JPH0261079A - Electrolytic protection device for full-titanium heat exchanger - Google Patents

Abstract

PURPOSE:To prevent the corrosion of the carbon steel part of a piping by electrolytic corrosion and to prevent the generation of hydrogen embittlement in a Ti part by constituting a part of a piping device connected to a heat exchanger made of Ti using sea water as a refrigerant of an insulating material such as rubber and mounting a sacrificial anode near to the lower part of the piping. CONSTITUTION:The inside of an outlet water chamber 9 of the condenser 2 of the full-Ti heat exchanger using the sea water as the refrigerant is coated with rubber 31 of an electrical insulator at the time of passing the sea water in a cooling pipe 3 to cool the high temp. clean to water. An expansion joint 19 and a lower part 31 thereof in the part L2 of an outlet circulating water pipe 10 in the lower part of the outlet water chamber 9 are made of rubber as well. The inside surface of a steel pipe part which is connected thereto and in which the sea water 6 passes is coated with a tar epoxy resin 32. The sacrificial anode 26 is mounted at the distance L3 from the outlet water chamber 9 in order to prevent the steel part in the boundary part between the part 32 coated with the epoxy resin and the rubber part 31 from being corroded by the sea water. Electrolytic corrosion current 27 is passed to this anode to prevent the corrosion of the steel of the circulating water pipe in the part L1 after subtraction of L2 from L3 by the sea water and to prevent the generation of the hydrogen embrittlement in the Ti part.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Field of Application) The present invention is aimed at preventing galvanic corrosion of piping equipment connected to an all-titanium heat exchanger that uses seawater as a refrigerant. This invention relates to a method and device for cathodic protection of all-titanium heat exchangers used in

(Prior Art) In general, a shell-and-tube type heat exchanger 9, for example, a condenser in a power generation plant, which uses seawater as cooling water is widely used. Since the cooling pipes of this condenser come into direct contact with seawater, the cooling pipes are made of noble metals that are difficult to corrode.For example, copper alloys, mainly aluminum brass, are used for the condenser tube sheets, and naval brass plates are used for the condenser tube sheets. is used. on the other hand,
Steel is used for the condenser water chamber, equipment and piping connected to the condenser. Monel and stainless steel are also used for instrumentation such as thermometer wells.

Hereinafter, an example of a condenser that returns steam in a power generation plant to water, and equipment, piping, and instrumentation in the vicinity of the condenser will be described using FIG. 7.

Steam 1 discharged from the steam turbine is led to a condenser 2, is cooled by contacting the surfaces of a plurality of cooling pipes 3 through which cooling seawater flows inside the condenser 2, and is condensed into condensed water. It becomes 5. This condensate is recovered from the condenser 2 by the condensate pump 4 for reuse in the power generation plant, and is sent to a feedwater heater (not shown).

Generally, aluminum brass pipes are used for the cooling pipes 3 of the condenser 2. On the other hand, the cooling seawater 6 is generally supplied through an inlet circulating water pipe 7 made of carbon steel sheet coated with anticorrosive coating or coating material such as tar epoxy resin, and is supplied through an inlet water chamber 8.
The heat of the steam 1 is absorbed through the cooling pipe 3, and while the temperature rises, it passes through the outlet water chamber 9 and the outlet circulation wood pipe 10 to the outlet ( discharged into the ocean). The inlet circulating water pipe 7 and the outlet circulating wood pipe 10 generally contain cooling seawater 6.
A butterfly valve 11 for stopping and switching the temperature, a thermometer 12 (temperature detection bed) and a pressure gauge 13 (pressure detection seat) for detecting and monitoring temperature, pressure, etc. are installed. Additionally, a ball cleaning device is installed to maintain the cleanliness of the inner surface of the cooling pipe 3. That is, the cleaning balls collected by the ball collector 14 from the cooling seawater are guided to the ball recirculation pipe 15, passed through the ball circulation pump 16, and transported to the ball collector 17, and from there, the balls are returned to the ball injection pipe 18. This is injected into the cooling seawater flowing through the inlet circulating water pipe 7, and by repeating this process, foreign matter adhering to the inner surface of the cooling pipe 3 is removed.

In addition, an inlet circulation water pipe 7 and an inlet water chamber 8. A rubber expansion joint 19 is attached to the connection between the outlet water chamber 9 and the outlet circulation water pipe 10 to absorb installation errors and minute displacements during operation.

Furthermore, an air vent pipe 20 and an air vent valve 21 are attached to the inlet water chamber 8 and the outlet water chamber 9 in order to vent air. Note that the reference numeral 22 in the figure indicates a tube plate.

By the way, in order to prevent seawater from corroding the parts of condensers and circulating wood pipes that come into contact with seawater, sufficient care is taken in the design, including selection of materials and protection with coatings on metal surfaces or anti-corrosion coatings. That is, in general, corrosion phenomena include natural corrosion in which a single metal is corroded in an acidic environment, and galvanic corrosion (hereinafter abbreviated as electrolytic corrosion) that occurs when dissimilar metals are in contact. Particular attention must be paid to this electrolytic corrosion, as the rate of corrosion is very fast. Electrolytic corrosion usually occurs when electrically connected dissimilar metals are placed in an electrolyte solution, and a natural potential difference is formed with the noble metal at the cathode and the base metal at the anode, and the anode metal interacts with metal ions. This is a phenomenon in which base metals are corroded by being eluted into the electrolyte solution. Figure 8 shows the natural potential of metals in seawater. Here, the natural potentials of seven types of metals are shown, where titanium is the metal that is most often used up, and zinc is the metal that is most often used on the shore.

