Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
  • G01F23/00—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
  • G01F23/22—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water
  • G01F23/28—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring the variations of parameters of electromagnetic or acoustic waves applied directly to the liquid or fluent solid material
  • G01F23/296—Acoustic waves
  • G01F23/2966—Acoustic waves making use of acoustical resonance or standing waves
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
  • G01F23/00—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
  • G01F23/22—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water
  • G01F23/28—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring the variations of parameters of electromagnetic or acoustic waves applied directly to the liquid or fluent solid material
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
  • G01F25/00—Testing or calibration of apparatus for measuring volume, volume flow or liquid level or for metering by volume
  • G01F25/20—Testing or calibration of apparatus for measuring volume, volume flow or liquid level or for metering by volume of apparatus for measuring liquid level
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S367/00—Communications, electrical: acoustic wave systems and devices
  • Y10S367/908—Material level detection, e.g. liquid level

Definitions

• the invention relates to methods for measuring a filling material level in vessels and for detecting filling material presence in vessels. DESCRIPTION OF THE RELATED ART
• Invasive methods require the presence of a measuring device's element inside the vessel; non-invasive metliods are limited to those that do not require a measuring device's element inside the vessel.
• the number of invasive methods is noticeably larger then the number of non-invasive methods.
• the former methods could utilize the principals of Time Domain Reflectometry of very short electrical pulses (TDR) that "...are propagated along a transmission line or guide wire that is partially immersed in the material being measured. ...
• TDR Time Domain Reflectometry
• Reflected pulses are produced at the material interface due to the change in dielectric constant. ... " The time difference between the launched and reflected pulses is used to determine the material level, as disclosed in U.S. Patent Nos. 5,610,611, 6,452,467 and 6,481,276. This approach is usable in continuous and set-point level measurement applications. [0005] Another known approach to the material presence detection and the filling material level measurement is based on monitoring the dynamic properties of a mechanical system comprised of an oscillatory structure directly contacting the filling material as disclosed in U.S. Patent Nos. 5,631,633, 4,896,536, 6,105,425 and 5,862,431.
• U.S. Patent 6,111,211 issued to Dziedzic et al serves as an example of the above-described invasive method for the set point level measurement.
• U.S. Patent No. 4,954,997 issued to Valesaint, et al. represents a set-point liquid level measurement solution that monitors changes in the parameters of the Lamb elastic waves in the detection plate. These waves are generated by a transmitter and are received by a receiver of the measuring system. The plate is installed at a predetermined level inside of a tank.
• the parameters of the Lamb wave change dramatically at the moment the detection plate contacts the filling liquid, thereby allowing the set-point level measurement.
• Scientific Technologies, Inc. manufactures another vibrating level sensor, NBS series.
• the sensor is described in the company website www.stiautomationproducts.com: "The VBS series is designed specifically for solid level detection in very small hoppers less than 3 ft (1 m) tall.
• the NBS is a compact diaphragm vibration switch for use with dry solids at atmospheric pressures.” "The sensitivity may vary depending on the apparent specific gravity and fluidity of the powder," thus the detection sensitivity depends on the buried portion of the diaphragm in the vertical direction.
• a large group of methods is based on the capacitive properties of the filling material. According to these methods, at least one member of the measuring capacitor is located within the container. The electrical capacitance of the measuring capacitor varies depending on the amount of filling material and could be calculated to correspond to the measured level.
• U.S. Patent os. 5,207,098 and 4,574,328 illustrate such invasive capacitive methods.
• every ultrasound, electromagnetic, and laser method for distance measurement and their combinations are usable for measuring the filling material level in vessels. Some of these methods are disclosed in U.S. Patent Nos. 5,877,997, 5,793,704, 6,122,602, 5,822,275, 5,699,151, 6,128,982 and 5,892,576 and illustrate the wave-train-based invasive approaches to the vessel's filling material level measurement.
• Radioactive methods are based on the fact that radioactive energy attenuates after passing through a vessel's walls and through filling material. Obviously, radioactive systems are dependent on the vessel's material and the filling material. These systems are not capable of continuous level measurement and these systems require special design and operational efforts to maintain a sufficient degree of safety.
• the example of a radioactive system usable for a set point level measurement is Radiometric Measuring System DG57 manufactured by Endress+Hauser.
• Gravitational systems require the exact knowledge of the empty vessel's weight and its dimensions including the internal dimensions. Gravitational systems are limited in their applicability due to problems with installation of the weight-measuring equipment and calculation of the actual level of filling material, which varies depending on the vessel's internal topology, mechanical properties of the filling material and environmental conditions, e.g., material viscosity or temperature. Nishay ⁇ obel of Sweden manufactures one such gravitational system.
• C k ⁇ ° A (1)
• C denotes the capacitance; ⁇ o - electric constant; k - relative permittivity; A - area of a flat rectangular conductive element; and d - distance between the conductive elements.
• d 0.01 m
• A 1.00 m
• k 2.5 (typical value for dielectric materials)
• a 10% change in the area of the conductive plates results in a 221.25 pF change in the capacitance.
