BMT stresses accuracy of SCR strain readings

Offshore staff

HOUSTON -- BMT Scientific Marine Services (BMT) has patented a strain measurement system and attachment scheme for use on ultra-deepwater steel catenary risers. The system is designed to be integrated into the insulation and anti-corrosion layers of the SCRs.

Production SCRs typically feature thick anti-corrosion and insulation layers that complicate strain measurement in the underlying pipe.

BMT says that full-scale bending strain measurement results from the touch down zone (TDZ) of two SCRs produced an accurate estimate of strain in the underlying pipe steel, without jeopardizing the integrity of the insulation and corrosion protection layers.

This technology was first deployed offshore Nigeria to monitor bending strain and fatigue on production gas export risers in the TDZ. BMT’s subsea strain sensors were configured to create a long-based “strain gauge”, the foundations for which were welded to the polypropylene insulating material of the subsea risers.

The arrangement ensured that the clamps expanded and contracted at the same rate as the insulation itself, preventing stresses from arising due to changes in temperature or pressure. The sensors can be securely attached to the pipe without removing or degrading the riser’s insulation.

Unlike a mechanical clamping system for insulated pipe, BMT claims, the process avoids the need for removal or degradation of the insulation. Additionally, the elements of the attachment system that would normally be subject to corrosion are eliminated.

05/06/2011