For example, when brass and iron on the shore are in contact with water in seawater, and the brass and iron are electrically connected, the natural potential difference V between these two metals causes the iron on the shore to This will result in electrolytic corrosion. In addition, when stainless steel (passive) and iron on the shore are in contact with each other in seawater, and the stainless steel (passive) and iron are electrically connected, there is a natural potential difference between these two metals. The steel on the shore is subject to electrolytic corrosion due to V. The same thing can be said for other metal combinations, and the greater the natural potential difference between these two metals, the more the electrolytic corrosion phenomenon progresses. Note that the shore side VSCE of the potential on the horizontal axis indicates the saturated sweet potential.

These phenomena can also occur in the seawater systems of power plants.

For example, electrolytic corrosion can occur between exposed metal on instrumentation such as cooling pipes, strainers, valves, thermometer wells, etc. used in heat exchangers. Additionally, in addition to the above-mentioned materials, the following materials can be considered. That is, in order to prevent corrosion of the steel surface, the inner surface of the piping equipment is coated with an anticorrosive coating or coating material so that the steel surface does not come into direct contact with seawater.

However, if the painted or coated surface is damaged for some reason, the steel surface will be exposed in seawater, and when the aforementioned noble metal material and base metal steel surface are electrically connected, the two metals will The steel surface on the shore side will be subject to electrolytic corrosion due to the natural potential difference. That is, for example, when an aluminum brass tube is used for the cooling pipe 3 of the condenser 2 and a naval brass plate is used for the condenser tube plate 22, the inlet and outlet water chambers 8, 9 and Since the inlet and outlet circulating water pipes 7 and 10 are usually made of steel plates, the steel plates are the metal on the shore side.

As mentioned above, the inlet and outlet water chambers 8 and 9 and the inlet and outlet circulating water pipes 7 and 10 are coated with anti-corrosive coating or coating material, but these coating or coating areas may be damaged due to poor construction or Damaged by seawater flow, etc.
When the underlying steel surface is exposed, the base metal steel surface is subject to electrolytic corrosion due to the natural potential difference between brass and iron, as described above.

This phenomenon will be explained in detail below with reference to the drawings.

In FIG. 9, a damaged coating 2 is shown in the outlet water chamber 9 of the condenser 2.
3a also has a damaged coating 23 on the outlet circulating water pipe 10.
Assume that b exists. Therefore, the damaged coating 23
A and 23b have exposed steel surfaces. Here, it is assumed that the condenser 2 is grounded 25 by a foundation or the like, and the outlet circulating water pipe 10 is also grounded 25 by a support of a piping device or underground piping. From the above, the electrical current flows from the coating damage part 23a of the outlet water chamber 9 and the coating damage part 23b of the outlet circulating water pipe 10, through the cooling seawater 6, through the tube plate 22 and the cooling pipe 3, and through the copper of the condenser 2. A circuit is formed, which causes the film damaged portions 23a, 2
3b to condenser tube plate 22. A corrosive current 24 flows into the cooling pipe 3, causing electrolytic corrosion to the damaged coating parts 23a and 23b. Note that this phenomenon occurs in the outlet water chamber 9 and the outlet circulation water pipe 1.
Of course, the situation is not limited to 0, and the same applies to the inlet water chamber 8 and the inlet circulating water pipe 7.

On the other hand, although the above phenomenon has been described for the case where the cooling tube 3 and the tube plate 22 are made of noble metal, the ball collector 14 shown in FIG. Ball injection tube 18. Butterfly valve 11. If the extraction parts of the thermometer 12 and pressure gauge 13 are made of stainless steel, etc., which is nobler than iron, a natural potential difference will occur between these stainless steels, etc. and the iron of the damaged coating parts 23a and 23b, and the same as described above will occur. Iron, a base metal, undergoes electrolytic corrosion.

This phenomenon will also be explained in detail with reference to FIG. In FIG. 10, a ball collector 14 made of a material such as stainless steel is installed in the outlet circulating water pipe 10.
A ball re-W4 ring pipe 15 is connected to this. Therefore, as explained in FIG. 9, the tube plate 22. Corrosion current 2 flowing through cooling pipe 3
In addition to 4, an electrical circuit is formed that runs from the coating damaged portion 23b of the outlet circulating water pipe 10, through the cooling seawater 6, through the ball collector 14, and through the outlet circulating wood pipe 10. As a result, a corrosion current of 2
4 will flow, and in this case too, the damaged coating portion 23b will be electrolytically corroded. This phenomenon is affected by the tube plate 22 and the cooling pipe 3 when the damaged coating part 23b is close to the condenser 2, and when the damaged coating part 23b is close to the ball collector 14, it is affected by the ball collector. Affected by 14. The stainless steel mentioned here has a stable passive IFJ, and as shown in Figure 8, the potential of stainless steel (passive) is usually 0 to -100 mV S.
Although it is about CE, if the thickness of the above-mentioned passive film is sufficient, brass becomes more base than stainless steel (passive).

