JP6891719B2 - Corrosion measurement system and corrosion measurement method - Google Patents

Description

The present invention relates to a corrosion measuring system and a corrosion measuring method. In particular, the present invention relates to a water storage tank, a corrosion measurement system for detecting corrosion of a pipe through which water flows from the water storage tank, and a corrosion measurement method.

Conventionally, a corrosion sensor has been used to detect the corrosion status of water storage tanks such as boiler cans and cooling towers and their pipes, and to detect the degree of scale of water flowing through them. For example, Patent Document 1 below discloses a corrosion rate monitoring device that includes an external power source and two electrodes, and monitors the corrosion rate based on the polarization resistance method.

Japanese Unexamined Patent Publication No. 2011-220717

As a power source for driving the corrosion sensor, a rechargeable battery is used in addition to the external power source. An external power source is used for long-term measurement, and a rechargeable battery is used for short-term measurement. May be used properly. At this time, as described later, when an external power source is used, noise may be mixed in the signal inside the corrosion sensor circuit, unlike the case where a rechargeable battery is used. As a result, the measurement results differ between the corrosion rate measured using an external power source and the corrosion rate measured using a rechargeable battery.

Therefore, an object of the present invention is to provide a corrosion measurement system capable of accurately measuring the corrosion rate while using an external power source to enable long-term corrosion measurement.

The present invention is a corrosion measuring system for measuring corrosion of water contained in a grounded water storage tank and / or flowing through a grounded pipe, and includes an insulating container, a corrosion sensor, and a switching power supply. The insulating container electrically separates the water in the water storage tank and / or the pipe from the water in the water storage tank and / or the pipe and stores the corrosion sensor in the insulating container. An electrode immersed in water and a corrosion sensor substrate for calculating a corrosion rate from a solution resistance value and a corrosion reaction resistance value measured using the electrode are provided, and the switching power supply is grounded and is an external power supply. The present invention relates to a corrosion measurement system that converts AC power from the above into DC power and supplies the DC power to the corrosion sensor substrate.

Further, it is preferable to further provide a pump for pumping water from the water storage tank and / or the pipe to the insulating container.

Further, the corrosion measuring method of the present invention is a corrosion measuring method for measuring the corrosion of water contained in a grounded water storage tank and / or flowing through a grounded pipe, and the insulating container is the water storage. The step of separating and accommodating the water in the tank and / or the pipe from the water in the water storage tank and / or the pipe, and the grounded switching power source convert the AC power from the external power source into DC power. The step of supplying the DC power to the corrosion sensor substrate of the corrosion sensor, and the solution resistance value measured in the corrosion sensor using an electrode in which the corrosion sensor substrate is immersed in water contained in the insulating container. It has a step of calculating the corrosion rate from the corrosion reaction resistance value.

Further, when the solution resistance value measured by the corrosion sensor exceeds the threshold value, it is preferable to further have a step of calculating the corrosion rate using the corrosion reaction resistance value measured by the Coulostat method.

According to the present invention, since it is possible to measure corrosion for a long period of time, it is possible to measure the corrosion rate with high accuracy while using an external power source.

It is explanatory drawing about the polarization resistance method. It is explanatory drawing about the polarization resistance method. It is explanatory drawing about the polarization resistance method. It is explanatory drawing about the polarization resistance method. It is a figure which shows the positional relationship between a cooling tower and the electrode of a corrosion sensor. It is a graph which shows the output waveform from a corrosion sensor. It is a figure which shows the positional relationship between a cooling tower and the electrode of a corrosion sensor. It is a graph which shows the output waveform from a corrosion sensor. It is a figure which shows the positional relationship between a cooling tower and the electrode of a corrosion sensor. It is a graph which shows the output waveform from a corrosion sensor. It is a figure which shows the positional relationship between a cooling tower and the electrode of a corrosion sensor. It is a graph which shows the output waveform from a corrosion sensor. It is an overall block diagram of the corrosion measurement system for comparing the presence or absence of a loop. It is a graph which shows the output waveform from a corrosion sensor. It is a graph which shows the output waveform from a corrosion sensor. It is a graph which shows the output waveform from a corrosion sensor. It is an overall block diagram of the corrosion measurement system which concerns on this invention. It is an overall block diagram of the corrosion measurement system in the prior art. It is a graph which shows the corrosion rate measured by the corrosion sensor in the prior art. It is a graph which shows the corrosion rate and each resistance value measured by the corrosion sensor in the prior art. It is a figure which shows the output from a corrosion sensor when an external power source is used and when a rechargeable battery is used. It is a graph which shows the change of voltage and current in a switching power supply.

