RU2750059C1 - Apparatus for grading volume flow meter pairs in heat meters for closed and open heat supply systems and method for implementation thereof - Google Patents

Abstract

FIELD: heating.SUBSTANCE: apparatus is intended for flow-line individual and pairwise grading (verification) of pairs of volume flow meters used in heat meters for closed and open water heat supply systems. The apparatus is comprised of supply and return pipelines and three reference volume flow meter units. The first reference unit is connected to the beginning (inlet) of the supply pipeline and measures the set flow value. The second (bypass) reference unit overlaps the measuring section of the return pipeline containing the verified (calibrated) volume flow meters and a controlled adjusting valve. The unit is connected to the return pipeline by two shut-off valves. The third reference unit similar to the second unit is connected to the supply pipeline. Part of the flow (accurately measured by the comprised reference flow meters) can be passed through the bypass units bypassing the graded (calibrated) flow meters located on one of the pipelines (supply or return) creating a set and accurately measured value of flow difference. The set value of volume water flow difference, positive or negative, is set by a part of the water bypassing the graded flow meters being passed by a controlled adjusting valve on the return (supply) pipeline through the corresponding reference bypass unit where the flow value is corrected by the controlled adjusting valves according to the readings of the reference flow meters of this unit to be as close as possible to the value of said flow difference. The operation of determining the value of flow difference by the measured value difference by the graded flow meters exhibiting an unacceptably large flow difference measurement error component is not executed therein.EFFECT: increased productivity and accuracy of grading of pairs of identical volume flow meters of any type within heat meters in reproducing volume flow differences in direct and return pipelines of water heat supply systems (WHST).5 cl, 5 dwg

Description

The invention relates to experimental measuring equipment and can be used at energy facilities, oil, chemical industry, housing and communal services, etc., where water heating systems are used.

A device for calibrating and evaluating the measurement error of flow meters is known. The block diagram of the flow meter calibration when the open heat supply system contains volumetric flow meters (water meters) of the supply and return pipelines, a hot water supply meter and a heat exchanger. The water meters and the heat exchanger are connected in series with each other. The water meter in the channel (water pipeline) of the hot water supply through two controlled valves of the direct and return water pipelines are connected in parallel with the direct and return channels (pipelines). The device of an open system is divided into two groups: an open one, consisting of two controlled valves and a hot water meter, and a closed one with leaks (water flow), consisting of two water meters and a heat exchanger. At the same time, in an open subsystem, the amount of coolant in the water supply is determined by the indication of the water meter in this channel, and the amount of heat energy according to the equation for a one-pipe heat supply system.

This solution allows you to calibrate volumetric flow meters of the coolant in different industries (How to reduce the measurement of heat energy and coolant leakage. Journal. Legal and Applied Metrology. No. 5, 2002 pp. 6-13, author I.Yu. Sheshukov).

Disadvantages of this device: the secondary device of the heat meter must correct the readings of the water meters, which increases the operating costs. The difference between the value of the new and old corrections is large and corresponds to an additional error in determining the amount of leakage. There is no standard and two flow meters are compared with each other, hence the high flow rate of the heat carrier has a high error of ± 10%, etc.

There is no possibility of in-line calibration of flow meters at each metering unit, when the conditions of use change, it is necessary to calibrate individually, which is associated with large time costs. Only authorized persons can re-calibrate flow meters for commercial settlements. During the calibration of flow meters, inconveniences arise associated with the termination of the heat supply to the consumer.

A known method of calibrating volumetric flow meters of the coolant and determining the error in the amount and flow rate of the coolant.

Determine the thermal energy according to the equation for a one-pipe device for heating hot water supply (DHW); Q _DHW = [h _{1 (2)} -h _x ] V ₃ ρ _{1 (2)} , where V ₃ is the volume according to the indication of the DHW water meter; ρ _{1 (2)} - density of water in the forward (return) pipeline; h _{1 (2)} - specific enthalpy of water in the forward (return) pipelines; h _x - specific enthalpy of cold water at the heat source.

The total amount of coolant leakage in the device is defined as: G = G _DHW + G _y, where G ^_ mass _DHW heat carrier selected on the WAN; G _y - coolant leak in the closed subsystem of the device.

Then the total amount of consumed energy in the closed subsystem of the device with leaks is determined. Then, the total error of the thermal energy is defined as: = δQ (δQ ⋅Q _{GVS GVS} + δQ _memory ⋅Q _3y / Q), where δQ _DHW and δQ _memory - the relative error in the subsystem and WAN devices in a closed subsystem of device leakage. The total amount of consumed thermal energy in the device is determined as: Q = Q _DHW + Q _ZU , where is the amount of thermal energy in the closed subsystem of the device with leaks.

This solution allows you to calibrate the volumetric flow meters of the coolant (How to reduce the error in measurements of thermal energy and coolant leakage. Journal. Legislative and Applied Metrology No. 5, 2002, pp. 6-13, author. I.Yu. Sheshukov).

The disadvantage of this method is that it is difficult to implement this method without additional typical techniques. For this, it is necessary to carry out a major reconstruction of the existing metering units and significantly complicate the design of the newly introduced metering units for heat energy and the amount of coolant. In addition, high costs for implementing the method in everyday life do not completely eliminate large errors in the conversion coefficient of flow meters.

A device for calibrating and evaluating the measurement error of flow meters is known. The device contains flow meters in the direct and return channels (pipelines). The diameters of pipes in the direct (direct) and return channels are the same (32 mm). A flow meter with a nominal diameter of 10 mm in the bypass channel simulates changes in the hot water supply (DHW) pipeline (channel). Scales are connected at the outlet of the return pipes and DHW channels. The value of the flow rate of the coolant through the flow meter of the hot water supply channel varied from 0.09 t / h to 2.8 t / h. In this case, the value of the flow rate of the flow meter of the direct channel was selected in such a way that the value of the flow rate of the return channel was constant. The measurements were carried out continuously for three days.

The maximum discrepancy with the weights is 23.3%, through direct pipelines 2.2%, reverse 3.3% and hot water supply 23.4%.

This solution allows you to calibrate volumetric flow meters and evaluate the calibration errors in open and closed heat supply systems (Methodical error in linear approximation of flow meter error characteristics. In the book symposium "The world of measurements. Water, heat, gas, November 9-11, 2004" Collection reports, St. Petersburg, 2004, pp. 138-148, authors A.G. Safin, V.M. Kuzovkov).

The disadvantage of this device: the measured value of the coolant leakage according to the difference between the readings of the flow meters of the direct and return channels up to 20% differs from the readings of the flow meter of the DHW channel, although the errors of all flow meters according to the results of individual calibration do not exceed ± 2%. The accuracy of determining the mass of the coolant leakage depends on the slope of the calibration characteristic of the DHW channel.

A known method of calibrating volumetric flow meters of the coolant and determining the error in the amount and flow rate of the coolant.

The essence of determining the volumetric flow rate of the coolant and assessing the measurement error is provided as follows.

- Determine the characteristics of the mutual discrepancy of the measurement results along the channels (pipelines).

- Analyze the measurement errors of the difference in flow rates, carried out using a linear approximation.

- Determine the thermal energy and the flow rate of the heat carrier in the heating system with an open water taps in a straight pipeline. The consumption of thermal energy Q for such a device is determined as: Q = M ₁ (h ₁ -h ₂ ) + (M _DHW -M _y ) (h ₂ -h _XB ), where M ₁ is the mass of the heat carrier passing through the supply pipeline; h ₁ , h ₂ - enthalpy of the coolant in the direct return pipelines, respectively; M _{DHW is the} mass of the coolant according to the indication of the water meter selected for the needs of DHW; M is the mass of the coolant leak; h _XB - cold water enthalpy.

- The mass of the leak is determined as: M _y = M ₁ -M ₂ -M _DHW , where M ₂ is the value of the mass of the coolant that has passed through the return pipeline.

- Together they solve the equations for Q and M _y and determine the consumption of thermal energy in systems with an open draw-off, i.e.

Q = M ₁ (h ₁ -h ₂ ) + (M ₁ -M ₂ ) (h ₂ -h _XB ).

- The operation of the heat meter is monitored by determining the dependence of M _DHW on the increment of M ₁ under the assumption that M _DHW does not depend on M ₂ , i.e. the device is idealized.

и построение зависимости М от

.- The second approach is artificial. Bring a device to a closed one using the expression

and plotting the dependence of M on

...

- Further, it is assumed that the increment of the value y depends on the increment of the value x in accordance with the expression: y _i -y _{i + 1} = x _i -x _{i + 1} + Δ (x _i ) -Δ (x _{i + 1} ), where Δ (x) - the relative position of the quantities x and y.

