BMT patents insulation strain measurement system for touch down zone of steel catenary risers
BMT Scientific Marine Services (BMT) has patented a strain measurement system and unique attachment scheme that can be integrated into the insulation and anti-corrosion layers on ultra deep water Steel Catenary Risers (SCRs). This technology was developed because production SCRs typically have thick anti-corrosion and insulation layers that make the measurement of the strain in the underlying pipe challenging.
Full scale bending strain measurement results from the Touch Down Zone (TDZ) of two Steel Catenary Risers show that BMT’s Insulation Strain Measurement System produces a very accurate estimate of the strain in the underlying pipe steel without threatening 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. The bending strain sensors are BMT’s Subsea Strain Sensors (SSSA) configured to create a long-based “strain gage,” the foundations for which are welded to the polypropylene insulating material of the subsea risers.
This assured that the clamps expanded and contracted at the same rate as the insulation itself so that no stresses developed due to changes in temperature or pressure. The process allows the sensors to be securely attached to the pipe without removing or degrading the riser’s insulation.
This attachment process has a number of advantages over a mechanical clamping system for insulated pipe. The process avoids the need for removal or degradation of the insulation and the integrity of the attachment system and concomitant data validity is not threatened by the substantial dimensional changes in the insulation layer due to changes in temperature and pressure of the contents of the pipe.
Furthermore, the elements of the attachment system that would be subject to corrosion are eliminated.
An SCR monitoring system employing BMT’s patented technology has been in service for three years offshore Nigeria, producing credible data which is driven by the motions of the associated FPSO. The measurements are aligned with accepted numerical models.