A pressure isolation device for a pipeline system is described. The pressure isolation device changes from an open position to a closed position when the pressure of a fluid flowing through the device exceeds a predetermined threshold pressure. In some embodiments, the pressure isolation device comprises a housing having an internal chamber, a main inlet, and a main outlet. An elongated member is disposed within the internal chamber between the main inlet and main outlet, and is biased towards the open position. As fluid pressure increases, the elongated member is pushed to the closed position and a portion of the elongated member blocks the fluid pathway from the main inlet to the main outlet. The pressure isolation device provides a simple mechanical solution to protecting and isolating downstream pipeline components from over-pressurization.