• Ultrasound non-invasive methods for level measurement require the attachment of one or more transducers to the external wall of a vessel for transmitting the acoustic energy toward the boundary surface separating the filling material from the remaining space inside of the vessel.
• the receiver of the measuring system gets the reflected ultrasound wave train and sends it to the device's echo processing electronics.
• these methods bear all the distinctions of well-known invasive ultrasound methods for the distance/level measurement.
• the ultrasound non-invasive method is advantageous because of its non-invasiveness.
• the ultrasound non-invasive approach to the filling material level measurement is limited by the homogeneity of the filling material.
• measuring systems of this method are used for homogeneous liquid filling materials. It is not applicable to loose materials or liquids with inclusions. In addition, this method is not applicable to relatively small-sized containers due to problems with acoustic pulse relaxation, reverberation and the size of transducers. Plus, the method is temperature-dependent, thereby requiring temperature compensation during measurement. If used for the set-point level measurement or material presence detection, the method is prone to creating false alarms due to the effect of some volume of a viscous filling material adhering to the internal surface of the container. Finally, the ultrasound-based non-invasive technologies require special treatment of the container's surface in order to create a conduit for ultrasound waves emitted by a transducer into the container.
• NesselCheck ST and SpotCheck of Cannongate Technology UK.
• the NesselCheck marketing material published on www.cannongatetecl nology.co.uk says: "With NesselCheck ST, there's no need to make holes in the vessel.
• the unique NesselCheck ST provides continuous measurement with no process connections, meaning nodown-time during installation.
• Two small ultrasonic transducers are clamped to the outside walls of the vessel. One is mounted on the bottom of the vessel and the other on the side, to compensate for variations in temperature and density.”
• spotCheck uses an ultrasonic "footprint" to determine the presence or absence of liquid inside a tank or pipe. ...
• the surface of the tank or pipe must be prepared correctly.” For instance, deseaming and gelling the wall's surface is required in the area in which the transducer is mounted.
• PPT Penetrating Pulse Technology
• the distinctive feature of PPT is generating a single short ultrasound impulse penetrating the vessel's wall toward the filling material.
• SONOMETER for the continuous level measurement
• SONOCONTROL for the set point level measurement are based on PPT.
• the company provides a comprehensive description of their method on the website www.hitmüch.com.
• the object of the present invention is to develop a method for the non- invasive measurement of the filling material level in the vessel free of the underlined limitations.
• a method for non-invasive evaluation of the level of filling material in a vessel is disclosed. The method may include the steps of initializing mechanical oscillation at least in a single predetermined point on the outside wall of the vessel; performing a Close Range Level Measurement Procedure (CRMP); performing a Long Range Level Measurement Procedure (LRMP); analyzing the outcome of the CRMP; analyzing the outcome of the LRMP; and evaluating the value of the filling material level in the vessel based on the result of the analysis of the CRMP and the LRMP outcomes.
• CRMP Close Range Level Measurement Procedure
• LRMP Long Range Level Measurement Procedure
• the method for evaluating the value of the filling material level may include one of continuous measurement of the level of the filling material in the vessel, continuous monitoring the deviation of the level of the filling material in the vessel from a set point level, set point measurement of the level of the filling material in the vessel, filling material presence detection in the vessel and switching based on the level of the filling material.
• the method may include joint performance of the CRMP and the LRMP for the filling material level evaluation having one or more points for the mechanical oscillation initiation on the external surface of the vessel.
• the method may include joint performance of the CRMP and the LRMP for the filling material level evaluation having one or more points for receiving a mechanical oscillation on the external surface of the vessel.
• the method may include measuring the value of the filling material level in the vessel based on the analysis of the outcome of the CRMP when the presence of the filling material in the vicinity of the point of mechanical oscillation initiation is known. [0021] The method may include monitoring a deviation of the level of filling material in the vicinity of the point of mechanical oscillation initiation based on the analysis of the outcome of the CRMP. [0022] The method may include evaluating the value of the filling material set point level in the vessel based on the analysis of the outcome of the CRMP.
• the method may include performing the filling material level switching in the vessel based on the analysis of the outcome of the CRMP.
• the method may include performing the filling material presence detection in the vessel based on the analysis of the outcome of the CRMP.
• the method may include measuring the value of the filling material level in the vessel based on the analysis of the outcome of the LRMP when the filling material level is not in the vicinity of the point of the mechanical oscillation initiation.
• the method may include having the point of the mechanical oscillation initiation and a point of a mechanical oscillation receiving both located at one of the top of the vessel and the bottom of the vessel.
• the method may include having the mechanical oscillation originate through a temporal mechanical load applied to an external surface of the wall of the vessel, the load being actuated by one of a solid material body percussion, an air-dynamic percussion, a fluid-dynamic percussion, a ballistic percussion and an electro-dynamic percussion; and a time diagram of the mechanical load having a form of one of a single pulse, a trainload of pulses and a continuous periodical load.
