KCB type gear pump;   What is the main function of a valve

KCB type gear pump; It is a rotary pump that relies on the change and movement of the working volume formed between the pump cylinder and the meshing gear to transport liquid or increase its pressure. Two enclosed spaces are composed of two gears, a pump body, and front and rear covers. When the gears rotate, the volume of the space on the disengagement side of the gears increases from small to large, forming a vacuum that sucks in the liquid. The volume of the space on the meshing side of the gears decreases from large to small, and the liquid is squeezed into the pipeline. The suction chamber and the discharge chamber are separated by the meshing line of two gears. The pressure at the discharge port of a gear pump depends on the magnitude of the resistance at the pump outlet.