. Если величина взаимного расхождения не зависит, расположены величины х, то угол наклона всегда равен единицы. В этом случае невозможно оценить взаимное расположение показаний. Если Δ(x_i)=δx_i, то угол наклона прямой характеризует величину взаимного расхождения β=1+δ. Если величина взаимного расхождения переменна, то угол наклона зависит от характера этой зависимости.In this case, the angle of inclination between the two values x and y is finally determined as:

... If the value of the mutual discrepancy does not depend on the values of x, then the angle of inclination is always equal to unity. In this case, it is impossible to assess the relative position of the readings. If Δ (x _i ) = δx _i , then the angle of inclination of the straight line characterizes the value of the mutual divergence β = 1 + δ. If the magnitude of the mutual discrepancy is variable, then the angle of inclination depends on the nature of this dependence.

по выражению:

где

Зависимость β_i от k почти гиперболическая.- It is assumed that at the points x _{i the} relative position of the values x and y is equal to Δ (x _i ) = 0.001x _i ; and at the point x _{i + 1} -Δ (x _{i + 1} ) = 0.009x _{i + 1} . Then the angle of inclination depends on the width

by expression:

Where

The dependence of β _i on k is almost hyperbolic.

This method allows you to calibrate volumetric flow meters for heat meters and evaluate the errors of their measurements in open and closed heat supply systems (Methodical error in the linear approximation of the characteristics of the error of flow meters. In the book. Symposium `` World of measurements. Water, heat, gas. November 9-11, 2004 ''. Collection of reports. St. Petersburg, 2004, pp. 138-148. Authors Safin A.G., Kuzovkov V.M.).

The disadvantages of this method for determining the flow rate of the coolant and assessing the measurement error are as follows. Replacing direct measurements of M _DHW with indirect measurements is mathematically equivalent, but not metrological. Determination of the mass of the coolant taken from the heat supply system based on the difference between the measured values of M ₁ and M ₂ can lead to a rather large methodological error in determining the mass of the coolant taken from the heat supply system.

The closest to the proposed invention, the technical solution is a device for calibrating pairs of volumetric flow meters of the coolant and assessing the error of its measurement.

This device contains pipelines direct, return and a block of bypass (reference blocks) open water heat supply systems. In the forward and return pipelines, one-by-one volumetric flow meters are connected in series. The volumetric flowmeter is connected in parallel with the volumetric flowmeter in the return pipeline, at the outputs of the return and bypass pipeline unit, a tank and a scale are connected. The device also contains at least one pair of volumetric flow meters, a controlled regulated return pipeline valve (OT), and a group of elbows. One or more volumetric flow meters are connected to each other in pipelines. Forward and return pipelines are separated by a group of elbows. At the beginning and at the end of the return line, controlled valves of the return line are connected. Each bypass pipeline with a return pipeline is connected in parallel through controlled variable valves, one or more parallel branches of the bypass pipelines. Controlled adjustable OT valves are connected in series with at least two volumetric reference flow meters in each branch of the bypass pipeline. In the device, water flows from the circulating tank into the measuring pipeline. A block of volumetric reference flow meters is connected to the inlet of the supply pipeline. And from the outlet of the return pipeline, water enters the original standards of volumetric flow rate, consisting of flow switches and volumetric measuring devices. All controlled and signal outputs of volumetric flow meters and controlled valves are connected to the indicator inputs.

Such a constructive solution makes it possible to calibrate pairs of volumetric flow meters and evaluate the calibration errors in open heat supply systems (Patent of the Russian Federation No. 2296959 '' Method for calibrating volumetric flow meters of a heat meter and a device for its implementation. '' Authors V.Yu. Teplyshev, M.N. Burdunin, A.A. Vargin).

The disadvantage of the proposed device is the inability to reproduce negative values of the difference in volumetric flow rates in this device (when the volumetric flow rate in the return pipeline exceeds the volume flow rate in the direct pipeline), since in practice such situations are not rare, especially in closed heat supply systems.

The closest to the proposed invention, the technical solution is a method of calibrating a pair of volumetric flow meters of the coolant and assessing the error of its measurement.

, а наибольшее

, где L искомое расстояние точки измерения до ближайшей градуировочной характеристики пары расходомеров по разности объемных расходов, L' - оценка наименьшего из возможных значений L, L'' - оценка наибольшего из возможных значений L. Расхождение показаний расходомеров в прямых и обратных каналах 20%. Точность определения расхода теплоносителя зависит от угла наклона градуировочной характеристики канала ГВС и числа точек, в которых проводилась градуировка.The main essence of the method for calibrating a pair of volumetric flow meters for heat meters of open water heat supply systems are as follows: Determine the volumetric flow rates. Reproduce, passing the coolant, in the direct, return and bypass pipelines (reference block). And, the conversion factors of the verified pairs of volumetric flow meters are determined. According to the readings of the volumetric reference flow meters, the volumetric flow rates in the direct pipeline are set. According to the indications of volumetric reference flow meters on bypass pipelines (reference blocks), discrete values of the positive difference in volumetric flow rates in the direct and return pipelines are set. It is determined that the characteristics of the calibrated pairs of volumetric flow meters are identical and linear. Each flowmeter is calibrated individually and in pairs. According to the readings of the flow meters of the reference blocks, the flow rate in the direct pipeline and the positive difference in volumetric flow rates in the forward and return pipelines are determined. With the help of an adjustable controlled flow valve, the bypass block is supplied with a flow slightly higher than the required value of the difference in flow in the forward and return pipelines. In this case, a family of calibration characteristics of the channel for direct measurement of the positive difference in flow rates in rectangular coordinates is built. Efforts to improve the accuracy of measuring volumetric flow rates by calibrating a pair of volumetric flowmeters with linear calibration characteristics. And direct measurement of the positive difference in volumetric flow rates in the direct and return pipelines from the value of the realized positive difference in the volumetric flow rates of the coolant. In this case, for a pair of flow meters, the dependences of the volumetric flow rates in the forward and return pipelines, on the output signals (voltage), are simultaneously determined. A direct measurement of the positive difference in flow rates is performed by the directly reproduced value of this positive difference in flow rates with a minimum specified error and flow averaging time for the m-th number of output voltages of volumetric flow meters. The dependence of the output voltage of the flow meter of the supply pipeline on the output voltage of the flowmeter of the return pipeline is plotted at predetermined errors of the reproduced differences in flow rates. Graphically show that the smallest possible error is

, and the greatest

, where L is the desired distance of the measuring point to the nearest calibration characteristic of a pair of flow meters based on the difference in volumetric flow rates, L 'is the estimate of the smallest possible value of L, L''is the estimate of the largest possible value of L. The discrepancy between the readings of flow meters in the direct and return channels is 20%. The accuracy of determining the flow rate of the coolant depends on the angle of inclination of the calibration characteristic of the DHW channel and the number of points at which the calibration was carried out.

This method is measured, allows you to calibrate pairs of volumetric flow meters and evaluate the calibration errors in open heat supply systems (Patent of the Russian Federation No. 2296959 "Method for calibrating volumetric flowmeters of a heat meter and a device for its implementation." Authors V.Yu. Teplyshev, MN Burdunin , A.A. Vargin).

The disadvantage of the proposed method is the inability to obtain a joint calibration characteristic of a pair of heat meter flow meters, with negative values of the difference in volumetric flow rates, which does not allow obtaining reliable measurement results. Especially in conditionally closed heat supply systems, since it is in them that the unfavorable consequences from the ratio of individual errors of flow meters with different signs are most significantly manifested. Moreover, the unfavorable combination of individual calibration characteristics of both flow meters of a pair, which can manifest itself under operating conditions and lead to a significant measurement error in the difference in volumetric flow rates, is not known in advance, is random and cannot be predicted. At the same time, this is the reason for the unreliable results of measurements of the values of the mass of the coolant taken from the heating network (normally and / or with leaks), and, as a consequence, heat energy.

The objective of the present invention is to improve the productivity and accuracy of calibration of pairs of volumetric identical flow meters of any type in the composition of heat meters when reproducing the differences in volumetric flow rates in the forward and return pipelines of water heat supply systems (WST). The accuracy of the calibration of pairs of volumetric flowmeters is increased due to the direct measurement of the positive and negative difference in volumetric flow rates in the direct and return pipelines. Taking into account the measured value of the difference in volumetric flow rates, the value of the mass of the coolant lost with leaks in the conditionally closed VST is calculated. or selected for hot water supply in open TSA. The productivity of the device is increased due to the simultaneous calibration of a batch of pairs of volumetric flow meters. For direct and return pipelines, both conditionally closed and open VST.