• the method may include having the time diagram being a function of a modulation of the load, the modulation being one of an amplitude modulation, a frequency modulation, a phase modulation, a pulse-code modulation, a pulse- width modulation and a combination thereof, and the mechanical load being originated by the transformation of a source of driving energy selected from one of a solenoid drive, a mechanical energy used in springs, a pneumatic apparatus, a hydraulic apparatus, and a ballistic percussive apparatus.
• the method may include having the CRMP analyse the mechanical oscillation obtained in at least one receiving point, the LRMP analyse the mechanical oscillation obtained in at least one receiving point, the outcome of the CRMP being stored for consequent analysis, and the outcome of the LRMP being stored for consequent analysis
• the method may include capturing the mechanical oscillation on the external surface of the wall of the vessel by the attachment of oscillation sensing means at the point of mechanical oscillation receiving. [0031] The method may include capturing the mechanical oscillation on the external surface of the wall of the vessel by using remote oscillation sensing means at the point of mechanical oscillation receiving.
• the method may include having the outcome of the CRMP include a variable or a vector of variables that allow a decision on the validity of the CRMP; the outcome of the LRMP include a variable or a vector of variables that allow a decision on the validity of the LRMP; the CRMP-relating variables include a vector denoted ⁇ c , and the LRMP-relating variables include a vector denoted ⁇ L .
• the method may include producing evaluating binary variables of the time domain, denoted ⁇ x and ⁇ 2 , with the variable ⁇ t indicating the presence or the absence of the filling material in the vicinity of the point of mechanical oscillation initiation and with the variable ⁇ 2 indicating that the LRMP generates a valid or an invalid outcome.
• the method may include using the vector ⁇ c for the production of the variable ⁇ j and using the vector ⁇ L for the production of the variable ⁇
• the method may include having the vector ⁇ c include a function of amplitudes of mechanical oscillation obtained at the point of the mechanical oscillation receiving, the function being defined on a predetermined time interval and the vector ⁇ c include a function of the number of periods of mechanical oscillation obtained at the point of the mechanical oscillation receiving, and the function being defined on the time interval.
• the method may include having the CRMP control the LRMP by providing information on the presence or absence of the filling material in the vicinity of at least one predetermined point of mechanical oscillation initiation.
• the method may include having the operation Calibration include the steps of positioning a point of mechanical oscillation initiation above a vicinity of the material interface in the vessel; obtaining a statistical sample of the output of the CRMP by repetitively performing a Basic Measurement Procedure (BMP); deriving a value, denoted ⁇ i, of an evaluating variable, denoted ⁇ , from the statistical sample that is associated with an upper saturation state of a measuring system's static transfer operator; positioning the point of mechanical oscillation initiation below the vicinity of the filling material interface in the vessel; obtaining a statistical sample of the output of the CRMP by repetitively performing the BMP; and deriving a value, denoted ⁇ 2 , of the evaluating variable ⁇ , from a statistical sample that is associated with a lower saturation state of the measuring system's static transfer operator.
• BMP Basic Measurement Procedure
• K denotes a slope
• ⁇ ° denotes an intercept of the measuring system's static linear transfer operator
• y lm i n denotes the minimal value yi obtained on the condition of the predetermined proximity between the two consequent readings of ⁇ ls
• y m i n denotes the minimal value y 2 obtained on the condition of the predetermined proximity between the two consequent readings of ⁇ .
• the operation Calibration may include the steps of positioning a point of mechanical oscillation initiation below a vicinity of the material interface in the vessel; obtaining a statistical sample of the output of the CRMP by repetitively performing a Basic Measurement Procedure (BMP); deriving a value, denoted ⁇ i, of an evaluating variable, denoted ⁇ , from the statistical sample that is associated with an lower saturation state of a measuring system's static transfer operator; positioning the point of mechanical oscillation initiation above the vicinity of the filling material interface in the vessel; obtaining a statistical sample of the output of the CRMP by repetitively performing the BMP; and deriving a value, denoted ⁇ 2 , of the evaluating variable ⁇ , from a statistical sample that is associated with a lower saturation state of the measuring system's static transfer operator.
• BMP Basic Measurement Procedure
• BMP Basic Measurement Procedure
• K denotes a slope
• ⁇ ° denotes an intercept of the measuring system's static linear transfer operator
• yi denotes a distance between the receiver and the lower point of saturation of the measuring system's static transfer operator
• y 2 denotes a distance between the receiver and the upper point of saturation of the measuring system's static transfer operator.
• the method may include setting parameters of a transfer operator of a measuring system, the parameters selected from one of ⁇ i, ⁇ 2 , y ls y , K, ⁇ ° and a combination thereof.
• BMP Basic Measurement Procedure
• the method may include having a Basic Measurement Procedure (BMP) include the steps of: initiating the mechanical oscillation by the application of a mechanical load non-tangentially aimed toward the vessel's external wall; capturing the moment in time of the mechanical oscillation initiation; receiving a mechanical oscillation that occurs on an outside surface of the wall of the vessel due to the mechanical oscillation initiation; obtaining parameters of the mechanical oscillation including amplitudes and frequencies corresponding with at least some periods of the captured oscillating process; and calculating a value of an evaluating variable denoted ⁇ by using the parameters of the mechanical oscillation as an input.