Therefore, unless an abnormal condition occurs, stainless steel (passive) will not be subject to electrolytic corrosion. However, if the operating conditions of the condenser 2 change and a part of the stainless steel surface becomes active due to special conditions, such as foreign objects in the seawater.

Stainless steel becomes less base, and a natural potential difference occurs between the naval brass plate of the tube sheet 22 and the aluminum brass tube of the cooling tube 3, and in this case, the stainless steel is subject to electrolytic corrosion.

This phenomenon will be explained with reference to FIG. In FIG. 11, it is assumed that a part of the ball collector 14 installed in the outlet circulating water pipe 10 is in an active state, and the other part is covered with a passive film. At this time, it is assumed that the area where the 5 active states have appeared is in area A in the figure.

In this case, the electrical circuit runs from the outlet circulating water pipe 10 to the exposed stainless steel ball collector 14, and then to the cooling seawater 6.
The circuit passes through the condenser tube plate 22 and the cooling pipe 23, and then through the shell of the condenser 2. As a result, the ball collector 14 is exposed through the area A of the ball collector 14 from the portion covered with the passive film, and then the tube plate 22. A corrosive current 24 flows into the cooling pipe 3, and in this case as well, the stainless steel ball collector 14 is electrolytically corroded mainly in the area A.

As a method of protecting equipment from such electrolytic corrosion phenomena in the inlet and outlet water chambers 8 and 9 and the inlet and outlet circulating water pipes 7 and 10, it is widely practiced to flow an anticorrosive current into the inlet and outlet water chambers 8.9. There is. On the other hand, in response to a similar phenomenon in the ball collector 14 and the like, an appropriate anti-corrosion current is passed in the vicinity of the ball collector 14 to prevent electrolytic corrosion.

Hereinafter, specific methods of cathodic protection will be explained focusing on these measures. In FIG. 12, reference numeral 26 designates a sacrificial anode, which is attached to generate an anticorrosive current 27.

Although not shown here, a similar device is also installed in the inlet water chamber 8, so that similar effects can be obtained.

In the above configuration, the anti-corrosion current 27 flows from the sacrificial anode 26 to the condenser tube plate 22. Cooling pipe 3. Damaged coating parts 23a, 23b
Corrosion current 24 (see FIG. 9) flowing from the damaged coating parts 23a and 23b is extinguished. This results in
Electrolytic corrosion of the damaged coating parts 23a and 23b can be prevented. Further, at this time, local corrosion of the tube sheet 22 and the cooling pipe 3 is also prevented.

Normally, when cathodic protection is performed, the metal is protected from corrosion by making the metal's natural potential about 200 to 250 mV more base. Generally, the natural potential of iron in seawater is -450 to -650m as shown in Figure 8.
It is about V S CE, and the anticorrosion potential of iron is set from this.

Furthermore, the corrosion prevention effect increases as the surface is placed closer to the car, but coating materials such as rubber and tar epoxy resin applied to the steel surface for corrosion protection have the problem that if placed too close to the car, the surface deteriorates and peels off. There is, and it cannot be set very much on the car side. Therefore, normally -650 to -900mV S
Set in the CE range.

On the other hand, if a stainless steel ball collector 14 is provided in the path of the outlet circulating water pipe 10, it is necessary to prepare for electrolytic corrosion of the stainless steel. In this case, cathodic protection is performed centering on the ball collector 14 as follows.

That is, in FIG. 13, reference numeral 28 indicates a sacrificial anode, which is attached to generate an anticorrosion current 29.

In the above configuration, the anticorrosion current flows from the sacrificial anode 28 to the ball collector 14. Corrosion current 24 (see FIG. 9) flowing to and from the damaged coating portion 23 is extinguished. Thereby, electrolytic corrosion of the damaged coating portion 23 can be prevented. At the same time, localized corrosion such as pitting corrosion and crevice corrosion of the ball collector 14 as well as active corrosion are also prevented.

Next, how can we deal with corrosion in a condenser where the main parts of the condenser 2, which is conventionally made of brass-based materials, are made of titanium, a metal that is more harmful than brass? Explain what you are doing.

Generally, a condenser made of titanium like this is called an all-titanium condenser, but the configuration of the condenser, peripheral equipment, piping, instrumentation, etc. is shown in Figure 7. There is no difference. A typical all-titanium condenser of this type is used in large-scale thermal power plants and M pre-power generation plants, and the tube sheets 22 and cooling pipes 3 are made of titanium material.

The tube plate 22 and the cooling pipe 3 made of titanium material have extremely excellent corrosion resistance, and as long as the corrosion caused by seawater itself is limited, these parts can be largely excluded. However, as mentioned above, metals other than titanium are used for other parts of the all-titanium condenser, and metals less base than titanium are also used for peripheral equipment, piping, and products. However, due to the potential difference between the titanium material and other metals, it is inevitable that electrolytic corrosion will occur on the metal on the car side.

