System for Delivering Gas Samples to Multiple Instruments

A system that samples gases at multiple remote locations and delivers the gases to two or possibly more gas-monitoring instruments (e.g., mass spectrometers) has been developed. The system includes a transport (suction) pump that draws the gases from the sampling locations, through transport tubes, into a plenum, which is large enough to act as a buffer against changes in pressure in the transport tubes. Connected to each transport tube at a location near the plenum are two or more sample tubes that are, in turn, connected to manifolds of sample-selector valves through which gases are drawn into the instruments. Each instrument is equipped with a sampling (suction) pump that draws gas from one of the transport tubes that has been selected by opening the corresponding sample-selector valve. Each sampling pump is operated under feedback flow and pressure control to maintain a steady instrument-inlet pressure needed to ensure stable instrument readings. The sample flow thus diverted from the transport tube is kept to one-fifth or less of the transport flow in order to minimize the perturbation of the transport flow and thus, further, minimize any effect of one instrument on the other.