JP2008267931A - Liquid level measuring device for liquid tank - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid level measuring device that improves liquid tank accuracy in measuring a liquid level, by preventing the occurrence of liquid level measuring errors produced by deviation of a liquid temperature generated in piping in piping constitution for measuring the liquid level of the liquid tank. <P>SOLUTION: The liquid level measuring device comprises the liquid tank 1, and a detector 9 mounted to upper liquid level detection piping 5 and lower liquid level detection piping 6 to detect the liquid level of balance pipes 4, by leading the liquid level of the liquid tank to the balance pipes 4 through upper piping 2 and lower piping 3 connected to the liquid tank, and the balance pipes 4. The height of a lower balance pipe branch point B is made coincident with the branch height of the lower liquid level detection piping, and the upper and lower liquid level detection piping parts are allowed to have temperature-reducing effect to attain the effect of reducing the temperature difference at a diaphragm part of a measuring instrument. Furthermore, a discharge piping 7 for discharging condensed water produced in the upper piping is installed to reduce the occurrence of deviation of diaphragm temperatures between measuring instruments, by preventing the occurrence of temperature difference between the balance pipes. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a liquid level measuring device used in, for example, nuclear power generation facilities, and more particularly to a liquid tank capable of improving measurement accuracy when measuring the level of the same tank with a plurality of level gauges. The present invention relates to a liquid level measuring device.

  The liquid level measuring device (also called water level measuring device) for tank equipment used in nuclear power generation equipment that has been generally adopted in the past is composed of a water level measuring pipe with an upper gas layer side and a lower liquid layer side in the tank body. The water level balanced between the tank body water level and the head pressure generated in the balance pipe connecting the pipe taken out from the upper part of the tank body and the pipe taken out from the lower part is detected by a float type meter or a differential pressure type meter. Yes. When measuring the water level in the same tank with a plurality of instruments, a plurality of balance pipes are installed, and each balance pipe water level is measured.

  In particular, when detecting with a differential pressure gauge, the water head pressure detection position of the balance pipe is at the same level, but the water level in balance with the tank body of each balance pipe differs depending on the change in the liquid temperature in the pipe. If this is the case, deviations will occur in the water level measurement.

  In addition, the condensate in the upper pipe is considered to flow into the balance pipe as a cause of the liquid temperature deviation in the balance pipe. In the differential pressure level gauge, the upper pressure detector and the lower pressure detector When a temperature difference occurs in the part, a water level measurement error occurs. However, in the conventional piping configuration, no consideration is given to preventing the temperature difference from occurring.

  As a conventional technique, as described in [Patent Document 1], a configuration in which a water reservoir is provided from the viewpoint of installing a plurality of instruments using a cross tee in a balance pipe and protecting the instruments. There is something that is.

  In [Patent Document 2], a liquid level maximum likelihood value is obtained from a plurality of liquid level meters provided in tower tanks, and a liquid for correcting an error due to a density change of the internal fluid of the tower tanks from a process variable. There is one that calculates a surface correction value and calculates a liquid level from the liquid surface maximum likelihood value and the liquid surface correction value.

JP-A-10-197683 JP 62-47520 A

  The prior art described in [Patent Document 1] does not consider the measurement error caused by the temperature difference in the diaphragm of the instrument and measures for improving the measurement accuracy when a plurality of balance tubes are installed. For this reason, the possibility that the temperature difference of the liquid in the balance pipe and the temperature difference in contact with the instrument occur is not considered, and there is a problem that a deviation may occur in the water level measurement.

  In addition, the conventional technique described in [Patent Document 2] calculates the liquid level from the liquid surface maximum likelihood value and the liquid surface correction value, and has a problem that a deviation may occur in the water level measurement itself. It was not a solution.

  An object of the present invention is to provide a liquid level measuring device for a liquid tank that reduces measurement errors due to the occurrence of a temperature difference in a balance tube and has high measurement accuracy.

  In order to achieve the above object, the liquid level measuring device for a liquid tank according to the present invention is such that the lower branch height of the balance pipe connected to the upper pipe and the lower pipe is the same height, and is connected to the balance pipe. The liquid level detection pipe is the lower branch height of the balance pipe.