In addition to this, all-titanium condensers are shown in Figures 12 and 1.
It is not enough to simply deal with the electrolytic corrosion phenomenon described in Figure 3; there are problems that must be tackled from a different perspective. This is the problem of hydrogen embrittlement, which is a unique phenomenon of titanium materials. Hydrogen embrittlement is a phenomenon in which metal materials become brittle due to the absorption of hydrogen.
00mV S CE When polarized toward the vehicle side, hydrogen absorption begins, causing this phenomenon. Therefore, when preventing electrolytic corrosion by the method shown in FIGS. 12 and 13, the corrosion protection potential must be set at a potential at which the titanium material does not develop hydrogen embrittlement.

FIG. 14 shows a construction method for cathodic protection in an all-titanium condenser, which is carried out based on the above points. In addition,
In the figure, the same parts as those shown in FIGS. 12 and 13 are designated by the same reference numerals.

In FIG. 14, numeral 26 indicates a sacrificial anode,
It is attached to generate an anti-corrosion current 27.

Note that the reference numeral 30 in the figure indicates earth. Although not shown here, a similar device is also provided in the inlet water chamber 8, so that similar effects can be obtained.

In the above configuration, the anti-corrosion current 27 flows from the sacrificial anode 26 to the tube plate 22. Cooling pipe 3. Corrosion current 24 flows to and from the damaged coating parts 23a and 23b.
(see Figure 9) is eliminated. Here, outlet water chamber 9
The potential at the bottom of the titanium material is set to be in front of -600 mV S CE in order to avoid hydrogen embrittlement of the titanium material. Further, the electric potential near the outlet of the circulating water pipe 10 is set to about -650 to -900 mV for iron.

Note that the method for dealing with the electrolytic corrosion phenomenon in the stainless steel ball collector 14 is the same as that described in FIG. 13.

(Problem M to be Solved by the Invention) As described above, in the all-titanium condenser, the coating damage portion 23a occurs in the outlet water chamber 9 and the outlet water pipe 10.

In order to prevent electrolytic corrosion on the exposed steel surface of 23b, a sacrificial anode 26 is provided in the outlet circulating water pipe 10, from which an anti-corrosion current 27 is supplied.
For example, in this case, the water is directed toward the damaged coating portion 23a existing in the outlet water chamber 9.

When the sacrificial anode 26 is brought extremely close to the outlet water chamber 9 side, the anti-corrosion current 27 flows into the damaged coating portion 23a, and at the same time, the anti-corrosion current 27 also flows into the tube plate 22 and the cooling pipe 3 which are not subject to corrosion protection.

When this loss current flows into the tube plate 22 and the cooling pipe 3,
Since the polarization characteristics of the titanium material vary depending on the magnitude of the current value, the titanium material exhibits a potential closer to the vehicle than the natural potential it exhibits in seawater. For this reason.

At the lower part of the outlet water chamber 9, the potential is closer to the car than the potential at which titanium material becomes hydrogen brittle, which is approximately -600 mV S CE.

As a countermeasure to this problem, it is conceivable to provide the sacrificial MI pole 26 at a location far away from the outlet water chamber 9. In this case, the loss current flowing through the tube plate 22 and the cooling pipe 3 becomes significantly smaller than in the case described above, and the potential at the bottom of the outlet water chamber 9 becomes lower than the above-mentioned approximately -600 mV S CE, and the titanium material Hydrogen embrittlement does not occur.

However, the fact that the potential in this area is reduced means that when looking at the entire inside of the outlet water chamber 9, the potential is further reduced in areas other than the lower part of the outlet water chamber 9. For example, in areas where the membrane is damaged. The anti-corrosion current 37 no longer flows in the vicinity of 23a.

At this time, if the sacrificial anode 26 is moved far away from the outlet water chamber 9, the anti-corrosion potential of iron is -650 to -900 mVSC.
If it were possible to make E even more base, this would be relatively easy to deal with and would be desirable.

However, if such a measure is taken near the outlet circulating water pipe 10 to which the sacrificial anode 26 is attached, there is a concern that the following problem will occur, and there is no possibility that it will actually be used. In other words, the surface of the coating material such as rubber or tar epoxy resin applied to the steel surface for corrosion prevention of the outlet circulation wood pipe 10 etc. is likely to deteriorate due to the corrosion prevention potential and current value which are further increased by such measures. There is a risk that these materials will peel off from the steel surface, which poses a major problem.

In this way, the corrosion protection potential of iron is simply -650 to -000 mV.
It is not preferable to bring the SCE to a more base side because it causes inconvenience to the coating material.

On the other hand, as mentioned earlier, the conventional cathodic protection method, which lacks the necessary consideration for the installation location of the sacrificial anode 26, cannot be said to be truly useful for preventing electrolytic corrosion, and improvements are needed. There is.

Therefore, the purpose of the present invention is to suppress the hydrogen embrittlement of titanium materials used in heat exchangers, and also to reliably prevent the steel surface from being corroded due to galvanic corrosion even in the carbon steel parts used together with the titanium materials. An object of the present invention is to provide a cathodic protection device for an all-titanium heat exchanger.

