Standard plumbing and installation drawing showing the major metrological components of a rack mounted liquified gas metering system. In a typical rack mounted liquified gas metering system, the storage tank supply line is connected to a flow control valve (on/off), a pump, an air eliminator or condensing tank, a strainer, a pressure gauge, a temperature sensor and test thermal well, a meter and register with a printer, a differential back-pressure valve, a flow control valve (quick acting for mechanical registering systems and automatic for electronic registers), and delivery hose and nozzle equipped with anti drain valve at the transfer point (delivery outlet). The air eliminator’s outlet and differential back-pressure valve are connected by piping to the vapour space of the storage tank or alternatively sense the vapour pressure from a sensing bomb contained in the condensing tank, if so equipped. If there are any deviations to a typical installation, the volumetric specialist should be contacted.