Thermal-based mass flow control for SDS gas delivery systems

The economic advantage of Safe Delivery Source gas source feed materials de pends largely on maximum use of cylinder contents. In early applications, m ore than 50% of the usable contents remained in the cylinder. Recent improv ements in flow control technology have made it possible to utilize as much as 90% of the gas cylinder contents with bottle pressures below 8 torr. Thi s article discusses the design and operating principles of thermal-based fl ow controllers and emphasizes design features for applications with inlet p ressures below 8 torr. It will also show some additional advantages for the rmal-based flow controllers designed for low input pressures over alternati ve mass flow control methods.