RU2441367C2 - Method of milk volume measuring in tank - Google Patents

Abstract

FIELD: measuring and refrigeration engineering.

SUBSTANCE: milk is mixed in advance. Then distance from a proximity sensor mounted on an overhead gauge to milk surface is measured. Removable ranging laser with integrated battery power can be used as an overhead gauge. Further, this value is deducted from the distance to the bottom of an empty tank, and milk volume in tank is calculated according to an individual rating table, composed by sequential tank filling from zero to max. level using reference volumeter with 50 litre increment.

EFFECT: increase in accuracy and convenience of milk volume measuring, easy to apply.

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Description

The invention relates to the field of measuring and refrigeration technology and can be used in the food industry, in the agricultural sector and is intended for non-contact measurement of the volume of predominantly chilled milk in sales shipments and purchases at dairies, dairy farms and farms for commercial accounting.

Known devices of the company Endress + Hauser: microwave radar level meters for liquids Micropilot S FMR531, using the registration of the distance from a proximity sensor with a transmitter. directly mounted on the upper bracket of the vertical cylindrical tanks, which are subtracted from the distance from the sensor to the bottom of the empty tank [1]. Prosonic M FMU 40/45 ultrasonic non-contact level gauges are also known [2]. consisting of a sensor and a measuring transducer, made in a single housing, working on the same principle. Westfalia Surge's Kryos milk cooler tanks [3] use an electronic submersible level sensor, with a measuring float and a rod, priced at 1,690 €.

The milk refrigeration unit according to the patent RU 2265322, А01J 9/04, 2005, uses a stainless steel measuring scale graduated through 50 liters as the simplest measuring instrument for the milk volume in the tank [4]. Dropping it through the hatch to the stop, note the level and volume of the product by the depth of immersion in milk on the appropriate division. A similar simple volumetric meter is used in the Westfalia Surge tank variant (without an electronic level sensor). On the other hand, the portable digital laser range finder (CLD) DLL 50 Professional by BOSCH [5] is known, the overall dimensions of which are 58 × 100 × 32 mm. weight 0.18 kg. 1 mm graduation, with built-in batteries, costing 150 €, designed to measure ranges, lengths, heights from the sensor to opaque, non-porous surfaces, using a narrow laser beam. It is used mainly for construction work - a kind of "laser roulette".

Stationary non-contact level meters for liquids Micropilot S FMR 531 and Prosonic M FMU 40/45 use the principle of radar and echolocation, respectively, come with calibration protocols and software, as well as the ability to set your own linearization table to convert the level to volume units. They contain a separate emitter and a programmable LCD display, they are complex, large-sized and expensive for use in milk cooler tanks, especially considering the low qualification of farm staff. In addition, the FMU 40 ultrasonic level transmitter is complicated by a built-in temperature sensor to correct accuracy. A similar disadvantage (complexity and low maintainability) is possessed by the capacitive float sensor of the Kryos tank level [3]. In addition, it is submersible and requires periodic cleaning of the rod and float to maintain accuracy.

The disadvantage of immersion rulers [4] is the low accuracy and tight calculation in liters when applying the scale, which does not allow to take into account the real technological variation (tolerance) of the sizes of each tank individually during its manufacture and calibration. Actual deviations of the diameter, length, height and width of the inner surface of the tanks [3, 4] up to 10 mm lead to errors of tens of liters, which must be taken into account by additional corrective tables. The length of the measuring line of a cylindrical tank of 6000 l is 2 m, which requires high ceilings in the milk collection point (up to 4.5 m) in order to be able to remove a two-meter ruler from the tank with a height of 2.3 m through the hatch. This leads to additional inconvenience in operation.

The closest in technical essence to the claimed invention (prototype) is a method of measuring the level (volume) of milk in the tank. implemented in the Micropilot S FMR 531 level gauge, which consists in recording the distance from the microwave radar sensor with a rod antenna stationary mounted on the upper stop of the tank to the surface of the milk, which is subtracted from the distance from the sensor to the bottom of the empty tank. The sensor (operating frequency 6 GHz) and the instrument’s measuring transducer are made in a single housing, they contain a four-line liquid crystal display with a full-color text menu, software for setting your own table for converting the measured level to liters, settings and linear calibration made at the factory. The base price of the microwave sensor FMR 531 is inclusive of VAT of 4,543 €, which is determined by its complexity and commensurate with the price of the milk refrigeration unit [4], which consists of a tank and a refrigeration unit. The stationary mounting of the sensor on the upper stop of the tank, operating in aggressive environments, forces manufacturers to dustproof design of the nodes, which also complicates and increases the cost of the device. The mass of the sensor (excluding the flange) is 4 kg, and the four-wire connection of the sensor to the display causes stationary separate placement of the sensor and display on the tank, which also makes installation more expensive and complicates the device.