The technical result is achieved by the fact that in a device for calibrating pairs of volumetric flow meters of heat meters, for closed and open heating systems, containing a direct, return pipelines, a controlled control valve of a return pipeline, two series-connected bends, a circulating tank, a measuring section, graduated pairs of volumetric flow meters, outlet pipeline, suction pipeline, injection block, block of the initial standard containing a distributor directing the water flow, two distribution pipelines, two water flow switches, two measuring tanks, two drain pipelines, the first, second reference blocks, an indicator, the first reference block contains at least two reference systems in each of at least two volumetric flow meters and a controlled control valve of the first reference block, the bypass second reference block contains at least two reference systems, each of which contains at least two volumetric flow meters and a controlled control the valve of the second reference block, shut-off valves that connect it to the return pipeline and provide or stop the water supply, the direct and return pipelines can be separated by a group of elbows or pulled in one line, the pipelines, direct and return, contain graduated pairs of volumetric flow meters from one pair and more, at the outlet of the return pipeline, a controllable control valve of the return pipeline is connected, at the inlet to the direct pipeline, the first reference unit is connected, into which water is supplied from the return tank by a blower through the suction pipeline, and in the process of calibrating volumetric reference flow meters, water enters through the outlet pipeline into the block of the initial standard, either into the measuring tank, or through the drain pipelines into the circulating tank, the block of the initial standard contains a water flow distributor, which, depending on the measured flow rate, directs water through the corresponding guide pipeline into the measuring tank of the corresponding volume, in which, when a command for measurement is given, the flow is directed by the appropriate water flow switch, all the controlled and signal outputs are connected to the indicator; in it, a third reference bypass unit is additionally introduced, a controlled control valve of the third reference unit, two stop valves, and the third reference bypass unit contains at least two reference systems, each of which contains at least two volumetric flow meters, a controlled control valve of a straight pipeline, both stop valves are connected to a straight pipeline, these valves are fully open or closed, then the water flow is either present or absent, the control variable valve of the third reference block is on the straight pipeline ensures the availability of water flow rate in the third reference block, and controlled control valves of the forward and return pipelines on the reference systems provide the set value of the negative difference in flow rates.

The technical result is achieved by the fact that in the method of calibrating pairs of volumetric flow meters, heat meters, for closed and open heat supply systems, which consists in creating the first operating mode of the device calibration: at the same volumetric water flow rates in the direct and return pipelines, this means at a zero difference in volumetric flows Δq = 0 in the direct and return pipelines, for calibrated pairs of volumetric flow meters at the measuring section by the direct measurement method, according to the developed algorithm and program, the direct method is implemented, measuring the difference in volumetric flow rates at Δq = q ₁ -q ₂ = 0, the values of the output signals are obtained from the outputs of volumetric flow meters on the forward U ₁ and return U ₂ , pipelines, for this, the control valve of the return pipeline on the return pipeline is fully opened, and the stop valves on the second reference block are completely closed, while also plotting the dependences of the output signals of the flow meter located on the return pipes line U ₂ , from the value of the signal from the flow meter on the direct pipeline U ₁ at each of the given values of flow rates in the forward and return pipelines and the difference in volumetric flow rates equal to zero Δq = 0, a calibration characteristic is obtained in the form of a straight line, it is entered into the indicator; reproduce the second mode of operation of the device, set the leaks of the coolant with the difference in volumetric flow rates of water in the forward and return pipelines greater than zero: Δq = q ₁ -q ₂ > 0, while the pairs of volumetric flow meters at the measuring section are calibrated by the method of direct measurement of the positive difference of flow rates by values, directly reproducible: the first reference block - the flow rate values in the direct pipeline q ₁ and the second reference block - the values of the difference in water flow rates Δq, with a predetermined small error, then the reproduced value of the flow rate difference Δq is associated with the output signals from each pair of calibrated flow meters: in the forward - U ₁ and return - U ₂ pipelines, which are brought into the indicator, set the values of the difference in volumetric flow rates of water greater than zero Δq = q ₁ -q ₂ > 0, set by the fact that a controlled regulating valve of the return pipeline on the return pipeline, a part of the water, bypassing the calibrated flowmeters on the return pipeline, passed through the second e a coupon block, where this flow rate value controlled by the control valves of the second reference block in the second reference block is corrected according to the readings of the reference flow meters of this block, as close as possible to the value of the set flow rate difference, a third operating mode of the device for calibrating pairs of volumetric flow meters is created in it - a negative flow rate difference in the direct and return pipelines, for this purpose, the volumetric flow rate of water is set in the return pipeline, which is greater than in the direct pipeline -Δq = q ₁ -q ₂ <0, the calibration characteristic is -Δq = q ₁ -q ₂ = ΔAq (U ₁ , U ₂ ) each pair of volumetric flow meters installed on the measuring section is obtained at the given values of the negative difference in volumetric flow rates -Δq = q ₁ -q ₂ <0 depending on the output signals of the calibrated pair of volumetric flow meters: where U ₁ is the voltage from the output of the volumetric flow meter on the direct pipeline and U ₂ - return pipeline, set a negative difference in volumetric flow rates in the forward and reverse pipelines with a fully open valve on the return pipeline and closed stop valves on the second reference block, cutting off the second reference block, that is, they create a completely unobstructed flow of the coolant through the return pipeline, then with a fully closed controlled control valve of the forward pipeline on the direct pipeline and open stop valves at the third reference block, the volumetric reference flowmeters of the third reference block are pre-calibrated according to the initial standard with the limits of the permissible relative error of volumetric reference flowmeters negligible compared to the permissible limits of the relative error of the calibrated volumetric flowmeters, the specific values of the negative difference in water flow rates in the direct and return pipelines are set as follows : by means of a controlled regulating valve in a straight line in a straight line a water flow rate corresponding to a reproducible volume difference volumetric flow rates are fed into the third reference unit, bypassing the calibrated flowmeters located on the direct pipeline, for this purpose, the third reference unit is first fed with a water flow rate slightly greater than the required value of the difference in volumetric flow rates Δq _j , then the required value of the negative difference in volumetric flow rates is set by controlled control valves the direct pipeline, the return pipeline and the third reference block, according to the readings of the volumetric reference flow meters located in the third reference block, are brought as close as possible to the set value of the negative difference in the volumetric flow rates of water, and, when performing the first stage, to completely fill the device with a coolant, open the controlled control valve of the direct pipeline on the direct pipeline and open the shut-off valves on the third reference block, at the second stage when the difference in flow rates in the forward and return pipelines is equal to zero Δq = q ₁ - q ₂ = 0, close the shut-off valves on the third reference the block and the control controlled valve of the direct pipeline on the straight pipeline are fully open, at the third stage, when the difference in flow rates in the forward and return pipelines is greater than zero Δq = q ₁ - q ₂ > 0, the controlled control valve on the straight pipeline is fully open, and the stop valves are fully open in the third reference the block is completely closed.

FIG. 1a shows a block diagram of a device for calibrating (checking) pairs of volumetric flow meters for heat meters and its individual units of FIG. 1b. FIG. 2 to FIG. 4 shows the calibration characteristics of a separate pair of flow meters by the method of direct measurement of the difference in volumetric flow rates obtained using the proposed device and estimates of the limits that make up the errors of the measuring channel of the difference in flow rates arising from such a calibration.

The block diagram of FIG. 1a device for calibrating pairs of volumetric, for example, electromagnetic flowmeters, contains a straight 1 return pipeline 2, (for general consumption they are used with nominal diameters from DN 15 to DN 300), a controlled control valve of a straight pipeline 3, two bends 4 connected in series (at least two bends 1 'and 2'), circulating tank 5, measuring section 6, graduated pairs of volumetric (for example, electromagnetic) flow meters 7-10, controlled control valve of the return pipeline 11, outlet pipeline 12. Suction pipeline 18, pumping block 19, block an initial standard 20 containing a distributor 21 directing the flow of water, depending on the flow rate into the directing pipelines 21 'or 21' ', two flow switches 22, 23, two measuring tanks 24, 25, two drain pipelines, 24', 25 ', the first , second, third reference blocks 26, 26 ', 26 ", indicator 38. The first reference block 26 of FIG. 1b, the second reference block 26 'and the third reference block 26' 'are arranged similarly. The first reference block 26 contains at least two reference systems in each of at least two volumetric flow meters 27 and 28 or 31 and 32 and a controlled control valve 29 of the first reference block and 30, the second reference bypass block 26 'contains at least two reference systems, each of which contains at least two volumetric flow meters 13 and 14 or 13 'and 14', a controlled control valve of the second reference block 15 or 15, shut-off valves 16 and 17, which connect it to the return pipeline. These valves are fully open or closed for the passage of water, i.e. the presence or absence of water consumption is ensured. The third reference bypass block 26 '' contains at least two reference systems, each of which contains at least two volumetric flow meters 33 and 34 or 33 'and 34', a controlled control valve of the third reference block 35 or 35, shut-off valves 36 and 37, which connected to the supply pipeline. These valves are fully open or closed for the passage of water, i.e. the presence or absence of water consumption is ensured.

The number of parallel branches with reference systems of flow meters in the first, second and third reference blocks 26,26 'and 26' 'depends on the problem being solved. The second and third reference bypass units 26 'and 26' 'have piping with smaller nominal diameters (typically DN 5 to DN 25) than the first master unit, which can have piping nominal diameters up to DN 100 or greater.

