JPH01207666A - Probe for polarization resistance measurement of heat exchanger or the like and automatic control method for iron ion concentration using this probe - Google Patents

Abstract

PURPOSE:To measure polarization resistance by an iron electrode even during plant operation by fixing a reference electrode material which is covered with an insulating tube and securely insulated from small-diameter metal and an electrode material by an in-tube insulating filler so that the material is exposed from a small hole. CONSTITUTION:An electric feeding electrode 2 is inserted fixedly into a pipe 1 made of the same material with an actual machine thin pipe through a rubber plug 6. Then the electrode 2 in the pipe 1 is coated with a thin insulating tube 2a. Then the reference electrode 3 is fixed in the hole bored previously in the pipe 1. The part of this electrode 3 in the pipe 1 is covered with the thin insulating tube 3a. Then a resin 4 is filled in the pipe 1 and then the external surface of the pipe 1 is insulated by a heat-shrinkable tube 5 except constant area. This probe is used to measure the polarization resistance by an iron electrode even during the plant operation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to a polarization resistance measuring probe for determining the quality of a protective film formed by iron ions generated by melting an iron electrode in a real condenser. The present invention also relates to a method for automatically controlling the concentration of iron ions using this method.

Conventional technology Conventionally, cathodic protection and iron ion implantation have been used in combination to prevent corrosion of condensers that use seawater or river water as cooling water. The main purpose of the iron ion implantation method is to prevent corrosion of the thin tubes of the condenser, which are mainly made of copper alloy, and to form a protective film with iron ions on the copper alloy to prevent corrosion caused by sulfides, etc. It is to be. Methods for this include an intermittent injection method of ferrous sulfate and a continuous injection method using an iron electrolytic cell, but these methods have recently become difficult to adopt due to environmental pollution and other concerns. Therefore, a method is being adopted that utilizes iron ions eluted by the corrosion protection current of an iron electrode used as a cathodic protection electrode. By the way, when implementing these corrosion prevention methods, it is important to fully understand the corrosion prevention status for proper maintenance and management at all times.

Conventionally, the corrosion protection status using iron ion implantation method has been evaluated by injecting iron ions for a certain period of time and then entering the water chamber for observation when the plant is shut down. This is done by taking out the installed test piece, observing the state of the anti-corrosion protective film formed on the surface, and analyzing its components. The evaluation is rather qualitative.

On the other hand, as a quantitative evaluation of anti-corrosion protective coatings, the polarization resistance method, which utilizes existing cathodic protection equipment during plant operation, is being used.

In general, the polarization resistance is calculated from the current density and the amount of polarization by turning on the current from the DC power source for cathodic protection at 0FFL, and after the potential on the tube plate surface has become almost stable, turning on the current again.

Alternatively, after energization is turned off and the potential on the tube plate surface becomes almost stable, the tube is cathodically polarized at 200 mV, and the current density after 10 minutes is calculated.

``Problems to be Solved by the Invention'' However, with the above-mentioned qualitative evaluation means, extubation (+) or removal of test pieces is limited to the time when plant operation is stopped, so there is a time constraint.

(2) It takes a lot of time and effort to observe the surface condition and analyze its components, and requires experience and skill.

There are other difficulties.

On the other hand, the quantitative evaluation methods described above require a considerable amount of time and effort, and may not be possible depending on the site.

Furthermore, although there has recently been a call for the need to automatically control the amount of iron ion implanted, the reality is that no suitable index has been found and ideal control has not been achieved.

The present invention has been made in view of the above-mentioned problems of the conventional technology, and its purpose is to make it possible to measure polarization resistance using iron electrodes even during plant operation, and to make it possible to measure the polarization resistance of existing and new condensers. Since it can be easily installed and removed from the outside into the water chamber using a watertight probe support, the state of the anticorrosion coating formed on the surface can be observed, making it possible to determine the comprehensive evaluation of the anticorrosion coating more easily and quickly than before. Furthermore, the present invention aims to provide a probe that can be used to automatically control the amount of iron ions implanted.

