UsingFerruleswithSRI GCs
Therearemany different typesand
sizes of
brassand stainless steel fer-
rules
, but their basic use and installation
is the same. Brass ferrulesare softer
andmore reliablewhen connections are
made and remade several timeswhile
stainless steel is best under operating
temperatures exceeding 300degrees.
Wewill illustrate how to install a
two-
part ferrule
with 1/8” copper carrier gas
tubing anda 1/8” Swagelok brass nut
and 1/8” two-piece ferrule.
Slip thenut over the tubingwith the
threaded opening facing outwards.
Place the brassback ferruleonto the
tubingwith the narrowend facingout-
wards. Slip the brass front ferruleonto
the tubingalsowith the narrowend fac-
ingoutwards. The two ferrulesarede-
signed to fit together.
Thread thenut either straight onto a
male fitting, or, preferably onto a
stainless-steel cap first and tightenwith
a 7/16” wrench (twowrenches if you are
usinga cap). It’sa good idea touse a
newand undamaged stainlessmale fit-
ting the first time you tighten up the fer-
rule because thiswill ensure the ferrule
takes the correct shape. Brass fittings
are sometimes deformed frompast over-
tightening.
You should turn thewrench approxi-
mately one-half turn past finger tight in
order to get the proper tightness. If the
ferrule is too loose it will not producea
gas-tight seal, if it is too tight the ferrule
can be smashed or deformed and also
prevent a gas-tight seal.
Page 2
Okay . . .
….but this isbetter because
the stainless cap ismore
likely to form the ferrule to
the proper shape than a
possibly deformed brass
fitting
