The compression values of the pump heads can provide valuable information for troubleshooting.
When
You observe pressure pulsation or shifts in retention time.
Follow these steps
In the Chromeleon software, check the Compression value for the pump heads (= CompressionDrv1).
The values indicate the compression of the last stroke in percent. The compression value should be less than 100%.
With isocratic conditions, the compression value should remain stable.
When running a gradient, the compression value changes roughly proportional to the pressure curve.
If the value is close to 100%, the required precompression may not be reached and pulsation may occur.
The table shows guide values for some solvents (pure solvent, degassed, delivered at 40 MPa) with the pump being purged and the pressure being stable for some time. In a range between 30 MPa and 60 MPa the values can be considered as linear to the pressure.
Solvent | Compression in % |
---|---|
Water | 25 % ± 10 % |
Methanol | 50 % ± 10 % |
Acetonitrile | 45 % ± 10 % |
Take remedial action if required.
Compression | Remedial Action |
---|---|
Lower than indicated in the table | The outlet check valve may be defective. Replace the valve cartridge. See Replacing the Outlet Check Valves. |
Higher than indicated in the table |
|
Very high (message "Compression limit reached" and low pressure) |
|