Runnable simulator field guide
Chemical-dosing PLC scenario: test checklist
Direct answer
The learner can separate recipe demand from equipment permission, command and measured result, stop on missing evidence and recover without silently repeating a dose.
Written for process-control learners programming a dosing pump, valves, tank conditions and measured addition under a declared safe training recipe.
Scenario setup
Training recipe, source and destination identity, level permissives, route, pump or valve capacity, requested quantity, flow or weight evidence, timeout, hold, abort and restart policy.
I/O and state map
Batch request through route confirmation, dosing output, measured transfer, totalized amount, stop command, residual motion, completion record and next state.
Normal run
One declared dose starts only with valid permissives and stops once at the target with coherent equipment feedback.
Boundary run
Empty source, full destination, no flow, leaking valve, pump trip, noisy measurement, overshoot, pause, abort, controller restart and power return.
Injected fault
A recipe, permissive, route, command, pump, valve, instrument, totalizer, timeout, completion or restart mismatch.
Target check
The production design reviewed against current process, chemical, equipment, environmental and safety requirements and validated on target.
What should a PLC chemical-dosing sequence prove?
It should prove the correct source, destination and route, confirm equipment response, measure the addition, stop at the bounded target and retain fault and completion evidence.
How should a dosing sequence recover after interruption?
Preserve how much was delivered, establish the physical state and require a deliberate rule for resume, abort or manual disposition instead of starting the dose again.