  In particular, in a piping configuration that employs a diaphragm type differential pressure transmitter as a liquid level gauge, the amount of heat released from the liquid level detection pipe is increased to reduce the temperature difference of the diaphragm, and By making the dimensions, gradient, and piping specifications of the side liquid level detection piping the same, the occurrence of temperature differences is reduced.

  In addition, by installing a discharge pipe in the upper pipe part as close as possible to the branch part of the balance pipe and making the pipe length from the discharge pipe to each balance pipe the same, it flows into each balance pipe Condensed water can be set to the same amount, and the occurrence of a temperature difference in the balance pipe is also suppressed.

  According to the present invention, the connection level of the branch point of the balance pipe and the liquid level detection pipe is the same height, and the lower liquid level detection pipe connected to the balance pipe is the lower branch height of the balance pipe. The water head pressure applied to the level detection pipe can be made to coincide at the branch reference level, and the same measurement can be performed for the liquid level detection of the water level meter installed in each balance pipe.

  A liquid tank liquid level measuring apparatus according to an embodiment of the present invention will be described with reference to FIGS.

  As shown in FIG. 1, an upper pipe 2 is attached to the upper part of the liquid tank 1 via a main valve 10, and a lower pipe 3 is attached to the lower part via a main valve 10. A branch portion is provided at a portion C of the upper pipe 2 and is connected to a branch portion of the lower pipe 3 by a discharge pipe 7. Thus, since the discharge pipe 7 is installed, the condensed water generated in the upper pipe 2 in the vicinity of the balance pipe 4 is discharged to the lower pipe 3 without going through the balance pipe 4.

  The upper pipe 2 is branched in two directions at the part A and is connected to the balance pipe 4 via the instrument inlet valve 11 respectively. The two balance pipes 4 are connected to the lower pipe 3 through a meter inlet valve 11 at a branch part B.

  A test valve 14 is attached to each upper part of the balance pipe 4, and an upper liquid level detection pipe 5 is attached to the lower part of the test valve 14. A lower liquid level detection pipe 6 is attached to the height position of the B part of the balance pipe 4. A detector 9 for measuring the liquid level is attached to the upper liquid level detection pipe 5 and the lower liquid level detection pipe 6 via an instrument diaphragm 8. In this embodiment, a diaphragm type differential pressure transmitter that detects the differential pressure in the diaphragm and measures the liquid level is used as the detector 9.

  The instrument diaphragm part 8 is comprised by the flange, uses the 2 hole flange 12, and has provided the water filling valve 13 in one piping connection part. By providing this water filling valve 13, the water meter can be easily filled with the instrument configuration of the water manometer and the upper liquid level detection pipe 5.

  In the piping configuration using such a diaphragm type differential pressure transmitter, the liquid pipe 1 to be measured, the upper pipe 2 and the lower pipe 3 connected to the liquid tank 1, and the upper pipe 2 and the lower pipe 3 are connected. The liquid level in the liquid tank 1 is guided into the balance pipe 4 by the balance pipe 4 thus generated, and the liquid level is generated in the balance pipe 4 at a height where the head pressure is balanced.

  In this embodiment, two balance pipes 4 are installed to multiplex the measurement system, and a main valve 10 that partitions the liquid tank 1 and the piping system and a meter inlet valve 11 that partitions the balance pipe 4 are installed. Thus, the calibration for each instrument can be performed by the piping configuration in which the balance tube 4, the instrument inlet valve 11, and the test valve 14 are installed for each instrument.

  In order to measure the head pressure of the liquid level generated in each balance pipe 4 by the diaphragm type differential pressure transmitter, an upper liquid level detection pipe 5 and a lower liquid level detection pipe 6 are provided, and the instrument diaphragm 8 is provided. The system is configured to be installed, and the system pressure measured on the upper side, the system pressure measured on the lower side, and the water head pressure are detected as differential pressures by the detector 9 to measure the liquid level.