[Structure of the invention]

(Means for Solving the Problems) In order to solve the above problems, the present invention has a pair of water chambers connected to a heat exchanger body, and allows seawater as a refrigerant to flow from one of the water chambers to the other through heat transfer tubes. In this case, each heat exchanger tube is made of titanium material together with the tube plate that supports the heat exchanger tube, and each water chamber is made of a metal electrically more base than titanium material together with the piping device connected to the water chamber. In cathodic protection equipment for all-titanium heat exchangers, which are manufactured using the same materials, the electrical insulation of the entire area inside each water chamber and a certain area connected to the water chamber in each piping device is maintained appropriately. In order to maintain the anti-corrosion potential in each water chamber and each piping device by covering the area with a relatively robust insulating material, it is possible to suppress the hydrogen embrittlement of the titanium material near the bottom of the tube plate in each water chamber. A sacrificial anode is installed to maintain the potential near the boundary of the area covered by the insulating material in each piping device, at least at a potential closer to the vehicle than the natural potential of iron in seawater.

Further, the cathodic protection device for an all-titanium heat exchanger according to the present invention has a pair of water chambers connected to the heat exchanger, and is configured to allow seawater as a refrigerant to flow from one of the front water chambers to the other through the heat transfer tube. In this case, each heat exchanger tube and the tube plate that supports the heat exchanger tube are made of titanium material, and each water chamber and the piping device connected to the water chamber are made of a metal material that is electrically less noble than titanium material. In the cathodic protection device for the all-titanium heat exchanger manufactured using the above-mentioned methods, the electrical insulation of the entire area inside each water chamber and a certain area connected to the water chamber in each piping device is maintained in a suitable manner. is covered with a relatively robust insulating material, and the corrosion protection potential at these points near the bottom of the tube plate in each water chamber and near the boundary of the area covered by the insulating material in each piping device reaches a predetermined value. The present invention is characterized in that sacrificial anodes are provided at a certain distance from each of the water chambers so as to maintain the temperature of the sacrificial anodes.

(Function) Figure 2 shows the potential distribution at the center of the outlet water chamber and the outlet circulating water pipe, which was determined through experiment and analysis. In the figure, the vertical axis shows the potential at the center of the pipe, and the horizontal axis shows the parts of the outlet water chamber 9 and the outlet circulating water pipe 10 shown above the graph. The potential distribution is obtained by changing the position of the sacrificial anode in the outlet circulating water pipe lO. In this case, it is a sacrificial anode mainly composed of zinc or aluminum, manufactured to keep the potential in seawater at approximately -1000 nV S CE, The distribution curves (a) (b) are created by connecting the potentials.
) (C). First, (a) shows the potential distribution when the mounting position of the sacrificial anode 26 is ideal. The potential inside the outlet water chamber 9 is greater than -500 mV S CE. In other words, the outlet circulation wood pipe 10 exhibiting a higher potential with a boundary point of approximately -770nV S CE and the outlet water chamber 9 following this may cause the steel surface to become electrically charged if appropriate measures cannot be taken. It is in an area that is easily attacked by eclipses. On the other hand, about -770nV S C
The area within the outlet circulating water pipe 10 exhibiting a potential less noble than E is an area where cathodic protection is effective, and there is little risk of electrolytic corrosion on the steel surface.

According to the above experimental and analytical results, in areas where the steel surface exhibits a potential of more than about -770nV S CE, where there is a risk of corrosion due to electrolytic corrosion, a material with particularly excellent electrical insulation properties is applied to the outlet water chamber 9. Approximately - in the inner and outlet circulation woodwind 10
Cover areas exhibiting a potential more noble than 770 nV S CE. On the other hand, a region exhibiting a potential less noble than about -770 nV S CE is coated with a material mainly having anti-corrosion properties in consideration of suppressing corrosion of the steel surface. Note that since the expansion joint 19 installed in the outlet circulating water pipe 10 is originally made of an insulating material (such as rubber), it may be excluded from the scope of electrical corrosion protection.

Next, (b) shows the potential distribution when the sacrificial anode 26 is closer to the outlet water chamber 9 side than in the case (a).Compared to 6 (a), the location showing a potential of about -770 nV is It is close to the Yosu outlet water chamber 9 side. That is, the area where the cathodic protection effect is applied is closer to the outlet water chamber 9 side than in (a), and the area covered by the electrically insulating material is reduced accordingly. However, the potential inside the outlet water chamber 9 is -500+eV S
Compared to (a) where CE is cut, it is significantly closer to the shore, and the potential is -600nV S due to the hydrogen embrittlement of the titanium material.
When approaching CE, if the potential changes significantly due to dirt on the tube plate 22 and cooling pipes 3 and swings toward the shore,
00 mV S CE may be reached, and (b), which has less margin than (a), has a higher risk of hydrogen embrittlement and is therefore difficult to adopt.

Furthermore, in contrast to (b), the potential distribution when the sacrificial anode 26 is attached at a position further away from (a) is shown as (c). In comparison with (a), the potential in the outlet water chamber 9 in this case is further shifted to a potential that poses no problem with regard to the hydrogen embrittlement of the titanium material. However, when comparing the potential inside the outlet circulation wood pipe 10 with (a), the point exhibiting a potential of about -770 nV S CE is located further away from the outlet water chamber 9. In other words, as the area affected by cathodic protection moves, the area covered by the electrically insulating material expands, and conversely, the area covered by the anticorrosive material narrows. In this way, extending the area coated with the electrically insulating material, in other words, expanding the area beyond the effect of cathodic protection, must be done with greater care, taking into account possible damage to the coating material. Furthermore, there is a limit to the application of economically expensive insulating materials. As a result, the sacrificial anode 26 is not attached to the position showing the potential distribution in (C), but is arranged so as to shorten the covered area. However, as described above, when the potential distribution becomes as shown in (b), there is a growing concern about hydrogen embrittlement of the titanium material.

