5. Factory acceptance — FAT witness rights
The Factory Acceptance Test is the buyer’s last chance to reject the pump while the vendor still has full leverage to fix it. Skipping FAT witnessing — or sending an unprepared witness — is the most common single procurement failure.
5.1 What FAT actually proves
A complete FAT measures:
| Test | Standard | What it proves |
|---|---|---|
| Hydrostatic | NFPA 20 §14.1.4 / API 610 §8.3.4 | Casing integrity at 1.5× max working pressure |
| Performance curve | HI 14.6 | Q, H, η across full operating range |
| NPSHr by 3% drop | HI 14.6 | Cavitation onset point at multiple flows |
| Vibration | HI 9.6.4 | Mechanical assembly quality |
| Bearing temperature rise | After 1 h continuous | No interference, lubrication functioning |
| Mechanical alignment | TIR ≤ 0.05 mm | Coupling-to-driver concentricity |
| Visual / dimensional | Buyer datasheet | Casing, nozzle, bolt-pattern conformity |
| Documentation handover | Buyer datasheet | Manuals, certificates, drawings |
A vendor who proposes “just hydrostatic and performance” is hiding the mechanical-quality measurements. Insist on the full set.
5.2 Pre-FAT preparation — buyer’s checklist
Two weeks before FAT:
- Confirm all materials of construction match purchase order
- Receive draft test plan from vendor 5 business days in advance
- Verify test bench calibration certificates current (within 12 months)
- Confirm flow meter, pressure transducers, and torque cell traceable to INMETRO
- Verify witness will have access to raw data, not just summary
- Confirm test fluid (typically water at 20-30 °C; do not accept higher temperature without justification)
- Confirm test speed = nameplate speed (or stated alternative with affinity-law conversion documented)
If the vendor cannot produce calibration certificates for the test-bench instrumentation, the test is not valid by HI 14.6 standards. Reschedule until calibrated.
5.3 During FAT — the witness’s job
The witness is not a passenger. The witness’s job is to verify that:
- Test data is captured at the moment of measurement — not “we recorded that yesterday and have it on file”
- Each test point is held long enough for steady state — minimum 5 minutes per point
- Instrumentation matches the calibration certificates — physically verify serial numbers
- Discrepancies are flagged and signed in real time, not glossed over
Bring to FAT:
- Purchase order
- Performance datasheet from RFQ
- Pre-printed test record forms (do not let vendor write the only record)
- Camera (with vendor’s permission) for visual evidence
- Calibration certificates for ALL instruments
- Calculator or laptop with affinity-law tools for any speed conversions
5.4 Performance curve verification
The single most-critical verification at FAT is the performance curve. Required at minimum:
- Test points at 0%, 50%, 75%, 100%, 110%, 120% of rated flow (HI 14.6 default; may add 60% / 90% / 105% if specified)
- NPSHr by 3% drop at rated flow AND at 120% rated flow
- All points plotted on the curve plot with a band showing tolerance
- Tolerance band per HI 14.6 grade (1U: ±5%/±3%/-3%; 1B: ±8%/±5%/-5%)
If any point falls outside tolerance, the witness has these options written into the contract (clause 4.6):
- Accept with documented reservations
- Require re-test after vendor remedy
- Reject
Most witnesses default to (1) — and discover at site acceptance that the issue propagates. (2) is usually the right choice when the deviation is borderline; (3) is right when the deviation is structural (e.g., shut-off head exceeds 140% — a fundamental geometric mismatch).
5.5 NPSHr verification — the often-skipped step
NPSHr is measured by progressively dropping suction pressure until pump head drops 3%. This requires either:
- A vacuum-capable suction system on the test bench (more common); or
- A throttling valve plus calibrated pressure transducer
What the witness should look for:
- Multiple NPSHr points across the curve (not just rated)
- Curve plot showing the head-drop process at each point
- Test data recorded automatically, not transcribed manually
- Suction temperature recorded — affects vapor pressure and NPSH math
A vendor who “stamps” NPSHr from a previously-tested same-model unit without re-testing this serial number is shortcutting. NPSHr varies unit- to-unit by ±10% — your unit must be tested.
5.6 Mechanical tests
After hydraulic, the bench transitions to mechanical:
| Test | Method | Pass criterion |
|---|---|---|
| Vibration | Accelerometer at bearing housings | RMS ≤ 5.0 mm/s (≤1.800 rpm) or ≤ 7.1 mm/s (>1.800 rpm) |
| Bearing temperature | Thermocouple at bearing housing | Rise ≤ 40 K, absolute ≤ 80 °C |
| Coupling alignment | Dial indicator (cold) | Parallel TIR ≤ 0.05 mm; angular TIR ≤ 0.05 mm/100 mm coupling diameter |
| Sound level | dB(A) at 1 m from pump | Per HI 9.4 OR contract spec |
| Lube oil sampling | Visual + ferrous particle count | No visible debris; ferrous count baseline established |
Vibration is the most-skipped of these; insist on the spectrum plot, not just the overall RMS. A spectrum showing a strong 1× rotation peak indicates mass unbalance; 2× indicates misalignment; 1×N (N = blade count) indicates impeller hydraulic imbalance. Each has different remediation.
5.7 Documentation handover
At end of FAT, the buyer must receive:
- Signed test certificate per HI 14.6
- Performance curve plot with tolerance bands
- Vibration spectrum plot
- Hydrostatic test certificate (lab-stamped)
- Bearing temperature log
- Coupling alignment record
- Lube oil sample analysis (if applicable)
- All certificates referenced in the contract clause 4.6
If any document is incomplete, FAT is not signed off. Vendor will ship anyway because shipping is on their schedule, but the warranty clock should not start until documentation is complete and accepted.
5.8 FAT sign-off authority
The witness signature on the FAT certificate is binding. The witness should have:
- Authority delegated in writing from the buyer organization
- Technical competence to evaluate the data presented
- A briefing from procurement on which deviations to escalate vs accept
Sending an unsupervised junior engineer to FAT is a common cost-saving move that produces tens of thousands of reais in remediation later.
The FAT witness is, for that day, the buyer’s hydraulic, mechanical, and contractual representative — staff accordingly.
Next section: Site acceptance and warranty.