Factory acceptance testing: the questions buyers actually ask
12 questions · Updated 2026-09-30
Short answer
A factory acceptance test only protects you if three things are in the contract before signing: measurable acceptance criteria, a payment milestone tied to a passed test, and an exit clause if the machine keeps failing. Below are direct answers to the questions buyers raise about criteria, failure and payments.
What should acceptance criteria for a factory acceptance test actually say?
Numbers, not adjectives. 'The line runs at 120 units per minute for four consecutive hours with less than 2% reject rate' is a criterion; 'the machine performs well' is not. Every criterion needs a measurable value, a test method, and a pass/fail threshold — written into the contract before signing, because after signature the manufacturer has no reason to accept new ones.
Who should write the FAT acceptance criteria — me or the manufacturer?
You own them, with the manufacturer's input. The manufacturer knows what the machine can demonstrably do; you know what your production needs. If the manufacturer writes the criteria alone, expect them to describe only what is easy to pass. The criteria belong in the RFQ stage, so every bidder prices the same test.
The machine failed the FAT — what happens now?
If the contract is written properly: the manufacturer fixes the issue and the test repeats at their cost, and the milestone payment tied to the test does not move. The failed items are documented in a punch list with deadlines. A failure caught at the factory is the process working — the same failure discovered on your site, after final payment, is a crisis with no leverage left.
How should the FAT be linked to the payment schedule?
Tie a meaningful payment milestone — typically 20–40% — to a passed FAT, not to a date. The sequence that protects you: deposit on contract signature, payment on witnessed and passed FAT, balance after commissioning on your site. If payments run on calendar dates while the test runs on results, the money is gone before the leverage arrives.
The manufacturer says a FAT is not necessary and we should trust their quality — is that normal?
It is a red flag, not a norm. Serious manufacturers run factory tests as standard practice and use them to protect themselves too. A refusal usually means the test was never priced into the offer, the factory has no test capacity, or the equipment is being subcontracted to someone you have never seen. Treat resistance to a witnessed test as a reason to slow down, not to concede.
Do I need to attend the FAT in person, or is a video call enough?
For equipment above roughly US$250,000, attend in person or send someone who represents you. A video call shows you what the manufacturer chooses to show; being there lets you pick which machine settings, raw materials and shifts to test. If travel is impossible, commission an independent third-party inspector with a written test protocol — but do not let the manufacturer be the only witness to their own test.
What should the FAT cover besides output speed?
Four areas buyers forget: safety functions (emergency stops, guards, interlocks), quality of output under real production materials — not the manufacturer's ideal test material, changeover and cleaning time if you run multiple products, and documentation (manuals, drawings, spare parts lists, certificates) delivered in your language. Speed alone passing means very little.
Can I require the FAT to run with my actual raw materials?
Yes, and you should — a machine that performs on the manufacturer's test material may fail on yours. Arrange to ship representative production material to the factory before the test, and write it into the test protocol. This is standard practice for process equipment; a manufacturer who refuses to test with your material is telling you something.
What should I receive in writing after the FAT?
A signed test report covering every criterion: measured values against each threshold, the punch list of open items with correction deadlines, photos or video of the test runs, and the serial numbers of the exact machines tested. This document is what your final payment, shipping release and later warranty claims rest on — no report, no payment milestone.
The machine passed the FAT — why do I still need a site acceptance test?
Because the factory is not your site. The FAT proves the machine works in the manufacturer's conditions; the SAT proves it works in yours — your utilities, your operators, your materials, integrated with your other equipment. Shipping, installation and reassembly can all change performance. Keep a final payment milestone for the SAT, or the FAT pass is where your leverage ends.
Who pays for the factory acceptance test?
The test itself — running the machine, factory time, basic materials — is the manufacturer's cost and should be priced into the equipment. Your costs are travel or the third-party inspector. If the FAT was never in the RFQ scope, expect it to appear later as a surprise line item; that is one more reason the test protocol belongs in the original RFQ.
The machine has failed the FAT twice — when do I walk away?
The contract should answer this before it happens: a defined number of retests or a correction deadline, after which you can cancel with the deposit returned. Without that clause, a failing manufacturer can hold your deposit in an endless fix-and-retest loop. Two failures on the same criterion is the point to invoke the exit clause, not to extend goodwill.
Summary
Write the criteria before the contract, tie the money to the result, and treat a failed test at the factory as the process protecting you. Global B2B Group structures acceptance testing as part of a human-reviewed procurement process — no supplier is contacted without approval.