Inlet/Outlet Check Valve Cartridge — Sales and Instrument Support

Replacement check valve cartridge for the inlet or outlet position of an HPLC pump head. A check valve is a passive one-way valve - typically a ruby ball seating on a sapphire seat - that is opened and closed by the flow itself on every piston stroke, which is why it is one of the highest-cycle parts in the instrument.

Almost every check valve failure is caused by something sitting between the ball and the seat: a buffer crystal, a particle from an unfiltered mobile phase, or an air bubble that will not clear.

Symptoms of a failing check valve

• Pressure fluctuating in time with the pump stroke instead of holding steady.
• The pump losing prime, or refusing to re-prime after a solvent change.
• Flow that falls away while the set flow rate stays the same.
• Pressure that will not hold when the pump is stopped.

A cartridge that has only picked up a salt crystal can often be recovered by sonicating it in 50:50 methanol and water; one that fails again after cleaning has a worn seat and should be replaced. Inlet and outlet cartridges are not always interchangeable - check the flow direction marking before fitting.