JPS5828199Y2 - Self-cooling strain detection device - Google Patents

Description

[Detailed description of the invention] The present invention relates to a load detection device that measures the stress generated when a load is applied to a structure, etc., and is particularly suitable for measurement in high temperature and high pressure atmospheres such as saturated steam. It is also made to withstand.

In addition to measuring loads, the load detection device according to the present invention can also be applied to devices that measure stress and displacement of objects to be measured, or to pressure gauges, vibration meters, accelerometers, and the like.

To measure loads and stresses applied to machines and structures, as well as displacements based on these, strain gauges such as resistance wire strain gauges have been used.

However, the maximum operating temperature of the gauges (strain detection parts) of these conventional strain meters is 200° C., considering its accuracy, and it has been difficult to use them in an atmosphere of 200° C. or higher.

In addition, when external pressure is applied, the wall thickness of this strain gauge must be increased, so there is a risk that the case will bear part of the load applied to the object to be measured, and the correct value will not be transmitted to the load detection rod. There is.

Even in a high-temperature atmosphere, if the pressure is low, the temperature of the gauge part can be lowered by using forced circulation cooling methods such as water or air.
It could not be used when attempting to measure the thrust force caused by fracture of a heat exchanger tube under high temperature, high pressure saturated steam (for example, 60 ata, 274° C. steam).

However, in order to accurately measure the safety strength of a boiler, it is necessary to statically or dynamically measure heat exchanger tube stress under actual operating conditions. The equipment was strong and weighed down the car.

The present invention is in response to the above-mentioned needs, and aims to provide a self-cooling type load detection device that can accurately measure the load, etc., being applied to an object to be measured under a high temperature and high pressure atmosphere in an adverse environment.

The configuration of the present invention to achieve such an object is to attach a load receiving plate to each end of a detection rod equipped with a detector, and attach a load receiving plate to one of the load receiving plates at both ends to surround the detector of the detection rod. A cylinder is provided on the other load receiving plate of the outer cylinder surrounding the inner cylinder so as to enable relative sliding movement in the axial direction between the cylinder and the inner cylinder. The inner cylinder and outer cylinder fitted together form a nearly hermetic vacuum expansion chamber that isolates the detection rod from an external high-temperature, high-pressure atmosphere, while the vacuum expansion chamber is opened to the atmosphere and the outer cylinder The high-temperature, high-pressure fluid that flows in from the gap between the inner cylinder and the inner cylinder is adiabatically expanded under reduced pressure in the reduced-pressure expansion chamber to reduce heat.

It is characterized in that the detector and the detection rod are cooled with the obtained low-temperature, low-pressure fluid.

The configuration of the present invention will be explained below based on one specific example shown in the drawings.

Load receiving plates 13 and 14 connected to an object to be measured (not shown) are respectively attached to both ends of a detection rod 12 to which a resistance wire strain gauge 11 serving as a detector is affixed to the center.

The detection rod 12 and the load receiving plate 13.14 are connected by screw connection, and a protrusion is formed on the end surface of the detection rod 12, so that the end surface of the detection rod 12 and the load receiving plate 13.14 are fastened together. Sometimes, the entire surface is provided so that it does not touch.

That is, by interposing an air layer between the detection rod 12 and the load receiving plates 13 and 14, consideration is given to reducing the temperature rise of the detection rod 12 due to heat conduction.

Between the twisted load receiving plates 13 and 14 at both ends, there is a plate surrounding the resistance wire strain gauge 11 in order to prevent high-temperature, high-pressure fluid entering from the outside from directly touching the resistance wire strain gauge 11. An inner cylinder 15 is formed protrudingly on the upper load receiving plate 13, while an inner cylinder 15 is formed on the lower load receiving plate 14.
An outer cylinder 16 surrounding the inner cylinder 15 is provided to enable relative sliding movement in the axial direction, and the inner cylinder 15 and the outer cylinder 16 that slide relative to each other allow the outer cylinder 16 to move outwardly. A reduced pressure expansion chamber 17 is formed which isolates the detection rod 12 from the high temperature and high pressure atmosphere in a substantially hermetically sealed manner.