  The upper liquid level detection pipe 5 has a structure for storing water so that the steam on the system side does not directly contact the instrument diaphragm 8, and the liquid is detected so that the temperature of the instrument diaphragm 8 satisfies the required value on the instrument. Specifies the slope and dimensions of the position detection pipe. Also, the lower liquid level detection pipe 6 has the same gradient and pipe dimensions as the upper liquid level detection pipe 5.

  The operation and effect of the liquid level measuring device of the liquid tank configured as described above will be described. Since the branch part where the two balance pipes branch from the lower pipe 3 is the B part having the same level, the liquid level of each balance pipe 4 is balanced with reference to the B part. For this reason, as shown in FIG. 2, if the liquid temperature in one balance tube 4 becomes high, the liquid level in the higher balance tube 4 rises, but the water head pressure in part B is Since the liquid head height is equal to the density and the head pressure is the same in the balance tube 4 and the portion B where the temperature is lower, no change occurs in the balanced state. In this way, by providing a pipe part having the same height as the B part which is a branch point of the balance pipe 4, and by setting the connection point of the lower liquid level detection pipe 6 to the same height as this B part, It becomes possible to detect the same water head pressure, and it is possible to perform measurement without being influenced by the liquid level difference generated in the balance tube 4 and without causing a deviation. Here, even when there are more than two balance tubes 4, as shown in FIG. 3, the measurement system can be secured by making the branch at the same level as the B part which is a branch point.

  4 and 5 are diagrams each showing a configuration of the liquid level detection pipe. As shown in FIG. 4, the upper liquid level detection pipe 5 and the lower liquid level detection pipe 6 are inclined downward from the connection point of the balance pipe 4 toward the instrument diaphragm 8. In this embodiment, the gradient is 1/10. The upper liquid level detection pipe 5 is configured to store water in the liquid level detection pipe so that the temperature is 100 ° C. or less depending on the usage conditions of the instrument diaphragm 8, so that the pipe slope can be radiated with a sufficient pipe length. I have to. As for the lower liquid level detection pipe 6, the temperature difference in the instrument diaphragm 8 is reduced and the measurement error due to the temperature deviation is reduced.

  As schematically shown in FIG. 5, the lower liquid level detection pipe 6 is filled with liquid, and the 1/10 descending portion and the instrument diaphragm 8 are also filled with liquid. The upper liquid level detection pipe 5 is filled with steam, and the 1/10 descending portion and the instrument diaphragm 8 are filled with liquid.

  FIG. 6 is a diagram illustrating an example of a temperature change in the piping gradient portion. The temperature of the joint part of the upper liquid level detection pipe 5 of the balance pipe 4 is high because of the state of steam, and the temperature of the joint part of the lower liquid level detection pipe 6 is liquid, so that the temperature is low. It has become.

  In this evaluation example, the temperature of the joint part of the upper liquid level detection pipe 5 of the balance pipe 4 is 230 ° C., the temperature of the joint part of the lower liquid level detection pipe 6 is 190 ° C., and there is a temperature difference of 40 ° C. For this reason, when measures for reducing the temperature difference are not taken, the temperature difference of the instrument diaphragm 8 is about the same as that of the balance pipe 4 and an indication error of about 20 mm is generated. By ensuring a sufficient gradient and a sufficient pipe length, the temperature difference can be reduced to about 5 ° C. at a pipe length of 56 cm, and the instrument indication error can be reduced to about 2.5 mm.

  When the measurement system is multiplexed, it is effective in reducing the water level deviation by using the same configuration of the piping of all the instruments. Furthermore, by adopting a configuration in which the temperature difference of the balance tube does not occur, the influence due to the temperature difference can be further reduced.

  One of the causes of the temperature difference in the balance pipe is that the condensed water generated in the upper pipe 2 flows into the balance pipe 4. In the configuration in which two balance pipes are installed, in order to keep the temperature of the balance pipe the same, it is necessary to uniformly control the inflowing condensed water, but it is difficult to adjust the connection shape of the pipes.

  From the viewpoint of preventing non-condensable gas accumulation, it is difficult to return the condensed water to the system side when the upper piping in the nuclear power generation facility has a downward slope toward the balance pipe. 7 is newly installed so that the condensed water is discharged to the lower pipe 3 without going through the balance pipe 4, so that the temperature difference in the balance pipe can be suppressed and the measurement accuracy is further improved. There is an effect that can be done.

