What lies beneath?

A number of months after the PDO was reported, a member of the crew noticed a lot of insulation and cladding debris on a walkway. Upon further inspection a flange was found on an adjacent access platform grating.

The flange weighed 73.2 kilograms and had dropped 20 metres, the potential consequence based on the DROPS calculator could have been a fatality.

Through the subsequent investigation, the damaged cladding had led to water ingress over time and resulted in severe corrosion under insulation (CUI) to the flange bolts. It was found that all four exhausts on this particular stack were originally designed and built using “T” pieced flanges. Had the arrangement drawings been checked, this PDO threat would have been fully understood and addressed sooner.