Abstract: A cryogenic circuit which comprises a tank for the liquid and vapor phase of the cryogen; there being a flow control valve connected at opposite ends to the liquid and vapor sides of said tank with a check valve being interposed between said vapor side and said flow control valve. The flow control valve contains a single outlet orifice directly connected to the vapor inlet. A valve arrangement is interposed between the liquid inlet of the said flow control valve and its single outlet; said valve arrangement comprising a ball valve with associated components between same and the liquid inlet to cause said valve to operate as a control valve and with a spring bearing against the upper side of said ball to adapt same for check valve usage when the associated control valve components are withdrawn under predetermined pressure conditions.