The dosing principle decides what the worst case is, which parts drift, and therefore which challenges an OQ must contain. A peristaltic filler and a piston filler can both hit the same target volume and still need quite different qualification protocols.
| Technology | Typical use | Worst case to challenge in OQ Wear or drift item to trend |
| Piston(volumetric) fillers | Syrups， suspensions and other moderate to high viscosity oral Liquids | Most viscous product， maximum speed， smallest fill on the largest cylinder Piston seals and valve wear， visible as a bias that grows overtime |
| Peristaltic pump fillers | Sterile injectables and smal-volume fils where low hold-up and quick changeover matter | Smallest fill volume， longest continuous run， product temperature after every tubing change Tubing lot and hours in use； re-verify fill weight after every tubing change |
| Gravity， time-pressure and overflow(level) fillers | Low-viscosity oral solutions， mouthwashes， topical liquids | Container dimensional variation， because a level fill delivers a constant height， not a constant volume Nozzle seals， and any change of container supplier or mould |
| Mass-flow or net-weigh fillers | Lines that dose by weight or flowmeter | Density and temperature change across the batch; flowmeter or load-cell calibration， as-found and as-left |
| Rotary and monoblock (fil-cap) machines | High-speed bottle and vial Lines， common in contract manufacturing | Maximum speed， every format change Star-wheel timing， closure torque |
| Aseptic systems(vials， ampoules， BFS， prefilled syringes) | Sterile products filled in Grade A RABS or isolators | Interventions， stoppages and restarts， aseptic process simulation performance Glove integrity， decontamination cycle |
