Thermo Scientific Accela Open Autosampler Hardware Manual page 110

6
Troubleshooting
Troubleshooting Considerations
Incorrect Pilot Distance
92 Accela Open Autosampler Hardware Manual
Do not overtighten the nut/ferrule. If a connection proves to be leaky, use another quarter
turn to tighten. Step-by-step tightening is the correct approach. Overtightening even
once will damage the seat, and the next connection can only be sealed using force. If the
seat is damaged, the ferrule will likely stick and require force or special tools (such as a
drill) to remove it.
If you use different materials, such as a polymer tubing and nut, together with a stainless
steel ferrule, then overtightening is always a danger. The ferrule will bite into the polymer
tube and block the flow.
When installing a tube with a narrow bend, typically a loop, fix one connection first; do
not simultaneously insert the second nut into the female counterpart. 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 making a
final seal as described earlier.
This stepwise installation of a bended tube is mandatory for PEEKsil tubing (fused silica
tubing sheathed with PEEK polymer).
2. The second rule to observe when installing nuts and ferrules is to never reuse them for
any other connection.
Do not install a tube for any other application with a nut/ferrule that is set for a specific
purpose. Cut a portion of the tube end until straight tubing is reached and remove the
ferrule.
This rule is valid for a loop as well. Never reuse a loop for another valve or reuse a valve
after exchanging the stator.
If a fingertight nut has been installed, replace it as well. If a stainless steel nut has been
used, ensure that you use the correct type.
Newly installed fingertight ferrules can hold a backpressure of up to 200 bar.
When making a new tube connection, be sure to follow these guidelines:
1. Slip the nut and ferrule over the tube. Make sure the end of the tube sticks out
approximately 50 mm (2 in.).
2. Press the tube end firmly into the female counterpart for the connection.
3. Move the nut and ferrule together into the female counterpart for the connection
(Figure 58). Make sure to maintain pressure on the tube to avoid the tube slipping
backwards, out of position.
4. Tighten the nut as described in the previous section.
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