JPH0362217B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention provides a gas corrosion tester for pre-testing the corrosion status of various materials such as metals, plastics, and various coating materials under various environments in which they are used. Regarding the improvement of

Conventional technology In a gas corrosion tester, in order to maintain the gas concentration in the test chamber at a constant value, the corrosive gas must be diluted with an inert gas. Measure according to numerical values,
It was common to mix both gases.

In many cases, to determine this flow rate, a rotor type flow meter, which has been widely used in the past, is used, or a metering device such as the one described in Japanese Patent Publication No. 35-1187 is used. was.

In addition to the above-mentioned mechanical devices, for example,
As described in the microfilm of Publication No. 2315, Japanese Patent Publication No. 56-34818, or Utility Model Application No. 154176/1988 (Utility Model Application No. 77942/1981), the gas concentration in the test tank is constantly detected and There is also a mechanism that opens a solenoid valve that sends corrosive gas by an electric signal when the concentration is insufficient to a predetermined level.

Problems to be Solved by the Invention However, in the above-mentioned prior art, the float-type flowmeter or fixed-rate pumping device, etc., is intended only to feed a fixed amount of gas;
Due to mechanical measurement errors, gas consumption in the tank, etc., it is difficult to maintain a constant concentration in the tank, and furthermore, it has the disadvantage that it cannot operate in response to the gas concentration in the test tank.

In addition, with mechanisms that use solenoid valves, the supply of corrosive gas is controlled by the opening and closing of the solenoid valve, so
The problem was that the gas supply was intermittent, causing the gas concentration in the test chamber to fluctuate in stages.

When these conventional techniques are used, corrosive gas,
For example, homogeneous mixing of sulfite gas, hydrogen sulfide gas, nitrogen oxide gas, etc. and inert gas, such as nitrogen gas, air, etc., tends to result in non-uniformity due to differences in the specific gravity of the two, poor compatibility, etc. The only work that could be done was to mix the mixture by dilution, stirring, diffusion, etc. in a large-capacity test tank and hoping that the mixture would be homogenized.

By the way, the most important thing in a gas corrosion tester is to always maintain the gas concentration in the test tank at a predetermined value, and if this condition is met, accurate corrosion tests can be performed. .

In particular, in the tank, highly reactive gas is consumed due to reactions with moisture, test pieces, etc., and the gas concentration decreases. The amount of gas consumed changes from moment to moment depending on the conditions inside the test tank, so even if the gas concentration fed into the test tank can be maintained constant, the concentration inside the tank will drop and its value will constantly fluctuate.

In addition, when sulfur dioxide gas, hydrogen sulfide gas, nitrogen oxide gas, etc., which are most commonly used as corrosive gases for gas corrosion tests, react with metals and exert a corrosive effect, the degree of corrosion progress depends on the concentration of the corrosive gas. However, the relationship between the degree of corrosion progress and gas concentration is strong at low concentrations, and at high concentrations, concentration fluctuations have no significant effect. For example, in the case of sulfur dioxide gas, hydrogen sulfide gas, etc., the degree of corrosion changes greatly when the gas concentration is between 3 and 10 ppm.

In particular, as research on corrosion due to the recent development of air pollution progresses, tests are required in environments with even lower concentrations as described above, and it is necessary to maintain the gas concentration in the tank at a low and constant value. There was a request to develop a gas corrosion tester.

The present invention has been made in response to such demands, and is capable of constantly maintaining the gas concentration in the test chamber at a predetermined value, and even when the concentration is low, it is possible to always maintain the gas concentration at a predetermined value. It provides a gas corrosion tester.

Furthermore, in a gas corrosion tester, it is necessary to continuously supply a constant amount of gas at a constant concentration.

For example, when conducting a corrosion test using sulfur dioxide gas at a concentration of 25 ppm, the corrosive gas (pure gas or pure gas diluted to some extent with nitrogen gas) is sent from a high-pressure cylinder through a pressure reducing valve to a flowmeter, and the flow rate per hour is measured. is kept constant and mixed with a calculated value of active gas for dilution (mostly air). Since a standard gas of about 3% is usually used as the corrosive gas, this corrosive gas must be diluted 1200 times. In a standard test chamber, the diluted gas is 20
It is continuously fed into the test chamber at a rate of approximately 1/2 min. In this case, the flow rate of the corrosive gas is 16-17 c.c./min. It has been difficult in the prior art to precisely measure such a small amount of gas.

