SECTION II
2.0 INTRODUCTION
2.1 The MMC Tri-Mode portable ullage, temperature and interface tape described
herein incorporates extremely accurate instrumentation to provide three vital
petroleum and other liquid tank measurements.
* Measurement of surface ullage level of oil or other fluids to an accuracy and repeat-
ability of ±1/8 inch.
* Determination of the exact location of the ullage level of the interface layer exists
when an oil-water mixture is contained within the same vessel.
* Measurement in either Degrees F or Degrees C of the temperature of the fluid within
a vessel, at any or several desired ullage levels, in rapid succession. Measurement is
given to the nearest 0.1 degree and is accurate to ±0.2°F over the calibrated
temperature ranges given in the specifications listed in Section I.
2.2 The MMC system utilizes a sensor suspended at the end of a fluoropolymer covered \
gauging tape wound on a reel assembly, The plastic covered steel gauging tape
contains two isolated side conductors to carry the signal and power to the electronic circuit
within the sensor barrel with the steel tape provides the ground return. The plastic surface of
the tape has been treated to make it sufficiently conductive to prevent the build-up of static
charges. Temperature indication is provided by a large digital liquid crystal display (LCD),
housed within a sealed reel driving assembly.
2.3 Ullage and interface detection is provided by an audible signal obtained from a horn in
the reel driving hub, when the bottom “U” gap in the sonic sensor is immersed in fluid. The
audible signal heard, will be a continuous tone in a non-conductive fluid such as oil,
gasoline, kerosene, etc., but will change to an interrupted tone when immersed in and fluid
which is electrically conductive, such as water.
2.4 The system is certified as intrinsically safe for electrical equipment in hazardous
atmospheres by Factory Mutual, BASEEFA /SIRA, CSA, and SAA.
2.5 The triple function temperature, interface, and ullage sensor is powered by a single 9 volt
battery contained within the hub assembly. Battery drain is extremely low, (Approximately
1-1/4 Mili-amperes in either the ullage, interface or the temperature mode), insuring very
long operation, without battery replacement. Low battery warning is provided at the upper left
corner of the temperature display LCD, when the battery voltage has dropped to a level that
would, with further operation, cause excessive errors in temperature readings.
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