Short answer. A rack washer should not be accepted because it powers on or because one tray looks clean. A defensible handover separates two gates. The Factory Acceptance Test (FAT) proves, before shipment, that the configured machine, controls, safety devices and documents match the purchase order. The Site Acceptance Test (SAT) proves, after installation, that the same machine works with the buyer’s actual power, water, drain, exhaust, detergent, racks and soil load.
For a food plant, SAT needs three different forms of evidence: mechanical and safety completion, thermal process evidence, and cleaning-effectiveness evidence. Passing one does not prove the other two.
FAT versus SAT: what each test owns
| Gate | Location | Main question | Typical evidence |
|---|---|---|---|
| FAT | Manufacturer | Was the ordered machine built and configured correctly? | Nameplate, dimensions, materials, I/O test, alarms, safety interlocks, dry/wet cycles, document pack |
| Pre-SAT | Customer site | Are utilities and civil works ready? | Electrical readings, water pressure/quality, drain-flow test, steam certificate if applicable, exhaust check |
| SAT | Customer site | Does the installed system meet agreed acceptance criteria on real loads? | Five repeat cycles, surface-temperature indicators, cycle CSV, visual score, ATP/protein/allergen results, punch list |
| Performance qualification | Production | Does the approved recipe remain capable across normal and worst-case loads? | Trend data, periodic swabs, exception review, revalidation record |
FAT is not a substitute for SAT: shipping, voltage, incoming-water temperature, drain backpressure and local detergent chemistry can all change performance. SAT is not a redesign session either; its acceptance criteria should be signed before the machine leaves the factory.
Step 1: freeze the acceptance criteria before FAT
Attach a one-page acceptance matrix to the purchase order. Define:
- Machine model, chamber clear opening and approved trolley envelope.
- Heating configuration, voltage, frequency, connected load and protection.
- Required cycle recipes and maximum agreed cycle time.
- Thermal target and how it will be measured.
- Representative soil/load families and the cleaning pass rule.
- Required exports: timestamp, machine ID, recipe, phase temperatures, alarms and pass/fail state.
- Documents, spare parts, training and warranty start point.
Avoid vague clauses such as “trays shall be clean.” Use a reproducible rule: for example, no visible residue under defined lighting, a site-established ATP limit, and—where allergen changeover matters—a validated allergen-specific test.
Step 2: run the FAT on the ordered configuration
The FAT should record serial numbers and calibrated test instruments. Verify chamber dimensions, SUS grade, weld finish, doors, spray arms, filters, pumps, heaters or steam coil, chemical dosing, emergency stop and guarding. Simulate low-water, over-temperature, door-open and motor-overload faults; confirm that the PLC blocks unsafe operation and records alarms.
Run at least one cycle per ordered recipe with water. Check phase timing, tank recovery, leaks, abnormal vibration, spray rotation, drain completion and CSV export. Photograph the completed nameplate and electrical cabinet. Close every FAT deviation or carry it into a signed punch list with an owner and due date.
Step 3: complete a utility-readiness check before SAT
Many “machine failures” are site failures. Before commissioning, measure voltage phase-to-phase under load, phase balance, protective earth, dynamic water pressure, inlet temperature and drain backpressure. Confirm detergent and rinse-aid pickup. For steam machines, verify available pressure, dry saturated steam quality, condensate return and isolation.
The PTW-1900 is offered as a 70 kW electric configuration or a 7 kW electrical-load steam configuration; the exact nameplate and destination electrical drawing govern the installation. Do not approve a cable or breaker from website copy alone.
Step 4: prove thermal performance correctly
The PLC tank sensor proves what the sensor saw—not automatically what every utensil surface experienced. During SAT, place irreversible registering temperature indicators or calibrated data loggers on representative cold spots: inside nested corners, lower rack positions and high-mass items. Run a cold-start challenge and normal consecutive cycles.