[Concept of invention]
First, the concept underlying the present invention will be described with reference to FIGS. 1 to 3D and 5 to 9.
1A to 1D are explanatory views of the concept of the polarization resistance method used by the corrosion sensor according to the present invention.

As shown in FIG. 1A, the two electrodes 52A and 52B of the corrosion sensor are immersed in the stored water stored in the water storage tank 51, and both AC and DC are used between the two electrodes using a power supply 53. The voltage of the above is applied, and the current flowing at that time is measured by the current meter 54, and the voltage applied at that time is measured by the voltmeter 55.

At this time, the circuit shown in FIG. 1B is schematically generated. That is, the corrosion reaction resistance 61 (with a resistance value of _RCT ), which is the difficulty of exchanging electrons with the electrode on the electrode surface, and the electric double layer 62 (capacity), which is a component of the capacitor formed on the electrode surface. is referred to as C _dl) and are arranged in parallel, in series with a set of these corrosion reaction resistance 61 and the electric double layer 62, the solution resistance 63 (resistance value is the reciprocal of the electric conductivity of the stored water A circuit is generated in which (let's call it _{RS) is arranged.}

When a DC voltage is applied between the electrodes, as shown in FIG. 1C, the current does not flow in the electric double layer 62 but flows only in the solution resistance 63 and the corrosion reaction resistance 61. Therefore, from the current and voltage in the case of applying a DC voltage between the electrodes 52A and 52B, the sum R _{S +} R _CT of the solution resistance R _S and corrosion reaction resistance R _CT are calculated.
On the other hand, when an AC voltage is applied between the electrodes 52A and 52B, as shown in FIG. 1D, the current does not flow through the corrosion reaction resistor 61, but flows only through the solution resistor 63 and the electric double layer 62. _{Therefore, the value of the solution resistance value RS} can be obtained from the current value and the voltage value when an AC voltage is applied between the electrodes 52A and 52B.

Therefore, by subtracting the solution resistance _{R S} of the sum _R S _{+ R CT} of the solution resistance _{R S} and corrosion reaction resistance _{R CT,} corrosion reaction resistance _{R CT} are calculated.
The corrosion reaction resistance value R _CT is small in the stored water that is easily corroded, and the corrosion reaction resistance value R _CT is large in the stored water that is not easily corroded. Further, as the corrosion reaction resistance R _CT is large, the corrosion rate decreases, as the corrosion reaction resistance R _CT is small, since the corrosion rate increases, by using a corrosion reaction resistance R _CT, and calculates the corrosion rate It is possible.

Here, in the prior art, as shown in FIG. 5, the corrosion sensor 78 includes a corrosion sensor substrate 75 and a carbon steel electrode 77 immersed in the stored water stored in the cooling tower 76. The corrosion sensor substrate 75 uses a set of a switching power supply 71 that converts AC power from the external power supply 72 into DC power and a DC power supply 73 that uses the DC power converted by the switching power supply 71 as a power source. At the same time, the internal rechargeable battery 74 can also be used. When the degree of corrosion of the stored water is measured using this corrosion sensor 78, as shown in FIG. 6, the case where the external power source 72 is used is more corroded than the case where the rechargeable battery 74 is used. The speed is calculated low.

FIG. 7 is a result of detailed measurement of the difference in the daily measurement results of FIG. 6 in hours. Figure 4 in the (a) is temporal change in the corrosion rate, (b) is a time course of corrosion reaction resistance R _CT, (c) the solution resistance R _S and corrosion reaction resistance value R by the DC measurement The time course of the total value of _CT is shown, and (d) shows the time course _{of the solution resistance value RS by AC measurement.} In (d), in addition to this, the electric conductivity of the stored water is measured with a commercially available electric conductivity meter (EC meter), the electric conductivity without temperature compensation is calculated from the measurement result, and further. _{The value of RS} calculated from the calculation result is shown as a reference example.

As can be seen in FIGS. 7A and 7B, the corrosion rate is lower and the corrosion reaction resistance value _RCT is calculated higher when the external power supply 72 is present than when the external power supply 72 is not present. Will be done. Also, comparing the results of the results and the AC measurement of the DC measurement, with respect to time change of the total value of the solution resistance R _S and corrosion reaction resistance R _CT by direct measurement, and with and without the external power supply However, regarding the change over time in the solution resistance value _{RS by AC measurement, the RS} is smaller when the external power supply 72 is present than when the external power supply 72 is not present. Further, after the external power supply 72 is disconnected, there is no difference in the value of _RS between the case where the external power supply 72 is present and the case where the external power supply 72 is not present.

