An interesting article Joe. I am still surprised it happened. I am used to an international framework where any pipelines or electrical distribution systems are only worked on with a permit to work system, where every aspect of the job is itemised, studied and documented with permissions renewed every shift change and signed off.
Piper Alpha was eerily similar. I thought the change in the regulatory framework after that disaster was worldwide. It certainly was in the exploration side of oil and gas. I find it hard to believe it did not occur on the downstream side as well.
Replacing a section of pipe without its previously installed checkvalve is criminal negligence in most places.