Pipelines 1 and 2 can be separated by a group of elbows 4, or extended in one line. The supply and return pipelines 1 and 2 (or channels 1 and 2) of open VST (OVST) or conditionally closed VST (UZVST) contain in each channel calibrated pairs of volumetric flow meters 7 - 8, 9 - 10 from one pair or more. At the outlet of the return line 2, a controllable control valve of the return line 11 is connected, which regulates the coarse water supply to the second reference block 26 'from zero to the highest value of the flow rate of water or heat carrier (heated water).

At the inlet to the straight pipeline, the first reference block 26 is contained, into which water is supplied from the circulating tank 5 by the blower 19 (pump) through the suction pipeline 18.

The largest number of calibrated pairs of flowmeters (on pipeline 1 there are flowmeters from the direct pipeline, and 2 from the reverse) depends on the dimensions of the device and the dimensions of the seats for each flowmeter, taking into account the required lengths of straight sections before and after the flowmeter in Fig. 1a.

In the process of calibrating volumetric reference flow meters 13, 14, 13 ', 14', as well as flow meters 27, 28, and 31, 32, water flows through an additional pipeline 12 into the unit of the initial standard 20, into the measuring tank 25 or 24, or through the drain pipelines 25 ' or 24 'into a circulating tank 5. The block of the initial standard 20 contains a water flow distributor 21, which, depending on the measured flow rate, directs water through a guide pipe 21' or 21 '' to a measuring vessel 25 or 24 of the corresponding volume, into which, when a command for measurement is given the flow is directed by the corresponding flow switch 22, 23. During a predetermined time (usually from 30 to 180 s), determined by the operator, based on the filling time of the reference vessel (measuring vessel) 25 or 24, water will flow into the measuring vessel, and then, when commands to the end of the measurement switch 22 or 23, will direct the flow through the drain lines 25 'or 24' into the return tank 5.

In the original reference block 20, instead of measuring tanks 25, 24, tanks can be used, in which the mass of the incoming water is determined using a scale and then converted into volume.

From the circulating tank 5 through the suction pipeline 18, water enters the measuring section 6 through the first reference unit 26 when pumped by the unit (pump) 19.

As a result, the first 26 and second 26 'reference blocks are calibrated against the initial reference flow rate 20, and only if the volumetric flow rate in the return pipeline is less and / or equal to the volumetric flow rate in the forward pipeline, i.e. there is a difference in volumetric flow rates positive or equal to zero, Δq = q ₁ -q ₂ > 0. The zero difference in flow rates is obtained with a fully open controlled control valve OT 11 and with closed shut-off valves 16-17. To obtain a positive difference in flow rates Δq = q ₁ -q ₂ > 0, shut-off valves 16-17. are fully open, and the controlled control valve OT 11 is partially closed, for the flow of a part of the water flow, bypassing the volumetric flow meters 9, 10, on the return pipeline to the second reference block 26 ', which contains the volumetric reference flowmeters 13, 14, 13', 14 'and the controllable control valves of the second reference fine tuning unit 15, 15 'of FIG. 1a. The flow rate of water passing through the second reference block 26 'is accurately measured using volumetric reference flow meters 13, 14, 13', 14 '.

A distinctive feature of the proposed device, FIG. 1a for the calibration of pairs of volumetric (electromagnetic) flow meters from the prototype is the introduction of a third reference bypass block 26 '', a controlled control valve of the direct pipeline 3, shut-off valves 36, 37 to reproduce the negative difference in flow rates in the direct and return pipelines. This makes it possible to determine the calibration characteristics of pairs of volumetric flow meters 7, 9 and 8, 10 for heat meters additionally with a negative difference in volumetric flow rates, that is, if the difference in volumetric flow rates Δq in the forward and return pipelines is less than zero. FIG. 4 shows the cases when, Δq = -5%, and Δq = -10% of the flow rate in the direct pipeline. Cases when the volumetric flow rate in the return pipeline exceeds the volumetric flow rate in the forward pipeline, -Δq = q ₁ -q ₂ <0, are often encountered in practice, especially in DCVTS. This occurs as a result of poor quality deaeration of the coolant (water), i.e. the gases inevitably contained in the air (nitrogen, oxygen, etc.) are not completely removed from the water. When leaving the source of thermal energy, when the pressure of the coolant is sufficiently high (as a rule, about 1.6 MPa), these gases are in a dissolved state and do not affect the accuracy of water flow measurements. However, with a drop in pressure, which manifests itself especially significantly according to the laws of hydraulics in the return pipeline, gases begin to evolve into a free state in the form of bubbles. And the coolant will be a water-gas mixture, the total volume of which turns out to be greater than the volume of the coolant (water) at a higher pressure in the direct pipeline. In addition, the amount of free air in the return pipelines of heat supply systems of facilities is increased by pumps operating at the facilities, especially circulation pumps.

To reproduce the negative flow rate, a third reference block 26 '' is introduced into the device.

To reproduce the set value of the negative difference in flow rates, -Δq = q ₁ -q <0, the controlled control valve OT 11 on the return pipeline is fully open, and the shut-off valves 16 and 17 of the second reference block are completely closed. The controlled control valve of the straight pipeline 3 on the straight pipeline is intended for coarse adjustment of the value of the water flow rate in the third reference block, and the controlled control valves on the reference systems of the third reference block are intended for fine adjustment of the set value of the difference in flow rates -Δq <0 according to the readings of reference flow meters of the reference systems of the third reference block.

The principle of operation of the device for calibrating a pair of volumetric (electromagnetic) flow meters is as follows.

, где Q - средний расход жидкости в м³ /с Питание катушек расходомера переменным или постоянным напряжением. Питание расходомера переменным напряжением устраняет электролитическую поляризацию расходомера, если частота достаточно высокая, а также позволяет использовать усилитель переменного тока (индикатор 38 содержит эти усилители) для усиления выходного сигнала расходомера. Выходное напряжение расходомера не зависит от режима течения потока ламинарный или турбулентный, и от формы профиля скорости потока, если он близок к осесимметричному. Однако значимая осевая не симметрия профиля скоростей потока может влиять на показания расходомера. Напряжение питания объемного электромагнитного расходомера 12 В.The coolant flows through the flow path of the electromagnetic flowmeter located in the magnetic field. The induction of the magnetic field of the flow meter is V. If the liquid, which in this case performs the functions of the core, flows through the flow path of the volumetric electromagnetic flowmeter with an average velocity v, then in the flowmeter, for example, a pair of volumetric flowmeters 7, 9 and 8, 10, an electromotive force is induced ( EMF) and a potential difference is formed at the outlet of the flow meter electrodes e = vBd, where d is the inner diameter of the flow part of the flow meter. This expression can be thought of as:

, where Q is the average liquid flow rate in m ³ / s. Power supply of the flow meter coils with AC or DC voltage. Powering the meter with an AC voltage eliminates electrolytic polarization of the meter if the frequency is high enough, and also allows an AC amplifier (indicator 38 contains these amplifiers) to amplify the output of the meter. The output voltage of the flow meter does not depend on the flow regime of the flow, laminar or turbulent, and on the shape of the flow velocity profile, if it is close to axisymmetric. However, significant axial non-symmetry of the flow velocity profile can affect meter readings. The supply voltage of the volumetric electromagnetic flowmeter is 12 V.

The operation of the device for calibrating pairs of volumetric flow meters in heat meters for conditionally closed and open heat supply systems is based on four operating modes:

- in idle mode, the device is completely filled with water, but the flow rate of water in the direct and return pipelines, in the first 26 and in the second and third bypass blocks 26 'and 26''is absent (equal to zero). In this mode, readings are taken from the electrodes of the calibrated volumetric electromagnetic flowmeters 7-10 on the supply return pipelines and reference volumetric electromagnetic flowmeters 27, 28, 31, 32, 33, 34, 33 ', 34' and 13, 14, 13 ', 14' the third and second reference blocks, i.e. in the absence of flow (determine the drift of the open circuit voltage of zero in the forward and reverse pipelines U _1x.x. and U _2x.x. or the additive error of the flow meters) and store it in the indicator 38.