• BMP Basic Measurement Procedure
• the method may include monitoring the parameters of the mechanical oscillation; storing the parameter values at each moment in time the operation Calibration is committed; comparing the monitored values of the parameters of the mechanical oscillation with the stored values of the parameters; establishing a vector, denoted as the
• Proximity Vector of values reflecting the proximity between the monitored values and the stored values of the parameters of the mechanical oscillation
• the method may include performing the BMP more than once for the purpose of improvement of the validity of measurement.
• [Ai, A 2 ] denotes a predetermined amplitude range satisfying a criterion of undisturbed mechanical oscillation processing
• the method may include calculating the evaluating variable's value by the formula:
• [cui, ⁇ 2 ] denotes a frequency range satisfying a criterion of non-generation of mechanical elastic waves, T; denotes an i-th full period of oscillation observed beginning at a moment to.
• the method may include providing for a high repeatability and high accuracy of measurement, and further including: wherein, ⁇ i(t) denotes the evaluating variable obtained by an i-th execution of the BMP, and b; denotes a weighting factor corresponding with the i-th execution of the BMP. [0054]
• the method may include evaluating variable ⁇ ;(t) as one of a function of amplitudes of mechanical oscillation obtained at the point of the mechanical oscillation receiving over a predetermined time interval, a function of the number of periods of mechanical oscillation obtained at the point of the mechanical oscillation receiving over a predetermined time interval, and a function of the presence or absence of the filling material in the vicinity of a predetermined point of mechanical oscillation initiation.
• the method may include monitoring mechanical oscillations in at least two different points on the surface of the vessel, wherein these points are consequently denoted Pi, p 2 , ... , p r with the r denoting the number of the points; and forming the evaluating variable ⁇ (t) based on the output from each point for mechanical oscillation receiving.
• the method may include applying a series of mechanical loads to the vessel's external wall per each measurement such that each application of the mechanical load is a percussion; generating the evaluating variable per each percussion in the series; validating each percussion-associated evaluating variable such that each evaluating variable is considered either valid or invalid; creating an array of the valid evaluating variables per each series of percussions; selecting those arrays that have a length greater or equal to a predetermined number; statistically treating each array for the purpose of determination of the presence or the absence of the filling material in the vicinity of the point for mechanical oscillation initiation; forming a binary status variable of the discrete time domain, denoted s(t), that indicates the presence or absence of the filling material in the vicinity of the point for mechanical oscillation initiating; and including the status variable into a vector-output of the CRMP.
• the method may include statistically processing each array of valid evaluating variables by an application of a Major Algorithm.
• the method may include performing a set-point level measurement by means of the CRMP with a modified operation Measurement.
• the method may include having the dead zone parameters ⁇ ls and ⁇ 2s being functions of saturation points ⁇ i and ⁇ 2 .
• the method may include applying the CRMP to more than one point on the external wall of the vessel and executing a repetitive CRMP (RCRMP), such that the level of the filling material is measured at several points.
• RCRMP repetitive CRMP
• BMP Basic Measurement Procedure
• the method may include applying a repetitive CRMP (RCRMP).
• RCRMP repetitive CRMP
• the method may include, prior to initializing the mechanical oscillation, mounting elements on the vessel's wall for setting boundary conditions for mechanical oscillation-induced elastic waves propagating in the vessel, to define a linear part of a level measurement system's static transfer operator.
• the method may include receiving at least one acoustical signal originated by an application of at least one percussion within a sequence of operations of a Basic Measurement Procedure (BMP) and calculating an evaluating variable resulting from the BMP using a measured mechanical oscillation and a measured acoustical signal associated with the mechanical oscillation.
• BMP Basic Measurement Procedure
• the method may include performing the LRMP by executing two operations wherein the first operation is an operation of calibration and the second operation is an operation of measurement.
• the operation of calibration for the LRMP may include the steps of: setting an initial value of the filling material level in the vessel; non-tangentially applying the mechanical oscillation to the vessel's external wall at a predetermined point to initiate a transverse wave; capturing an occurrence of the transverse wave at a predetermined transverse wave receiving point; and measuring and storing the value of a time interval denoted ⁇ T* between the moment of the transverse wave initiation and the moment of the wave occurrence capturing, such that the time interval ⁇ T* is associated with a distance between the point of transverse wave initiation and the filling material interface, denoted y*.
• the operation of measurement for the LRMP may include the steps of: non- tangentially applying the mechanical oscillation to the vessel's external wall at a point of a transverse wave initiation; capturing an occurrence of the transverse wave at a predetermined transverse wave receiving point; measuring and storing a value of a time interval denoted ⁇ T between the moment of the transverse wave initiation and the moment of the wave occurrence capturing, such that the time interval ⁇ T is associated with a distance between the point of transverse wave initiation and the filling material interface, denoted y; and calculating the measured level denoted L fm , by the formulas:
• Lfin H - y - d wherein, d denotes a known distance between a top of the vessel and the point of transverse wave initiation.