Therefore, in (a) there are few areas that are not covered by cathodic protection,
Furthermore, it can be said that the potential distribution is such that hydrogen embrittlement of the titanium material does not occur.

On the other hand, in another experiment and analysis, the potential of the sacrificial anode 26 was changed from the potential of about -1000 mV S CE in the above experiment to about -1600 nV S CE in seawater using a sacrificial anode 26 mainly composed of magnesium. Using this sacrificial anode 26, approximately -1600
The potential distribution was measured by increasing the voltage to mV S CE. This is the distribution curve shown by the dashed line in the figure. If we compare it with (a), it is clear that the area where the effect of cathodic protection extends is even wider than in (a), but simply increasing the potential setting will only cause more harm than good. . That is, the potential inside the outlet water chamber 9 is -600 mV S
As it approaches CE, the risk of hydrogen embrittlement becomes higher and higher, and since it is set closer to the shore than -10100OS CE, it becomes easier for the insulating material to peel off.

Therefore, it is desirable to use a sacrificial anode 26 whose main component is zinc or aluminum, and to set the potential of the sacrificial anode 26 to about -1000 mV S CE.

In addition, the lower limit of corrosion protection potential is -45, which is the natural potential of iron in seawater.
(+-650mV S CE, approximately -650mV
SCE.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, the interior of the outlet water chamber 9 is covered with an electrically insulating covering material, for example a rubber 31 having a robust structure. A sacrificial anode 26 is attached to the lower part of the outlet water chamber 9 so that its potential is set lower than -600 mV S CE to prevent hydrogen embrittlement of the titanium material. In addition, L2 connected to the outlet water chamber 9 of the outlet circulation water pipe 10
The region is also covered with a similar gore 1131. Usually, the expansion joint 19 is made of rubber, and there is no exposed steel surface in the region L2.

In addition, the area other than L2 of the outlet circulating water pipe 10 is covered with tar epoxy resin 32, which is a coating material with anti-corrosion properties. is -770mV
The position of the sacrificial anode 26 is taken into consideration so that it is closer to the shore than the S CE so that the steel surface is not attacked by electrolytic corrosion.
is set up.

On the other hand, the sacrificial anode 26 is mounted at a distance of from the outlet water chamber 9. Therefore, the target area for cathodic protection is Ll, which is obtained by subtracting L2 from L3.

Hereinafter, L is approximately 4.8 m, the inner diameter of the outlet circulating water pipe 10 is 2.4 m, and the potential of the sacrificial anode 26 is approximately -1000 mV.
The measurement results of the potential and current value in the lower part of the outlet water chamber and the potential distribution in the outlet circulating water pipe in the case of SCE will be described.

First, changes in the potential at the bottom of the outlet water chamber will be explained.

In FIG. 3, the vertical axis indicates the potential at the center of the outlet circulating water pipe 10, and the horizontal axis indicates the distance from the sacrificial anode 26 to the heat exchanger side.

When Ll is about 4.8 m (L,/D clause 2), that is, the potential up to a distance of about 4.8 m from the sacrificial anode 26 is shown as a curve (g), and the lower part of the outlet water chamber 9 It is understood that the potential is in front of 1600 mV S CE. In this case, the potential is in front of 1600 mV S CE in the range of about 3.3 m from about 4.8 m,
Within this range, hydrogen embrittlement of titanium material does not occur.

By the way, in FIG. 3, the cases where L3 is about 2.4 m and the case where L3 is about 1.2 m are shown as curves (h) and (i). They are 1.0 times and 0.5 times the inner diameter.

The potential of curves (h) and (i) is -600 mV SC
Hydrogen embrittlement occurs in the titanium material because it is always on the shore side of E. Therefore, the distance was set twice as far as the inner diameter (g
) should be the goal.

Next, changes in current value will be explained.

In FIG. 4, the vertical axis represents the current value from the sacrificial anode 26, and the horizontal axis represents the distance from the heat exchanger to the sacrificial anode 26. The distance from Figure 4 is approximately 4.
When it becomes larger than 8m, it becomes almost constant at less than 2 amperes. Moreover, when it becomes smaller than this, the current value increases rapidly. Next, the potential distribution inside the outlet @ water circulation pipe 10 will be explained. Note that the conditions are the same as those in FIGS. 3 and 4, except that the potential of the sacrificial anode 26 is approximately -1600 mV S
The case of CH is also shown.

In FIG. 5, the vertical axis represents the potential at the center of the outlet circulating water pipe 10 on the heat exchanger side from the sacrificial anode 26.
Further, the horizontal axis indicates the distance from the sacrificial anode 26 to the heat exchanger side.

