Pressure is limited only by the bursting strength and available power of the pump.
For this reason, relief valves are always fitted on the pump discharge. With close clearances, these pumps must be operated at relatively low speeds to obtain reliable operation and maintain capacity over an extended period of time. The main features of gear and screw pumps will be discussed briefly in the following paragraphs. As they turn, the gears unmesh and liquid flows into the pockets which are vacated by the meshing gear teeth. This creates the suc-tion that draws the liquid into the pump.