How to Replace the PTFE Frit of the Purge Valve in LC Pumps

Created by Paola Labarbuta over 2 years ago | Last modified by Xu Li-hua over 1 year ago

This Information Applies To: 1100, 1200 and 1260 Infinity I and 1260 Infinity II LC Pumps (Excluding preparative pumps with electromagnetic purge valve (EMPV): G1361A. Not applicable to any of the 1290 Infinity II modules with automatic purge valve: G4220X, G7104X, G7120X).

Issue:

Replacement of the Polytetrafluoroethylene (PFTE) frit is recommended every three months to avoid sample contamination and pressure issues.
Blockage of PTFE frits leads to increased system pressure. If high pressure is detected after opening the purge valve (around 10 bar), the PTFE frit is blocked and it must be replaced.

General overview:

Purge Valves (PV) are manual valves used to divert the flow from the column to the waste. A PTFE frit inside the purge valve catches solvent particles or seal wear.

Figure 1 illustrates the PV components.

Figure 1. Purge Valve Assembly components.
1. Seal cap, 2. PTFE frit, 3. Nut, 4. Purge valve body.

Steps to follow:

Warning: When opening capillary or tube fittings, solvents may leak out. Wear PPE as described in the material handling and safety data sheet supplied by the solvent vendor, especially when toxic, or hazardous solvents are used.

Release the pressure by opening the Purge Valve, disconnect the outlet capillary and the waste tube.
Remove the body of the Purge Valve (PV) from the Pump Head using a thin 14 mm wrench (p/n 8710–1924) to loosen the nut counterclockwise. Do not turn the body of the PV to unscrew it, since it is fixed on the pump head.
Gently remove the Seal Cap with your hands without damaging it.
Remove the PFTE frit using a needle, fine tweezers, or a flat screwdriver if necessary.
Insert a new PFTE frit inside the PV. Make sure that the orientation is correct: the cut-side must face outside.
Place the Seal Cap back by pressing it with your finger. If the Seal Cap is visibly damaged or deformed, then replace it with a new one to avoid leak issues.
Assemble the PV body back into the Pump Head using a 14 mm wrench. Mind the orientation of the connection ports, it varies depending on the pump model (Figure 2). Hold the purge valve in the correct orientation to ensure the purge valve stays in this correct orientation during nut tightening.
Reconnect outlet capillary and waste tube.
Test the LC system backpressure with the purge valve open. The pressure value should now be less than the pressure value before replacing the filter.

Figure 2. Correct orientation of PV connection port.