Further, the specific gravity of many corrosive gases is greater than that of air, and many of them have poor compatibility with air.
Conventionally, it has been difficult to continuously and uniformly mix these gases with air several hundred times or more than a thousand times.

The present invention was made to solve these difficulties, and aims to continuously supply a constant amount of gas even in a small amount, and uniformly mix corrosive gas and inert gas. The present invention provides a gas corrosion tester that can perform

Means for Solving the Problems The present invention solves the above problems, and includes:
The contents will be explained below using drawings corresponding to the embodiments. Cylinder 1 containing corrosive gas
is connected to a gas corrosion test tank 10 via a pressure reducing valve 2, a solenoid valve 3, a corrosive gas constant pressure storage tank 4, and a quantitative dilution mixer 9. The constant pressure storage tank 4 is supplied with high pressure corrosive gas from the cylinder 1 through the pressure reducing valve 2 and the solenoid valve 3, and temporarily reduces the pressure to almost atmospheric pressure, but slightly higher than atmospheric pressure. It is a device for storing and sending it to the quantitative dilution mixer 9,
A manometer 5 for maintaining a constant pressure of the corrosive gas is connected to the storage tank 4.

This manometer 5 consists of water 14 and three electrodes 13.
When the water level in the manometer 5 rises and falls in response to slight fluctuations in the gas pressure in the storage tank 4, conduction between the electrodes is interrupted and the solenoid valve 3 of the gas supply circuit is connected via the relay circuit 6. It opens and closes, adjusts the supply of corrosive gas from the cylinder 1, and maintains the corrosive gas in the storage tank 4 at a constant pressure with a very small positive pressure almost close to atmospheric pressure.

On the other hand, the air compressor 7 is connected to the gas corrosion test tank 1 via a flow rate regulator 8 and a quantitative dilution mixer 9.
0 has been contacted.

A quantitative dilution mixer 9 for mixing and diluting a corrosive gas and an inert gas in a quantitative ratio includes a thick tube 15 and a thin tube 1.
Consisting of 6 double pipes, the inside of the thick pipe 15 is filled with inert gas,
A corrosive gas passes through the thin tube 16 and the thick tube 15
A constricted portion 18 is provided in the middle of the tube, and the tip opening 17 of the thin tube 16 faces this constricted portion 18 .

When a large amount of pressurized inert gas flows through the thick tube 15, the tip opening 17 of the thin tube 16 becomes negative pressure, and the corrosive gas inside the thin tube 16 is sucked into the thick tube 15 and flows out. mixed with.

The end of the thin tube 16 is connected to a shaft 2 operated by thermal expansion or contraction using a piston type or diaphragm type, etc.
4, the narrow tube opening 17 and the thick tube constriction 1
By changing the interval 8, the negative pressure changes, the suction force against the gas inside the capillary increases or decreases, and the amount of gas flowing out from the capillary is adjusted. The control of this shaft 24 is performed by detecting the gas concentration in the test tank by the automatic concentration detection device 11 and in response to the signal.

Due to rapid changes in flow velocity, pressure, and flow when the mixed gas passes through the constricted portion 18, the mixed gas is instantaneously mixed in the mixing portion 27 regardless of any properties that prevent uniform mixing, such as the compatibility or specific gravity of both gases. It mixes uniformly and adjusts and maintains the gas concentration in the test chamber at a constant level.

Function The corrosive gas in the cylinder 1 is introduced into the corrosive gas constant pressure storage tank 4 via the pressure reducing valve 2 and the solenoid valve 3. When the gas pressure in the storage tank 4 rises by about +50 mmH ₂ O from the atmospheric pressure at that time, the solenoid valve 3 closes via the relay circuit 6. On the other hand, when it decreases to about +20 mmH ₂ O, the solenoid valve closes via the relay circuit 6. 3 is made to open.

As the gas in the storage tank 4 flows toward the quantitative dilution mixer 9, the gas pressure in the storage tank 4 decreases, and in the water column of water 14 in the manometer 5, the water level on the right side rises and the water level on the left side falls. .

The water level on the left side drops to the position A and becomes below the electrode A. The relay circuit 6 is activated and the solenoid valve 3 opens, and the corrosive gas is removed from the cylinder 1, the pressure reducing valve 2, and the solenoid valve 3.
It enters storage tank 4 through.

When the pressure of the storage tank 4 increases, the water level of the water 14 on the left side rises, and when it reaches the position of the electrode RO, the relay circuit 6
is activated, the current is cut off, and the solenoid valve 3 is closed.

