DimensionXcan range from0.080” to0.170”amongvariousmanufacturers.
X
X
X
X
Figure 7
MaleNut
Ferrule
ReceivingPort
DimensionX
Figure 6
IfDimensionX is too long, leakswill occur
Ferrule cannot seat properly
Figure 8a
IfDimensionX is too short, adead-volume,
ormixing chamber,will occur
Mixing chamber
Figure 8b
FittingsPrimer
Interchangeability
Becauseswagedstainlesssteel ferrulesarepermanentlyattachedtothe
tubing, interchangeability isalmost impossiblewithstainlesssteelfittings.
Thekey factor that limits interchangeabilityof stainless steel fittings is
“DimensionX”—the lengthoftubingthatextendspastaswagedferrule
(Figure6; seepage184 for detailson swaginga ferrule intoplace).
DimensionXvariesamongmanufacturers (Figure7).DimensionXcan
also vary for the samemanufacturer due toproduction tolerances.
Becauseof thesedifferences, if youareusingall stainlesssteel fittings
we recommend youonly use swaged fittings in theport where they
were initiallyswaged (Figure8a). Interchangingfittingassembliesand
receivingports can introduce leaks and/or dead-volume chambers
to theflowpath (Figure8b). Therefore, for stainless steel fittings, we
generally recommendnewfittings,new ferrules,andnewconnections
each time receivingports arechanged.
Eventhough interchangeability isaproblemwithstainlesssteelfittings,
it is generally not aproblemwithpolymer fittings. Becausepolymer
ferrulesdon’tpermanentlyattach to the tubingwall,DimensionXcan
beadjustedeach time thefittingassembly isconnected toa receiving
port.Thishelpsensureagoodconnectionwithminimaldeadvolume.
If Your Fittings Leak
1. Check tomake sure your tubing is seated properly.
When
usinguniversal Fingertightfittings, the tubingmustbottomout in the
receivingportbefore thenutand ferruleare tightened. Ifagentle tug
disengagesyour tubingafter thefittingshavebeen tightened, loosen
thenut and ferruleand tryagain.
2. The fittingmay not be tightened enough.
Stainless steel nuts
and ferrulesrequireawrenchtotightenthem,evenafterrepeateduse.
Fingertightfittingsalso requireagood turn;however,using toolsmay
lead toover-tighteninganddamage to thefitting, andas such, tools
shouldbeusedwithcautiononFingertight fittings.
3. You may be using incompatible fittings.
Make sure you are
usinganut and ferrule that are compatiblewitheachother andwith
the components of your system. To avoid this problem andensure
compatibility,use IDEXHealth&ScienceuniversalFingertightfittings.
Because the ferruledoesnotpermanently swageontoyour tubing, a
Fingertightcanbeused repeatedly forseveral cycles inmostsystems.
4. Check the condition of the sealing area.
After repeateduse, a
fitting’s“sealingarea” (at the tipof thefittingor ferrule),willgradually
becomedeformed to thepoint of being incapableof creatinga seal.
Assuch, it isagood idea tokeepanextrasupplyof thefittingsyouare
usingsoyoucanreplacethemquicklyandavoidunnecessarydowntime.
5. Check the receiving port for damage.
Sometimes a leaking
connectionhas nothingat all todowith thenut and ferrule, butwith
the receivingport. Ports that havehad stainless steel fittings swaged
into themareespecially susceptible todamage. Check the receiving
port for visibleburrsor scratches and replace if necessary.
6. Evaluate chemical compatibility.
Usingfittingsmadeofmaterial
incompatiblewith yourmobilephase is a surewayof creating leaks.
Pleasevisit the IDEXHealth&Sciencewebsite,www.idex-hs.com, for
more informationabout chemical compatibility.
TELLTALE SIGNSOF SYSTEM LEAKS
Before you see thefirstdripofmobilephase, your systemcanwarn you
that aproblemexists. Themost common signsof system leaksare:
1.
Nofloworpressure
2.
Pumppressuresup, but there isnoflow
3.
Noisybaseline
4.
Baselinedrift
Whileall of these symptoms couldalso indicateproblemsunrelated
to leakingconnections, it isalwayseasiest to start there.Not onlyare
leakingconnectionsusuallyeasy to repair, theyarealso typically the
least expensiveoption.
X=0.080”
X=0.090”
X=0.130”
X=0.170”
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Fittings Primer