The invention is aimed at simplifying and reducing the cost of measuring the volume of milk in a tank for commercial accounting while improving accuracy and convenience.

The specified technical result is achieved by the fact that when registering the distance from the proximity sensor mounted on the upper stop of the tank to the surface of the milk, which is subtracted from the distance to the bottom of the empty tank, ACCORDING TO THE INVENTION, a removable digital laser range finder with built-in batteries is used as a sensor, moreover before measurement, milk is mixed, and after measurement, the volume is determined according to the individual calibration table of the levels obtained by sequentially filling the tank m zero to a maximum at the reference flow meter with steps, for example, 50 liters.

The invention is illustrated by drawings. Figure 1 shows a diagram of the registration of the level of milk in a cylindrical tank, figure 2 is an individual calibration table of a cylindrical tank with a nominal volume of 3000 l, figure 3 is a drawing of the placement of the upper stop when measuring the level (volume) of milk through a closed hatch, 4 is an assembly drawing of a removable digital laser rangefinder (CLD) with a persistent flag.

The method of measuring volume, V [l]: milk in the tank (Fig. 1) is based on recording the actual distance N _f from the digital laser rangefinder CLD 1 (its upper end 2) to the surface of milk 3 by the laser beam 4, and subtracting this value from the initial the distance B between the CLD 1 and the bottom of an empty tank. To obtain the volume of milk in the tank V [l], an individual calibration table is used to translate the CLD readings 1 N _f [mm] into the milk volume V [l], for example, for a three-ton cylindrical tank of figure 2 with dimensions: D = 2R = 1274 mm - the diameter of the internal cavity of the tank, L = 2560 mm - its length.

The calculated values of H [mm] in FIG. 2 are given for an ideal cylinder with a horizontal reservoir on adjustable supports without taking into account the offset of the reference end 2 of the CRD 1 above the cut of the hatch at a distance of a = 298 mm, including the height of the stop in the shell of the hatch, the size of the stop flag and the length of the sensor itself (100 mm). The calculated dependences V (Н) and Н (V) are obtained by numerical methods from the trigonometric equation of the volume of milk in the tank with a level h = 2R-H:

H>R

H> R

The actual readings of the CLD N _f should be obtained from the results of calibrating the volumes of milk in the tank with a reference meter - flow meter, for example, a cold water meter (CW), passport PDEK.407223.002 PS, manufacturer of the city of Arzamas, CJSC Rosaviaspetskomplekt, nominal flow rate 25 l / min, the division price of the lowest level 1 liter cost - 400 rubles. Measurements of H _f are carried out after 50 l with successive filling of the tank up to the cut of the hatch.

For the convenience of measurement with a closed hatch, the position of which can vary within the flexibility of the elastic cuff of the shell, a fixed flag 5 is fixedly mounted on the removable CLD 1 (Fig. 3, Fig. 4), fixed on the housing of the CLD 1 by a fixing screw 6. When measuring and calibration, the stop flag 5 of the removable CLD 1 through the slot 7 with a rubber shutter in the manhole cover 8 is inserted into the stop 9 welded to the shell 10. Thereby, the distance from the CLD 1 to the milk level is rigidly fixed. For tightness, the measuring holes 11 in the manhole cover 8 are closed by a transparent plexiglass 12 glued to the upper plane of the cover 8. Measurements through the transparent glass 12 performed by the CLD 1 show identical results compared to the open holes 11, i.e. clear glass 12 does not distort the measurement results. CLD 1 is powered by four standard batteries 13 4 × 1.5 V, installed under the housing cover.

When measuring according to the instruction manual, press button 14 (measurement) three times, after which a recorded result appears on display 15, for example, 0.821 m of CRD 1 can be removed from slot 7 and readings that will be held for 5 minutes. To turn off the CLD 1, you can de-energize by pressing the button 16.

