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Figure F5. Plot of SF6 manifold calibration results, Expedition 327. Stainless steel coils attached to the eight-port switching valves (Fig. F4) were calibrated by injecting air into the valves at known pressures and monitoring the volume of air at standard temperature and pressure (STP) that exited the manifold. The latter measurement was made by inverting a 1 L bottle filled with water in a bucket full of water and determining the volume of water displaced by air resulting from a known number of valve actuations. This experiment was repeated multiple times at several differential pressures, developing a linear relation between differential pressure and the volume of gas (at nominal STP conditions) that was passed through the manifold for each valve actuation. The differential pressure used for much of the tracer injection experiment was ~80 psi (~540 kPa), so that the nominal injection rate was ~116 mL/valve actuation of SF6 gas at STP, although values for each of the two valves were slightly different (as indicated by different slopes on plot). The SF6 bottles were run one at a time, but two switching valves were operated throughout the period of tracer injection, each switching at 30 s intervals, giving a nominal injection rate of 474 mL STP/min of SF6 gas.

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