Abstract: Direct insertion of fiber optic probes into production streams to monitor chemical composition is an attractive concept from a cost and sampling standpoint. Goals including closed loop process control, raw material identification, and waster stream reduction cannot be realized if the fiber optic interface leaks or its signal output deteriorates. A successful long term probe interface must be a rugged and reliable as a conventional process transducer, yet allow normal maintenance activity. The wide variety of materials and environments encountered in production areas forces the designer to integrate technology from diverse fields and to capitalize on combinations which generate reliable results. Viable approaches include spring energized seals and adjustable pathlength in-line transmission cells. Although certain designs may operate effectively for limited periods of time, long term success demands identification and correction of failure modes in prototypes and utilization of construction materials compatible with the temperature, pressure, flow, and corrosion extremes at the sample point. The designs discussed herein can be scaled and modified at minimal additional cost to suit the current application.!4
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