JP2001056309A - Conductivity detection electrode and conductivity measuring apparatus using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a conductivity detection electrode excellent in corrosion resistance and capable of accurately measuring the fine fluctuations of conductivity and a conductivity measuring apparatus using the same. SOLUTION: A pair of electrode main bodies 1 are held on an electrode holder 2 in a watertight state and noble metal cover pieces 3 are bonded to at least the leading end surfaces exposed from the electrode holder 2 of the electrode main bodies 1 to constitute a conductivity detection electrode excellent in corrosion resistance and capable of accurately measuring the fine fluctuations of conductivity. Since the electrode main bodies 1 are held on the electrode holder in a watertight state, the electrode main bodies themselves are hard to come into direct contact with water in which chemicals are charged and not almost corroded by chemicals. Since the noble metal coating layers are formed to at least the parts exposed from the electrode holder of the electrode main bodies 1, even if the electrode main bodies are immersed in water in which water treatment chemicals are charged for a long period of time, the noble metal coating layers are hard to generate a chemical change and the electrode main bodies show good corrosion resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductivity detection electrode used for water quality control of a boiler, a cooling tower, and the like, and a conductivity measuring device using the same.

[0002]

2. Description of the Related Art Conventionally, boilers and cooling towers have been widely used in various industrial fields. In the boiler, circulating water (steam) is used as a heat medium, and in the cooling tower, circulating water is used as cooling water. As described above, water plays an important role in each industrial field, and the water quality of circulating water as described above is also an important management item for operations of factories and the like.

For example, taking the case of a boiler as an example, deterioration in the quality of circulating water not only causes scale adhesion and corrosion, but also causes troubles such as carryover and forming. If these phenomena become severe, they could lead to major accidents such as rupture of pipes or water leaks.

In order to control the quality of the circulating water, impurities are removed by a water treatment device such as coagulation sedimentation, filtration, or ion exchange. Daily operating expenses are also expensive. For this reason, the water quality of low-cost boilers is controlled by water treatment chemicals, especially in medium and small boilers.

As such water treatment chemicals, alkaline chemicals such as caustic soda, sodium phosphate, sodium sulfite, hydrazine and the like are used, and they have an effect of suppressing scale and preventing corrosion. Since the concentration of these water treatment chemicals changes as the operation time of the boiler becomes longer, it is necessary to conduct a water quality test on the boiler can water to make the chemicals work effectively, and to maintain the water quality at or above a certain level. Is being done.

[0006] As part of such water quality inspection, a part of boiler can water is taken out as sample water and its conductivity and the like are measured. In other words, the conductivity increases as the impurity concentration of boiler water increases,
By maintaining the conductivity at a level below a certain value, the water quality can be maintained at a certain level or more.

[0007] In such a conductivity measuring device for measuring conductivity, a pair of electrode rods positioned at a predetermined distance are placed in sample water, and the conductivity or resistance value of the sample water is determined from the current flowing between the two electrodes. Is measured directly, or a resistance value or conductance is measured and converted into conductivity. Since the measurement object is water containing a large amount of chemicals, the electrode used in the conductivity measuring device is generally stainless steel excellent in corrosion resistance.

[0008]

However, although stainless steel electrodes have good corrosion resistance, they have a specific resistance of 7%.
It is 0-82 μΩ · cm, and it cannot be said that the current collection rate is good. For this reason, despite the fact that the conductivity must be measured by flowing a current between the two electrodes, the current is diffused into the sample water due to conduction between the electrodes and pipes, and the conductivity is measured. There is a problem that a minute fluctuation cannot be measured accurately.

Therefore, it is desirable that the electrode for measuring conductivity has a small specific resistance and a small temperature coefficient of volume specific resistance. Materials exhibiting such characteristics include copper and aluminum.
There is a problem that it is inferior in corrosion resistance to alkaline water to be measured and cannot withstand long-term use. Under these circumstances, there has been a strong demand for the development of a conductivity detection electrode having excellent corrosion resistance and capable of accurately measuring minute fluctuations in conductivity.

The present invention has been made in view of such circumstances, and a conductivity detection electrode which is excellent in corrosion resistance and can accurately measure minute fluctuations in conductivity, and a conductivity measurement electrode using the same. The purpose is to provide the device.

[0011]

In order to achieve the above object, in a conductivity detecting electrode according to the present invention, a pair of electrode bodies are held in a watertight manner by an electrode holder, and at least the electrode body is exposed from the electrode holder. The gist is that a noble metal coating layer is formed on the portion that has been formed.

