196
Technical Resources
Dimension X can range from 0.080” to 0.170” among various manufacturers
X
X
X
X
Figure 7
Male Nut
Ferrule
Receiving Port
Dimension X
Figure 6
If Dimension X is too long, leaks will occur
Ferrule cannot seat properly
Figure 8a
If Dimension X is too short, a dead-volume,
or mixing chamber, will occur
Mixing chamber
Figure 8b
Fittings Primer
Interchangeability
Because swaged stainless steel ferrules are permanently attached to the
tubing, interchangeability is almost impossiblewith stainless steel fttings.
The key factor that limits interchangeability of stainless steel fttings is
“DimensionX”—the lengthof tubing that extends past a swaged ferrule
(Figure 6; see page 195 for details on swaging a ferrule into place).
Dimension X varies among manufacturers (Figure 7). Dimension X can
also vary for the same manufacturer due to production tolerances.
Because of these differences, if you are using all stainless steel fttings
we recommend you only use swaged fttings in the port where they
were initially swaged (Figure 8a). Interchanging ftting assemblies and
receiving ports can introduce leaks and/or dead-volume chambers
to the fow path (Figure 8b). Therefore, for stainless steel fttings, we
generally recommend new fttings, new ferrules, and new connections
each time receiving ports are changed.
Even though interchangeability is a problemwith stainless steel fttings,
it is generally not a problem with polymer fttings. Because polymer
ferrules don’t permanently attach to the tubing wall, Dimension X can
be adjusted each time the ftting assembly is connected to a receiving
port. This helps ensure a good connection with minimal dead volume.
Fittings Primer
If Your Fittings Leak
1. Check to make sure your tubing is seated properly.
When
using universal Fingertight fttings, the tubing must bottom out in the
receiving port before the nut and ferrule are tightened. If a gentle tug
disengages your tubing after the fttings have been tightened, loosen
the nut and ferrule and try again.
2. The ftting may not be tightened enough.
Stainless steel nuts
and ferrules require a wrench to tighten them, even after repeated use.
Fingertight fttings also require a good turn; however, using tools may
lead to over-tightening and damage to the ftting, and as such, tools
should be used with caution on Fingertight fttings.
3. You may be using incompatible fttings.
Make sure you are
using a nut and ferrule that are compatible with each other and with
the components of your system. To avoid this problem and ensure
compatibility, use IDEX Health & Science universal Fingertight fttings.
Because the ferrule does not permanently swage onto your tubing, a
Fingertight can be used repeatedly for several cycles in most systems.
4. Check the condition of the sealing area.
After repeated use, a
ftting’s “sealing area” (at the tip of the ftting or ferrule), will gradually
become deformed to the point of being incapable of creating a seal.
As such, it is a good idea to keep an extra supply of the fttings you are
using so you can replace themquickly and avoidunnecessary downtime.
5. Check the receiving port for damage.
Sometimes a leaking
connection has nothing at all to do with the nut and ferrule, but with
the receiving port. Ports that have had stainless steel fttings swaged
into them are especially susceptible to damage. Check the receiving
port for visible burrs or scratches and replace if necessary.
6. Evaluate chemical compatibility.
Using fttings made of material
incompatible with your mobile phase is a sure way of creating leaks.
Please visit the IDEX Health & Science website, www.idex-hs.com, for
more information about chemical compatibility.
Before you see the frst drip of mobile phase, your system can warn you
that a problem exists. The most common signs of system leaks are:
1. No fow or pressure
2. Pump pressures up, but there is no fow
3. Noisy baseline
4. Baseline drift
While all of these symptoms could also indicate problems unrelated
to leaking connections, it is always easiest to start there. Not only are
leaking connections usually easy to repair, they are also typically the
least expensive option.
Telltale Signs of System Leaks
X = 0.080”
X = 0.090”
X = 0.130”
X = 0.170”
FOR ORDERING & DISTRIBUTOR INFORMATION +1 800 426 0191 • +1 360 679 2528 • www.idex-hs.com