Abstract: A fluid mass flow controller, particularly adapted for controlling mass flow rates of toxic and reactive gases used in semiconductor device fabrication, includes a control circuit connected to pressure sensors for sensing the differential pressure across a flow restrictor in the mass flow controller for controlling a valve to control the fluid mass flow rate to a setpoint. The control circuit compares the differential pressure with the downstream pressure at a measured temperature with a data set of a gas passing through the flow controller for a range of differential pressures and downstream pressures and adjusts the flow control rate accordingly. The flow controller is mechanically uncomplicated including a two part body for supporting the pressure sensors, a remotely controllable flow control valve and the flow restrictor.

Abstract: A composite elevated storage tank is constructed utilizing precast concrete panels for a pedestal which supports a steel storage tank. The precast concrete panels are poured in a controlled environment not subject to the difficulties inherent with sitecast concrete construction. A simple and practical method of attaching the panels to each other as well as to the foundation and steel tank ensures the concrete pedestal behaves as a shell to sustain all loads. This method, which uses cast in plates welded together at vertical joints and vertical aligned threaded rods for horizontal joints, serves to reduce the length of time required to construct a composite elevated tank and also reduces the construction costs.

Abstract: A composite elevated storage tank is constructed utilizing precast concrete panels for a pedestal which supports a steel storage tank. The precast concrete panels are poured in a controlled environment not subject to the difficulties inherent with sitecast concrete construction. A simple and practical method of attaching the panels to each other as well as to the foundation and steel tank ensures the concrete pedestal behaves as a shell to sustain all loads. This method, which uses cast in plates welded together at vertical joints and vertical aligned threaded rods for horizontal joints, serves to reduce the length of time required to construct a composite elevated tank and also reduces the construction costs.