  FIG. 7 is a perspective view showing a position where the discharge pipe 7 is provided. As shown in FIG. 7, it is desirable to shorten the distance L between the A portion that is the branch point of the upper pipe 2 and the balance pipe 4 and the C portion that is the branch point of the discharge pipe 7.

  According to this embodiment, the lower branch height of the balance pipe connected to the upper pipe and the lower pipe is the same height, and the lower liquid level detection pipe connected to the balance pipe is the lower branch height of the balance pipe. Therefore, even if a deviation occurs in the water level of the balance pipe due to the temperature difference in the balance pipe, the water head pressure applied to the lower liquid level detection pipe can be made to match at the branch reference level and installed in each balance pipe. In addition, the same measurement is possible for the liquid level detection of the water level gauge.

  In particular, in a pipe configuration that employs a diaphragm type differential pressure transmitter as a liquid level gauge, the temperature difference due to the influence of the liquid temperature on the balance pipe side, etc. in the diaphragm section that detects the pressure It is possible to reduce the temperature difference of the diaphragm part by increasing the size of the upper and lower pipes, so that the dimensions, gradients, and pipe specifications of the upper and lower pipes are the same.

  In addition, a drain pipe that discharges condensed water to the lower pipe side is installed in front of the branch part of the upper balance pipe, so it is possible to prevent the condensed water generated in the upper pipe from flowing into the balance pipe. A temperature difference can be prevented from occurring.

  Condensate water generated in the upper pipe usually flows to the balance pipe side and flows into the balance pipe due to the pipe gradient, but the condensed water is a high temperature close to the steam temperature on the system side and is a factor that raises the temperature of the balance pipe. . In the water level meter configuration with a plurality of balance pipes, it is difficult to dispose of the condensed water generated in the upper pipe evenly into each balance pipe. Condensed water flowing into each balance pipe by installing a discharge pipe in the upper pipe part as close as possible to the branch part of the balance pipe and having the same pipe length from the discharge pipe to each balance pipe Can be made the same amount, and the occurrence of a temperature difference in the balance tube can also be suppressed.

It is a partial cross section figure of the liquid level measuring apparatus of the liquid tank which is one Example of this invention. It is explanatory drawing of the liquid level measurement of the balance pipe of a present Example. It is a figure which shows the branch method of the multiplexed balance pipe | tube of 3 or more series. It is a perspective view of a liquid level detection piping part. It is a longitudinal cross-sectional view of a liquid level detection piping part. It is a figure explaining the heat dissipation effect of a liquid level detection piping part. It is a perspective view which shows the example of installation of a discharge pipe.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Liquid tank 2 Upper piping 3 Lower piping 4 Balance pipe 5 Upper liquid level detection piping 6 Lower liquid level detection piping 7 Outlet pipe 8 Instrument diaphragm part 9 Detector 10 Main valve 11 Instrument inlet valve

Claims (4)

  A tank in which liquid is stored; an upper pipe communicating with the upper part of the tank; a lower pipe communicating with the lower part of the tank; and a plurality of balance pipes connected to the upper pipe and the lower pipe via branch parts. An upper liquid level detection pipe connected at the upper part of the balance pipe, a lower liquid level detection pipe to which the branch portions of the plurality of balance pipes are connected at the same height, the upper liquid level detection pipe and the lower liquid pipe A liquid level measuring device for a liquid tank provided with a detector connected to a side liquid level detecting pipe via an instrument diaphragm.   The liquid level measuring device for a liquid tank according to claim 1, wherein the upper pipe and the lower pipe are connected by a discharge pipe.   The liquid level measurement of the liquid tank according to claim 1 or 2, wherein a descending slope portion is provided between the upper liquid level detection pipe and the lower liquid level discharge pipe and the instrument diaphragm, and the pipe length is long. apparatus.   The liquid level measuring device for a liquid tank according to claim 1, wherein a water filling valve is provided in the instrument diaphragm.

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