According to another aspect of the present invention, there is provided a conductivity measuring device for correcting a conductivity detected by a conductivity detecting electrode, a temperature detecting means, and a conductivity detected by the conductivity detecting electrode based on a temperature detected by the temperature detecting means. The gist of the present invention is to include a rate correcting means.

That is, in the conductivity detecting electrode of the present invention, since the electrode main body is held in a water-tight manner by the electrode holder, the electrode main body itself hardly comes into direct contact with the water into which the chemicals or the like are charged. It is hardly affected by In addition, since the noble metal coating layer is formed on at least the portion of the electrode body exposed from the electrode holder, even if the noble metal coating layer is immersed in water mixed with a water treatment chemical or the like for a long time, the noble metal coating layer undergoes a chemical change. It shows good corrosion resistance because it is hard to cause. In addition, the noble metal coating layer that comes into contact with the water to be measured has a relatively low electric resistance value, so that there is a continuity between the electrode and the pipe or the like as when directly measuring with a conventional stainless steel electrode. This almost eliminates the problem and makes it possible to accurately measure minute fluctuations in conductivity. In this manner, a minute change in conductivity can be accurately measured over a long period of time.

Further, since the conductivity measuring device of the present invention includes the conductivity detecting electrode according to the first aspect, a minute change in conductivity can be accurately measured over a long period of time, as described above. Further, since the resistance value of the metal changes depending on the temperature, for example, when measuring relatively high-temperature water such as boiler water, it becomes impossible to measure the electrical conductivity accurately. Since the conductivity measuring device of the present invention includes a temperature detecting means and a conductivity correcting means for correcting the conductivity detected by the conductivity detecting electrode by the temperature detected by the temperature detecting means, the electrode body based on the temperature and the noble metal A change in the detection value of the conductivity due to a change in the resistance value of the coating layer is corrected, and more accurate measurement can be performed.

In the electric conductivity detecting electrode and the electric conductivity measuring device of the present invention, when the electrode main body is formed of a corrosion-resistant material, the corrosion of the electrode main body is further suppressed, and stable measurement can be performed for a long period of time. .

[0016]

Next, embodiments of the present invention will be described in detail.

FIG. 1 shows an embodiment of the conductivity detecting electrode of the present invention. This device includes a pair of electrode bodies 1 and an electrode holder 2 for holding the electrode bodies 1 in a substantially watertight manner. Then, the tip end surface of the electrode main body 1 is exposed from the electrode holder 2, and the noble metal coated piece 3 is adhered to the exposed portion.

The electrode body 1 has a substantially rod-like shape having a circular cross section. The tip end (left side in the figure) is formed in a slightly large diameter portion, and the rear end side (right side in the figure) is formed in a small diameter portion. A threaded portion is formed at the rear end of the portion. A peripheral groove 6 into which the O-ring 5 is fitted is formed in the large diameter portion near the front end.

The materials constituting the electrode body 1 include:
There is no particular limitation as long as the material has conductivity, and various metal materials and inorganic materials such as graphite can be selected. In particular, when measuring chemical-injected water such as circulating water in boilers and cooling towers, various stainless steels such as austenitic, ferritic and martensitic stainless steels having excellent corrosion resistance and chemical resistance, C
Various high-nickel corrosion-resistant steels such as r-Ni-Mo and Cr-Ni-Mo-Cu, nickel-based corrosion-resistant alloys such as Monel, Hastelloy, and Inconel, various titanium alloys, and corrosion-resistant materials such as pure titanium are preferably used. .

Among these corrosion-resistant materials, SUS316 and SUS3 are considered to be easily available, relatively easy to process and relatively inexpensive, and exhibit relatively good corrosion resistance.
Austenitic stainless steel such as 04 is preferably used.

As the noble metal material forming the noble metal coated piece 3, various kinds of noble metals can be used as long as they are relatively hard to cause a chemical change. For example, Au, Ag
And Pt group metals of Ru, Rh, Pd, Os, Ir and Pt. These may be used alone,
Various gold alloys, silver alloys, and platinum alloys may be used. Therefore, not only the above-mentioned noble metals but also Ni, Cu, Zn, Sn,
Those containing alloy elements such as Fe and Pb can also be used.