When assessing the accuracy of the method, it should be noted that the laser beam 4, due to some transparency of milk, penetrates deep into the surface of level 3 by a distance Δ = 5 mm (Fig. 1) with normal fat content of 3.6 ... 3.8%

Measurements with a DLE 50 Professional BOSCH sensor with a wavelength of 635 nm show that a decrease in milk fat content to 1.5% and 1%, respectively, increase the depth of penetration of the beam Δ to 9 mm and even up to 13 mm, respectively. Milk sludge and the release of cream with a fat content of 15 ... 20% on the surface reduce the penetration of the beam into surface 3 to Δ = 1 mm. Therefore, to increase the accuracy before measuring the milk must be mixed for 1 ... 2 minutes. For this purpose, a stirrer is used in the milk cooler tanks (Fig. 1), ensuring its uniform density (homogenization) throughout the volume during storage. Normal fat content of chilled or paired homogenized milk of 3.6 ... 3.8% ensures stable penetration of the beam Δ = 5 mm at any levels h and actual readings Н _f , regardless of temperature, which guarantees high accuracy and stability Н _f in combination with other constants rigidly determining the position of the reading end 2 of the cylinder head 1 above the cut of the hatch at the time of measurement (a = 298 mm).

For deliveries to farms, the column H _{f of the} calibration table (Fig. 2) contains blank columns and only after the installation of the tank with a slope of 1 ... 2 ° is calibration carried out through the reference meter-flowmeter, therefore, all deviations from the ideal design dependence H _f (V) due to the slope, as well as tolerance fields for the manufacture of the inner cavity of cylinders with a diameter of D = 2R and a length of L, do not affect the accuracy of volume measurement.

Consider measuring the level and volume of milk between the nodal (tabular) points, for example, with N _f = 821 mm at an intermediate level. Note on the calibration table (figure 2) the closest values, for example, H _f = 832 mm and H _f = 87 obtained as a result of calibration, which corresponds to the calculated levels of h = 736 mm and h = 751 mm in a real tank, as well as the volume V = 1950 l and V = 2000 l. Given a piecewise linear approximation between nodal points, the measured volume will be

To reduce the initial error of the Δ method due to the penetration of the laser beam 4 deep into the surface of the milk by Δ = 5 mm, when adjusting the position of the bend of the stop flag 5 in slot 9, the spot of beam 4 should be brought closer to the drain pipe of the tank by 150 ... 200 mm along the longitudinal axis. In this case, the first liter of milk at the initial filling of the tank, taking into account a slope of 1 ... 2 ° towards the drain pipe, will give a level h of the order of 9 ... 12 mm. All subsequent fillings of level h will be linearly recorded with high accuracy (up to 1 mm) in decreasing readings of CPD 1.

Thus, the level h is taken into account with an accuracy of 1 mm, and the volume V - with an accuracy of 1 l. Consequently, the actual accuracy of the method for determining the volume of milk in the tank is due to the accuracy of the reference meter-flow meter, since measurements of the accuracy of the DLE 50 Professional CLD (laser "roulette") at the reference distance show an error of not more than 1 mm within 0 ... 3,000 m.

When delivering reservoirs with TsLD to farms, each product is equipped with SHV - PDEK flow meter and is calibrated according to the table (figure 2) for commercial accounting in the presence of the buyer and seller. The passport error of SHV PDEK.407223.002 PS does not exceed 3%. In controversial cases, the error of the method can be reduced by manually filling the tank with a reference capacity of 50 liters of milk.

Given the limited flow rate (25 l / min) through the standard meter-flow meter СХВ, the sequential filling of a three-ton reservoir through 50 l according to the table (Fig. 2) with 64 control points for recording Н _f using CRD 1 will take about three hours (each point - 2 …3 minutes). Therefore, filling a three-ton tank with milk due to possible losses (acidification) is impractical. To simplify the calibration of the tank, the kit also comes with a plastic plate made of polystyrene with a thickness of 3 mm, a depth of 20 mm and a diameter of 200 mm, which is filled with 6 ... 8 mm whole milk. It is installed on the bottom of an empty tank under the laser beam 4 of the CLD sensor 1, which penetrates deep into whole milk at the mentioned constant Δ = 5 mm. Sequentially filling the tank with water through the storage water at a flow rate of 25 l / min, shut off the tap every 2 minutes and take readings from CPL 1 after 50 l. A plate on the water pops up, while the level of milk in the plate, to a fraction of a millimeter, coincides with the level of the water, and the measurement with a laser beam 4 using the CLD completely simulates a reservoir filled with milk. Thus, in the process of calibrating the tank, the exact volume of water is set through 50 l using SHW and the milk level N _f in the floating plate is measured with a high-precision CLD 1, with the results recorded in the table (figure 2). We obtain an exact correspondence of the level N _f [mm] to the volume of milk V [l] in the tank, and the manufacturing errors of the tank and the adjustment of its slope do not affect the measurement accuracy.

