A split pressure vessel for processing of two flows encountered with energy exchange devices, consisting of two opposite facing end caps 1,2 having each a side port for low pressure 3,5 and one axial port 4,6 preferably in the same plane as the side ports. Each end cap has internal structurally integrated manifolds for high pressure 17,22 and low pressure manifold 19,24 connecting to axial ports of the internal energy exchange device. The high pressure side of one end cap may be structurally integrated with a circulation pump or booster 26 having a submersible or external motor.