"Means for Solving the Problems" In order to achieve the above object, the probe of the present invention has a small diameter current-carrying electrode from one end of a small diameter metal tube made of the same material as the condenser tube plate and thin tube. Insert the electrode material into the small-diameter metal tube, exposing the length necessary for energization from the other tube end, cover the electrode material with an insulating tube so that it does not come into contact with the small-diameter metal tube, and fix and hold the electrode material with an insulating filler. The outer surface of the small-diameter metal tube is made to be energized so as to act as a counter electrode to the current-carrying electrode, and a small hole is bored in the outer surface of the small-diameter metal tube,
A reference electrode material covered with an insulating tube and reliably insulated from the small diameter metal and the electrode material by an insulating filling inside the tube is exposed and fixed from inside the tube so as to enable measurement of the potential on the outer surface through the small hole. This is what happens.

Preferably, the probe is coated with an insulating coating leaving a certain area or length on the outer surface that acts as a counter electrode, so that it can be easily attached and detached by passing it through a watertight probe support fitting attached to the outer wall of the container. .

In addition, we electrically connected the small diameter metal tube for the probe of the above-mentioned probe to the box of the condenser water chamber, and estimated the formation of iron ion skin S on the probe by the branched anticorrosive current flowing into the probe. An automatic cathodic protection method for condenser tube sheets and thin tubes is provided, which is characterized in that the amount of iron ions generated is controlled using a current value as one of the control variables.

``Function'' The probe described above is like a zinc reference electrode inserted into the condenser water chamber, so it can be used with the existing probe installed on the water chamber wall.
It is removably attached to the newly installed electrode fixing cock.

In the actual condenser, the amount of iron ions injected by the iron electrode and the polarization resistance Rp of the 10-p installed in the water chamber change almost correspondingly, although there are slight differences, and can be measured even during plant operation. The adhesion state of the anti-corrosion protective film can be estimated from the polarization resistance, and since there is a certain correlation between the polarization resistance and the current flowing into the probe, the adhesion state of the anti-corrosion protection film due to iron ions can be estimated from the inflow current. The iron ion concentration is automatically controlled using the inflow current as an index.

"Example" Examples will be described with reference to the drawings.

FIG. 1 shows a longitudinal section of the probe of the present invention.

The energizing electrode 2 is inserted and fixed through a rubber stopper 6 into a pipe 1 made of the same material as the actual thin tube. At this time, the current-carrying electrode 2 in the pipe 1 is covered with a thin insulating tube 2a. Next, the reference electrode 3 is fixed in a pre-drilled hole in the pipe l.

At this time as well, the portion of the reference electrode 3 inside the pipe 1 is covered with a thin insulating tube 3a. After filling the inside of the pipe 1 with the resin 4, the outer surface of the pipe 1 is insulated with a heat shrink tube 5, leaving a certain area. In the figure, 7 is a discharge point (connection point) provided for the pipe 1.

FIGS. 2 and 3 a and 3 b show how the probe is installed on an actual machine, with FIG. 2 being a schematic diagram and FIGS. 3 a and 3 b being a detailed view of the installation and a conceptual diagram of the installation situation.

In the example shown in FIG. 3a, the probe 8 is an existing zinc reference electrode 1 attached to the water chamber cover 9 of the actual machine, which is equipped with cathodic protection (potential control) using iron electrodes and iron ions injected.
5. It was inserted and fixed into the water chamber using the fixing pot 10. The probe 8 is transverse to the condenser tube 12. Then, by connecting 13 one lead wire 11 of the discharge point 7 to the water chamber body, the probe 8 receives a portion of the cathodic protection current and is protected from cathodic corrosion as in the actual machine. receive.

In addition, 14 in the figure indicates iron ion generation and cathodic protection current.

After installation, the potential (Ec mV) of the probe is measured with the built-in reference electrode 3 while the probe 8 is connected to the main body of the actual machine every month or so, and the current flowing into the probe 8 (ImA) is measured. After measuring, remove the lead wire 11 between the actual device and the probe, and check the natural potential of the probe 8 (En n+
V) was measured using the reference electrode 3.

Polarization resistance Rp was calculated from the following formula.

Rp(Ω・rrf)=(Ec −En)/(I/
(1) Here, S is the area (a) of the counter electrode portion of the probe 8. FIG. 4 shows the relationship between the amount of iron ions implanted by the iron electrode and the polarization resistance Rp.

