The KDC/GVD valve is a pressure control valve. The valve controls the discharge pressure of the compressor to ensure fast build-up of pressure and lubrication pressure. The valve also acts as a check valve in the discharge line of the compressor. The KDC/GVD valve is force-controlled so that when pressure in the oil separator becomes 2 bar (29 psi) higher than the suction pressure, the spring is compressed, and the valve opens. In low-pressure units (boosters), the spring requires a differential pressure of 0.5 bar (7 psi) for the valve to open.