is for the seal tobe
madeat the ferrule. This leaves the
possibilityof seepageuparound the
tubeand into theminutecavities
between theendof the ferruleand
thebottomof the ferrule seat. The
probabilityof this seepage increases
when there isanexcessivevariance
between the tubingODand the
diameterof thecounterboredpilot
inwhich it sits,andbetween the
ferruleODand the ferrule IDat the
pointwhere it“bites”or crimps the
tubing. Thepossibility isvirtually
eliminated inVICI’sfittings,which
aremanufacturedwith theprecise
dimensions that chromatographic
applicationsdemand. UseofVICI
precut tubing,which ismanufactured
toquality standards inexcessofmost
commercial tubing, further assures the
bestfittingconnection.
CHROMalyticTECHnologyPtyLtdAUSTRALIANDistributors e-mail:
: 03 97622034