From this figure, although there are some differences between the iron ion implantation amount and Rp depending on the mounting position of the probe 8 and the season, there is a relationship that as the implantation amount increases, Rp also increases, and as the implantation amount decreases, Rp decreases. It changed accordingly.

Therefore, it was found that Rp can be used as an index for estimating the adhesion status of the anti-corrosion protective film due to iron ions.

Further, FIG. 5 shows the relationship between Rp and current density i (1/S). From this figure, Rp and i have a very good correlation,
By measuring the current flowing into the probe 8, Rp can be determined.

Therefore, from the results shown in FIG. 4, it was found that the adhesion status of the anti-corrosion protective film due to iron ions could be estimated by measuring summer, and that the concentration of iron ions implanted could be automatically controlled by utilizing .

As shown in FIG. 6, it is possible to construct an automatic control circuit for controlling the amount of iron ions implanted by using the current I flowing into the probe 8 of the present invention.

"Effects of the Invention" Since the present invention is configured as described above, it produces the following effects.

i) Polarization resistance can be measured using iron electrodes even during plant operation.

ii) In an actual condenser, the amount of iron ions injected by the iron electrode and the polarization resistance Rp of the probe installed in the water chamber change almost correspondingly, although there are some differences, and Rp is due to the anticorrosion protection by iron ions. The adhesion state of the film can be estimated.

1ii) There is a very good correlation between Rp and the current flowing into the probe (2), and Rp can be determined by I. Therefore, from the above results, it is possible to estimate the adhesion state of the anti-corrosion protective film due to iron ions based on I, and the iron ion implantation concentration can be automatically controlled by utilizing the change in ■.

iv) If an abnormality or damage occurs to the probe, the removable structure makes inspection and replacement easy.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal sectional view of the probe of the present invention, Fig. 2 is a schematic illustration of the installation of the probe of the invention to an actual condenser, Fig. 3 a and b are detailed illustrations of the installation of the probe of the invention, and illustrations of the installation concept;
Figure 5 shows the iron ion implantation amount and R using the probe of the present invention.
A chart showing the change relationship of p, a correlation chart between Rp and i, and FIG. 6 are a diagram of an automatic control circuit for iron ion concentration constructed using the probe of the present invention. 1... Pipe, 2... Current-carrying electrode, 2a...
Insulating tube, 3... Reference electrode, 3a... Insulating tube, 4... Resin, 5... Heat shrink tube, 6... Rubber stopper, 7... Discharge point (connection point ), 8... Probe, 9... Water chamber cover, 10... Fixing cock, 11... Lead wire,
12... Condenser tube, 13... Connection, 14...
Electrode for cathodic protection, 15... Zinc reference electrode. Time (day) Woro (t)

Claims (3)

[Claims] (1) For example, in a condenser, etc., use a small diameter metal tube made of the same material as the container, insert a small diameter energizing electrode from one tube end, and expose the length necessary for energization from the other tube end, The electrode material is fixedly held by covering the small diameter metal tube with an insulating tube so as not to come into contact with the small diameter metal tube, and the outer surface of the small diameter metal tube acts as a counter electrode to the current-carrying electrode. In addition to making it conductive, a small hole is made in the outer surface of the small diameter metal tube, and a reference electrode material, which is covered with an insulating tube and reliably insulated from the small diameter metal and the electrode material by an insulating filling inside the tube, is inserted into the small diameter metal tube. 1. A probe for measuring polarization resistance in heat exchangers, characterized in that the probe is exposed and fixed from inside a tube through a hole so that the potential of the outer surface can be measured. (2) By applying an insulating coating to the outer surface of the probe, leaving a certain area or length that acts as a counter electrode, the structure can be easily attached and detached by passing the watertight probe support fitting attached to the outer wall of the container. The probe for measuring polarization resistance according to claim 1. (3) Formation of an iron ion film on the probe by electrically connecting the small diameter metal tube for the probe of the probe according to claim 1 or 2 to the box of the condenser water chamber, and by branching anticorrosion current flowing into the probe. An automatic cathodic protection method for condenser tube sheets and thin tubes, characterized by estimating the current value and controlling the amount of iron ion generation using this current value as one of the control variables.