Over time, both the Petroleum Safety Authority Norway (PSA) and the industry have had a focus on structural incidents with major accident potential. They are included as an indicator in RNNP.
There has not however been a similar focus on structural incidents associated with auxiliary structures and the fastening of equipment, so-called tertiary structures.
Although failure of such structural elements does not have major accident potential, it can nevertheless have fatal consequences for individuals. For fastening structural elements such as railings, gratings and cable ducts, fastenings other than traditional welding are often used.
To contribute to knowledge development and learning at industrial level, the PSA commissioned DNV to conduct a study. The purpose of the study is to assess the hazard and accident risks pertaining to falling structures in which joints have been made by methods other than traditional welding.
In the study, DNV identified experiences of explosion welding between steel and aluminium and other "non-conventional" fastening of tertiary components. The study also includes an identification of threats and risk mitigation measures.
The review of selected standards and best practices shows that there are limited requirements for the non-conventional fastening of tertiary objects. The focus has mainly been on structural bolt connections and traditional welding.
NORSOK M-001 Amendment defines some requirements for materials selection and how to avoid galvanic corrosion between steel and aluminium by means of electrical insulation. These primarily concern through bolts.
See the report for further details.