Subsea Gas Pipeline Risk Assessment During Hot Tapping Installation

Abstract

This paper examines the risk to subsea gas pipeline during hot-tapping installation process. Hot tapping is one method to connect new pipeline to existing pipeline while they remain in service. In this study it is considered that hot tapping is installed using crane barge. To assure the crane barge in steady position, the crane barge is moored by means of mooring chain at several locations. These mooring activities and hot tapping installation possess potential risk to existing subsea facilities. Hence, in general there are two objectives in this study such as: determining the safe distance between mooring chain for and the existing facilities, and performing risk level due to external load that may occurs during installation. The risk level is determined by analyzing frequency and its consequence then will be mapped into risk matrix according to DNV-RP-F107. From mooring distance analysis, the result can be used as a reference for positioning the mooring point of crane barge. Based on the result of risk assessment to facilities, risks due to external load such as dropped anchor, dragged anchor, ship sinking and dropped object are in the as low as reasonably practicable (ALARP) region which mean, in the practical life risks are acceptable as long as the frequency is maintained in the lowest rank.