• Performing the LRMP may include the steps of: arranging for monitoring a presence of a transverse wave at a plurality of receiving points on the external wall of the vessel to compensate for possible variations in propagation speed of the monitored waves through the material of the vessel's wall; non-tangentially applying the mechanical oscillation to the vessel's external wall at the point of a transverse wave initiation; capturing the transverse wave's presence at each wave's receiving point of the plurality of points; measuring and storing each value of a time interval denoted ⁇ T; between a moment of the transverse wave initiation and a moment of the wave capturing at an i-th point of the plurality of points, such that each time interval ⁇ Tj is associated with a distance between the i-th receiving point and the filling material interface, denoted y,; and calculating the level by solving the following system of algebraic equations of the order m:
• L fm denotes the level of filling material in the vessel
• H denotes a height of the vessel
• ⁇ T denotes a vector of time intervals between the moment of the transverse wave initiation and the moment the wave capturing at the i-th point of the plurality of points
• d denotes a known distance between a top of the vessel and the point of transverse wave initiation
• m denotes the number of the transverse wave receiving points.
• the method may include calculating the variable ⁇ T by the formula: wherein, ⁇ T j denotes a travel time obtained at j-th measurement in the series of m measurements.
• the method may also include providing a first impact load at a predetermined load point on an external wall of the vessel to initialize a first oscillation in the wall of the vessel and in the filling material in the vessel; receiving a measure of the first oscillation at a first predetermined receiving point; analyzing the measure of the first oscillation received at the first predetermined receiving point to determine a first evaluating variable; and determining a level of the filling material in the vessel based on the first evaluating variable
• Fig. la is a schematic of the method implementing system of one embodiment of the present invention with in-plane positioning of the striker and the receiver and with the filling material interface below the center of impact;
• Fig. lb is a schematic of the method implementing system of another embodiment of the present invention with coaxial positioning of the striker and the receiver;
• Fig. 2 depicts a simplified non-linear dynamic spring-mass model associated with the Close Range Level Measuring Procedure of the method of the present invention
• FIG. 3 shows a vertical section of a pipe partially filled with a material
• Fig. 4 shows a non-linear static transfer characteristic of the tested measuring system of Fig. 3;
• Fig. 5a depicts an oscillogram of mechanical oscillations in the experimental setting of Fig. 3 for a fiberglass pipe of 3.175 cm (1.25 inches) diameter and
• Fig. 5b depicts an oscillogram of mechanical oscillations in the experimental setting of Fig. 3 for an empty fiberglass pipe of 3.175 cm (1.25 inches) diameter and 3 mm wall thickness;
• Fig. 6a depicts an oscillogram of mechanical oscillations for a pipe filled with water, showing time, frequency and amplitude;
• Fig. 6b depicts an oscillogram of mechanical oscillations for an empty pipe, showing time, frequency and amplitude.
• DETAILED DESCRPTION OF THE PREFERRED EMBODIMENTS [0089] The method of the present invention is based on monitoring the oscillatory motion of the vessel's outside wall; such motion, for example, being initiated by the application of a mechanical load directed at the wall.
• the method utilizes a Close Range Level Measuring
• CRMP Non-invasively measure the level of the filling material within a vessel.
• CRMP exploits the properties of the mechanical dynamic system that includes the wall of the vessel and the filling material near the load point. At a relatively short distance between the load point and the filling material's interface, the oscillation of the mechanical dynamic system, i.e. the "instantaneous associate filling material mass and the instantaneous associate vessel's wall(s) mass,” is used to obtain the level of the filling material measurement.
• the method utilizes a Long Range Level Measuring
• LRMP LRMP
• the method of the present invention provides for automatically switching from the CRMP output to the LRMP output, and vise versa, while producing the measurement.
• the decision on which procedure's output contributes to a valid level reading depends on a joint evaluation of the output of CRMP and the output of LRMP.
• the developed method may be a sequence of the following steps: 1. initializing vibration at at least a single predetermined position on the vessel's outside wall; 2. substantially simultaneously performing CRMP and LRMP; 3. evaluating the output of CRMP and the output of LRMP; and 4. calculating the value of the filling material level in the vessel based on the result of the joint evaluation of the CRMP and LRMP outputs.
• Step 1 includes initializing vibration at at least a single predetermined position on the vessel's outside wall.
• the vibration may originate in the neighborhood of a mechanical impact with its center located on the outside wall of the vessel.
• the impact load's time diagram could be of various forms including a single pulse, a trainload of pulses or a continuous periodical load.
• Each impact load-type of Step 1 may utilize any kind of modulation, for example, Amplitude Modulation, Frequency Modulation, Pulse- Code Modulation or their combinations.
• the particular realization of the vibration- generating load depends on the method's measurement procedures (LRMP / CRMP).
• a mechanical impact at the wall could be originated by the application of any suitable energy source depending on the technical requirements of the particular measurement project. Examples of impact sources include, but are not limited to, a solenoid, a spring, a hydraulic and an air pressure-based drive.
