Apparatus and method for controlling the charging of NGV cylinders from natural gas refueling stations

A method for the rapid, substantially adiabatic, filling of containers with a fluid, under pressure, wherein each container has a known pressure rating at standard ambient pressure and temperature, and an unknown amount of residual gas remaining therein, the method comprising:

• providing a container to be filled, having an unknown quantity of residual gas therein;
• connecting the container to a source of gas, the gas being deliverable at a pressure sufficient to fill the container with a mass of gas equivalent to a filled container at a standard temperature and pressure;
• sensing the ambient temperature in the vicinity of the container to be filled;
• sensing the pressure of the gas being supplied from the source;
• sensing the initial pressure, prior to filling, of the residual gas within the container to be filled;
• determining an appropriate cut-off pressure within the container to be filled, based upon the ambient temperature, the initial pressure of the container to be filled, and the source pressure, and presuming that substantially no heat transfer occurs between the container and the surrounding environment, during the filling of the container.;
• initiating and maintaining a substantially continuous and uninterrupted flow of gas from the source into the container to be filled;
• monitoring continuously the pressure within the container to be filled, while the flow of gas from the source remains uninterrupted;
• comparing the monitored pressure with the determined cut-off pressure;
• and
• interrupting the flow of the gas from the source to the container to be filled when the monitored pressure achieves a predetermined fraction of the predetermined cut-off pressure.