In this way, the gas in the storage tank 4 is maintained at a constant pressure slightly higher than atmospheric pressure, and new gas flows in as the gas flows out, yet the gas pressure does not become significantly higher than atmospheric pressure.

The gas sent out from the storage tank 4 is mixed and diluted with air from the air compressor 7 by a quantitative dilution mixer 9, and then sent to the test tank 10.

In the mixer 9, the relationship between the relative position of the thin tube opening 17 and the thick tube constriction 18 and the amount of gas flowing through the conduit 19 is as shown in FIG. As the force increases, the gas amount increases, and after reaching the maximum value, as it gets closer, the gap between the opening 17 and the constriction 18 narrows, and as the flow rate of the inert gas decreases, the suction force also decreases and the gas amount decreases. do.

Therefore, when the shape and dimensions of the opening 17 and the constriction 18 are constant, the values corresponding to those shown in FIG. 5 are actually measured, and the opening 17 and the constriction 18 operate within the range shown in FIG. 5A. If the positions of the piston 23 and the thin tube 16 are set so that It is possible.

The amount of diluted gas sent into the test tank is determined as an important condition for corrosion tests, but in commonly used gas corrosion testers, the capacity of the test tank is
150 to 200, in which case the diluted gas feed rate is about 20/min.

The content of corrosive gas in this diluted gas is about 2000 to 20 ppm under normal test conditions.
The concentration of the gas sent into the tank may be adjusted by keeping the flow rate of the diluting gas constant and changing only the flow rate of the corrosive gas. A portion of the diluted gas entering the test chamber 10 is consumed by moisture, reaction with the test piece, and so on. Since the consumption amount constantly changes during the test, the gas concentration in the tank changes constantly.

Therefore, a part of the gas in the tank is continuously sampled, the concentration is continuously detected by the automatic concentration detection device 11, and the value is converted into an electric signal and sent to the conductor 25 as a current amplified by the current amplifier 12. Feed heating coil 2
2, the olefin liquid 21 is heated, and the flow rate of the corrosive gas flowing in is adjusted by changing the position of the opening 17 in the mixer 9, which is interlocked with the action described above. In response to such fluctuations, density correction is immediately performed.

Automatic gas concentration detection devices usually use instrumental analysis for sulfur dioxide gas, hydrogen sulfide gas, carbon dioxide gas, and nitrogen oxide gas, such as the Cybex line analysis method,
Known analytical instruments such as infrared analysis, flame light analysis, and electrochemical analysis can be applied.

We will explain the case where a corrosion test is performed using 3% standard sulfur dioxide gas as the corrosive gas and air as the dilution gas, maintaining the sulfur dioxide gas concentration (dilution gas) in the corrosion tester at 20 ppm.

In order to synthesize 20ppm gas from 3% high concentration sulfur dioxide gas, it is calculated that it needs to be diluted 1500 times with air.

Test tank capacity: 200, approximately 20ppm of diluent gas in the tank
It is assumed that the gas is fed at a flow rate of 20/min, and an analyzer based on the Cybrite line analysis method is used to detect the concentration of the gas, so that an electric signal inversely proportional to the concentration is sent to the conductor 25 of the quantitative dilution mixer 9.

According to the experimental results, the quantitative dilution mixer 9
In the figure, air 1 is drawn from the conduit 20 with dimensions of a thick tube with an inner diameter of 12 mm, a thin tube with an inner diameter of 1.5 mm, and a narrowed part with an inner diameter of 3 mm.
Kg/cm ² , 20/min, pressure 30mmH ₂ O from conduit 19
, the gas flow rate is about 20 ml/min, and the flow rate ratio of each of the conduits 19 and 20 is at least about 1:1000. In other words, it can be diluted a minimum of about 1000 times.

By changing the distance between the opening 17 and the constriction 18, it is possible to adjust to any magnification of 1000 times or more, and this magnification is continuously changed by the operation of the automatic concentration detection device 11 according to changes in the concentration in the test layer. , no special weighing is required.

Next, regarding the corrosive gas constant pressure storage tank 4 and the manometer 5, in Fig. 2, the storage tank 4 has a volume of approximately 2
This communicates with the manometer 5 outside the gas inlet and outlet. The manometer 5 is a U-shaped tube with a height of about 20 cm, with electrodes A and B on one side and C on the other side inserted into the water in the relative positions as shown in the figure.