- in the first operating mode, the volumetric flow rates in the direct and return pipelines are equal, Δq = q ₁ -q ₂ = 0, while the controlled control valves on the return 11, on the direct 3 pipelines are open and shut-off valves 16, 17 to the second, 36 and 37 to the third reference blocks are closed. This case, the calibration characteristics of a pair of volumetric flow meters 7, 9 and 8, 10 in two pipelines is shown in FIG. 2 to FIG. 4 registered, and their current-collecting, controlled outputs carrying information about the difference in flow rates Δq = q ₁ -q ₂ = 0 are connected to the indicator 38;

- in the second operating mode, the volumetric flow rate of the coolant in the direct pipeline is greater than the volumetric flow rate of the return pipeline Δq = q ₁ -q ₂ > 0, while the controlled control valve of the direct pipeline 3 on the direct pipeline is open, the shut-off valves 36 and 37 of the third reference block are closed, and the shut-off valves 16 and 17 of the second reference block are open. This case, the calibration characteristics of a pair of volumetric flow meters 7, 9 and 8, 10 in two pipelines is shown in FIG. 4 registered, and their current-collecting, controlled outputs carrying information about the difference in flow rates Δq = q ₁ -q ₂ > 0 are connected to the indicator 38;

- in the third operating mode, the volumetric flow rate in the return pipeline exceeds the volumetric flow rate in the forward pipeline, that is, -Δq = q ₁ -q ₂ <0, while the controlled control valve OT 11 on the return pipeline is open and the shut-off valves: 16, 17 to the second reference block - closed, and shut-off valves 36 and 37 of the third reference block are open. This case, the calibration characteristics of a pair of volumetric flow meters 7, 9 and 8, 10 in two pipelines is shown in FIG. 4 registered, and their current-collecting, controlled outputs carrying information about the difference in flow rates are stored in the indicator. The voltages at the electrode output of pairs of volumetric calibrated electromagnetic flow meters U ₁ , U ₂ carrying information are proportional to the measured volume flow rates q ₁ , q ₂ and the negative difference in volume flow rates -Δq = q ₁ -q ₂ <0 are recorded in the indicator and their current-collecting leads are connected to the indicator 38.

The device contains controlled outputs of volumetric reference flow meters 13, 14 and 33, 34, and 13 ', 14', 33 ', 34', variable control valves, 15, 15, '35, 35', 11, 3, graduated pairs of volumetric flow meters 7, 9, and 8, 10, consisting of three reference blocks, 26, 26 "and 26 ', 26" are connected to the indicator input. And at the output of the indicator, the results of calibration are obtained, for example, of volumetric electromagnetic flow meters: individual q ₁ = q ₁ (U ₁ ) and q ₂ = q ₂ (U ₂ ) AND In a pair Δq = q ₁ -q ₂ = Δq (U ₁ , U ₂ ).

Control of all technological processes - water supply, regulation of output voltage levels of volumetric electromagnetic flowmeters, open, closed, intermediate positions, controlled variable flow valves is carried out by the command of the indicator. The measurement results are processed in the indicator, and a passport or a form of the established form is issued for each pair of flow meters.

FIG. 1a, b in three reference blocks 26, 26 'and 26' 'show two reference flow lines, but if necessary, their number can be increased. The presence in each of the three reference blocks of several reference systems (lines) of volumetric flow meters, in each of which two or more sequentially installed reference flowmeters, improve the accuracy and reliability of volumetric flow measurements, which is regulated by GOST R 8.608. Each of the three reference blocks 26, 26 'and 26' 'corresponds to the circuit shown in FIG. 1b;

A block diagram is shown in FIG. 1a devices for calibrating pairs of volumetric electromagnetic flow meters by reproducing the most important operating conditions of flow meters in open (according to GOST 26691) or conditionally closed water heat supply systems (in Russia, they exist, and not ideally closed heat supply systems, such as in the European Union).

In the device, valves 36-37 are controlled ball valves that allow you to completely open or stop the water supply. Controlled variable valves 35, 35 'with feedback allow you to adjust the water flow in the pipelines based on the readings of volumetric reference flow meters 33, 34, 33', 34 '. All valves and flowmeters are standard, commercially available from the industry.

Reservoirs 24, 25 are measuring instruments of the second category in accordance with GOST 8.400 - 2013. If the volume of the liquid is determined, or if the mass of the liquid is determined, simple reservoirs with an anti-corrosion coating, they provide complete drainage of the liquid after the measurement, including ensuring minimal liquid adhesion on the inner surface.

Used in the device, FIG. 1a, reference blocks 26, 26 'and 26' 'contain reference systems of flow meters, each of them, according to GOST R 8.608, at least two flow meters (it is preferable to use electromagnetic). A prototype of reference blocks is assembled based on the presence of valves, flow meters, pipelines, etc. in production.

The display unit 38 is made on the basis of a personal computer PC.

The device allows to calibrate (verify) pairs of vortex, ultrasonic, turbine, electromagnetic flow meters. In the device, reference flow meters must be electromagnetic only. Since only such flow meters provide the necessary calibration characteristic in this case, which is closest to linear (R 50.2.026-2002 Resistance thermocouples and electromagnetic flow meters in commercial heat metering units).

The main characteristics of the layout of the device for calibration in pairs of volumetric electromagnetic flowmeters.

1. Kinds of graduated volumetric flow meters, any, but electromagnetic are preferable.

2. The number of pairs of graduated flow meters simultaneously from one or more.

3. Working time of calibration of steam flow meters is from two hours or more.

4. Coolant flow rate for flow meters in vapors from 6 liters per hour or more.

5. The values of the difference between positive and negative volumetric flows, up to 30% of the flow rate in a straight pipeline.

6. The rate of flow of the coolant in pipelines is up to 10 m / s.

7. The largest excess pressurized coolant in pipelines is up to 1.6 MPa.

8. Temperature of water (heat carrier) in pipelines from 1 to 150 ° С.

9. Ambient temperature: with a monoblock version from +5 to + 50 ° С, with a separate version, flow sensors from -30 to + 50 ° С, and their electronic units from +5 to + 50 ° С.

10. Measurement error of volumetric flow rates up to ± 2%; and the difference in volumetric flow rates up to ± 6%.

11. Composition of measuring instruments, standard voltmeters, not less than 50 mV.

12. Mains supply voltage from 187 to 242 V.

13. Power consumption from the network at the rate of 20 W for a pair of verified flow meters.

14. The working position is horizontal.

15. The largest overall dimensions are 6000 × 2000 × 3000 mm.

16. Weight 1000 kg.

The method of calibration of pairs of volumetric flow meters in heat meters for conditionally closed and open heat supply systems is carried out as follows:

Stage 1. Measure the voltage values given by the electromagnetic flowmeters of the device in the idle mode with the magnetized states of pairs of calibrated 7, 9 and 8, 10 and volumetric reference flowmeters 27, 28, 31, 32, 13, 14 and 33, 34, and 13 ', 14 ', 33', 34 ', alternating voltage 12 V. In this case, for the calibration of pairs of volumetric electromagnetic flow meters 7, 9 and 8, 10, direct 1, reverse 2 pipelines, the device is placed in the operating position, horizontally or vertically, without distortions relative to the base ( places of the regular working location) Fig. 1a. From the circulating tank 5 by the injection unit (pump) 19 through the first reference unit 26, the coolant is supplied to the supply pipeline 1, with a flow rate within the measuring range of the calibrated flowmeters (for an electromagnetic flowmeter with a nominal diameter of the flow sensor DN 50, the measuring range is from 0.06 up to 60 m ³ / h) while opening the controlled control valves in the return 11 and direct 3 pipelines, open the stop valves 16, 17 in the second reference block, open the stop valves 36, 37 in the third reference block and fill the device completely with the coolant.

The strained open circuit U _{1x.x is measured.} and U _2x.x. from the outlet of the calibrated volumetric electromagnetic flowmeters 7-10 at a water flow rate equal to zero, FIG. 7a. These tense U _1x.x. and U _2x.x. carry information about device noise and external electromagnetic interference, where indices 1 and 2 are numbers of forward and return pipelines. The measurement results are stored, recorded in the indicator 38.

Stage 2. Determine (create) the first mode of operation (calibration) of the device of FIG. 1a at the same volumetric flow rates of water (coolant) in the direct and return pipelines, and therefore, set a zero difference in volumetric flow rates Δq = 0 in pipelines straight 1, reverse 2. for pairs of volumetric flow meters 7, 9 and 8, 10 at measuring section 6. According to the compiled algorithm and program, a method of direct measurement of the difference in volumetric flow rates at Δq = q ₁ -q ₂ = 0 is implemented. Achieve the creation of equality of volumetric flow rates of water in pipelines 1, 2, i.e. q ₁ = q ₂ at all points of the measuring range of flow rates of calibrated flow meters. At the same time, the shut-off valves on the second 16, 17 and third 36, 37 reference blocks are closed. The control valves on the direct line 3 and on the return line 11 are fully opened. The characteristics of the volumetric flow meters inside each graduated pair are chosen to be identical, then as a calibration characteristic with the difference in volumetric flow rates equal to zero Aq = O, an ideal straight line passing through the origin of coordinates and symmetrically to the coordinate axes of Fig. 2. In this case, the same values of the output voltages are obtained from the outputs of the volumetric flow meters 7, 9 on the forward U ₁ and reverse U ₂ pipelines (Fig. 2).

