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The line pressure probe shown above is installed permanently on the pressurized <br />line in the turbine sump. It consist of a strain gauge and a current -loop <br />transmitter mounted in a waterproof aluminum housing. This probe has a <br />maximum operating pressure of 100 psi and operates in a range of 0 to 50 <br />psi. The precision of the probe is 0.15 % of full scale or approximately 0.0125 <br />psi. The SOC monitors this device continuously to detect leaks of 3 gallons <br />per hour at 10 psi and 0.1 gallons per hour at 40 psi. This particular probe <br />has been evaluated to EPA protocol by a nationally recognized laboratory <br />and their certified results have established a Probability of Detection (Pd) <br />100% and a Probability of False Alarm (Pfa) = 0%. <br />The main "noise" factors that introduce errors into monitoring pressure decay to <br />detect leaks are: bulk modulus (elasticity) of the line, and temperature <br />differences between product in the line and the surrounding soil. The <br />influence of these factors must be accounted for in the SOC programs that <br />perform the line leak algorithms. These programs are the primary difference <br />between manufacturers. <br />This probe is currently being used on both single and double wall fiberglass lines <br />and on the new Enviroflex lines. <br />Control Engineers, U.S.A. Page 9 <br />