In this study a lower-bound analytical solution for propagation pressure of PIP systems is proposed. Hyperbaric chamber tests are conducted on 1.6 m aluminium (Al-6060-T5) PIP system with parameters shown in Table 1. The experimental result is used to validate the FE model. A parametric study is conducted on the effect of diameter, wall-thickness and yield stresses of the outer and the inner pipe on propagation buckling capacity of the PIP. Results are compared with empirical expressions proposed by Kyriakides (Kyriakides, 2002) and Gong and Li (Gong and Li, 2015).