Process for making a tight coating around a pipe for conveying hydrocarbons and the resulting hydrocarbon conveying pipe line

Claim 1

A process for the formation in situ of a tight coating around a hydrocarbon-conveying pipe, said coating being located in an annular space between the pipe and an envelope externally protecting said pipe and consisting of a sheath made of material containing pores that is capable of stopping a hydrocarbon leak due to a perforation of the pipe, by the choking resulting from an expansion of said material when contacted with hydrocarbons, said expansion being at least partly absorbed by a volume decrease of the pores in the sheath, said process comprising the following successive steps of: a. covering the pipe with a sheath of expansible material, to which is incorporated at least one curing agent and at least one porophoric agent, by winding of a strip of said expansible material around said pipe, said sheath covering substantially the whole length of the pipe on its entire periphery; b. placing a tubular envelope around said sheath, and c. subjecting said sheath to a thermal treatment by circulating through the pipe a heating fluid at a temperature and for a period so selected as to produce the curing of the sheath, together with the formation in situ of stable pores within said sheath by expansion in the annular space between the pipe and said envelope.