The part where the conductor (C) enters the U-shaped tube is airtight. The height interval between electrodes A and B is 30 mm. The water level is set so that when the water level in the left side of the U-shaped tube is at the position of electrode A, the water level in the right side tube is 20 mm below electrode A.

By repeating the above-mentioned operations, the internal pressure of the storage tank 4 is always maintained at a slight pressure of 20 to 50 mmH ₂ O, and the pressure does not rise or fall below atmospheric pressure. If the atmospheric pressure is 10,000 mmH ₂ O, this pressure fluctuation of 30 mmH ₂ O at the maximum is only a fluctuation of 0.3% vo1.

This means that the volume of corrosive gas sent to the quantitative dilution mixer 9 will only change within ±0.15% if the temperature is constant, so it will always be in a state of almost slight pressure or constant pressure. Therefore, it is sent to mixing 9.

As described above, by the related operations of the storage tank 4, manometer 5, and mixer 9, if the amount of air entering the conduit 20 is measured by the flow rate regulator 8 and the pressure is set to 20/min and the pressure is set to 1 kg/ ^cm2 , the mixer 9 By adjusting the position of the capillary opening 17, the mixing ratio of sulfur dioxide gas to air becomes 1/1000 at maximum, and the sulfur dioxide gas in the diluted gas at this time is 30000 ppm x 1/1000 =
It is 30ppm.

That is, by adjusting the position of the capillary opening 17, the concentration of the diluent gas delivered from the mixer 9 can be adjusted to a maximum of 30 ppm.
You can freely lower it below this level.

In this state, if the automatic concentration detection device 11 is set to maintain the gas concentration in the test tank 10 at 20 ppm, the mixer 9 will respond to slight changes in the gas concentration in the test tank 10. Since the mixed gas concentration is constantly adjusted, the concentration in the test tank can always be maintained constant.

According to experiments, the fluctuation of gas concentration in the tank is less than 0.1 ppm.

Next, using pure sulfur dioxide gas (liquid gas),
The case of synthesizing 1 ppm dilution gas will be explained. In this case, the first
One set of the solenoid valve 3 to mixer 9 shown in the figure may be connected in series.

In the device of the first solenoid valve 3 to mixer 9,
The 100% corrosive gas is diluted to about 1/1000 (1000 ppm), and further diluted to 1/1000 by the second solenoid valve 3' to mixer 9' to a concentration of about 1 ppm.
In this case, in the device of the first solenoid valve 3 to the mixer 9, the position of the thin tube 16 of the mixer 9 is fixed,
There is no need to make any adjustments; it is sufficient to simply allow the secondary capillary tube 16' to move in response to the signal from the automatic concentration sensing device 11.

Example An example of implementation of the quantitative dilution mixer 9 in the gas corrosion tester of the present invention will be described.

What is shown in FIG. 3 is a piston-operated quantitative dilution mixer, in which 15 is a thick tube, 16 is a thin tube, 17 is a thin tube opening, 18 is a constriction of the thick tube 15, and 19 is a corrosive gas from the storage tank 4. 20 is a conduit for introducing air from the air compressor into the thick tube 15, 21 is an olefin liquid filled in a sealed cylinder, and 22 is a periphery of the cylinder. A heating coil 23 wound around the olefin liquid is a piston portion that moves slightly within the cylinder due to thermal expansion or contraction of the olefin liquid, and is fixed to the thin tube 16 by a shaft 24.

25 is a gas automatic concentration detection device 11 in the test tank 10
This is a conducting wire for converting an electric signal from the heating coil 22 into a current amount amplified by the current amplifier 12 and passing the current through the heating coil 22. 26 is an auxiliary spring for assisting the force of the piston 23 to retreat when the olefin liquid 21 contracts; 27 is an inert gas from the thick pipe 15;
The mixture of corrosive gases from the capillary tube 16 rapidly expands and diffuses, forming a vortex and passing through the mixing section, where both gases are forcefully mixed instantaneously and uniformly.

Next, as a mechanism for adjusting the position of the thin tube 16 of the quantitative dilution mixer, a diaphragm system as shown in FIG. 4 may be adopted. In this case, the heating element 28 is activated by a signal from the automatic concentration detection device 11, and the gas sealed in the diaphragm expands or contracts in proportion to the amount of heat generated, and this is transmitted to the thin tube 16 by the shaft 29. . 30 is a thin tube 16
31 is an expansion diaphragm, and 32 is a conduit.

