When
Pressure pulsation, shift in retention times, and/or poor reproducibility can indicate possible piston seal leakage.
If messages regarding piston seal leakage appear in the chromatography software, for example, "The piston seal leakage has exceeded the recommended limit (code 4121)".
Parts and additional items required
Backpressure capillary (from Diagnostics tool kit) (optional)
Isopropanol
Follow these steps
From the Chromeleon software, start a seal wash cycle.
When the seal wash cycle is complete, disconnect the tubing from the seal wash detector (port labeled in).
No. | Description |
---|---|
1 | Seal wash detector |
2 | Tubing connection port (port labeled in) |
Remove some liquid from the tubing, for example, by shaking the tubing.
Set up the system in such a way that the backpressure indicated in the table is produced.
For example, install an appropriate backpressure capillary on the pump outlet (outlet of the static mixer).
Pump Type | Backpressure |
---|---|
VC-pumps | 60 MPa (approximately) |
VF-pumps | 80 MPa (approximately) |
Apply a flow rate of 2 mL/min using isopropanol.
To evaluate possible leakage, observe the liquid level in the tubing. Finish the observation before a new seal wash cycle starts (after one hour).
Depends on your observation:
Observation | Remedial Action |
---|---|
Liquid level in the tubing remains unchanged | The piston seals seal tightly. Reconnect the seal wash tubing to the seal wash detector (port labeled in). This completes the test. |
Liquid level in the tubing is decreasing | The seal wash seals are leaky: 1. Replace the seal wash seals. 2. Reconnect the seal wash tubing to the seal wash detector (port labeled in). 3. Repeat the test starting with step 1. |
Liquid level in the tubing is increasing | One or more piston seals are leaky. Isocratic pump and quaternary pump: 1. Replace the piston seals in the pump head. 2. Reconnect the seal wash tubing to the seal wash detector (port labeled in). 3. Repeat the test starting with step 1. Binary pump and dual pump: Continue with the next steps. |
On the right pump head, remove the seal wash tubing that connects the left pump head to the right pump head.
Depends on the pump type:
Pump Type | Action |
---|---|
Binary pump | Apply a flow rate of 2 mL/min for 100% solvent A using isopropanol. |
Dual pump | Apply a flow rate of 2 mL/min for the left pump using isopropanol. |
For about 5 minutes, observe the liquid level in the tubing. Finish the observation before a new seal wash cycle starts.
Depends on your observation:
Observation | Remedial Action |
---|---|
Liquid level in the tubing is increasing again | 1. Replace the piston seals in the left pump head. 2. Reconnect the seal wash tubing to the right pump head. 3. Reconnect the seal wash tubing to the seal wash detector (port labeled in). 4. Repeat the test starting with step 1. |
Liquid level in the tubing does not increase again | 1. Replace the piston seals in the right pump head. 2. Reconnect the seal wash tubing to the right pump head. 3. Reconnect the seal wash tubing to the seal wash detector (port labeled in). 4. Repeat the test starting with step 1. |
TIP
If you observe leakage from a pump head, verify that the seal wash tubing is properly connected to the pump head. If the tubing is not properly connected or if the tubing is crimped or kinked, seal wash liquid may leak into the pump.