FIG. 3 show that the real calibration characteristic (dashed line) at Δq = 0 according to the measurement results may not coincide with the ideal one (solid line), but be within the tolerance field. Further, depending on the problem to be solved, the calibration of the pairs of flow meters is carried out at several selected flow rates from the range of measurements of the flow meters of the selected pair. In this case, equal values of the flow rates in the direct and return pipelines are set, q ₁ = q _2, and, therefore, the difference in volumetric flow rates is obtained equal to zero Δq = 0. In this case, the dependences of the output signals (voltage) of the flow meter located on the return pipeline U ₂ (corresponds to q ₂ ) on the voltage from the flow meter on the forward pipeline U ₁ are also plotted. (corresponds to q ₁ ) For given values of flow rates in the forward and return pipelines and the difference in volumetric flow rates equal to zero Δq = 0. A calibration characteristic is obtained in the form of a straight line of Fig. 2, it is entered into the indicator 38.

Stage 3. The second mode of operation of the device is reproduced, water (coolant) leaks are set, and the difference in the volumetric flow rates of water in the direct and return pipelines is set to be greater than zero Δq = q ₁ -q ₂ > 0. At the same time, pairs of volumetric flow meters 7, 9 or 8, 10 are calibrated (verified) in the measuring section 6 by the method of direct measurement of the positive difference in flow rates according to values directly reproducible: the first reference block 26 is the flow rate value in the direct pipeline q ₁ and the second reference block 26 'values the value of the difference in water flow rates Δq, with a predetermined small error. Further, the reproduced value of the difference in flow rates Δq is associated with the output signals (for electromagnetic flowmeters EMR - voltage) from each pair of calibrated flowmeters: strained by the forward U ₁ and reverse U ₂ pipelines, which are entered into the indicator 38. According to the compiled algorithm and program, this operation is performed , as a rule, at no less than five points on the flow rate in the direct pipeline q _1i (i = 1… 5) and at least at three points on the difference in flow rates (j = 1… 3). For each given value j = 1 ... 3, a relationship is plotted between the reverse voltage U ₂ and the forward U ₁ pipelines of the calibrated pairs of volumetric flow meters 7, 9 or 8, 10, which are approximated by the straight lines of FIG. 2 to FIG. 4. These straight lines are the calibration characteristics of the channel for direct measurement of the positive difference in the volumetric flow rates of water at the given values of the positive difference Δq _j > 0. (the conversion factor of calibrated EMFs with a nominal diameter of DN 15 is several μV / m ² ). Stress quantities U ₁ . and U ₂ shown in FIG. 2-4, as a percentage of the upper measurement limit of the flow meters (the same for all simultaneously calibrated pairs of flow meters 7, 9 or 8, 10).

Direct measurement of the given positive difference in volumetric flow rates Δq = q ₁ -q ₂ > 0 is carried out when the controlled control valve of the straight pipeline 3 on the straight pipeline is fully open, and the shut-off valves 36 and 37 are closed by the third reference bypass block 26 '', and the second reference bypass block 26 'the shut-off valves 16, 17 are open. Coarse adjustment of the flow rate of the coolant (water) supplied to the second reference block 26 'is carried out by a controlled control valve OT 11 on the return pipeline. Then, the values of the difference in volumetric flow rates of water are set greater than zero Δq = q ₁ -q ₂ > 0, so that a part of the water on the return pipeline controlled by the control valve OT 11 (the flow of which is slightly greater than the set flow rate difference, by about 10-15%) flow meters 9, 10 on the return pipeline, passes through the second reference block, where this flow rate is accurately measured by reference flow meters 13, 14, 13 ', 14'. Further, the value of this flow rate controlled by the control valves 15, 15 'in the second reference block according to the readings of the reference flow meters 13, 14, 13', 14 'is as close as possible to the value of the set flow rate difference. The number of repetitions of these cycles, for each value of the reproducible difference in flow rates Δq = q ₁ -q ₂ > 0, is determined depending on the requirements of the problem being solved. But to be able to use the well-known criteria for gross blunders, the number of such cycles should be at least four. With repeated repetition of the experiment, the accuracy of the calibration of the pairs of flow meters is increased.

Stage 4. A third operating mode is created for the device for calibrating pairs of volumetric flow meters 7, 9 and 8, 10 - the negative difference in flow rates in the direct and return pipelines. For this, the volumetric flow rate of water is set in the return pipeline, which is greater than in the direct pipeline -Δq = q ₁ -q ₂ <0. Calibration characteristic -Δq = q ₁ -q ₂ = -Δq (U ₁ , U ₂ ) of each pair of volumetric flow meters 7, 9 and 8, 10, installed on the measuring section 6 at given values of the negative difference in volumetric flow rates -Δq = q ₁ - q ₂ <0 depending on the output signals of the calibrated pair of volumetric flow meters: where U ₁ - voltages from the outlet of the volumetric flow meter on the forward pipeline and U ₂ - return pipeline, and obtained as:

- set a negative difference in volumetric flow rates in the direct and return pipelines with a fully open valve OT 11 on the return pipeline 2 and closed shut-off valves 16, 17 on the second reference bypass block 26 ', cutting off the second reference block, that is, they create a completely unobstructed flow of the coolant through the pipeline 2. Then, with a fully closed controlled control valve of the straight pipeline 3 on the straight pipeline 1 and open shut-off valves 36, 37 in the third reference bypass block 26 '', the volumetric reference flow meters 33, 34 and 33 ', 34' are pre-calibrated against the original standard 20.with the limits of the permissible relative error of volumetric reference flow meters 33, 34 and 33 ', 34' are negligible in comparison with the permissible limits of the relative error of the calibrated volumetric flow meters 7-10. For this, the ratio of the limits of permissible errors of reference flow meters 33, 34 and 33 ', 34' and verified flow meters 7 - 10 provide no more than 1: 3. This ratio of errors for reference flow meters and calibrated (verified) flow meters 7-10 is set for all reference blocks (first, second, third). This is achieved by calibrating against the original standard 20 with a set of representative statistics of the calibration results. The presence in each reference block in each reference system, two or more sequentially installed reference flow meters, achieve an increase in the accuracy and reliability of volumetric flow measurements, which is regulated by GOST R 8.608.

The specific values of the negative difference in water flow rates in the direct and return pipelines are set as follows. Using a controlled control valve 3, a water flow corresponding to a reproducible difference in volumetric flow rates (-5; -10%, etc., of the flow rate in the return line 2, for example, for an EMF with a nominal diameter of DN50 from 0.06 to 60 m ³ / h) is fed into the third reference bypass block 26 '' bypassing the calibrated flow meters 7, 8 located on the straight pipeline. For this, the third reference bypass unit 26 '' is first fed with a water flow rate slightly greater than the required value of the difference in volumetric flow rates Δq _j . Then the required value of the negative difference in volumetric flow rates is set by the controlled control valves of the third reference block 35, 35 'according to the readings of the volumetric reference flow meters 33, 34. 33' 34 'located in the third reference bypass unit, as close as possible to the set value of the difference in volumetric flow rates of water Δq _j . To build a calibration characteristic of a pair of each pair of volumetric flow meters at a given value of the difference in volumetric flow rates Δq _i. , the experiment is carried out at least at five values of the flow rate q _2i (ie i = 1, ..., 5), in the return pipeline in the measurement range of the calibrated EMR. In this case, the flow rate values in the direct pipeline are determined as q _1i = q _2i -Δq _j . Further, for a given value Δq _{j, a} calibration characteristic is plotted in the form of a straight line in FIG. 4. Similar calibration characteristics are plotted for at least three predetermined values of the difference in volumetric flow rates Δq _j . (i.e. j = 1, ..., 3).

Conversion coefficients of each pair of graduated volumetric flow meters are determined and stored by indicator 38.