Among them, relatively inexpensive and easily available, having relatively small specific resistance (1.62 μΩ · c)
Ag, which is smaller than that of copper and 1.69 μΩ · cm of copper, and whose temperature coefficient of volume resistivity is relatively small (less than 0.0038 and 0.0039 of copper) are preferably used. Further, Ag has a thermal expansion coefficient of 18.9 × 10 ⁻⁶ / ° C. and a thermal expansion coefficient of stainless steel of 18.4 × 10 ⁻⁶ / ° C.
Since the temperature is close to ° C., when stainless steel is used for the electrode body 1, there is an advantage that the electrode body 1 is hardly peeled off even when expanded and contracted by heat, and has high durability.

The above-mentioned noble metal coated piece 3 can be formed by a surface coating method such as plating. However, in order to obtain better corrosion resistance, the plate-shaped noble metal coated piece 3 must be
It is preferable to adhere to the front end surface of the base material by, for example, welding using silver solder or the like. The thickness of the noble metal-coated piece 3 is preferably set to be about 0.1 mm or more and 5 mm or less. The upper limit of the thickness is more preferably about 3 mm, and the lower limit is more preferably about 0.5 mm.
If the thickness of the noble metal coated piece 3 is less than 0.1 mm, corrosion resistance is insufficient and durability is not preferable, and if it is more than 5 mm, the cost increases.

The electrode holder 2 is made of resin, has a substantially columnar shape as a whole, and has two electrode holding holes 7 into which the electrode body 1 is inserted. Rear end face (right side shown)
Is formed with a recess 8 in which a nut 4 for fixing the electrode main body 1 is accommodated.
A peripheral groove 9 into which 0 is inserted is formed.

The electrode holder 2 holding the electrode body 1 is
The rear end side is connected to the holder 11 via the O-rings 10 and 12.
It is housed and fixed in. Reference numeral 13 denotes a cable connected to each of the electrode bodies 1, and reference numeral 14 denotes a cap.

The conductivity detecting electrode can be assembled, for example, as follows. That is, first, as shown in FIG. 2, an O-ring 5 is fitted into a peripheral groove of the electrode main body 1 having the noble metal coated piece 3 adhered to the tip end surface, and then the electrode main body 1 is Inserted into the electrode holding hole 7,
The nut 4 is engaged with the screw portion at the rear end and fixed.

Next, as shown in FIG.
The cable 13 and the electrode body 1 are connected by tightening the tip with a nut 4 fitted to the rear end of each electrode body 1. Next, after the O-rings 10 and 12 are fitted into the peripheral groove 9 of the electrode holder 2 and the step on the inner peripheral surface of the holder 11, the holder 11 is fitted into the electrode holder 2 as shown in FIG. Insert.

As described above, the electrode body 1 and the electrode holder 2
Since the O-rings 5, 10, and 12 are interposed between the electrode holder 2 and the holder 11, respectively, the electrode body 1 is held in a water-tight manner, and the water into which the chemicals are injected is directly applied to the electrode body. Thus, the electrode body 1 hardly contacts the electrode body 1 and corrosion of the electrode body 1 can be prevented.

Then, a resin material such as an epoxy resin is filled from the rear end opening of the holder 11 and solidified, and then a cap 14 is attached (see FIG. 1). Then, as shown in FIG. 5, the holder 11 is engaged with the sample water pipe 15, and the tip side of the electrode body 1 is inserted into the sample water pipe 15. In this state, the noble metal-coated piece 3 at the tip of the electrode body 1 comes into contact with the sample water flowing through the sample water pipe 15, and the conductivity of the sample water is detected.

FIG. 6 shows an example of a conductivity measuring device using the above-mentioned conductivity detecting electrode. This example shows an example in which the present invention is applied to a boiler.

In the figure, reference numeral 25 denotes a boiler, and a blow-out pipe 26 branched to a blow pipe 28 and a sample pipe 27 communicates with each other. The blow pipe 28 has a heat exchanger 29
And a blow valve 30. On the other hand, the conductivity detection electrode 18 and the temperature detection electrode 1
9 are provided.

As the temperature detecting electrode 19, for example,
A platinum measurement temperature resistor or the like is used, but the temperature is not limited to this, and another temperature sensor such as a thermocouple may be used.

The conductivity detecting electrode 18 is connected to the conductivity detecting means 20, and the sample water flowing in the sample tube 27 flows from the current flowing between the noble metal coating pieces 3 of the electrode body 1 of the conductivity detecting electrode 18. Is detected. The temperature detecting electrode 19 is connected to the temperature detecting means 21 and detects the temperature of the sample water flowing in the sample tube 27.

