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Flow Through Needle (FTN) ACQUITY H-Class or I-Class system with pump overpressure error message - WKB9936

Article number: 9936


  • Pump overpressure
  • System overpressure error
  • Pressure is normal when FTN is switched from inject to load on interactive control


  • Flow Through Needle (FTN) Sample Manager
  • ACQUITY H-Class
  • ACQUITY I-Class


  • Blockage in the needle, needle seat, or tubing


  1. Disconnect the pump line from port 5 of the inject valve.
  2. Disconnect the active preheater from port 6 of the inject valve.
  3. Connect the pump line to port 6 of the inject valve.
  4. Put LC/MS grade water on A and prime.
  5. Pump water for at least 30 minutes through the inject valve. If it is still overpressure, try a lower flow rate or warm water. 
  6. Keep increasing the flow rate to 1 mL/min.
  7. Once confident that blockage is cleared, reconnect the pump and active preheater lines to ports 5 and 6 respectively. 


  • If the active preheater (APH) is blocked this can be reverse flushed by removing the column and attaching the back end of the APH to port 6 of the inject valve
  • Can also try flushing with 50/50 water/organic or straight organic depending on what the blockage is

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