• Step 2 includes substantially simultaneously performing CRMP and LRMP.
• a mechanical vibration captured by the receiver of the measuring system is the input for CRMP and for LRMP. Each procedure executes independently.
• the output of CRMP and the output of LRMP are used jointly to determine the control variable of the method.
• Step 3 includes evaluating the output of CRMP and the output of LRMP.
• the CRMP output and the LRMP output which are used for the evaluation, could be a procedure-relating variable or a vector of variables that allow a decision on the sensitivity of the procedure to be made.
• the CRMP-relating variables compose a vector denoted ⁇ c
• the LRMP-relating variables compose a vector denoted ⁇ L
• ⁇ c ⁇ ! denotes the subset of the CRMP-relating vectors ⁇ c that are associated with the absence of the filling matter in the vicinity of the center of the impact
• ⁇ Cf3 denotes the subset of the CRMP-relating vectors ⁇ c that are associated with the presence of the filling matter in the vicinity of the center of the impact
• ⁇ Lv denotes the subset of the LRMP- relating vectors ⁇ L that are associated with a valid distance measurement between the receiver and the filling material interface
• ⁇ Ln denotes the subset of the LRMP-relating vectors ⁇ L that are associated with an invalid distance measurement between the receiver and the filling material interface.
• Step 4 includes calculating the value of the filling material level in the vessel based on the result of the joint evaluation of the CRMP and LRMP outputs.
• the method of the present invention requires knowledge of the distance between the receiver of vibration and the filling material interface; the distance being denoted y.
• the level of the filling material denoted L ⁇
• H the known height
• the distance y obtained by the execution of the CRMP is denoted y c .
• the distance y obtained by the execution of the LRMP is denoted y L .
• this space includes the body of any mechanical source of the impact and the body of a sensing element if the former is used in some method's application for the mechanical oscillation initiation and the latter is used in other method's application for the mechanical oscillation receiving by being attached to the outside wall of the vessel.
• the source of the impact has a mechanical origin.
• the sensing element is attached to the wall of the vessel.
• a time-dependent mechanical load is applied to the vessel's outside wall by a small moving body of mass m s ; such moving body being called a "Striker”.
• the sensing element that receives the mechanical oscillations resulting from the impact is attached to the vessel's external surface and that it has a mass m r .
• a vessel 16 having a wall contains filling material 12.
• a striker 18 is shown contacting the external surface of the wall of the vessel.
• the striker has a mass, m s .
• a receiver 20 is shown attached to the external surface of the wall of the vessel.
• the receiver has a mass, m r .
• the effective associate mass of the matter that fills the excited space surrounding the center of impact of striker 18 is denoted as item 10.
• the center of the impact is denoted as a dashed line.
• the arrows denote the distance between the center of impact and the filling material interface.
• receiver 20 is shown aligned with striker 18.
• Ci denotes the stiffness of the leg between mass m s and mass m e ;
• m e denotes the associate effective mass of the matter that fills the excited space surrounding the center of the impact.
• the value of m e depends on the container's geometry, the density of the wall(s) and density of the matter inside the space involved in the oscillating process.
• the value of m e also depends on the amount of mechanical energy induced into the filling material through the wall.
• C 2 denotes the stiffness of the leg between mass m r and mass m e .
• ⁇ i and ⁇ 2 denote damping coefficients in parallel with stiffnesses d and C 2 , respectively.
• a substantial non-linearity of the model may arise, on one hand, by the possibility of losing a mechanical contact between the striker and the vessel's wall and, on the other hand, by the possibility of losing a mechanical contact between the vessel's wall and the receiver of mechanical oscillations.
• non-linearity may arise due to the violation of the mechanical medium continuity of the filling material itself, for example, a granulated material.
• the above-mentioned non-linearity is reflected in the spring-mass model of Fig. 2 in the form of two parallel lines, item 22, attached to the beginning end of each spring 24.
• the dimensions of the excited space and the energy relaxation property of the filling matter have a strong inverse relationship, such that the higher the mechanical energy dissipation of the filling material, the smaller the dimensions of the space involved in the mechanical oscillation.
• the filling matter typically is comprised of two major components: gaseous and non-gaseous.
• the gaseous component is air and the non-gaseous component is fluid or loose/solid material with air-filled gaps between solid kernels. Examples of such loose material include cotton web or balls, PVC pellets or seeds.
• the amount of the oscillating matter within a container is associated with the center of the impact and it effectively depends on the level of the filling material and the type of the material.
• the vessel 16 For example, consider the vessel 16 to be a pipe 26 of internal diameter 2-r and wall thickness ⁇ ; such a vessel is depicted in Fig. 3.
• Fig. 3 shows a vertical section of pipe 26 partially filled with a material 12 and air 28.
• the position of the center of impact 14 and all geometrical dimensions of the pipe and the filling material needed for the reasoning of the effective associated mass concept are shown on the drawing.
