Agilent Technologies 1290 Infinity User Manual page 153

Nut and Ferrule Tightening
Stepwise Tightening
Overtightening
C A U T I O N
Overtightening even once will damage the seat and the next connection can only be
sealed using force. If the seat is damaged, there is a considerable chance that the
ferrule will stick and cannot be removed without force or special tools (such as a drill).
If different materials are used, such as polymer tubing and nut together with a
stainless steel ferrule, then over-tightening is always a danger. The sst ferrule will bite
into the polymer tube and block the flow.
➔
The first important rule when tightening a nut and ferrule is to proceed
stepwise:
1 Tighten the nut by hand as much as possible.
2 Continue to tighten using a wrench until resistance is felt. Add one or two
3 Open the connection and remove the assembly to inspect the pilot distance,
4 Install the assembly again and tighten the nut manually first. Use the
5 Check the seal when liquid is pumped through the system. In case a leak is
Installing a tube with a narrow bend, typically a loop, it is advisable to fix one connection
N O T E
first and not inserting the second nut into the female counterpart at the same time. After
tightening open the connection as described above. Start preparing the second connection
without inserting the first nut. Open the second connection again and check the pilot
distance. The last step is inserting the complete tubing with the two connections and make
a final seal as described above.
This stepwise installation of a bended tube is mandatory for PEEKsil tubing (fused silica
tubing sheathed with PEEK polymer).
Agilent 1290 Infinity LC Injectors HTC/HTS User Manual
Do not over-tighten the nut/ferrule. If a connection proves to be leaky, use another
quarter turn to tighten. Step-by-step tightening is the correct approach.
quarter turns to reach the sealing point.
see Figure 71 on page 152.
wrench to reach the same sealing or resistance point as reached in the step
before and add one quarter turn extra for the final seal.
observed, tighten once more by another quarter turn. The rule is to always
come from leaking to tightly sealed and never back from an over-tightened
situation.
LC Injector HTC/HTS Description and Installation
3
Troubleshooting
153