What's the phrase: Trust but verify?
I've worked in the oil & gas business for quite awhile where "critical" or "unspared" equipment receives greater attention than the usual run-of the mill machine. Of course, the specs for a critical unit are also tougher than those for units that are backed up by redundant units, or where the plant can operate at reduced capacity with one unit out.
Most tests have worked out very well, and the customer had nothing to worry about. There have been several occasions where the purchase order specified a witness test, and up to the last minute, that impression was maintained. The end user felt that the manufacturer would be "on his toes" during the manufacturing process and do a better job if he was held accountable.
One large west coast refinery sends their rotating engineer to ALL motor/generator tests (2300 V & above), and he is known to bring his own calibrated test meters! Another will go for critical machines and the first couple of tests with a manufacturer new to them. I remember a specific case where a 1500 Hp unit had very, very high vibration due to rotor mis-manufacture. It took the engineer an entire afternoon to track someone in authority doen, complain to him and personally reject the machine!
On the near disaster side, I did have the field poles of a 3500 Hp synchronous motor come apart and scrape through the 4 kV insulation of the stator winding. What a fireworks display. The concern was that this was in a Class I, Division 1, Group B (Hydrogen) area. To compound the error, its twin brother did the same thing the next day, seems that they had nearly the same hours of operation, which led directly to evaluate the fatigue failure of the main components. Turned out to be a hat trick: bad design, use of corroded bolts, and negligence in assembly.
You might want to take a look at the American Petroleum Institute standards
541 (induction), and 546 (synchronous) for guidance. They may take a bit of reading, but they are very thorough.
As a last comment, I've been on the manufacturer's side of the aisle twice, and am now on the driven equipment side of the coupling. My previous employers (and competition) realize that I know the tricks, dodges and evasions of the game. This doesn't bother me since it has raised my credibility with the end user who feels more confident in the overall package.
TG