JPS60235013A - Measuring apparatus of vertical micro-displacement with temperature compensation - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention includes a plurality of measuring containers each containing a measuring liquid, which are disposed in communication with each other at different heights, and the difference in mutual displacement of the measuring height positions is determined by measuring the liquid in the measuring containers. The present invention relates to an apparatus for measuring minute displacements in the vertical direction and having a temperature compensation function that measures differences in surface displacements.

[Prior art and its problems]

Measuring minute displacements in the vertical direction between multiple objects is necessary when measuring alignment changes between bearings in machines that have a large number of bearings, such as steam turbine power generation equipment, thermal deformation of concrete foundations, uneven settlement, etc. Become. In measurement in such a case, it is necessary to accurately measure a displacement difference of 1/1oo, 1 unit, and the principle of the conventional measurement method is shown in FIG.

In FIG. 1, one of the plurality of measurement height positions is defined as a reference height position 10, and the measurement container is placed at this position. In this case, this measurement container serves as a reference and will be hereinafter referred to as the reference container. Then, the measurement container 2 is placed at the measurement height position 20, and both containers 1.2 are connected by the measurement pipe 3a. Although not shown, the other measurement pipe 3b connected to the measurement container 2 is connected to a measurement container installed at another measurement height position. Then, the measuring liquid 4 is added to these measuring vessels and measuring pipes.
Put in.

Measure the height hl of the liquid level 4a of the measurement liquid 4 in the reference container l, for example, the height hl of the liquid level 4a from the upper edge of the reference container 1 as shown in the figure, and similarly measure the height of the liquid level 4b with respect to the measurement container 2. h2
Measure. If the difference in height between the reference height position 10 and the measured height position is δ as shown in the figure, and the measured height position is displaced upward or downward by Δδ from that state, then
The height h2 of the liquid level 4b relative to the measurement container 2 changes by Δh2, and the liquid level height in the reference container 1 also changes by Δh1. Accordingly, the internal cross-sectional area of container 1.2 and Δh1. Determining the displacement Δδ from Δh2 can be easily done by calculation. It is also possible to measure the change in height from the upper edge of another measurement container (not shown) to the liquid level, and similarly calculate the displacement difference from the reference height position.

Figure 2 shows an example of a method for electrically measuring the amount of vertical displacement of a float due to changes in the height of the liquid using a displacement sensor. An eddy current type non-contact displacement sensor is installed on the top lid of the container. The change in the gap X between the upper end surface of the metal float 6 and the upper end surface is measured by the output 51.

Note that an open hole 71 is provided in order to always make the pressure in the space 7b above the liquid level 4b of the measurement container 2 equal to atmospheric pressure. In addition to the above-mentioned eddy current type non-contact displacement sensor, a differential transformer type displacement meter, a capacitance type displacement meter, etc. are used as means for detecting the vertical displacement of the float.

However, as mentioned at the beginning, for measurement targets such as steam turbine power generation equipment, there is a large change in the environmental temperature in which the measurement container and piping are installed, from the cold state of the machine that has been fully prepared for measurement to the hot state of the machine in operation ( 50 to 70° C.), it is extremely difficult to measure minute displacements in units of 1/100 degrees Celsius using this measurement method for the following reasons.

Figure 3 shows reference container 1. This is an example showing the state of temperature change at measurement height positions 1.0 and 20 where measurement container 2 is installed.When the machine is stopped (when cold) for measurement preparation, both of the machine's temperature changes with respect to t1℃. In the operating state (hot machine), the temperature rises to t2°C at measurement height position 10 and to t4°C at measurement height position 20. Here, T-T indicates the turbine chamber wall, and the measurement height position 20 is located inside the turbine chamber. This will be explained using a table.

Table 1 Table 1 summarizes the influence of the components of the liquid level measuring device on which the float floats on the vertical behavior of the float when the environmental temperature of the measurement container rises from t1°C to t4°C.

Here, assuming that the inner diameter of the measuring container is r, the outer diameter of the float is d, the density of the measuring liquid is ρ, and the volume of the measuring liquid inside the container is 1v, the displacement of the float due to temperature rise is shown in Table 1. The direction decreases as the inner diameter of the measuring container increases or the density ρ of the measuring liquid decreases, and the buoyancy decreases, and it rises as the outer diameter d of the float increases or the volume V of the measuring liquid increases. The error is expressed as the sum of the float displacement errors due to the temperature described above. If the measurement container and float are made of a low thermal expansion material such as invar, the errors that often occur in these components will be greatly reduced, but in reality, changes in the density and volume of the measurement liquid will occur. This element alone dominates the overall error, and for example, if t, -t, and y are 50°C, it is 1/□. An error of ~1 m+ unit occurs.