• a number of the granules do not oscillate due to a high mutual friction between the granules creating an "Oscillon" phenomenon and reducing the effective oscillating space including the pipe walls and the filling material and increasing the frequency of oscillations, respectively.
• the presence of the compressed granulated material in the vicinity of the impact makes that portion of the oscillating space immobile, thereby creating an effect of the rigid attachment that causes the mechanical system oscillate at higher frequencies.
• a combination of different physical processes in the oscillating system of the granulation-filled vessel causes a repeatable observable effect: an increase in the dominant frequency of the vessel's wall mechanical oscillations accompanied by a decrease in the dominant oscillation's logarithmic decrement.
• the brackets create predictable and stable boundary conditions for mechanical oscillations in the vicinity of the center of the impact.
• these brackets had the shape of a half-pipe cut along the pipe's longitudinal axis.
• Each bracket had a length of 150 mm.
• the use of the brackets secured the repeatability and the accuracy of measurement and provided for the linearity of the level measurement.
• the static transfer operator obtained for the tested embodiment is a linear function with saturation at h* « + L , L b denotes the length of the bracket.
• the static transfer characteristic of the tested measuring system is shown in Fig. 4.
• Fig. 4 shows a typical non-linear static transfer characteristic obtained by the method of the present invention of a system wherein the diameter of the vessel is substantially smaller than the length of the vessel.
• CRMP cardiovascular disease
• CRMP includes two major operations: calibration and measurement.
• Calibration includes the following five steps. (To simplify mathematical notations, beginning here, the subscript "c" of the variable ⁇ c will be omitted.)
• BMP Basic Measurement Procedure
• the output of each BMP is the value of the evaluating variable, denoted ⁇ (y), which is directly and unambiguously linked to the position of the filling material's interface relative to the center of the impact.
• the distance from the center of the impact to the filling material interface is denoted y.
• K denotes the slope and ⁇ ° denotes the intercept of the measuring system's static linear transfer operator.
• the measurement operation for CRMP includes the following two steps: a. Performing BMP, which output is the value of the evaluating variable ⁇ (t) obtained at the moment t of time the BMP has been committed. b. Calculating the level of the filling material in the vessel by the following formulas:
• H denotes the height of the center of impact
• Lfm denotes the level of the filling material in the vessel.
• BMP Basic Measurement Procedure
• BMP includes the following four steps: a. applying an impact load toward the vessel's external wall surface, such that the direction of the impact is not tangent to the vessel's external wall surface, passing through the center of the impact and indicating the moment of impact; b. receiving a mechanical vibration that occurs on the external surface of the wall because of the impact; c. measuring primary parameters of the vibration, including, for instance, amplitudes and frequencies, after implementing a predetermined delay from the moment of the impact; and d . calculating the value of the evaluating variable using the vibration primary parameters as input.
• the evaluation variable ⁇ (t) may be the average of the frequencies within a predetermined amplitude range:
• the evaluation variable may be the summation of the sine of the full periods of oscillation within a predetermined frequency range.
• ⁇ m i(t) denotes the evaluating variable obtained by the i-th implementation of BMP
• b m i denotes a weighting factor corresponding with the i-th implementation of BMP
• q denotes the number of implementations of BMP.
• the values of the weighing factors depend on the technical application the method is being applied.
• mechanical oscillations in at least two different points on the external surface of the vessel may be monitored. These points are denoted pi, p 2 , ... p r , with r denoting the number of these points. This approach also improves the accuracy and repeatability of the measurement.
• the validation of the evaluating variable can be based on the criterion of constancy of the difference between the measured distances y pl , y p2 from each point to the filling material interface.
• the method of the present invention requires: a. calculating the evaluating variable per each impact and storing its value for further processing as an element of the series of evaluating variables; b. statistically treating the obtained series of evaluating variables and selecting at least one valid series; c. determining the fact of the filling material presence or absence within the vicinity of the center of impact per each impact; d. applying a Major Algorithm to each valid series of evaluating variables for the determination of the presence or absence of the filling material in the vicinity of the center of impact; e.
• ⁇ (t r ), t] wherein, F[ ] denotes a function defined on the evaluating variables in the valid series, which output is the CRMP's resulting evaluating variable.
• F[ ] denotes the aggregating function defined on the set of evaluating variables obtained at each i-th impact in the valid sequence of r impacts.
• F[ ] denotes the aggregating function defined on the set of evaluating variables obtained at each i-th impact in the valid sequence of r impacts.
• the method's predetermined dead zone parameters denoted ⁇ ls and ⁇ 2s are functions of the saturation points ⁇ i and ⁇ 2 ; s(t) denotes the status variable.
• ⁇ or
• Figs. 5a and 5b depict sample oscillograms of mechanical oscillations for a fiberglass pipe filled with water and an empty pipe, respectively.
• the method for the remote level measurement is based on the repetitive execution of CRMP, denoted RCRMP, and is realizable by a distributed measuring system.
• the distributed measuring system may utilize either a sequential method or a parallel method to determine the measured level.
