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0 9 <br /> Pressure changes , due to bubble outlet-liquid level resis- <br /> tance, are sensed by a precision bellows , connected to the re- <br /> corder pens . A change of 0.01 inch in liquid level is detected. <br /> The recorder pressure system is calibrated before the actual test <br /> period by carefully submerging a known volume, 0.05/gallon, rod <br /> into the fillpipe liquid. The chart pen deflection, lines per <br /> volume , is recorded on data sheet. <br /> The coefficient of expansion of the tank storage liquid is <br /> determined from American Petroleum Institute (API) tables by <br /> measuring the (hydrometer) density at the ambient temperature. <br /> Standardized hydrometers , and thermometers are used. <br /> Product temperature for the small fillpipe tank test is <br /> measured with a liquid filled probe. The sensing probe, 46 <br /> inches long, is centered vertically in the tank liquid. The <br /> probe liquid has a known coefficient of expansion, and volume <br /> change versus temperature is read on a sight-tube connected to <br /> the probe, and positioned above the fillpipe opening. A tempera- <br /> ture change of 0.034®F will result in a (1) one inch probe liquid <br /> level change. The temperature probe system is checked or com- <br /> pared with the electronic thermocouple system, a 25 ft. platinum <br /> coil sensing wire with digital readout to 1/1000°F. This unit <br /> was checked/calibrated by Horner Creative Metals, April 10, 1985. <br /> -5- <br />