A sample test matrix for foam, coating and recipe changes

Create one row per meaningful transition

A practical starting matrix has six rows: clean air to product A; product A to drained residue; residue to product B; product B to process foam; product to cleaning liquid; and final rinse to drained air. These are examples, not a mandatory sequence. Remove irrelevant rows and add the actual difficult conditions for the installation.

For every row, record the initial state, final state, required output, maximum acceptable delay, sensor settings, sample temperature and observed result. Include a photograph or description of the tip after draining so that a future trial can reproduce the residue condition.

Write acceptance criteria before adjusting settings

For example, a process owner may require the PLC input to indicate uncovered within a defined time after drainage, while allowing a brief transition during cleaning. The actual time and permitted behavior must come from the process design. Do not choose the acceptance threshold after seeing the sensor result.

Define what happens when foam covers the tip. Some duties must detect it; others need to distinguish foam from product. These are opposing requirements. A demonstration that ignores this distinction may prove the wrong behavior.

Vary the conditions that cause uncertainty

Use representative temperature and concentration ranges, not only a room-temperature sample. Include the wettest expected foam and realistic coating. If the trial cannot reproduce a limiting state, record that gap rather than marking the application approved. Repeat the transitions enough to expose variation; the number of repetitions should reflect the process and the consequences of a missed state.

Keep sensor and control-system results separate

Record both the sensor indication and the PLC tag with timestamps. If the sensor switches but the PLC does not, investigate output compatibility, wiring, input filtering and program logic. If both switch but the pump does not stop as intended, the remaining issue lies further along the control path.

Archive the final configuration with the matrix. A change in recipe, firmware, geometry or cleaning process may require selected rows to be repeated. This turns a one-off demonstration into a maintainable qualification record.

What to confirm for your application

• Initial and final states for each transition
• Required output and process-defined delay
• Settings, temperature and representative sample condition
• Sensor indication and PLC response recorded separately
• Unreproduced conditions and retest triggers listed