FAT vs SAT: Factory & Site Acceptance Testing Guide
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FAT vs SAT: Factory & Site Acceptance Testing Guide
If you are procuring a 2 MVA oil-immersed transformer for a substation in Chile, or a 1300 mm solventless laminator for a flexible packaging plant in Egypt, the contract will almost certainly require a FAT (Factory Acceptance Test) before shipment, and a SAT (Site Acceptance Test) after installation. These are not paperwork exercises - they are the contractual events where the buyer confirms the equipment meets specification, and where latent defects are caught while the manufacturer still owns the problem.
XIAOPAI runs FAT on every oil-immersed transformer we manufacture and on every SINSTAR solventless laminator we integrate. For high-voltage units we routinely host the buyer's engineering team at our workshop for a 2-3 day FAT. This guide explains how the FAT and SAT cycles actually run, what is tested, and how to plan your participation.
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1. WHAT IS FAT VS SAT?
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FAT - Factory Acceptance Test - is the formal test performed at the manufacturer's workshop, witnessed by the buyer (or their third-party inspector). It happens before the unit leaves the factory. Successful FAT is the contractual trigger for shipment and usually for the final payment milestone.
SAT - Site Acceptance Test - is the post-installation test at the customer's site. It confirms that the unit has arrived undamaged, has been installed correctly, and performs to specification in its real operating environment. SAT is the trigger for the warranty period to start.
For some projects there is also a "Pre-FAT" or "Internal FAT" - the manufacturer's own internal test before showing the buyer in.
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2. WHEN IS FAT REQUIRED?
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FAT is always recommended and is usually contractually required for:
• Power transformers rated 1 MVA and above (always)
• VCB and switchgear assemblies (always)
• Custom-packaged substations (always)
• High-value packaging lines (solventless laminator, slitter, CI flexo)
• Multi-unit orders where any deviation in the production batch must be detected
For small commodity items (e.g. standard 100 kVA control transformers, small-format accessories) a routine test certificate is normally sufficient - no FAT required.
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3. FAT SCOPE FOR A POWER TRANSFORMER
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A typical FAT for a 3 MVA oil-immersed transformer takes 2-3 days and includes:
Day 1 - Routine tests per IEC 60076-1 / IEEE C57.12.90:
• Measurement of winding resistance
• Measurement of voltage ratio and check of vector group
• Measurement of short-circuit impedance Uk and load loss Pk
• Measurement of no-load loss P0 and no-load current
• Dielectric tests: applied voltage / induced voltage / lightning impulse on request
• Insulation power-factor test (tan delta)
• Oil tests: dielectric breakdown voltage, moisture content, dissolved gas analysis (DGA) baseline
Day 2 - Functional and mechanical checks:
• Tank pressure leak test
• Bushing creepage verification
• Tap-changer operation across full range (visual + electrical)
• Marshalling box wiring check, current transformer polarity
• Paint thickness and adhesion test
• Nameplate and warning sign verification
Day 3 - Optional / customer-witnessed:
• Heat run (type test) - usually not repeated at FAT, certificate accepted
• Noise level measurement
• Witness of the buyer's third-party inspector (SGS, Bureau Veritas, TUV, CTC)
Full documentation pack: routine test report, type test report (from design family), material certificates, oil test report, nameplate drawing, GA drawing, schematic, bill of materials, packing list. We deliver this as a PDF pack plus one printed hard copy.
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4. FAT SCOPE FOR A SOLVENTLESS LAMINATOR
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A SINSTAR solventless laminator FAT at the SINSTAR factory in Chongqing takes 1-2 days and covers:
• Mechanical run: all dancer / tension / nip / cooling sections run at production speed with the customer's substrate
• Lamination quality: bond strength (peel test) on customer-specified film combination, target 1.5-3.0 N/15 mm depending on structure
• Residual solvent test: gas chromatography on laminated samples, target below 1 mg / m square
• Cure test: 24-hour cure followed by bond-strength re-test
• Coating weight: gravimetric verification on the customer's substrate
• Glue system: mixer ratio accuracy, temperature control stability, tank purge cycle
• Safety interlocks: light curtain, guard door, emergency stop, main isolator
• Operator console HMI walkthrough, recipe save / load, alarm log review
• Witness test with the customer's film samples supplied in advance
For XIAOPAI's scope we additionally verify the integration of glue supply, substrate handling and the upstream / downstream equipment (unwind, corona treater, slitter).
