Define the surface and flow path being washed
The solvent dissolves or dislodges the target residue; the pump delivers it to the wash port. External needle washing does not automatically clean the internal needle, injection valve or sample loop. Those paths require the correct fluid connections and valve sequence.[1]
Evaluate DPL30 first where its operating range fits
| Candidate | Reason to evaluate | Required confirmation |
|---|---|---|
| DPL30 | Routine liquid wash delivery within its installed operating envelope | Its 300 mL/min free-flow value is not the flow through narrow tubing, filters and a wash nozzle. |
| DPL30H | A path with a demonstrated higher outlet-pressure requirement | The 600 kPa rated pressure is not a default selection reason. Confirm pressure limits for the complete path and usable flow at load. |
Use the DPL30 selection guide to compare the pump configuration with the wash formulation and operating point before increasing pump size or pressure capability.
Convert wash volume and available time into installed flow
Nominal average delivery requirement equals wash volume divided by effective delivery time. For example, 2 mL delivered in 5 seconds requires an average 24 mL/min at the wash port. This initial calculation excludes startup delay, flow establishment and pulsation.
A DPL30 free-flow value of 300 mL/min does not prove stable, controllable delivery at 24 mL/min. Confirm the drive adjustment range, installed flow curve and start/stop repeatability. If the required low flow cannot be controlled, reassess the pump or fluid-path arrangement.
Where the wash circuit has a demonstrated higher-resistance requirement, consult the DPL30H selection guide. Verify achievable flow at that load; maximum pressure and free-flow values are not a simultaneous operating point.
Specify weak and strong wash formulations, not only their names
Provide each liquid's solvent identities, mixing ratios, additives and temperature. Evaluate continuous exposure as well as residual liquid during idle periods across every wetted component.
When multiple solvents share a pump and line, the first liquid after switching contains the previous contents. Determine replacement volume from path volume and residue testing. Separate supply branches can reduce shared-path carryover but require extra space and components; choose from the acceptance requirement.
Judge cleaning by blank recovery, not pump flow alone
Run a representative high-concentration sample followed by blanks. Compare solvent composition, effective wash time, delivered volume and wash repetitions. Measure the recovery that matters to the analytical method rather than assuming more flow is cleaner.
- Confirm that the needle exterior and seat-contact regions receive the intended coverage.
- Evaluate internal-path cleaning separately from external washing.
- Observe splashing, droplets, foaming and liquid accumulation during the full cycle.
- Check the first wash after reservoir replacement and the first cycle after idle.
Prepare the supply-pump acceptance specification
| Input | Required detail |
|---|---|
| Media | All wash recipes, temperatures, viscosity range and compatibility requirements |
| Duty | Volume per wash, effective supply time, cycle frequency and daily running hours |
| Installed path | Tube sizes and lengths, lift, filter and nozzle restriction |
| Integration | Permitted pressure, drive/control, noise, space and service access |
| Result | Carryover limit for representative samples, acceptable drips and restart recovery |
Common wash-supply questions
Does higher flow always improve cleaning?
No. Solvent action, contact time and surface coverage also matter. Excess flow can cause splashing, consume more solvent and overwhelm the drain. Use the high-sample/blank result to select a suitable program.
Should the pump use a brushed or brushless motor?
Compare the available versions against daily running time, start/stop frequency, maintenance interval and budget. A brushless drive does not by itself guarantee low carryover or stable very-low-flow operation.