In addition, if a certain degree of variation in the concentration in the test tank is allowed, such as when performing a gas corrosion test at a corrosive gas concentration of about 100 ppm or more, the pressure of the corrosive gas sent to the quantitative dilution mixer may be slightly lower than atmospheric pressure. The device for maintaining a constant positive pressure, that is, the solenoid valve 3, high concentration gas constant pressure storage tank 4, manometer 5, and relay circuit 6, is omitted, and two pressure reducing valves 2 are connected in series to reduce the gas pressure to 0.01. Even if the gas concentration is maintained at approximately Kg/cm ² and the gas is directly connected to the conduit 19 of the quantitative dilution mixer 9 and sent, it is possible to maintain the gas concentration in the test chamber within ±10% of the predetermined value.

Effects of the Invention Therefore, according to the present invention, the gas concentration in the test tank in the gas corrosion tester can always be maintained at a predetermined value, and by satisfying this condition, it is possible to perform an accurate corrosion test. It can be carried out.

In particular, in the tank, highly reactive gas is consumed due to reactions with moisture, test pieces, etc., and the gas concentration decreases. The amount of gas consumed changes from moment to moment depending on the conditions inside the test tank, and the concentration of the gas fed into the test tank can be adjusted in response to this change.

Further, according to the present invention, even when the gas concentration in the test tank is low, it can always be maintained at a predetermined value.

Furthermore, the present invention is capable of continuously feeding a constant amount of gas at a constant concentration into the test chamber.

In addition, the present invention provides a method for controlling a certain amount of gas even if it is a small amount.
It can be fed continuously and uniformly mix corrosive gas and inert gas. In other words, due to rapid changes in flow rate, pressure, and flow when the mixed gas passes through the constricted part of the quantitative dilution mixer, the mixing part does not change regardless of the compatibility, specific gravity, or other properties that prevent uniform mixing of both gases. The gas concentration in the test chamber can be adjusted and maintained at a constant level.

[Brief explanation of drawings]

The drawings show an example of the implementation of the present invention, and FIG. 1 is an explanatory block diagram of a gas corrosion tester, FIG. 2 is an enlarged front view of a manometer, and FIG. 3 is an enlarged front view of a quantitative dilution mixer. FIG. 4 is an enlarged front view of another embodiment of the quantitative dilution mixer, and FIG. 5 is an explanatory diagram showing the relationship between the distance between the capillary opening and the constriction and the corrosive gas flow rate. 1... cylinder, 2... pressure reducing valve, 3... solenoid valve,
4...Constant pressure storage tank, 9...Quantitative dilution mixer, 5...
... Manometer, 6 ... Relay circuit, 7 ... Air compressor, 8 ... Flow rate regulator, 10 ... Gas corrosion test tank, 11 ... Automatic concentration detection device, 12 ...
...Current amplifier, 23 ... Piston, 31 ... Diaphragm, 18 ... Constriction, 15 ... Thick tube, 1
6...tubule, 24...shaft, 17...tip opening.

Claims (1)

[Scope of Claims] 1. In a gas corrosion tester in which a corrosive gas such as sulfur dioxide gas, hydrogen sulfide, or nitrogen oxide gas is diluted and mixed with an inert gas such as nitrogen gas or air, and the mixture is introduced into a gas corrosion test tank. , a cylinder 1 containing a corrosive gas is passed through a pressure reducing valve 2, an electromagnetic valve 3, and a corrosive gas constant pressure storage tank 4 to a thick pipe 15 having a constricted portion 18.
A manometer 5 is connected to the storage tank 4, and this manometer 5 is connected to a relay circuit 6.
The air compressor 7 is connected to the quantitative dilution mixer 9 via the flow regulator 8, and the mixer 9 is connected to the gas corrosion test tank 1.
0, and the mixer 9 and the test tank 10 are connected by an automatic concentration detection device 11 and a current amplifier 12. Concentration detection device 11
Depending on the current value generated, the piston type 23 or diaphragm type 31 of the quantitative dilution mixer 9 is actuated using thermal expansion and contraction to adjust the amount of corrosive gas fed, and to constantly maintain the gas concentration in the test chamber 10. A gas corrosion tester characterized by constant maintenance. 2. The gas corrosion tester according to claim 1, wherein a shaft 24 operated by thermal expansion or contraction is connected to one end of the thin tube 16 by a piston type or diaphragm type. 3. The gas corrosion tester according to claims 1 and 2, characterized in that the tip opening 17 of the thin tube 16 faces the constriction 18 of the thick tube 15.