Session: Session 2. Asset Integrity Under Extreme and Disruptive Events

Paper Number: 118542

118542 - Falling Structures - Risk Associated to "Non-Conventional" Connections of Tertiary Components 

This paper reports methods of and experiences with "non-conventional" fastening of tertiary components like explosion welding between steel and aluminum to identify associated risk in the oil and gas industry. With non-conventional we mean other methods than fusion welding.

The objective is three fold. Firstly, to adress the risk awareness associated with other parts of the structure than main structure. Secondly, report on methods and incidents for these components. And thirdly discuss need for standards.

We have identified and categorized different non-conventional fastening systems, described the methods and identified
typical experience, damage, and integrity challenges in the industry. The non-conventional fastening methods can be
divided in welding and non-welding.

A review of selected standards and best practices shows that there are limited requirements towards non-conventional
fastening of tertiary items. The focus for an operator is mainly on structural bolted connections and traditional welding.
NORSOK M-001 Amendment has some requirements towards selection of material and how to avoid galvanic corrosion
between steel and aluminum by electrical insulation however, these are mainly for through-bolts. To our understanding
the most common fastening material is stainless steel alloy 316.

The review of industry experience, selected incidents from Petroleum Safety Authority (Norway) Incidents database and
Investigation reports has identified that galvanic corrosion between the fastener and the tertiary component and overload/fatigue due to wind are the most common threats leading to dropped objects. The challenge is that tertiary components can be fastened to structural items ,and blind bolts have been used in RHS profiles leading to water ingress and internal corrosion of the structural steel member.

It appears as no regulations exist for non-conventional fastening system.

Presenting Author: Morten Andre Langøy Petroleum Safety Authority, Norway

Presenting Author Biography: Principal engineer PSA