Further, a communication pipe 18 opened to the atmosphere is connected to the decompression expansion chamber 17, and is provided so as to open the depressurization expansion chamber 17 to the atmosphere.

Therefore, this decompression expansion chamber 17 is approximately 1 at
The pressure a is maintained at all times.

Of course, it is also possible to connect to a low pressure source other than the atmosphere, for example a lower pressure source.

19 is a lead wire extension tube for extending the lead wire of the resistance wire strain gauge 11 to the outside.

This lead wire is a resistance wire strain gauge 1.
It is connected to a device that determines the load being received from the load receiving plate 13, 14 based on the signal of 1.

A gap 20 is provided between the inner cylinder 15 and the peripheral edge of the outer cylinder 16 in contact with the inner cylinder 15 so that the reduced pressure expansion chamber 17 and the high temperature and high pressure atmosphere outside the outer cylinder 16 are communicated with each other. It is provided.

The size of this gap 20 is mainly determined by the following two factors.

For one thing, when the inner cylinder 15 and the outer cylinder 16 mutually move in the axial direction together with the detection rod 12 which expands and contracts in response to an external load, they slide so as not to restrict each other's axial movement. The objective is to ensure that it is possible.

On the other hand, in order to freely move the inner cylinder 15 and the outer cylinder 16 in the axial direction, there is a gap 20 between the inner cylinder 15 and the outer cylinder 16.
However, if the gap 20 is made larger, a large amount of high-temperature, high-pressure fluid will flow into the decompression expansion chamber 17, and the area around the resistance wire strain gauge 11 will also be exposed to the outside. This naturally creates a high-temperature, high-pressure atmosphere, making it impossible to measure the load with high accuracy. Therefore, by minimizing the inflow of this high-temperature, high-pressure fluid and allowing it to flow into the low-pressure decompression expansion chamber 17, This fluid is expanded adiabatically under reduced pressure,
This is to cause heat to drop.

Therefore, a gap must be provided to allow mutual sliding movement between the outer cylinder 16 and the inner cylinder 15, and the gap must also be large enough to prevent a large amount of external high-temperature, high-pressure fluid from flowing in. Must be.

Therefore, as shown in FIGS. 3 to 5, there is no need to provide gaps 20 of different sizes at regular intervals.

The reason for this configuration is that the minute gap for sliding movement and the gap for controlling the inflow amount of high-temperature, high-pressure fluid are made separate.

It is also optional to form a uniform gap over the entire circumference.

Note that the inner tube 15 and the outer tube 16 include not only cylindrical shapes but also rectangular tube shapes such as square shapes and triangular shapes.

Next, based on the temperature-entropy (T, S) diagram shown in FIG.
The self-cooling principle and operation of this device will be explained using a boiler heat exchanger tube rupture experiment using saturated steam (47°K) as the external high-temperature, high-pressure fluid.

However, in this diagram, reversible adiabatic changes are represented by vertical lines.

In the self-cooling load detection device of the present invention, for example, one of the two load receiving plates 13 and 14 is connected to the heat exchanger tube and the other is connected to a testing machine, and the load applied to the heat exchanger tube by this testing machine is This is used when measuring by detecting the strain that occurs in the detection rod 12, but as mentioned above, when the environment of the heat transfer tube casing is a saturated steam atmosphere, this saturated steam is It flows from the gap 20 of the device into the reduced pressure expansion chamber 17 where the pressure is low.

The cooling effect of the resistance strain gauge 11 utilizes the heat drop phenomenon that occurs when the saturated steam flows into the decompression expansion chamber 17 and is adiabatically reduced in pressure or expanded.

In Figure 6, 0-6-l-8-2-10 is pressure 1
isobar diagram of ata, 0-5-7-3-9-4 is pressure 60
It is an isobars diagram of ata.