In view of such conventional problems, a known technique (Japanese Patent Publication No. 5B, 1983) has been proposed in which the volume of the float is increased or decreased according to the temperature change of the liquid in order to eliminate the error caused by the temperature change of the liquid.
There is a liquid level gauge float introduced in -8452. This monitors the amount of liquid in the tank by measuring the liquid level with a float, and FIG. 4 is a cutaway partial sectional view of the structure of this float.

In FIG. 4, the temperature sensing operation section 54 expands and contracts in the longitudinal direction due to changes in liquid temperature, and this movement is transmitted to the expansion and contraction section 53, which is a part of the float 52 floating on the liquid 51, via the connecting rod 55. , the volume of the float, or buoyancy, is controlled according to the liquid temperature,
The liquid level indicator provided at the end of the connecting rod 56 is used to measure the corrected liquid level. However, even this method is not a sufficient means for obtaining measurement accuracy of 1/1ooIllI unit. The reason for this is that it is not easy in terms of manufacturing technology to incorporate a correction device into a float as small as several tens of cubic centimeters, and even if it were possible to manufacture it, it generally has nonlinear characteristics with respect to changes in liquid density and temperature. However, it may be difficult to faithfully correct the float to account for density changes.
The change in the buoyancy of the float due to the change in the density of the liquid to be measured is primarily determined by the temperature of the liquid to be measured. Regarding the vertical displacement, when multiple containers with floats floating are connected, the liquid level will be the same due to the difference in the height position of the containers, but there will be a difference in the amount of liquid in the containers, making it difficult to correct the temperature. This is because. However, if the amount of liquid in the measurement container is determined in advance, it is possible to correct this amount, but adjusting the amount of liquid is not preferable because it greatly increases the preparation time for measurement.

[Purpose of the invention]

In view of the above-mentioned drawbacks, this invention provides a simple method for measuring displacement errors due to environmental temperature with sufficient accuracy when measuring minute displacements in the vertical direction by measuring displacements at measurement height positions using liquid level measurements. It is an object of the present invention to provide a compensation measuring device for minute displacements in the vertical direction.

[Summary of the invention]

This object is achieved according to the present invention, in which measurement containers that communicate with each other are provided so as to be able to change in height, and the height displacement between the containers is detected from the amount of displacement of the measurement liquid contained in the measurement containers. A compensating means containing a measuring liquid of the same quality as the measuring liquid up to the same level in a compensating container having the same structure as the measuring container is provided under the same temperature conditions as the measuring container, and the measured liquid in the compensating container is calculated from the displacement of the measuring liquid in the measuring container. This is achieved by subtracting the displacement of .

[Embodiments of the invention]

The present invention will be described in detail below based on the drawings.

FIG. 5 is a diagram showing the main parts of a liquid level measuring device that measures the vertical displacement of a float using an eddy current type non-contact displacement sensor (hereinafter referred to as a displacement sensor) according to an embodiment of the present invention. In addition,
In the figures after FIG. 5, the same parts as in FIGS. 1, 2, and 3 are given the same reference numerals. In FIG. 5, the measuring container 2 and the compensating container 2a as temperature compensating means are adjacently connected by pipes 3], 32 and pulp 9, and are installed at a measuring height position 20. The end of the pipe 3 is connected to a measurement container that is paired with a compensation container installed at another measurement height position (not shown).

The compensating means, in which the compensating container 2a is filled with a constant liquid to be measured and filled with Pel 1, is constructed by the following procedure. That is, a pair of containers, the measurement container 2 and the compensation container 2a, are installed at the measurement height position, the pulp 9 of the connection pipe is opened and connected, and the containers are filled with the measurement liquid and floats 6.6a are floated in each container. Ethylene glycol used as the measurement liquid here has strong hygroscopicity, and in order to prevent changes in specific gravity due to water absorption and evaporation in high-temperature environments, equal amounts of liquid paraffin are added to each container to separate ethylene glycol 4,4a and air. Layers 8, 8a are formed on the interface. After installing the displacement sensor, the compensating means is ready by closing the pulp 9.

After this, when the environmental temperature around the container changes, the float 6.6a
will result in the displacement error shown in Table 1, but
Since both containers 2 and 2a are placed at the same environmental temperature, the amount of displacement of both floats 6 and 6a due to temperature changes is equal. In other words, the float 6 of the measurement container 2 measures both the vertical displacement of the measurement height position 20 and the displacement error due to environmental temperature changes, but since it is independent from the measurement system of the float 6ai of the compensation container 2a, the environmental Only the displacement error due to temperature is measured.