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5. WITNESSING FAT - PRACTICAL GUIDANCE
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If you are sending a buyer engineer to witness a FAT:
• Plan 2-3 working days on site, including travel
• Bring your specified test procedures, sample of the actual film you will run, your acceptance criteria in writing
• Confirm in advance which test instruments are the factory's responsibility (typically: ratio bridge, impedance meter, oil tester) and which are yours (typically: third-party witness's own calibration)
• Agree the punch-list format and the rectification timeline before the visit starts - if a deviation is found, who fixes it, in how many days, and at whose cost
• Request the FAT schedule 1 week before so your engineer can prepare visual inspection of the specific items that matter most to you
For a typical 3 MVA transformer FAT at our workshop, two engineers spend three days on site. For a SINSTAR laminator FAT in Chongqing, one engineer spends two days. Travel and accommodation are normally at the buyer's expense unless otherwise agreed in the contract.
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6. SITE ACCEPTANCE TEST (SAT) - WHAT COMES AFTER DELIVERY
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SAT happens at the customer's site after installation. For a power transformer SAT typically covers:
• Visual inspection after transport - check for any transit damage (bushing, radiator, paint, oil leak)
• Oil sampling and dielectric test on arrival oil (in case of transit moisture ingress)
• Energisation sequence: pre-energise checks, no-load energise, load step-up, tap-changer verification under load
• Protection relay settings verification
• SCADA / communication integration test
• 24-72 hour soak test under partial load before handover
For a packaging line SAT covers:
• Mechanical installation alignment
• Pneumatic / hydraulic connections
• Glue supply plumbing integrity
• First-pass production on customer's substrate
• 8-hour continuous production trial at rated output
• Final bond-strength and residual-solvent test on production roll
SAT findings typically take the form of a punch list - the manufacturer rectifies each item within an agreed window (usually 30 days). Warranty starts after SAT punch-list closure.
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7. WHY XIAOPAI'S PROCESS SUPPORTS A CLEAN FAT / SAT
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We run FAT on every transformer we manufacture, against IEC 60076-1 routine tests and the buyer's specification. We document the full chain from raw material certificate to final test report. For our quality management system see Transformer Quality & Certifications.
For packaging lines, our partner SINSTAR runs FAT at their Chongqing factory, and XIAOPAI sends a senior engineer to co-witness every FAT for our export orders. The complete FAT / SAT document pack is delivered with the unit. For the post-installation side, see Transformer Installation & Maintenance for what the SAT pass looks like on the power side.
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8. FAQ
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Q1: Can the buyer refuse to accept the unit after FAT?
A: Yes, but only on specification-compliance grounds. If the FAT results match the contract's datasheet, the buyer is expected to issue the shipment release. If a deviation is found, it goes to the punch list and the manufacturer has a contractual window to fix and re-test. An arbitrary refusal is a contractual dispute - the contract should specify the remediation timeline before signing.
Q2: Is FAT mandatory for low-voltage dry-type transformers?
A: Below 100 kVA, normally not - the routine test certificate is sufficient. Between 100 kVA and 1000 kVA, it depends on the buyer; many EPCs request a witnessed FAT. Above 1000 kVA, FAT is the norm.
Q3: Can we do a remote FAT by video instead of sending an engineer?
A: Yes, for routine tests. Live video with the manufacturer's test engineer running the test and showing readings is now accepted by most buyers, especially after COVID. For type tests and impulse tests we still recommend an in-person witness or a third-party inspector (SGS / Bureau Veritas) acting on the buyer's behalf.
Q4: How long does SAT take after the unit arrives on site?
A: For a single transformer: 2-5 working days including energisation soak. For a full packaging line: 5-14 working days depending on complexity. The civil works (foundation, cabling, piping) are typically the customer's scope and drive the overall SAT start date.
Q5: What happens if a latent defect is found during SAT?
A: It depends on the contract's warranty clause. Most contracts state that defects arising from manufacturing quality (not from site handling, transit damage or improper installation) are the manufacturer's liability for 12-24 months from SAT acceptance. A clear SAT punch list with photograph and meter readings is the basis for any subsequent warranty claim.
RELATED GUIDES
- Transformer Quality & Certifications | XIAOPAI
- Meet SINSTAR, Our Authorized Solventless Laminator Partner
- Transformer Installation & Maintenance | XIAOPAI
IEC 60076-1:2011 (Power Transformers - General)
IEEE C57.12.00-2021 (Liquid-Immersed Transformers)
ISO 9001:2015 (Quality Management Systems)
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