Air Terminal Requirement for Offshore Platform’s Vent Stack: Assessment and Mitigation Plans

On a new offshore platform construction project, as part of lightning protection system (LPS), an air terminal (AT) was designed to be installed at the platform’s process vent tip to mitigate potential ignition at that area during coincident existence of hydrocarbon release and lightning occurrence phenomenon. The AT was designed as part of compliance to company’s standardized technical practice on LPS, which is intended to prevent any accidental ignition at the vent tip area that may result in flame getting propagated into the vent system. Calculated hazardous zone radius of 7.01 meters, requires the AT designed height to be approximately 8 meters to ensure it is outside of the hazardous area cloud. This height is deemed impractical. Dimension of the AT contributes to major impact on the vent stack structural design as it leads to additional construction material which results to increase in platform weight. From project execution perspective, this will increase overall cost and lengthen the project execution schedule. Risk assessment was done on not having to install the AT on vent stack and several means are identified to manage the risk through appropriate mitigation plans. These mitigation plans support project management team decision to deviate from company’s standardized technical practice on LPS.