Therefore, by taking the difference between the two measured values, the correct vertical displacement of the height of the measurement position can be measured. In this embodiment, the measuring container 2 and the compensating container 2a are placed on the same level and communicated through the valve 9, so that the measuring solution 4, 4 in both containers is
It has the feature that the water surface position of point (a) can be easily adjusted.

Figure 6 shows an example of an arithmetic circuit that measures the vertical displacement difference between a reference height position and a measurement height position based on one of the measurement height positions where a plurality of measurement vessels are installed. , the outputs of the displacement sensors 11 and 11 of the pair of reference containers and compensation containers installed at the reference height position 10 are passed through the respective preamplifiers 12 and 12a to a computing unit 13 such as a differential amplifier. Enter. The output 14 after the calculation is the true vertical displacement after removing the error due to the temperature change (1+→t2° C.) at the reference position height 10.

Similarly, at the height position 20 to be measured, the true value is transmitted between the displacement sensors 21 and 21a of the pair of measurement containers and the compensation container, the preamplifiers 22 and 22a, and the arithmetic units such as the differential amplifier. A vertical displacement 4 of Obtainable.

Figure 6 shows an example in which there are two measurement height positions, but if the number of measurement height positions increases, adding a calculator will allow accurate vertical minute displacement with temperature compensation. can be easily obtained. Furthermore, if the measurement height position where there is almost no environmental temperature change, for example, the reference height position used as a reference, is a position where there is almost no environmental temperature change, a compensation container for temperature compensation should be placed adjacent to this position. Of course, there is no need to install it.

By the way, when the environmental temperature rises, the air dissolved in the measurement liquid becomes bubbles and flows into the measurement piping of the container, and as the bubbles increase, the communication function is lost and the liquid level in each container is equal. Also, since the measurement piping is made of a synthetic resin material made of a flexible polymer material with circular visibility that is convenient for removing air bubbles, the vapor of the measurement liquid passes through the pipe wall and the measurement liquid This may cause errors in long-term measurements. Therefore, in order to prevent the generation of bubbles, it is desirable to use the ethylene glycol liquid used in the Examples. This means that the dissolution rate of air is small,
It was far superior to the incavitol aqueous solution used as the manometer solution, and the generation of bubbles was negligible even in continuous environmental tests at 80°C. In addition, in order to prevent the permeation of vapor from the walls of the measurement piping, a high-density polyethylene tube is desirable; for example, the water vapor permeability of this tube is 0.02 to 0.04 gr/24hn, i,
m, crnHg (21°C), which is several tenths of that of the conventionally used hard vinyl chloride tube, so there is no problem in long-term measurements.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, a compensating means filled with a measuring liquid to the same level as the measuring liquid is provided in a compensating container having the same structure as the measuring container under the same temperature condition as the measuring container. By subtracting the displacement of the measurement liquid in the compensation container from the displacement of the measurement liquid in the measurement container, it is possible to eliminate measurement errors caused by thermal expansion of the measurement container, density changes, volume changes, etc. of the measurement liquid. ,
Long-term measurements in high-temperature environments are now possible.

[Brief explanation of the drawing]

Figure 1 is a diagram explaining the principle of the conventional method using the water level measurement method, Figure 2
Figure 3 is an explanatory diagram showing an example of a conventional water level measuring means, Figure 3 is an explanatory diagram showing an example of temperature change at a measurement height position, and Figure 4 is a cutout showing an example of a float of a conventional water level measuring means. 5 is an explanatory diagram showing an embodiment of the present invention, and FIG. 6 is a circuit diagram for calculating a displacement difference according to an embodiment of the present invention. 2...Measurement container, 2a...Compensation container, 4.4a...
・Measuring liquid, 5, 5a... Displacement measuring device, 6, 6a...
- Float, 9... Pulp, 10 - Reference height position, 2o - Measurement height position. Figure 1 55 Figure 4 Figure 5 Figure 6

Claims (1)

[Scope of Claims] 1) In a device in which measurement containers that communicate with each other are provided so as to be able to change in height, and a height displacement between the containers is detected from the amount of displacement of a measurement liquid contained in the measurement containers, the measurement A compensating means containing a measuring liquid of the same quality as the measuring liquid up to the same level in a compensating container having the same structure as the container is provided under the same temperature conditions as the measuring container, and the displacement of the measuring liquid in the measuring container is calculated based on the displacement of the measuring liquid in the compensating container. A temperature-compensated vertical minute displacement measurement device that subtracts displacement. 2. A vertical minute displacement measuring device with temperature compensation according to claim 1, characterized in that the measurement container and the compensation container are placed at the same level and communicated through a valve.