Pipe freezing offshore: safety implications

Pipe freezing (freeze sealing) is a technique which can be used on liquid filled pipelines to produce a solid, pressure resistant plug which can be used for the temporary isolation of a section of pipe. The safety implications of using this technique offshore are concerned with the risk of plug failure, risk to the integrity of the pipe and the use of cryogenic liquids. These issues are addressed through a discussion of their associated parameters and the principal areas of concern are highlighted. Operational considerations include categorisation of the freeze isolation and risk assessment in addition to the choice of appropriate freezing method. This paper addresses these issues based on experience gained from extensive research into pipe freezing and, whilst no attempt is made to reconcile these to detailed offshore practices, attention is drawn to the main factors that should be considered