Method and apparatus for leak detection with float excitation and self-calibration

A leak detecting float system for use in a tank storing fluid product to measure a surface level of the fluid product, the leak detecting float system comprising:

• a float for floating on the surface of the fluid product;
• a plurality of magnets connected to the float and positioned at regular intervals around a circumference of the float, wherein each of the plurality of magnets has a first pole and a second pole and each of the number of magnets is aligned so that the first pole points upwardly at a predetermined angle towards a central axis of the float;
• a float enclosure surrounding the float positioned vertically in the tank and extending at least to the surface of the fluid product;
• and
• a first excitation coil positioned in proximity to the float enclosure and having first and second vertical segments extending along a desired length of travel of the float for generating a first electromagnetic field within the float enclosure when an excitation current passes through the first excitation coil;
• a second excitation coil positioned in proximity to the float enclosure and having third and fourth vertical segments extending along the desired length of travel of the float for generating a second electromagnetic field within the float enclosure when an excitation current passes through the second excitation coil, the first and second excitation coils positioned so that the first, second, third and fourth vertical segments are substantially 90 degrees from each other, the first and second magnetic fields controllably moving the float with respect to the surface level of the fluid product so as to finally position the float at a repeatable position with respect to the surface level of the fluid product;
• a control circuit coupled to the first and second excitation coils for providing the first and second excitation currents;
• means for measuring the position of the float;
• and
• a self-calibration apparatus positioned at a fixed distance from the means for measuring, the self-calibration apparatus providing a calibration signal to the means for measuring.

A leak detecting float system for use in a tank storing fluid product to measure a surface level of the fluid product, the leak detecting float system comprising:

• means for generating a measurement signal;
• a float for floating on the surface of the fluid at a variable distance from the means for generating;
• a first means for reflecting the measurement signal from the means for generating to provide a first reflected signal, the first means for reflecting connected to the float;
• a second means for reflecting the measurement signal from the means for generating to provide a second reflected signal, the second means for reflecting positioned at a fixed distance from the means for generating, wherein the second means for reflecting only reflects the measurement signal when it is energized;
• means for controllably energizing the second means for reflecting;
• and
• means for receiving the first and second reflected signals;
• and
• means responsive to the first and second reflected signals for determining a position of the float.

A method for operating a leak detecting float system for use in a tank for storing fluid product to measure a level of a surface of the fluid, the method comprising the steps of:

• initially positioning a float in the fluid product, the float having at least one magnet positioned therein;
• providing an electromagnetic field in proximity of the float to finally position the float by causing the float to move with respect to the fluid product so as to break the surface tension between the float and the fluid product and to settle the float near a true buoyancy position;
• and
• measuring the position of the float.

A method for operating a leak detecting float system for use in a tank storing fluid product to measure a surface level of the fluid product, the method comprising the steps of:

• initially positioning a float in the fluid product, the float having at least one magnet positioned therein;
• providing an initial electromagnetic field in proximity of the float to abruptly move the float to break the float from surface tension of the fluid product;
• providing a final electromagnetic field in proximity of the float to gently move the float to a final position near a true buoyancy position;
• measuring the position of the float, including the steps of:
• i) transmitting a measurement signal to the float,
• ii) reflecting the measurement signal from the float to provide a first reflected signal,
• iii) detecting the first reflected signal,
• iv) determining a first elapsed time between step i) and step iii), and
• v) calculating the position of the float from the first elapsed time,
• vi) repeating step i) through step iv) a predetermined number of times;
• determining a calibration measurement including the steps of:
• a) transmitting a measurement signal to a fixed position calibration apparatus,
• b) reflecting the measurement signal from the calibration apparatus to provide a second reflected signal,
• c) detecting the second reflected signal,
• d) determining a second elapsed time between step a) and step c), and
• e) calculating the calibration measurement from the second elapsed time,
• f) repeating step a) through step e) a predetermined number of times;
• and
• calculating a compensated position measurement of the float using the calculated position of the float and the calibration measurement.