где U_1Общ., U_1х.х. и U_1Общ., U_2х.х.. Эти пары сигналов в прямом и обратном трубопроводах между собой не коррелированны, то есть коэффициент корреляции равен нулю. Следовательно, получают на выходе полезные сигналы U₁, U₂ градуируемых объемных расходомеров без шумов от устройств и внешних электромагнитных помех. И, эти сигналы несут информацию о значениях и качестве объемных расходов прямом U₁ ~ q₁, обратном U₂ ~ q₂ трубопроводах и разностях объемных расходов пар расходомеров 7, 9 и 8, 10 положительных Δq=Δq(U₁, U₂)>0; равных нулю Δq=Δq(U₁, U₂)=0; отрицательных; - Δq=-Δq(U₁, U₂)<0 измерительном участке 6 с методом прямого измерения определяют и запоминают в индикаторе.Stage 5. Based on the results of measurements at stages 1-4. To obtain at the output pairs of calibrated volumetric flow meters 7-10 useful voltages U ₁ , U ₂ . free of noise and interference voltages (open circuit voltage U _1x.x. , U _2x.x. ), from the measured total voltage value U ₁ , U ₁ , separate the no-load voltage, for three operating modes of the device. In this case, the differences in volumetric flow rates by a pair of graduated volumetric flow meters are set equal to zero Δq = q ₁ -q ₂ = 0, positive Δq and negative -Δq. Then useful signals are determined at the output of the specified pair of volumetric flow meters for each case as:

where U _{1 General.} , U _1х.х. and U _{1 General} , U _2х.х. ... These pairs of signals in the forward and backward pipelines are not correlated with each other, that is, the correlation coefficient is zero. Consequently, useful signals U ₁ , U _{2 of} calibrated volumetric flow meters are obtained at the output without noise from devices and external electromagnetic interference. And, these signals carry information about the values and quality of volumetric flow rates in the forward U ₁ ~ q ₁ , reverse U ₂ ~ q ₂ pipelines and the differences in the volume flow rates of pairs of flow meters 7, 9 and 8, 10 positive Δq = Δq (U ₁ , U ₂ ) >0; equal to zero Δq = Δq (U ₁ , U ₂ ) = 0; negative; - Δq = -Δq (U ₁ , U ₂ ) <0 measuring section 6 with the direct measurement method is determined and stored in the indicator.

Stage 6. It is taken into account that the negative difference in volumetric flow rates when measuring thermal energy and the mass of the coolant taken from the heating network in the overwhelming majority of cases occurs in the UZVST. It is also taken into account that heat meters are measuring systems of the type IS-1 in accordance with GOST R 8.596. The algorithm for calculating the thermal energy Q and the mass of the coolant taken from the heat network AM is based on the direct implementation of the equations for measuring these quantities given in MI 2412-97 GSOEI `` Water heat supply systems. For UZVST, the equation of measurement of equalization of measurements of thermal energy is used, which has the form:

where m _i = ρ _i (P _i , t _i ) q _i , m _i - mass, q _i - volumetric flow; ρ _i = ρ _i (P _i , t _i ) -density, ah _i = h _i (P _i , t _i ) is the enthalpy of the coolant as a function of pressure P _i and temperature t _i in the measuring section of the i-th pipeline, calculated by GSSSD 187-99 Water. Specific volume and enthalpy at a temperature of 0 ... 1000 ° C and pressures of 0.001 ... 1000 MPa. Tables of reference data GSSSD, Gosstandart, M: Publishing House of Standards, 1999. The subscripts for the values of flow rate, density, temperature, pressure and enthalpy correspond to: i = 1 direct, and i = 2 return pipelines; h _{XB is the} enthalpy of cold (make-up) water (heat carrier), τ is the time varying in the interval from τ ₀ - the beginning, τ ₁ - the end of the reporting period.

Moreover, for ideally closed systems (in which the leakage of the coolant is negligible, i.e. when the difference in the mass flow rates of the coolant is zero, m ₁ -m ₂ = 0;) the equation for measuring the thermal energy Q ₁ turns into the following measurement equation:

Moreover, the equation for measuring thermal energy Q ₀ corresponds to the measurement equation for a closed water heat supply system, established in the regulatory document `` Methodology for the implementation of commercial metering of thermal energy, heat carrier ''. Approved by Order of the Ministry of Construction of Russia dated 17.03.2014 N 99 / PR and registered with the Ministry of Justice of Russia on 12.09.2014, No. 34040.

Whereas in the prototype, the equation for measuring thermal energy is used, which has the form:

When the coolant leakage is negligible, i.e. m ₁ -m ₂ = 0; the equation Q ₂ does not go over into the equation Q ₀ .

According to the compiled algorithm and program, all mathematical actions at all stages of calibration of pairs of volumetric flow meters are recorded in an indicator unit, which is functionally connected with the main units of the device.

The channel for direct measurement of the difference in volumetric flow rates is a complex measuring channel in accordance with GOST R 8.596, the inputs of which are supplied with output electrical signals from flow meters installed in the forward and backward pipelines. When determining the values of the difference in volumetric flows in two pipelines using a channel by the method of direct measurement of the difference in volumetric flows, the operation of subtracting volumetric flows is not used, and is a source of a large methodical total error in measuring heat energy measured by flow meters.

With individual calibration of pairs of volumetric flow meters 7, 9 and 8, 10, the highest accuracy is achieved for flow meters with a linear calibration characteristic. This requirement is best met by electromagnetic flow meters, which is confirmed by the regulatory document R 50.2.026-2002.

The technical and economic effect in the invention is increased due to the introduction in the heat meter of a channel for direct measurement of the difference in volumetric flow rates. Increase the accuracy of direct measurement of zero, positive and negative differences in volumetric flow rates. In conditionally closed and open water heat supply systems. Using the method of calibrating pairs of volumetric flow meters installed in the flow and return pipelines without the use of such actions as subtracting the values of volumetric flow rates. Thus, they solve the assigned tasks, i.e. increase the accuracy of measurements of thermal energy and mass of the coolant taken from the network in conditionally closed and open water heat supply systems. And, in particular, in contrast to the prototype, pairs of volumetric flow meters are calibrated at negative values of the difference in volumetric flow rates, and retain the possibility of in-line calibration (verification) of pairs of heat meters.

In the limited liability company "Alternative Energy Technologies" LLC AET, it was found that a significant increase in accuracy is achieved by measuring the negative difference in volumetric flow rates, due to which it is much more accurate to establish the fact of clogging of the heating network water. This means that water contains free air in the form of bubbles, this significantly increases the measurement error, in addition, it brings enormous harm, since free oxygen from the air leads to rapid oxidation of the metal and, as a consequence, a significant acceleration of the wear of heating networks and their early removal from building.

The release of air into a free state also leads to a significant increase in the measurement error of the mass of the coolant taken from the network, since the density of the water-air mixture is determined from the measured values of temperature and pressure, as well as the dependences of GSSSD 188-99, intended for deaerated water. In addition, mass flow meters are not used in heat meters due to their high cost and insufficient measurement range, which is much smaller in comparison with volumetric flow meters.

Let the readings of the flow meters be M ₁ and M ₂ , and the values of their relative errors during measurements will be δ ₁ and δ ₂ . It is required to find the measurement error of the difference

ΔM = M ₁ -M ₂ ,

The absolute errors of the measured values are defined as

Δ ₁ = M ₁ δ ₁ and Δ ₂ = M ₂ δ ₂ .

The measured values of the mass of the coolant, taking into account the error of a pair of flow meters, are determined as

M ₁ + Δ ₁ = M ₁ + δ ₁ M ₁ and M ₂ + Δ ₂ = M ₂ + δ ₂ M ₂ .

The absolute measurement error of the difference ΔM is, by definition, equal to

Δ _ΔM = (M ₁ + δ ₁ M ₁ -M ₂ -δ ₂ M ₂ ) - (M ₁ -M ₂ )

Then the relative measurement error of the difference ΔM will be written as

after bringing similar members, they finally receive

It should be noted that formula (8) is valid for the difference in the values of any physical quantities (temperatures, pressures, flow rates, etc.), as well as errors δ ₁ and δ _{2 of} any signs. With regard to the measurement of the difference in the masses of the coolant in the direct and return pipelines, this formula is given in the normative document MI 2553-99. GSOEE. '' Heat energy and heat carrier in heat supply systems. Measurement error estimation technique. Basic Provisions ''.

For clarity of application of the formula for determining the error 6, a number of practical examples are considered in the device for calibrating a pair of volumetric flow meters, in which the relative error in measuring the mass of the coolant conditionally taken from the network is determined.

For simplicity, the examples below only take into account flowmeter uncertainty. The limits of the permissible relative error of both flow meters as part of the heat meter are ± 1%. (consequently, the same by the condition will be the error limits of mass measurements for each pipeline).

Let the measured values of the mass of the coolant on the direct pipeline M ₁ = 90 tons, on the return _{pipeline M 2} = 100 tons. These data are hypothetical, since they are realized with a very strong clogging of water with air. In this case, the error in measuring the mass is determined as: a. The pair of flow meters is not matched. Let the actual values of the flow meter errors obtained on the calibration device be δ ₁ = -0.6% and δ ₂ = + 0.3%, substituting them (δ), we obtain

b. The pair of flow meters is coordinated. Let the actual values of the errors of the flow meters on the calibration device, in absolute value, be the same as in example a, but their signs will be the same, negative, i.e. δ ₁ = -0.6% and δ ₂ = -0.3%. Then get

It can be seen that matching of flow meters in terms of metrological characteristics gives a tangible increase in the measurement accuracy.

in. Let a pair of matched flow meters be selected, and the values of their errors, as in example 6, will be δ ₁ = -0.6% and δ ₂ = -0.3%, but the measured values of the mass will be M ₁ = 99 t and M ₂ = 100 t, then

Consequently, for the case considered in the last example, matching flow meters according to metrological characteristics does not give any effect.