Curve (j) indicates that the potential of the sacrificial anode 26 is approximately -1000 mV.
The potential distribution of the exit circulating woodwind lO in the case of SCE is shown. 1770 within a distance of approximately 2.4m from the sacrificial anode 26
The electric potential distribution is closer to the car than mVscE, and the desired corrosion protection result on the steel surface can be obtained. On the other hand, the part exceeding this (the shaded part) becomes a potential nobler than -770 mV S CE, and no anticorrosion effect can be obtained.

To contrast with curve (j), the potential of the sacrificial anode 26 is approximately -
The potential distribution at the center of the outlet water chamber 9 and the outlet circulation water pipe 10 in the case of 1600 mV S CE is shown as a curve (k).

1770mV within a distance of approximately 4.1m from the sacrificial anode 26
The potential distribution is closer to the vehicle than the SCE, and the anticorrosion effect extends over a wider range than the above potential, but this potential is a potential that keeps the potential at the lower part of the outlet water chamber 9 at an appropriate value as shown in (g) in Figure 3.
-1000 mV S CE ) and cannot be relied upon.

Based on the above figures 3, 4, and 5, when the sacrificial anode 26 is installed at a position of about 4.8 m, the corrosion protection effect can be obtained within a range of about 2.4 m, so L2= L3-
L1=4.8-2.4=2.4, and the area covered by the insulating material in this case is about 2.4 m or more.

Next, another embodiment of the present invention will be described.

In this embodiment, the area other than L2 of the outlet circulating water pipe 10 is coated with tar epoxy resin 32, which is a coating material having anti-corrosion properties. Assuming the natural potential of iron in seawater (-450 to -650 mV S CE ), the upper limit of the natural potential is approximately -650 mV S CE : fS
It is set to i degree. This is done by setting the potential to the front side to lower the current value compared to the above embodiment, and by reducing the potential at the bottom of the water chamber 9 to completely eliminate the hydrogen embrittlement of the titanium material. This method is especially conceivable when it is desired to further increase the economical effect by reducing the covered area.

In FIG. 6, similarly to the embodiment described above, the inside of the outlet water chamber 9 and the region L2 connected thereto are covered with a rubber 31 having a robust structure, and there are no exposed portions of the steel surface at these locations. Note that the area L2 includes the expansion joint 19.

Further, the area other than L2 of the outlet circulating water pipe IO is covered with tar epoxy resin 32. The sacrificial anode 26 is installed at a position within this coating area, and L□, which is obtained by subtracting L and KARI, becomes the area to be subjected to cathodic protection in this case.

Below, L3 is approximately 4.8 m, and the inner diameter of the outlet circulating water pipe 10 is 2.
．． 4m, the potential of the sacrificial anode 26 is approximately -1000mV
The measurement results of the potential in the lower part of the outlet water chamber 9, the current value, and the potential distribution in the outlet circulating water pipe 10 in the case of SCE will be explained.

First, changes in the potential in the lower part of the outlet water chamber will be explained. In this embodiment, compared to the above embodiment, the portion L2 of the outlet circulating water pipe 10 covered with the rubber 31 having a robust structure is shorter, and the area other than L2 of the outlet circulating water pipe 10 is covered with the tar epoxy resin 32. The range of Ll is lengthened. Therefore, if the positions of the sacrificial anodes 26 are the same,
The curve is the same as curve (g) in FIG.

When L3 is approximately 4.8rn (L3/D”=2),
In other words, the potential up to a distance of about 4.8 m from the sacrificial anode 26 is the same potential as the curve (g). Therefore,
As mentioned earlier, at this time, the potential at the lower part of the outlet water chamber 9 is in front of -600 mV S CE, so hydrogen embrittlement of the titanium material does not occur.

Next, regarding the change in current value, the position of the sacrificial anode 26 is the same as in the previous embodiment, and the fourth
From the figure, if the path flow from the heat exchanger to the anode is approximately 4.8 m, the current will be approximately constant at a little less than 2 amperes. Furthermore, when the distance becomes smaller than this, the current value increases rapidly.

Next, the potential distribution within the outlet circulating water pipe 10 will be explained with reference to FIG. 5. The potential distribution is such that the potential of the sacrificial anode 26 is 1100
The curve (j) is for 0 mV S CE. Approximately -650mV S within a distance of approximately 2.9m from the sacrificial anode 26
The potential distribution is closer to the car than CE, and corrosion protection on the steel surface is in an area where there is almost no problem. On the other hand, the part exceeding this is about -65
It becomes more anterior than 0 mV S CE and no anticorrosion effect can be obtained.

Based on the above FIGS. 3, 4, and 5, when the sacrificial anode 26 is installed at a position of about 4.8 m, the range in which the anticorrosion effect can be obtained is about 2.9 m, so L.

=L, -L1. =4.8-2.9=1.9, approximately 1
．． In this case, the area covered by the electrically insulating material is 9 m or more.

The set potential of the outlet circulation water pipe 10 in this embodiment is at the limit of the natural potential of iron in seawater, and is 770 mVSCE in the above embodiment.
Although the reliability will be somewhat impaired because the cost will be more wasted than the above, if economic efficiency is important, this embodiment makes it possible to obtain a corresponding effect.

