The report is pretty interesting. The ship was not designed that way. The nuts were installed as part of routine maintenance:
> By mid October, the Iwo Jima had been operating in the Persian Gulf for approximately two months and had developed some leaks and other repair needs in the ship's 600 psi steam propulsion plant.
> The ship was granted permission to dock in Manama, Bahrain (a country on a group of islands in the Persian Gulf, between Qatar and Saudi Arabia) and conduct repairs. A variety of maintenance items were planned, including overhauling the main steam valve that supplies steam to one of the ship's turbine-driven electrical generators. This valve, incidentally, could also be considered a boiler-boundary stop valve. The overhaul of this large, rising-stem, bolted-bonnet gate valve was contracted to a local ship repair company, under the supervision of U.S. Government inspectors.
The mechanic conducting the repairs didn't know the requirements:
> Ultimately, what was found was that a series of mistakes and misunderstandings led to this accident.
> First, the mechanic wanted to replace the fasteners, but he did not have any. He also did not speak English very well. Allegedly, the mechanic asked one of the boiler room personnel for new nuts and bolts, and was given permission to look through the boiler room's spare parts bins. He selected parts that he thought would work.
And an inspection that might have caused the problem got lost in the shuffle:
> Secondly, with the case of the authorized inspection agency, it must be taken into consideration that there was a massive build-up of troops and ships in the Persian Gulf. It was assumed that the office was not staffed for the increased workload. Consequently, many inspections were not being conducted.
> And finally, the boiler room supervisor thought that one of his subordinates had conducted an inspection. Sadly, it was never concluded that an inspection had been made. If someone had conducted an inspection, possibly he was not familiar with fastener markings, nor the job specifications.
> The end result was that incorrect fasteners were chosen, and controlled inspections and testing were not fully accomplished.
Really, what surprises me the most about this is that the Navy apparently doesn't repair its own ships!