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
repeatability 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 ±0.5°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 a fluid
which is electrically conductive, such as water.
2.4
The system is certified as intrinsically safe for electrical equipment in hazardous
atmospheres by SIRA, CSA, BV, DNV.
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 Milliamperes in either the ullage, interface, or the temperature
mode), ensuring 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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