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OTO 2000/058

Assessment of strengthening clamp from the Viking offshore platform : Phase II

The Viking platform was decommissioned recently and one of the strengthening clamps was obtained by HSE for assessment. The objectives of the second phase of this assessment were: to dismantle one half of the clamp; to carry out compression tests on samples of grout ; to assess the residual fatigue life of the studbolts ; to measure the fracture toughness and impact toughness of parent plate, weld ; metal and heat affected zone (tubulars); to measure the fatigue crack growth rate and threshold stress intensity in the parent plate (tubulars). One half of the clamp was dismantled successfully; there was no indication of any significant deterioration. The residual fatigue life of the studbolts was consistent with what would be expected from new bolts. The fracture toughness and impact toughness of the tubular material were within the range normally expected for 50D steel. The fatigue crack growth rate and the fatigue crack threshold stress intensity were consistent with values reported previously for this material. The grout annulus was in relatively good condition but the presence of a layered structure within the grout material may have had an effect on the strength of the clamp.

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Updated 2010-03-19