_{Therefore, while measuring the solution resistance value RS} of the same stored water, when there is an AC external power supply 72, the solution resistance value _RS is smaller than when there is no AC external power supply 72. Therefore, it is estimated that the current value is measured larger than the actual value when there is an AC external power supply 72.

Therefore, in order to confirm the signal measured inside the corrosion sensor substrate 75, as shown in FIGS. 8A1 and 8B, a switching power supply that converts an AC external power supply into a DC power supply was used as the power supply. In both cases and when a rechargeable battery is used as the power source, an oscilloscope is connected to the corrosion sensor and the output waveform is observed. The graphs (a2) and (b2) of FIG. 8 are the output waveforms as a result when the circuits are (a1) and (b1), respectively.

As can be seen from the graph of FIG. 8 (b2), when a rechargeable battery is used, a signal caused by the voltage applied at a cycle of 5 msec can be confirmed. On the other hand, as shown in the graph of FIG. 8A2, when a switching power supply is used, noise is mixed in the signal.

In the switching power supply, where the current as shown in FIG. 9 (b) is originally output in response to the pulsed voltage reciprocating in the positive and negative regions as shown in FIG. 9 (a), FIG. 8 (a1). ), As shown in FIG. 9C, noise is also mixed in the current waveform due to the presence of noise as shown in the graph of). Therefore, the current value read by the ammeter is also larger than the original current value. When the current value is read larger than the original value, the value of the solution resistance value _RS is calculated to be small, and the value of the corrosion reaction resistance value R _CT is calculated to be large. Therefore, the corrosion rate is calculated to be smaller than the actual rate.

That is, it can be said that the reason why the corrosion rate is calculated to be smaller than the actual value is the noise mixed in the signal of the external power supply. As shown by the dotted line in FIG. 5, this noise is caused by the AC external power supply 72, switching. It is caused by an electrical loop through the power supply 71, the corrosion sensor substrate 75, the cooling tower 76, and the ground.

2A to 2H show a graph of the positional relationship between the actual cooling tower 76 and the electrode 77 of the corrosion sensor 78, and the output waveform from the corrosion sensor 78.
As shown in FIG. 2A, when the electrode 77 is directly immersed in the stored water of the cooling tower 76, the output amount is -3000 (mV) to 3000 (mV) as shown in FIG. 2B due to the mixing of noise. It fluctuates with the width. On the other hand, as shown in FIG. 2C, an iron plate 79 is provided above the water surface of the stored water in the cooling tower 76, and a beaker 80 from which the stored water is drawn is placed on the iron plate 79, and the beaker 80 from which the stored water is drawn is placed in the stored water in the beaker 80. When the electrode 77 is immersed, the noise is reduced, and as shown in FIG. 2D, the output amount varies in the range of −200 (mV) to 200 (mV). As shown in FIG. 2E, the pedestal 81 is installed on the iron plate 79 provided above the water surface of the stored water in the cooling tower 76, and then the beaker 80 from which the stored water is drawn is placed on the pedestal 81. When the electrode 77 is immersed in the stored water in 80, the amount of noise is further reduced as shown in FIG. 2F. Further, as shown in FIG. 7G, when the beaker 80 from which the stored water is drawn is placed outside the cooling tower 76 and the electrode 77 is immersed in the stored water in the beaker 80, as shown in FIG. 2H, FIG. Noise is reduced to the same extent as in the case.
That is, it can be said that the lower the degree of formation of the electrical loop, the smaller the amount of noise mixed in the signal of the external power supply.

3A to 3D show the results of reproducing the case in which the electrode of the corrosion sensor is immersed in the stored water of the actual cooling tower shown in FIGS. 2A to 2H in the laboratory.
As shown in FIG. 3A, the voltage of the external power supply 72, which is a 100 V AC power supply, is converted to direct current by the external switching power supply 71. Further, the corrosion sensor substrate 75 includes a rechargeable battery 74 as an internal power source. As the power source used by the corrosion sensor 78, it is possible to switch between the external power source 72 and the rechargeable battery 74. The internal DC power supply 73 converts the DC voltage generated by the switching power supply 71 or the voltage of the rechargeable battery 74 into a DC voltage having a value that is easy to use inside the circuit, and supplies the converted voltage to the corrosion sensor substrate 75. .. The electrode 77 connected to the corrosion sensor substrate 75 is immersed in the stored water drawn by the stainless steel beaker 82.

