Reliably-sealed external pressure test device for marine glass fiber reinforced plastic GRE pipe

The invention discloses a reliably-sealed external pressure test device for a marine glass fiber reinforced plastic GRE pipe. The device comprises an external pressure tank mechanism and an internal support mechanism, the external pressure tank mechanism comprises flange sealing assemblies, the two flange sealing assemblies sleeve a to-be-tested pipe, and a connecting shell is connected between the two flange sealing assemblies; an out-pipe test cavity is formed among the connecting shell, the two flange sealing assemblies and the outer wall of the to-be-tested pipe, the internal supporting mechanism comprises a left supporting assembly, a right supporting assembly and door-shaped fixing pressing frames, the left supporting assembly and the right supporting assembly are consistent in structure and symmetrically installed at the two ends in the to-be-tested pipe, and the two door-shaped fixing pressing frames are installed at the two ends of the to-be-tested pipe respectively; and an in-pipe test cavity is for