Wednesday 20 June 2012

Level off West Africa

Emerson’s Rosemount® Guided Wave Radar enables accurate and reliable level measurements in challenging process conditions off the west coast of Africa

BP Exploration has replaced unreliable level transmitters previously used on a floating production, storage and off-loading (FPSO) vessel with guided wave radar (GWR) transmitters from Emerson Process Management. The more accurate and reliable level readings from Emerson’s Rosemount® 5300 Series GWR transmitters have helped BP Exploration increase safety, reduce shutdowns and increase production.

Operating 160 km (100 miles) off the west coast of Africa, the BP FPSO processes and stores oil production for export. At 310 metres in length, it has an oil storage capacity of 1.77 million barrels and can process up to 240,000 barrels per day.

Changing process conditions and the presence of foam and vapour, as well as dirty sticky fluids, made this a difficult application for measuring level. The original GWR transmitters (supplied by another vendor) had compatibility issues with the FPSO’s FOUNDATION fieldbus network, and their limited capabilities in detecting low-dielectric hydrocarbons required coaxial probes to increase the strength of the surface signal. Such probes are susceptible to the build-up of sticky solid materials entrained within the production fluid, which led to a significant number of unplanned shutdowns with resulting lost production.

To address these issues, BP Exploration worked with Emerson to replace existing GWR units with Rosemount 5300 GWRs. With Emerson’s advanced signal-processing technology that ensures detection of low dielectric fluids, the Rosemount GWR is able to send and receive a cleaner, stronger signal. This allows the use of single-lead probes that increase tolerance to solids build-up and coating, and eliminate trips due to false readings. In addition, the Rosemount 5300’s FOUNDATION fieldbus interface made installation and configuration both quick and easy.

The improved level detection enabled by the new instruments has also helped BP Exploration improve safety. The susceptibility of the existing GWRs to material build-up on the co-axial probes and their inability to distinguish the presence of a light hydrocarbon layer on top of the water meant that the level measurements were unreliable. This unreliability compromised one of the layers of protection used to ensure safe operations.

Following the installation of the Rosemount 5300 GWR transmitters, the process data has confirmed the accuracy and reliability of the instruments and their suitability for the widely varying process conditions of the FPSO.

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