Fluid metering system

Abstract

A fluid metering apparatus includes a gas inlet, a first regulator in fluid communication with the gas inlet and configured to emit the gas at a first gas pressure, and a second regulator in fluid communication with the gas inlet and configured to emit the gas at a second gas pressure. A first valve is in fluid communication with the first regulator and a second valve is in fluid communication with the second regulator. A switch mechanism has two actuators which, when separately actuated, causes either the first valve to be open and the second valve to be closed or the first valve to be closed and the second valve to be open. The apparatus further includes a fluid pressure regulating device having a fluid inlet port which receives a fluid at a fluid inlet pressure, a gas inlet port and a fluid outlet port. The fluid pressure regulating device delivers the fluid to the fluid outlet port at a device outlet flow rate which is proportional to a predetermined ratio of the fluid inlet pressure and either the first gas pressure if the first actuator is actuated or the second gas pressure if the second actuator is actuated. The apparatus further includes a fluid outlet and an orifice fitting in fluid communication with the fluid outlet port and configured to effect a pressure drop between the fluid outlet port and the fluid outlet.