Reference numeral 22 denotes a conductivity corrector which receives the detected values of conductivity and temperature detected by the conductivity detector 20 and the temperature detector 21 and corrects the conductivity based on the temperature of the sample water. . That is, the resistance value of the metal changes depending on the temperature, and the resistance value tends to increase as the temperature increases. Therefore, a change in the detected value of the conductivity due to a temperature change is corrected, and a minute change in the conductivity due to a change in water quality can be accurately measured.

Reference numeral 24 denotes blow valve control means, which automatically opens the blow valve 30 and starts blowing when the conductivity of the sample water corrected by the conductivity correction means 22 reaches a predetermined value. When the conductivity drops to an appropriate value, the blow valve 30 is automatically closed to stop blowing. Reference numeral 23 denotes a display for displaying the conductivity of the sample water corrected by the conductivity corrector 22.

As described above, according to the conductivity detection electrode,
Since the noble metal-coated piece 3 is formed on the tip end surface of the electrode body 1, the current from one electrode flows to the other noble metal-coated piece 3 having a lower resistance value than the sample liquid, so that the current flows into the sample liquid. The current is collected almost without being diffused, and an accurate conductivity can be detected. In addition, even when immersed in the sample water for a long time, the noble metal-coated piece 3 hardly undergoes a chemical change, and thus exhibits good corrosion resistance.

In the above-described embodiment, the conductivity is measured directly from the current flowing between the two electrodes. However, the present invention is not limited to this. Alternatively, the conductance can be measured and converted into conductivity. In this case, the same operation and effect can be obtained.

[0038]

As described above, according to the conductivity detecting electrode of the present invention, since the electrode main body is held in a water-tight manner by the electrode holder, the electrode main body itself is directly in contact with water into which a chemical or the like is charged. Since it is hard to contact, it is hardly affected by chemicals and the like.
In addition, since the noble metal coating layer is formed on at least the portion of the electrode body exposed from the electrode holder, even if the noble metal coating layer is immersed in water mixed with a water treatment chemical or the like for a long time, the noble metal coating layer undergoes a chemical change. It shows good corrosion resistance because it is hard to cause. In addition, the noble metal coating layer that comes into contact with the water to be measured has a relatively low electric resistance value, so that there is a continuity between the electrode and the pipe or the like as when directly measuring with a conventional stainless steel electrode. This almost eliminates the problem and makes it possible to accurately measure minute fluctuations in conductivity. In this manner, a minute change in conductivity can be accurately measured over a long period of time.

According to the conductivity measuring apparatus of the present invention,
Since the conductivity detection electrode according to the first aspect is provided, a minute change in conductivity can be accurately measured over a long period of time, as described above. Further, since the resistance value of the metal changes depending on the temperature, for example, when measuring relatively high-temperature water such as boiler water, it becomes impossible to measure the electrical conductivity accurately. Since the conductivity measuring device of the present invention includes a temperature detecting means and a conductivity correcting means for correcting the conductivity detected by the conductivity detecting electrode by the temperature detected by the temperature detecting means, the electrode body based on the temperature and the noble metal A change in the detection value of the conductivity due to a change in the resistance value of the coating layer is corrected, and more accurate measurement can be performed.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a conductivity detection electrode according to an embodiment of the present invention.

FIG. 2 is a sectional view showing an assembled state of the conductivity detection electrode.

FIG. 3 is a cross-sectional view showing an assembled state of the conductivity detection electrode.

FIG. 4 is a sectional view showing an assembled state of the conductivity detection electrode.

FIG. 5 is a sectional view showing an assembled state of the conductivity detection electrode.

FIG. 6 is a configuration diagram illustrating a conductivity measuring device using the conductivity detection electrode.

[Explanation of symbols]

 1 electrode body 2 electrode holder 3 noble metal coated piece

Claims (2)

[Claims] 1. A conductivity detection method, wherein a pair of electrode bodies are held in a watertight manner by an electrode holder, and a noble metal coating layer is formed on at least a portion of the electrode body exposed from the electrode holder. electrode. 2. A semiconductor device comprising: the conductivity detection electrode according to claim 1; a temperature detection means; and a conductivity correction means for correcting the conductivity detected by the conductivity detection electrode based on a temperature detected by the temperature detection means. Characteristic conductivity measuring device.