Since the decompression expansion chamber 17 is connected to the atmosphere through the communication pipe 18, the pressure within the chamber is maintained at approximately 1 ata.

Now, if the high-pressure fluid is at a low temperature, only adiabatic decompression from point 5 to point 6 causes almost no heat drop.

However, this does not affect measurement accuracy.

This is because this device is intended for use at high temperatures of 200° C. or higher, and when used at low temperatures of 200° C. or lower, it is not necessary to lower the gauge because it can be adequately measured with a conventional gauge.

Next is the case where the fluid is at high temperature. In this case, the degree of heat drop differs depending on the state.

(a) In the case of subcooled water or highly humid steam, the heat drop is large because it expands under reduced pressure from point 7 to point 8 (or from point γ' to point 8') in an adiabatic manner, and the atmospheric temperature of the reduced pressure expansion chamber 17 is 100 It becomes ℃.

0) In the case of highly dry steam In the case of highly dry steam, it is easy to undergo an isoenergetic change (the state changes from point 9 → 9'-+2 → 10), so the fluid after expansion becomes superheated steam and reaches 100℃ or more. Heat drop worsens as the temperature rises.

However, if the atmospheric temperature of the depressurized expansion chamber 17 is 200° C. or lower, measurement can be performed with guaranteed accuracy.

As described above, according to the present invention, even if the outside is in a high-temperature, high-pressure atmosphere, the atmosphere inside the vacuum expansion chamber surrounding the internal detector (resistance wire strain gauge) can be stabilized at around 100 degrees Celsius due to the heat drop phenomenon caused by adiabatic state changes. Since the temperature can be lowered to a certain temperature, the load applied to the object to be measured can be measured with high precision using this detector.

Furthermore, since the ambient temperature around the detector can be stabilized at a constant temperature, temperature compensation can be easily performed.

In addition, since the cylinder and outer cylinder that make up the decompression expansion chamber are installed so that they can slide relative to each other in the axial direction, all of the load applied to the upper load receiving plate is transmitted to the detection rod, allowing accurate measurement. We can expect measurements.

[Brief explanation of the drawing]

Fig. 1 is a central vertical cross-sectional view showing a specific example of the self-cooling type load detection device of the present invention, Fig. 2 is a bottom view thereof, and Fig. 3 is the first
A sectional view taken along the line X-X shown in the figure, Figure 4 is A shown in Figure 1.
FIG. 5 is a perspective view showing a gap provided in the outer cylinder, and FIG. 6 is a temperature-entropy diagram showing isobar diagrams of 1 ata and 60 ata. In the drawing, 11 is a resistance wire strain gauge which is a detector, 12
13 and 14 are the detection rods, 13 and 14 are the load receiving plates, 15 is the inner cylinder, 16 is the outer cylinder, 11 is the reduced pressure expansion chamber, 18 is the communication pipe that connects the atmosphere and the reduced pressure expansion chamber, and 20 is the sliding part with the inner cylinder. It is a gap that makes it possible.

Claims (1)

[Scope of utility model registration request] A load receiving plate is attached to both ends of a detection rod provided with a detector, and an inner cylinder is provided on one of the load receiving plates at both ends to surround the detector of the detection rod, and an axial direction is provided between the inner cylinder and the inner cylinder. The inner cylinder and the outer cylinder are provided on the other load receiving plate of the outer cylinder surrounding the inner cylinder so as to enable relative sliding movement, and the inner cylinder and the outer cylinder are fitted so as to be able to move relative to each other. A nearly hermetically sealed reduced pressure expansion chamber is formed to isolate the detection rod from an external high temperature and high pressure atmosphere, while the reduced pressure expansion chamber is opened to the atmosphere, and the air flows in through the gap between the outer cylinder and the inner cylinder. A self-cooling load detection device characterized in that a high-temperature, high-pressure fluid is adiabatically expanded under reduced pressure in a reduced-pressure expansion chamber to reduce heat, and a detector and a detection rod are cooled with the obtained low-temperature, low-pressure fluid.