The advantages of the method include the absence of direct sunlight in closed milk cooler tanks, which can distort the results of laser measurements.

The advantage of the proposed measurement method over the simplest measuring ruler with engraved levels applied after 50 l is its high accuracy, which excludes measurements of the manufacturing of the tank and its slope adjustment during installation on farms. The overall dimensions of the CLD with a persistent flag are much smaller than the measuring line and do not require high ceilings when measuring. In addition, there is no need to open the hatch in the mode of recording the level of milk volume, while the integrity of the tank is not violated.

Compared with the prototype (microwave radar level transmitter FMR 531), the advantages of the proposed method are a significant simplification of the design, reducing the size, reducing the cost by an order of magnitude, ease of measurement, calibration and maintenance. Obviously, the prototype, like the proposed method, needs to be calibrated to improve accuracy, however, to implement this it still requires appropriate software, built-in reprogrammable memory devices, appropriate staff qualifications and microcomputer support, which is unrealistic in the conditions of Russian farms . A big advantage of the proposed method is the quick-detachable design of the sensor, in contrast to the built-in rod antenna of the prototype, which allows storing the CRD between measurements in normal climatic conditions.

Thus, the use of the proposed method for measuring the volume of milk in the cooler tanks can significantly improve the accuracy of its commercial accounting during storage and delivery. It is possible to realize this by the simplest means and at affordable prices for peasants (about 1 ... 3% of the cost of a complete supply).

That is why immediately after the introduction of this method into the products of Scientific Research Institute Avtomat LLC (Kovrov), 30% of orders for open and closed milk cooler tanks from December 2007 are completed with laser digital rangefinders DLE 50 Professional with counters and flowmeters СХВ ПДЕК.407223.002 PS, calibration table and plastic plate-float.

Literature

1. Micropilot SFMR 531 microwave radar level gauge for non-contact level measurement of liquids. In the book of Chelyabinsk Teplopribor Plant OJSC: 2006, 454047, Chelyabinsk, ul. 2nd Paveletskaya 36: dealership ENDRESS + HAUSRR. pg. 267-269; website http: www.tpchel.ru.

2. A compact ultrasonic level gauge for liquids Prosonic M FME 40. Book of Chelyabinsk Teplopribor Plant OJSC: 2006, 454047, Chelyabinsk, ul. 2nd Paveletskaya 36: dealer center ENDRESS + HAUSER. p. 271-272: website: www.tpchel.ru.

3. Tank milk cooler Kryos Westfalia Surge. 2006 Advertising Booklet p. 2. 3, 6, website: www.westfalia surge.ru. Moscow, ul.Semenovsky Val, 6, building 1, tel. 937-57-63.

4. Milk refrigeration unit. Patent RU No. 2265322, A01J 9/04, 2005

5. Digital laser rangefinder DLE 50 Professional. BOSCH. Operating Instructions, pp. 143-150. In Russian. LLC "Robert Bosch". Service center for the maintenance of power tools. 129515, Moscow, Academician Korolev St. 13, building 5, tel. 935-71-93, website: www.bosch-pt.com.

Claims (1)

The method of measuring the volume of milk in the tank, which consists in recording the distance from the proximity sensor mounted on the upper stop to the surface of the milk, which is subtracted from the distance to the bottom of the empty tank, characterized in that the sensor uses a removable digital laser range finder with built-in battery power, moreover, the milk is mixed before the measurement, and after the measurement, the volume is determined by the individual calibration table of the levels obtained by sequentially filling the tank from zero to about the maximum through the reference counter-flowmeter with a resolution of, for example, 50 l.

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