〔Effect of the invention〕

As explained above, the present invention uses a relatively robust insulating material to maintain electrical insulation of the entire area inside each water chamber and a certain area connected to the water chamber in each piping device. In order to maintain the anti-corrosion potential in each water chamber and each piping device, we maintain a potential that can suppress the hydrogen embrittlement of the titanium material near the bottom of the tube plate of each water chamber, and insulating material in each wiring device. Since sacrificial anodes are installed near the boundary of the covered area to maintain a potential on the vehicle side that is at least higher than the natural potential in seawater, there is no risk of hydrogen embrittlement in the titanium material, and the material is made of carbon steel. This has the excellent effect of reliably preventing electrolytic corrosion in parts.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the apparatus applied to the method of the present invention, FIG. 2 is a potential distribution diagram showing the state of potential distribution in the present invention, and FIG. 3 is an embodiment shown in FIG. 1. FIG. 4 is a characteristic diagram showing the change in electric potential at the lower part of the outlet chamber, FIG. 5 is a characteristic diagram showing the distribution of electric potential in the outlet circulating water pipe, and FIG. 7 is a block diagram showing another embodiment of the device applied to the method of the present invention, FIG. 7 is a system block diagram showing a conventional condenser and piping equipment connected to it, and FIG. 8 is a block diagram showing various types of equipment in seawater. Characteristic diagrams showing the natural potential of metals; Figures 9, 10, and 11 are explanatory diagrams showing electrolytic corrosion phenomena in condensers; Figures 12, 13, and 14 are diagrams of conventional condensers. It is a block diagram showing an example of the electrolytic protection device in. 2... Condenser 3... Cooling pipe 7... Inlet circulating water pipe 8... Inlet water chamber 9... Outlet water chamber
10... Outlet circulating water pipe 22... Tube plate
26.28...Sacrificial anode 27, 29...Electrolytic corrosion current
31...Rubber 32...Tar epoxy resin agent Patent attorney Rule Ken Chika Yudo Daishimaru Ken Figure 1 Distance from the anode (m) Figure 1 Distance from the heat exchanger to the anode (m) Figure 1-6 Figure 1 - Figure Otsu

Claims (5)

[Claims] (1) It has a pair of water chambers connected to the heat exchanger body, and is configured to flow seawater as a refrigerant from one of the water chambers to the other through the heat transfer tubes. An all-titanium heat exchanger made of titanium material together with the tube plate that supports the heat tubes, and each of the water chambers and the piping devices connected to the water chambers made of a metal material that is electrically less noble than titanium material. In the cathodic protection device for the equipment, in order to maintain suitable electrical insulation of the entire area inside each water chamber and a certain area connected to the water chamber in each piping device, the said area is made of relatively robust insulating material. In order to maintain the anti-corrosion potential in each of the water chambers and each piping device by coating, a potential that can suppress hydrogen embrittlement of the titanium material near the bottom of the tube plate in each of the water chambers and in each of the piping devices is maintained. A cathodic protection device for an all-titanium heat exchanger, characterized in that a sacrificial anode is installed in the piping equipment so as to maintain at least a potential on the more base side than the natural potential in seawater near the boundary of the area coated with an insulating material. . (2) Cover the entire area of each water chamber and the approximately 2.4 m area from the bottom of the water chamber in the piping equipment with an insulating material to maintain the anticorrosion potential in each water chamber and the piping equipment. A potential of approximately -600 mVSCE is applied near the bottom of the tube plate in the water chamber, and a potential of approximately -7 mVSCE is applied at a point approximately 2.4 m away from the bottom of each water chamber.
2. The cathodic protection device for an all-titanium heat exchanger according to claim 1, characterized in that sacrificial anodes are installed in the piping equipment so as to maintain a potential of 70 mVSCE. (3) It has a pair of water chambers connected to the heat exchanger body, and is configured so that seawater as a refrigerant flows through the heat exchanger tubes from one side of the front water chamber to the other, and at this time, supports each of the heat exchanger tubes. Cathodic protection of an all-titanium heat exchanger in which the tube sheets are made of titanium material, and each of the water chambers and the piping devices connected to the water chambers are made of a metal material that is electrically more base than titanium material. In the device, the entire area inside each water chamber and a certain area connected to the water chamber in each piping device are coated with a relatively robust insulating material so that electrical insulation is suitably maintained; An electrolytic corrosion protection device for an all-titanium heat exchanger, characterized in that sacrificial anodes are provided within the piping system at a certain distance from each of the water chambers so that the corrosion protection potential at the point can be maintained at a predetermined value. (4) The installation location of the sacrificial anode is approximately 4.8 meters from the bottom of each water chamber.
2. The cathodic protection device for an all-titanium heat exchanger according to claim 1, characterized in that the cathodic protection device is provided in a device spaced apart by m. (5) Cover the entire area inside each water chamber and the approximately 1.9 m area from the bottom of the water chamber in the piping equipment with an insulating material to maintain the anti-corrosion potential in each water chamber and the piping equipment. A potential of approximately -600 mVSCE is applied near the bottom of the tube plate in the water chamber, and approximately -
The cathodic protection device for an all-titanium heat exchanger according to claim 1, characterized in that sacrificial anodes are installed in the piping equipment so as to maintain a potential of 650 mVSCE.