System monitors annulus gas in real time

NKT Flexibles has extended the capability of its optical monitoring system from strain and temperature readings to real-time measurements of annulus gas concentrations in flexible pipes.

Offshore staff

COPENHAGEN -- NKT Flexibles has extended the capability of its optical monitoring system from strain and temperature readings to real-time measurements of annulus gas concentrations in flexible pipes.

The system has been developed with the Laser Science Group at Houston's Rice University. The patented QEPAS technique (Quartz-Enhanced Photo-acoustic Absorption Spectroscopy) employs laser light to produce sound waves in the gas.

These are then collected using a quartz tuning fork to provide what NKT claims is a high-accuracy measure of concentrations of gases including H2S, CO2, and CH4. It adds that the technique is superior to traditional gas sampling as it measures all constituents of the gas simultaneously and continuously.

This monitoring activity is critical to maintaining the operational performance of flexible pipes beyond their design life.

QEPAS' sensing unit requires only a fiber-optic connection to work, and can therefore be easily deployed in hazardous areas. The esonance quartz tuning fork makes the system immune to external noise while remaining sensitive. Early tests have demonstrated accuracies of 2.2ppm for H2S, 28ppm for CO2, and 0.35ppm for CH4 at sampling times of less than one min.

Following the completion of the current test program, a commercial prototype will be built and installed on an oil platform. These results will be presented at OTC's "Advances in Flexible Riser Technology" session on May 5. A commercial version should be available towards the end of this year.

04/28/2009

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