• the sequential method may include the following sequence of operations: a. installing a single measuring system capable of originating and monitoring wall's oscillation at m predetermined points along the vertical axis of the vessel; b.
• ⁇ i, ⁇ 2 and K respectively denote the upper and lower saturation points and the gain factor of the aggregated transfer operator of the distributed measuring system implementing RCRMP
• y* denotes the spread distance corresponding with the linear part of the measuring system's transfer operator
• H denotes the height of the starting position for the measuring system
• the parallel method may include the following sequence of operations: a. installing a plurality of measuring systems for originating and monitoring the wall's vibration in certain predetermined points along the vertical axis of the vessel; b. substantially simultaneous applying BMP and determining the ordering number of the device, for which condition (19) is satisfied; and c. calculating the measured level using formula (20) where H denotes the height of the receiver's position for the first measuring system.
• LRMP Long Range Level Measurement Procedure
• LRMP could employ any prior art distance measuring method including, but not limited to, pulse- based and continuous echo-processing techniques such as the Pulse Transit Time Method, Phase Difference Method, and Amplitude Change Method as disclosed in U.S. Patent Nos. 5,793,704, 5,822,275, 5,877,997, 6,040,898 and 6,166,995 and other very sophisticated methods developed for seismic analyses [Note Online: Refraction Seismic Methods. www.mines.edu] .
• LRMP will be described below with the assumption that the measurement technique is based on the Pulse Transit Time paradigm. This technique seems to be particularly suitable for vessels with heights greater than 1.0 meter. LRMP can be implemented as a two-step procedure or as a one-step procedure.
• the two-step LRMP includes two major operations — calibration and measurement. Calibration may be accomplished by the following two steps: 1. in the vessel with the known distance denoted y* between the filling material interface and the receiver of vibration, applying a mechanical load toward the vessel's external wall surface such that the direction of the impact is not a tangent passing through the center of the impact and indicating the moment of the impact; and 2. monitoring the reflected wave, measuring and storing the value of the time interval, ⁇ T*, between the moment of the impact and the moment the response to the impact has been indicated, such that the time interval ⁇ T* is unambiguously associated with the distance y*.
• Measurement for the two-step LRMP may be accomplished by the following three steps: 1.
• the one-step LRMP may be accomplished by the following four steps: 1 . installing one or more additional receiver(s) of vibration at one or more predetermined distance(s) from the center of the impact to compensate for possible variations in the speed of the monitored waves propagation through the material of the vessel's wall. Therefore, the measuring system implementing the method is equipped with one master receiver and with at least one compensating receiver; 2. applying a mechanical load toward the vessel's external wall surface such that the direction of the impact is not a tangent passing through the center of the impact and indicating the moment of the impact; 3 .
• the first equation, (22a), represents the relationship between the distance from the master receiver and the filling material interface
• the second equation, (22b) represents the relationship between the distances from a plurality of compensatory receivers and the filling material interface.
• the above system of equations demonstrates one of several well- known approaches to the determination of a physical variable with the use of compensatory measuring devices and serves for the purpose of illustration.
• ⁇ T H - y
• y* and ⁇ T* denote the aggregated calibrating distance and the aggregated calibrating wave travel time obtained with the help of n compensating receivers in the measuring system. It is clear that any kind of filtering or aggregation is applicable to the output of LRMP.
• the variable ⁇ T in the formulas (21) and (23) plays the same role as the evaluating variable ⁇ (t) that was defined in the CRMP.
• ⁇ T can be calculated as follows:
• ⁇ Tj denotes the travel time obtained at the j-th measurement in the series of measurements of number m.
• the method of aggregation depends on the particular application for which the proposed method is being used and is not limited to formula (24).
• the evaluating variables that were defined in the formulas (21), (23) and (24) may serve as components of the vector ⁇ L in the integral description of the method of the present invention; refer to expression (2).
• the above-disclosed method provides for a truly non-invasive measurement of a filling material level in a variety of vessels regardless of the vessel's dimensions and the vessel's material, as well as regardless of the physical properties of the filling matter.
• the present invention may be utilized to determined other physical parameters or properties of the filling material which have an effect on the mechanical oscillations of the system, including, for example, the density of the filling material.

Priority Applications (2)

Applications Claiming Priority (2)

Publications (2)

Family

ID=34738831

Family Applications (1)

Country Status (5)

Cited By (3)

Families Citing this family (34)

Family Cites Families (36)

• 2004
  • 2004-12-23 US US11/020,700 patent/US7162922B2/en active Active
  • 2004-12-23 EP EP04815459A patent/EP1709149A4/en not_active Withdrawn
  • 2004-12-23 BR BRPI0418141A patent/BRPI0418141A2/pt not_active IP Right Cessation
  • 2004-12-23 CN CNB2004800420394A patent/CN100445703C/zh not_active Expired - Fee Related
  • 2004-12-23 WO PCT/US2004/043385 patent/WO2005062945A2/en active Application Filing
• 2006
  • 2006-11-14 US US11/599,505 patent/US7481106B2/en active Active

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events