FIG. 3B shows the output when the external power supply 72 is used and the above electrical loop is present. As shown in FIG. 3B, the output amount varies in the range of −150 (mV) to 150 (mV) due to the mixing of noise.
On the other hand, as shown in FIG. 3C, by using the rechargeable battery 74, when the electric loop is broken, a signal caused by the voltage applied at a cycle of 5 msec can be confirmed. The same applies when the electrical loop is broken while using the external power supply 72 as shown in FIG. 3D.

That is, for example, by cutting the electrical loop passing through the AC external power supply 72, the switching power supply 71, the corrosion sensor substrate 75, the cooling tower 76, and the ground, noise is prevented from being mixed into the signal of the external power supply 72. It is a basic concept of the present invention to measure the corrosion rate with high accuracy.

[Construction of the invention]
FIG. 4 shows the overall configuration of the corrosion measurement system 100 according to the present invention.

The corrosion measurement system 100 includes a corrosion sensor 1, an insulating container 3, a switching power supply 6, and a pump 8.

The insulated container 3 electrically separates the water stored in the water storage tank 7 from the water storage tank 7 and stores the water.
In FIG. 4, the insulating container 3 is installed in the water storage tank 7, but the present embodiment is not limited to this, and the water stored in the water storage tank 7 is electrically transferred from the water storage tank 7. The insulating container 3 can be installed at an arbitrary position as long as it is separated and housed in.
Further, the insulating container 3 is provided with a drain port 31, and the water pumped into the insulating container 3 can be overflowed by using the pump 8 as described later. It should be noted that this overflow is carried out so that the water droplets do not connect, so that the above-mentioned electric loop is maintained in a disconnected state.

The corrosion sensor 1 includes a corrosion sensor substrate 10 and electrodes 20.
The electrode 20 is immersed in water contained in the insulating container 3. The corrosion sensor substrate 10 calculates the corrosion rate from the solution resistance value and the corrosion reaction resistance value measured using the electrode 20.

The switching power supply 6 is grounded, converts AC power from the external power supply 5 into DC power, and supplies the DC power to the corrosion sensor substrate 10.

The pump 8 pumps water from the water storage tank 7 into the insulated container 3. It should be noted that the pumping of water is carried out so that the water droplets do not connect, so that the state in which the above-mentioned electric loop is cut is maintained.

Since the corrosion measurement system 100 has the above configuration, when measuring the corrosion rate using the corrosion measurement system 100, the AC external power supply 5, the switching power supply 6, the corrosion sensor substrate 10, the water storage tank 7, and the ground are used. The electrical loop that passes through is cut, and the corrosion rate can be measured accurately.

[Effect of Embodiment]
According to the corrosion measurement system 100 described above, for example, the following effects are achieved.
The corrosion measurement system 100 of the present invention includes an insulating container 3, a corrosion sensor 1, and a switching power source 6, and the insulating container 3 electrically separates the water in the water storage tank 7 from the water in the water storage tank 7. The corrosion sensor 1 is a corrosion sensor substrate that calculates the corrosion rate from the electrode 20 immersed in water contained in the insulating container 3, the solution resistance value and the corrosion reaction resistance value measured using the electrode 20. It is provided with 10.

Therefore, when measuring the corrosion rate by the corrosion sensor, the connection between the water in the insulating container 3 in which the electrode 20 is immersed and the water in the water storage tank 7 is cut, so that the electrode 20, the corrosion sensor substrate 10, and the ground are connected. The crossing electrical loop can be cut off, the influence of noise from the external power source can be removed, and the corrosion rate can be measured accurately.

Further, the corrosion measurement system 100 further includes a pump 8 for pumping water from the water storage tank 7 to the insulating container 3.

Therefore, when pumping water into the insulating container 3, the pumping operation can be automated by using the pump 8.

Further, in the corrosion measurement method of the present invention, the insulating container 3 separates and stores the water in the water storage tank 7 from the water in the water storage tank 7, and the grounded switching power supply 6 is an AC from the external power supply 5. In the step of converting the electric power into DC electric power and supplying the DC electric power to the corrosion sensor substrate 10 of the corrosion sensor 1, and in the corrosion sensor 1, the corrosion sensor substrate 10 is immersed in the water contained in the insulating container 3. It has a step of calculating the corrosion rate from the solution resistance value and the corrosion reaction resistance value measured by using the electrode 20.

