GRP shelters provide advanced protection for offshore process analyzers

lightness and corrosion resistance simplify application in harsh North Sea environment

Shelters fabricated from glassfibre-reinforced polyester are protecting gas metering instrumentation from the harsh North Sea environment on an offshore platform upgrade project engineered by Oil & Gas Systems Limited. Two outdoor shelters - supplied by Intertec-Hess - provide lightweight and corrosion-resistant protection for gas chromatograph analyzers and process transmitters mounted above new natural gas export pipelines connecting the platform to an onshore UK terminal. The instrumentation provides critical monitoring data on gas quality as part of the custody transfer metering system.

This particular platform upgrade project presented a number of challenges, including the harsh operating environment of the southern North Sea, and the space and weight restrictions of adding the new facilities onto a working platform.

Glassfibre-reinforced polyester (GRP) materials were specified to protect the instrumentation. This allowed weight to be reduced significantly compared with metal shelters. GRP construction also provided excellent protection against both the harsh weather in the offshore location, and the local environmental conditions. Intertec-Hess was selected to build the custom GRP shelters because of previous good experience of working with the company on projects, including shelters and enclosures already installed in the same gas field.

The lightness of GRP compared to steel helped to reduce the size and weight of the metalwork structure that mounts the shelters directly above the export pipelines. The location - in the middle of a crowded working platform - also presented access difficulties. So, natural ventilation according to IEC EN DIN 61285 was specified. This eliminates routine maintenance visits that would be required with other shelter ventilation approaches such as fans or an HVAC system.

To support natural ventilation for safe operation in the hazardous environment, Intertec supplied explosion-proof heaters and installed louvre panels at the top and bottom of shelter walls. This maintains the interior environment a few degrees above ambient temperature, and ensures an efficient convection cycle to meet the air change requirements.