Thus, it can be seen from the above examples that the main source of error in measuring the difference in mass is the application of the method for measuring the difference in mass from the difference in readings of flow meters. The error in measuring the difference in mass, when subtracting the readings of the flow meters, is unacceptably high, even if the errors of both flow meters are within acceptable limits and are matched in sign.

Analysis of the formula for the error in determining the mass of the coolant taken from the network based on the difference in flow meter readings allows us to draw the following conclusions:

If the signs of the errors of both flow meters coincide, this means that the error in the measurements of the difference in mass decreases. However, it is not advisable to select flowmeters in a matched pair on a flow metering unit, since the errors of both flow meters on real objects are of a random nature, and do not remain stable over time, even while remaining within the permissible limits.

A decrease in the value of the measured value M ₁ -M ₂ leads to an increase in the error of its measurements, regardless of the values and signs of errors of both measuring instruments.

Thus, to increase the accuracy of measurements of the mass difference, one can only abandon the use of the indirect measurement method and go, as proposed in the proposed invention, to the method of direct measurement of the desired difference.

Errors in measuring the volumetric flow rate of the heating medium can occur due to stray voltage between the electrodes of the flow meter. These voltages arise due to galvanic potentials between electrodes and other metal parts, as well as when the flow meter is polarized with a DC voltage. The magnitude of random noise arising in the flow meter and the influence of external electromagnetic fields increase with an increase in the resistance of the coolant between the electrodes.

The best results when calibrating (checking) pairs of electromagnetic flowmeters by the difference in flow rates can be achieved for heat meters released from production with proven technology and high-quality assembly. For example, heat meters of the KM-5 type are used in the proposed device.

Claims (5)

1. A device for calibrating pairs of volumetric flow meters in heat meters for closed and open heat supply systems, containing a direct, return pipelines, a controlled control valve of a return pipeline, two bends connected in series, a circulating tank, a measuring section, graduated pairs of volumetric flowmeters, an outlet pipeline, a suction pipeline, a pumping block, a block of an initial standard containing a distributor directing the flow of water, two distribution pipelines, two switches for water flow, two measuring tanks, two drain pipelines, the first, second reference blocks, an indicator, the first reference block contains at least two reference systems, each at least two volumetric flow meters and a controlled control valve of the first reference block, the bypass second reference block contains at least two reference systems, each of which contains at least two volumetric flow meters and a controlled control valve of the second reference block, shut-off valves that connect it to the return pipeline and provide or stop the water supply, the direct and return pipelines can be separated by a group of elbows or extended in one line, the direct and return pipelines contain graduated pairs of volumetric flow meters from one pair or more, at the outlet of the return pipeline a controlled control valve of the return pipeline is connected, at the inlet to the straight pipeline, the first reference block is connected, into which water is supplied from the return tank by a blower through the suction pipeline, and in the process of calibrating volumetric reference flow meters, the water flows through the outlet pipeline to the block of the original standard, or to the measurer, or through the drain pipelines into the circulating tank, the block of the initial standard contains a water flow distributor, which, depending on the measured flow rate, directs water through the corresponding directing pipeline to a measuring vessel of the corresponding volume, into which, when a command for measurement is given, sweat ok is directed by the appropriate water flow switch, all controlled and signal outputs are connected to the indicator, characterized in that the third reference bypass unit, the controlled control valve of the third reference unit, two stop valves are additionally introduced, and the third reference bypass unit contains at least two reference systems, each of which contains at least two volumetric flow meters, a controlled control valve of a straight pipeline, both stop valves are connected to a straight pipeline, these valves are fully open or closed, then the water flow is either present or absent, the control variable valve of the third reference block on the straight pipeline provides the presence of a water flow rate in the third reference block, and the controlled control valves of the forward and return pipelines on the reference systems provide the set value of the negative difference in flow rates. 2. A method of calibrating pairs of volumetric flowmeters of heat meters for closed and open heat supply systems, which consists in creating the first operating mode of calibration of the device: at the same volumetric flow rates of water in the direct and return pipelines, it means at a zero difference in volumetric flow rates Δq = 0 in the direct and return pipelines, for the calibrated pairs of volumetric flowmeters at the measuring section by the direct measurement method, according to the developed algorithm and program, the method of direct measurement of the difference in volumetric flow rates at Δq = q ₁ -q ₂ = 0 is implemented, the values of the output signals from the outputs of the volumetric flowmeters on the direct U ₁ and the return U ₂ pipelines, for this, the control controlled valve of the return pipe on the return pipe is fully open, and the stop valves on the second reference block are completely closed, while also plotting the dependences of the output signals of the flow meter located on the return pipe U ₂ on the value of the signal c flow rate pa on the direct pipeline U ₁ , at each of the given values of the flow rates in the direct and return pipelines and the difference in volumetric flow rates equal to zero Δq = 0, a calibration characteristic is obtained in the form of a straight line, it is entered into the indicator; reproduce the second mode of operation of the device, set the leaks of the coolant with the difference in volumetric flow rates of water in the forward and return pipelines greater than zero: Δq = q ₁ -q ₂ > 0, while the pairs of volumetric flow meters at the measuring section are calibrated by the method of direct measurement of the positive difference of flow rates by values, directly reproducible: the first reference block - the flow rate values in the direct pipeline q _x and the second reference block - the values of the water flow rate difference Δq, with a predetermined small error, then the reproduced value of the flow rate difference Δq is matched with the output signals from each pair of calibrated flow meters: - U ₁ and return - U ₂ pipelines, which are brought into the indicator, set the values of the difference in volumetric flow rates of water greater than zero Δq = q ₁ -q ₂ > 0, set by the fact that a controlled regulating valve of the return pipeline on the return pipeline, a part of the water, bypassing the calibrated flowmeters on the return pipeline, passed through the second e a coupon block, where this is the flow value controlled by the control valves of the second reference block in the second reference block according to the readings of the reference flow meters of this block is corrected, as close as possible to the value of the set flow rate difference, characterized in that the third operating mode of the device for calibrating pairs of volumetric flow meters is created - a negative flow rate difference in the direct and return pipelines, for this purpose, the volumetric flow rate of water is set in the return pipeline, which is greater than in the direct pipeline - Δq = q ₁ -q ₂ <0, the calibration characteristic is -Δq = q ₁ -q ₂ = -Aq (U ₁ , U ₂ ) of each pair of volumetric flow meters installed on the measuring section is obtained at the given values of the negative difference in volumetric flow rates - Δq = q ₁ -q ₂ <0, depending on the output signals of the calibrated pair of volumetric flow meters: where U ₁ are the voltages from the output of the volumetric flow flow meter in the direct pipeline and U ₂ - in the return pipeline, and set a negative difference in volumetric flow rate in the forward and return pipelines with a fully open valve on the return pipe and closed stop valves on the second reference block, cutting off the second reference block, that is, they create a completely unobstructed flow of the coolant through the return pipe, then preliminarily with a fully closed controlled control valve of the direct pipeline on the direct volumetric reference flowmeters of the third reference block are pre-calibrated according to the initial standard with the limits of the permissible relative error of volumetric reference flowmeters, negligible compared to the permissible limits of the relative error of the calibrated volumetric flowmeters, the specific value of the negative difference in water flow rates in the straight line and return pipelines are set as follows: with the help of a controlled control valve of the direct pipeline on the direct pipeline, the water flow corresponding to the of the volumetric flow rate difference to be removed, is fed to the third reference block, bypassing the calibrated flow meters located on the direct pipeline, for this purpose, the third reference block is first fed with a water flow slightly higher than the required value of the volumetric flow rate difference Δq _j , then the required value of the negative volume flow rate difference set by controlled control valves of the direct pipeline, return pipeline and the third reference block according to the readings of the volumetric reference flow meters located in the third reference block, as close as possible to the set value of the negative difference in the volumetric flow rates of water. 3. A method of calibrating pairs of volumetric flow meters in heat meters for closed and open heat supply systems according to claim 2, characterized in that when performing the first stage, to completely fill the device with a coolant, open the controlled control valve of the straight pipeline on the straight pipeline and open the shut-off valves on the third reference block ... 4. The method of calibration of pairs of volumetric flow meters in heat meters for closed and open heat supply systems according to PP. 2, 3, characterized in that at the second stage, when the difference in flow rates in the supply and return pipelines is equal to zero Δq = q ₁ -q ₂ = 0, the shut-off valves on the third reference block are closed and the control valve of the direct pipeline on the direct pipeline is completely opened ... 5. Method of calibration of pairs of volumetric flow meters in heat meters for closed and open heat supply systems according to PP. 2, 3, 4, characterized in that at the third stage, when the difference in flow rates in the supply and return pipelines is greater than zero Δq = q ₁ -q ₂ > 0, the controllable control valve of the direct pipeline on the straight pipeline is fully open, and the shut-off valves on the third reference block completely closed.

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