Unexpected Failure of Critical Subsea Connector Bolts

The University of Nicosia & Shamoon College cordially invite you to the following event:

Unexpected Failure of Critical Subsea Connector Bolts

Abstract

The unexpected failure of critical subsea connector bolts is keeping the industry alert because the “root cause” has yet to be fully identified. Failures of critical subsea bolts are continuing for more than a decade in spite of replacing more than 10,000 bolts and following several investigations and quality control recommendations from industry subject matter experts.

The present study focuses on the role three different parameters play with regards to the failure mechanism of standard ASTM A193 Grade (steel) B7 bolts (AISI 4140). These comprise different levels of preload torque, intensities of subsea water currents and the influence of standard corrosion protection methods such as galvanized bolts.

The experimental system we have set-up consists of a flange which features eight 5/8-inch diameter and four 3/4-inch length bolts screwed to sixteen nuts. The festering flange whose individual bolt-nut units were subjected to different levels of torque was immersed in an aquarium filled with a 3.5% NaCl aqueous solution for a period of 3 weeks. In addition, a finite element method (FEM) analysis was performed to predict the vulnerable areas of the bolts. Corrosion tests were also conducted at the areas which displayed different corrosion rates at particular bolt locations. Visual and scanning electron microscope inspection offers new insights as to the parameters which affect the failure mechanism. The corrosion rate at the vulnerable location of the bolt is higher than in the edge of the bolt by 34%; the high subsea water currents increase the corrosion rate by 39% and considerable levels of torque accelerate the corrosion rate by 45%. Simultaneous combination of all 3 parameters cause the corrosion rate to surge even more dramatically up to 279%!

Speaker’s bio:

Mr. Ofer Medlinsky is currently a PhD student in Oil, Gas & Energy Engineering at the University of Nicosia. He holds a BSc and an MSc in Materials Engineering from the Ben-Gurion University, Israel, and an MBA from Herriot-Watt University-Israel campus Ramat Gan. He worked as a lubricants department manager for Chevron Israel between 2007-2011 and as a Group Leader for Intel (fab28) between 2012-2016. Ever since 2017, Mr. Medlinsky is employed as an Adjunct Lecturer at the Mechanical Engineering Department at SCE – Sami Shamoon College of Engineering. Ofer research interests focus on materials science and metallic corrosion. In his spare time, Ofer likes camping with his family and friends and he is an avid table tennis player.

The talk to be delivered in English will be lived stream online via Zoom:
https://sce-ac-il.zoom.us/j/86723178541 │Meeting ID: 867 2317 8541

Date & Time: Mon. 16th, Nov. 2020 from 16:00 to 17:00.


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