Polyurethane Based Grouts for Deep Off-Shore Pipe-in-Pipe Application

The force transfer mechanisms in the pipe-in-pipe (PIP) system during installation and operation are of interest in order to protect the electrical heating tabs (connections). One method of achieving the optimum PIP configuration is to fill the annular space with quality dielectric grout. In this study, the behavior of PIP with pipes of 10 in. (25.4 cm) and 16 in. (40.6 cm) diameters held together by various grouts in the annular space was investigated. In order to screen the grouts and understand the interaction between the grouts and the pipes, a small scaled model test was used to characterize the shear bonding strength developed by the grouts under various curing conditions. Three grouts with and without aggregates were tested. Limited full-scale tests were performed to verify the model test results. The model test results showed that Grout-1 (with aggregate), Grout-2 and Grout-3 had good bonding strength in the PIP configuration. The average PIP capacities for Grout-1 with aggregate, Grout-2 and Grout-3 were 71,300 lb/ft (1,040,980 kN/m), 106,600 lb/ft (1,556,360 kN/m), and 115,450 lb/ft (1,685,570 kN/m) respectively. The PIP load capacity from the full-scale tests was higher than the average PIP load capacities from the model tests because the end effects were smaller in the full-scale tests than in the model tests.