The 2022 FDA Food Code requires an irreversible registering temperature indicator to be available for hot-water mechanical warewashing, while NSF describes NSF/ANSI 3 as covering materials, design, construction and performance of commercial warewashing equipment. Your signed acceptance threshold must follow the applicable jurisdiction, machine classification and approved process—not a generic internet number.
Step 5: prove cleaning effectiveness separately
Temperature cannot remove a baked-on starch or protein film that the chemistry and spray impact failed to detach. Use the buyer’s real worst-case load, with a documented soil age and loading pattern. Score every item after air drying.
Use layered verification:
- Visual and tactile inspection: no food film, grease, scale or detergent residue.
- ATP swabs: rapid evidence of residual biological material, using limits established for that site’s device and surfaces.
- Protein or allergen-specific tests: required when changeover claims depend on removing a named allergen.
- Microbiological testing: used where the HACCP plan or customer standard requires it.
USDA FSIS guidance treats ATP as a rapid sanitation-verification tool and notes that the instrument manufacturer defines acceptable zones. The UK Food Standards Agency also warns that ATP results are not interchangeable with allergen-specific tests. Therefore, “ATP pass” must never be written as “allergen-free.”
Step 6: run a repeatability challenge
A useful SAT is not one showcase cycle. Run five consecutive representative cycles after warm-up. For every cycle, retain the load ID, recipe, start/end time, temperatures, chemical dose or concentration check, visual result, rapid-test result and alarms. A single unexplained failure opens a deviation; it should not be averaged away.
Also challenge one credible worst case: cold inlet water, the heaviest approved trolley, the most difficult approved soil, or rapid back-to-back loading. The objective is not to abuse the machine—it is to prove the operating window that production will actually use.
Step 7: close the handover package
The acceptance file should include the signed FAT and SAT protocols, calibration certificates, utility readings, as-built electrical and piping drawings, parts list, manuals, approved recipes, baseline test results, training attendance, open punch-list items and warranty start date. Store the master digitally and link the cycle-log retention rule to the site’s HACCP or food-safety system.
Revalidate after a change that can affect the result: detergent chemistry, cycle recipe, heater or steam-valve replacement, spray-manifold change, PLC software revision, chamber modification, relocation, or a repeated adverse trend.
Acceptance decision: pass, conditional pass or fail
| Decision | Use when | Required action |
|---|---|---|
| Pass | All safety-critical and performance criteria pass; documents complete | Sign acceptance and release for production |
| Conditional pass | Only minor, non-safety items remain and performance is proven | Sign a dated punch list; hold final payment if contract allows |
| Fail | Safety interlock, thermal criterion, cleaning criterion or repeatability fails | Do not release for production; correct and repeat affected tests |
Frequently asked questions
How long should FAT and SAT take?
A focused FAT normally requires one working day after internal testing. Site commissioning and SAT commonly require one to three days once utilities are genuinely ready.
Is an ATP number universal?
No. Swab, luminometer, surface, soil and sampling technique affect the reading. Establish a baseline and alert/action limits for the site’s chosen system.
Can the PLC temperature record replace a surface indicator?
Not for initial validation. Correlate the PLC record with an independent calibrated indicator at representative load surfaces; thereafter, the validated PLC trend can support routine verification.
Who should sign SAT?
At minimum: the supplier commissioning engineer, the buyer’s engineering/maintenance owner, production owner and food-safety or quality representative.
Related engineering guides
- PTW-1900 installation: pit versus ramp
- Water temperature and sanitization standards
- Industrial rack washer detergent chemistry
- PLC control and MES integration
- Maintenance checklist
Planning a project? Request a configuration-specific quotation and FAT/SAT document list. V-TAI can align the PTW-1900 acceptance matrix with your trolley, utilities, soil families and audit requirements before manufacture.
Sources checked 8 August 2026: FDA Food Code 2022; NSF food-equipment standards; USDA FSIS sanitation-verification guidance; UK Food Standards Agency allergen-cleaning review.