Therefore, when measuring the corrosion rate by the corrosion sensor, the connection between the water in the insulating container 3 in which the electrode 20 is immersed and the water in the water storage tank 7 is cut, so that the electrode 20, the corrosion sensor substrate 10, and the ground are connected. The crossing electrical loop can be cut off, the influence of noise from the external power source can be removed, and the corrosion rate can be measured accurately.

[Modification example]
Although the preferred embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and can be implemented in various forms.

For example, in the above embodiment, the insulating container 3 separately stores the water in the water storage tank 7 from the water storage tank 7, and the corrosion sensor substrate 10 is immersed in the water contained in the insulating container 3. The corrosion rate of water contained in the grounded water storage tank is calculated from the solution resistance value and the corrosion reaction resistance value measured using No. 20, but is not limited to this. For example, the insulating container 3 stores the water of the pipe separately from the water of the pipe in place of the water of the water storage tank 7 or in addition to the water of the water storage tank 7, and the corrosion sensor substrate 10 provides this insulation. The corrosion rate of water flowing through the pipe may be calculated from the solution resistance value and the corrosion reaction resistance value measured by using the electrode immersed in the water contained in the container.

Further, for example, using the corrosion measurement system 100, the corrosion rate is calculated from the solution resistance value and the corrosion reaction resistance value of the water to be inspected by the polarization resistance method, and when this solution resistance value exceeds the threshold value, The corrosion rate may be calculated using the corrosion reaction resistance value measured by a known Coulostat method.
Here, the coulostat method is a method of calculating the corrosion rate by measuring the change in electricity when a certain electric charge is applied between the electrodes. That is, in order to measure a dynamic phenomenon, a method of delaying the response of the electric circuit and taking noise countermeasures cannot be adopted. In this regard, it is possible to calculate the corrosion rate with high accuracy by calculating the corrosion rate by the Coulostat method after taking measures against noise using the method of the present invention.

1: Corrosion sensor 3: Insulated container 5: External power supply 6: Switching power supply 7: Water storage tank 8: Pump 10: Corrosion sensor substrate
20: Electrode 31: Drain port 51: Water storage tank 52A 52B: Electrode 53: Power supply 54: Current meter 55: Voltmeter 61: Corrosion reaction resistance 62: Electric double layer 63: Solution resistance 71: Switching power supply 72: External power supply 73: Switching power supply 74: Rechargeable battery 75: Corrosion sensor substrate 76: Cooling tower 77: Electrode 78: Corrosion sensor 79: Iron plate 80: Beaker 81: Pedestal 82: Beaker 100: Corrosion measurement system

Claims (4)

A corrosion measurement system that measures the corrosion of water contained in and / or grounded pipes in a grounded water storage tank.
Equipped with an insulated container, a corrosion sensor, and a switching power supply,
The insulating container electrically separates and stores the water in the water storage tank and / or the pipe from the water in the water storage tank and / or the pipe.
The corrosion sensor includes an electrode immersed in water contained in the insulating container, and a corrosion sensor substrate for calculating a corrosion rate from a solution resistance value and a corrosion reaction resistance value measured using the electrode.
A corrosion measurement system in which the switching power supply is grounded, AC power from an external power supply is converted into DC power, and the DC power is supplied to the corrosion sensor substrate. The corrosion measurement system according to claim 1, further comprising a pump for pumping water from the water storage tank and / or the pipe to the insulating container. A corrosion measuring method for measuring the corrosion of water contained in a grounded water storage tank and / or flowing through a grounded pipe.
A step in which the insulated container separates and stores the water in the water storage tank and / or the pipe from the water in the water storage tank and / or the pipe.
A step in which the grounded switching power supply converts AC power from an external power supply into DC power and supplies the DC power to the corrosion sensor substrate of the corrosion sensor.
In the corrosion sensor, a step of calculating the corrosion rate from the solution resistance value and the corrosion reaction resistance value measured by the corrosion sensor substrate using an electrode immersed in water contained in the insulating container.
Corrosion measurement method with. The corrosion measuring method according to claim 3.
A corrosion measuring method further comprising a step of calculating a corrosion rate using the corrosion reaction resistance value measured by the Coulostat method when the solution resistance value measured by the corrosion sensor exceeds a threshold value.

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