Cleaning and Testing Check Valves 

Technology: Ion Chromatography 

How do you know you have this problem?

Check valves in the high-pressure pump can become blocked or fail if they allow liquid to flow in the reverse direction. Often, this failure can result in low IC pressure. Pulsation in the baseline can also be observed.  Below is a description of how to test and clean the check valves. 

Examples below show common baseline noise:

Cleaning and Testing Procedure 

• See video Ion chromatography guide | Metrohm > High Pressure Pump > Inlet Valve / Outlet Valve.
• Remove the outlet valve.
  • Unscrew the connection capillary to the auxiliary piston from the outlet valve holder (1).
  • Start by loosening the outlet valve holder with the adjustable wrench, unscrew it by hand (2), and remove it. 
  • Remove the outlet valve from the outlet valve holder (3).

• Remove the inlet valve.
• • Disconnect the eluent line leading into the high-pressure pump.
  • Start by loosening the inlet valve holder with the adjustable wrench (1) and then unscrew it by hand (2) and remove it. 
  • Remove the inlet valve from the inlet valve holder (3).

• Clean the outlet and inlet valves.
  • Start by rinsing the valve in the direction of the eluent flow as indicated by the arrow using a wash bottle filled with ultrapure water, RBS solution, acetone, or alcohol. 
  • The rinsing solution must come out at the valve outlet. If no solution comes out, the check valve is blocked. 
    • If blocked, the check valves can be placed in an ultrasonic bath for a maximum of 20s. Ultrasonic baths that last longer than 20s can damage the ruby ball inside the valve. 
    • Test for the blockage again. If it remains clogged, the check valve must be replaced.
    • NOTE: If check valves are not blocked do NOT ultrasonicate. Ultrasonication can cause damage. 
  • Rinse the valves in the opposite direction of the arrow. The rinsing solution should only be observed in the direction of the arrow. The check valves must be replaced if the flow is observed in both directions. 
• Insert the outlet valve into the pump head.
  • Insert the outlet valve into the cover (1). Make certain that it is an outlet valve, not an inlet valve!
  • Carefully thread the cover into the pump head, being sure not to cross-thread (2). Using only two fingers on the wrench, tighten until additional movement is no longer possible. Avoid overtightening!  
  • NOTE:  It is normal to see about three threads outside of the pump head.  Do NOT force the cover all the way down or the pump will be damaged.

• Insert the inlet valve into the pump head.
  • Insert a new inlet valve into the cover.  Make certain that it is an inlet valve and not an outlet valve!
  • Carefully thread the cover into the pump head being sure not to cross thread.  Using only two fingers on the wrench, tighten until additional movement is no longer possible.  Avoid overtightening!  
  • NOTE:  It is expected to see about three threads outside of the pump head.  Do NOT force the cover all the way down, or the pump will be damaged.

Recommendations

• If failure of only (1) check valve is observed by either blockage or flow observed in both directions, replacing both the inlet and outlet check valve is best practice.  
• New check valves should be readily available to prevent extended periods of downtime. 

Part Numbers:

6.2824.170 Inlet Valve; 6.2824.160 Outlet Valve; 6.2739.000 Wrench 

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