Design of Enveloper Pipe Installations and To Grout or Not to Grout

Abstract

The design requirements of enveloper pipe installations, or what is sometimes called a “pipe in a pipe”, often causes confusion among designers, installers, and asset owners alike. Often the design intent or purpose of the enveloper is not understood and there is confusion as to whether it is part of the temporary or permanent works. This paper explores the historical use of enveloper pipes, their purpose, how they might be installed, and what are the design requirements for both the enveloper and the product pipe. The paper provides a summary of different authority requirements in both Australia and New Zealand for enveloper pipes and the installation requirements. The paper also discusses the requirements for grouting on the outside of the enveloper pipe, grouting of the annulus in between the enveloper and the product pipe, and the requirements for pipe spacers. Finally, the paper provides some interesting case studies on various enveloper pipe installations.