Directional control valve A valve to control the flow of air in a certain direction. The quantity of contaminant a filter element can trap and hold before the maximum allowable back pressure or delta P level is reached. Disc The movable seating surface in a valve. Discharge piping Is the piping between the compressor and the aftercooler, the aftercooler separator and the air receiver. Velocity pressure is considered only with dynamic compressors.
Discharge temperature Is the temperature existing at the discharge port of the compressor.
A machine where a static pressure rise is obtained by allowing successive volumes of gas to be aspirated into and exhausted out of a closed space by means of the displacement of a moving member. Disposable filter a filter element intended to be discarded and replaced after one service cycle. Drag Occurs when a valve does not close completely after popping and remains partly open until the pressure is further reduced. Drain valve A device designed to remove surplus liquid from the compressed air system. Manual units range from petcock to a ball, gate or globe valve.