JP2015063734A - Electric anticorrosion system and pump device equipped with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lengthen the life of a sacrificial anode used in a pump device such as a seawater pump, thereby lengthening the life of an electric anticorrosion system of a seawater pump device.SOLUTION: In a pump device 30, a measuring part 20 is provided on a part of a casing 33, immersed in seawater, and an anticorrosion system 70 having a temperature control device 17 is provided in a pump device installation part. In the anticorrosion system 70, a sacrificial anode 3 is provided which is electrically conducted to the casing 33 to be temperature controllable. The temperature control device 17 controls the temperature of the sacrificial anode 3 using a heating/cooling part 11 attached to the sacrificial anode 3.

Description

  The present invention relates to an anticorrosion system and a pump device including the same, and more particularly to an electrocorrosion system suitable using a sacrificial anode and a pump device including the same.

  An example of corrosion protection of equipment used in a conventional seawater environment is described in Patent Document 1. In this publication, in order to prevent corrosion of a duplex stainless steel device equipped with an expanded graphite sealing material, in the vicinity of the duplex stainless steel portion where the sealing material is mounted, the stainless steel portion and It is made of a metal material with a standard electrode potential lower than that of the two-phase stainless steel of the corrosion-protected part on the surface of the two-phase stainless steel material part that is joined and integrally constitutes the conductor on the side in contact with the seawater fluid. One or more sacrificial anodes are installed and electrically connected.

  Patent Document 2 describes that a sacrificial anode is provided in a seawater intake pump, and Patent Document 3 describes that a magnesium alloy is used as a sacrificial anode material.

JP 2005-194624 A Japanese Patent Laid-Open No. 2003-34886 JP-A-10-306388

  In the sacrificial anode described in Patent Document 1 and Patent Document 3, the elution rate cannot be controlled unless the surface area or the installation position of the sacrificial anode is changed. In other words, in order to increase the life of the sacrificial anode to a predetermined value or more, an amount of anode material more than the amount obtained by multiplying the reduction amount of the sacrificial anode per unit time measured in advance by the required life is required, and a large number of sacrificial anodes are installed. Must. As a result, there is not enough difficulty in the heat exchanger etc. where there is room for the sacrificial anode installation or the addition of the sacrificial anode is easy, but there are many restrictions on the installation location of the sacrificial anode such as a seawater pump. It is difficult to secure a large installation position of the sacrificial anode. Moreover, since the magnitude of the anticorrosion current flowing through the sacrificial anode is determined by the electrolyte, the material and shape of the anticorrosion object, and the shape of the sacrificial anode, the design of an appropriate anticorrosion system according to the anticorrosion object is restricted.

  Moreover, in the seawater intake pump device described in Patent Document 2, the sacrificial anode is made longer by limiting the corrosion-preventing site by the sacrificial anode, but against unexpected corrosion occurring outside the limited site. It will be difficult to respond.

  The present invention has been made in view of the above-mentioned problems of the prior art, and its purpose is to extend the life of a sacrificial anode used in a pump device such as a seawater pump, and to extend the life of an anticorrosion system of the seawater pump device. is there.

  A feature of the present invention that achieves the above object is that the anticorrosion system includes a metal member to be protected against corrosion, a temperature-controllable sacrificial anode electrically connected to the metal member, and the metal member to be protected against corrosion. And a temperature control device for controlling the temperature of the sacrificial anode.

  Another feature is that the metal member to be anticorrosion is a casing of the pump device, and the sacrificial anode is attached to the portion where the casing is immersed in the electrolyte in a conductive state with the casing. is there.

  According to the present invention, since the temperature of the sacrificial anode used in a pump device such as a seawater pump can be controlled to a temperature different from the ambient seawater temperature in which the pump device is immersed, the elution rate of the sacrificial anode can be controlled, and sacrificial The life of the anode can be extended. Thereby, lifetime of a pump apparatus and the cathodic protection system with which it is provided can be extended.

It is a block diagram of one Example of the pump apparatus which concerns on this invention. It is a graph explaining the cathode polarization curve in the seawater of stainless steel SUS316L. It is a graph explaining the cathode polarization curve in the seawater of duplex stainless steel S31803. It is a graph explaining the anodic polarization curve in the seawater of a zinc alloy. It is a graph explaining the anodic polarization curve in the seawater of carbon steel. It is a graph explaining anticorrosion current. It is a schematic diagram of the example of an apparatus which measures the current density which flows into a sacrificial anode. It is a flowchart which shows the measuring method using the measuring apparatus shown to Fig.7 (a). It is a flowchart which shows the measuring method using the measuring apparatus shown in FIG.7 (b). It is a block diagram of one Example of the anticorrosion apparatus which concerns on this invention. It is a flowchart which shows the measuring method using the measuring apparatus shown in FIG.

  When using metal materials as equipment for use in environments where corrosion is likely to occur, such as in seawater, such as intake pump casing materials for seawater desalination pump facilities, measures to suppress the occurrence of corrosion in metal materials Any one of sacrificial anode type anticorrosion method, external power source type anticorrosion method, surface coating method, and high corrosion resistance material method is mainly used. Among them, the sacrificial anode type anticorrosion method is a method of bringing a sacrificial anode, which is relatively easy to install and has a low material cost, into contact with an object, and has been widely used in recent years.

  The cathodic protection method is an anticorrosion method for controlling electron transfer in the corrosive action. In the sacrificial anode type anticorrosion method, a metal material having a low standard electrode potential, that is, a lower potential, is brought into contact with a metal material used as a structural member of a device to be protected against corrosion. A metal material having a low standard potential elutes metal ions so as to have the same potential as the metal material to be protected in a solution environment, and transfers electrons to the metal material side to be protected. At that time, the metal material to be protected against corrosion moves the potential to the cathode side where the anodic dissolution reaction is reduced by receiving an electron supply, thereby suppressing the anodic corrosion reaction. A base metal material having a low standard potential to be brought into contact with the metal material is a sacrificial anode.

  The metal materials subject to corrosion protection are steel materials such as cast iron, rolled steel, carbon steel for machine structures, die steel, nickel cast iron, copper alloys such as bronze and brass, and nickel-based alloys such as cupronickel and monel. Austenitic stainless steel, ferritic stainless steel, duplex stainless steel, martensitic stainless steel, precipitation hardened stainless steel, and other stainless rolled steel or cast steel are also subject to corrosion protection. On the other hand, as a material for the sacrificial anode, carbon steel, aluminum, zinc, magnesium, and an alloy mainly composed of this non-ferrous metal are used. The sacrificial anode is consumed with the elution reaction. Further, since the structural member has a possibility of corroding, the impeller of a seawater pump to be subjected to corrosion prevention is brought into contact with a sacrificial anode having a low standard potential and a large area to suppress the corrosion.

  An example of the anticorrosion system using such a sacrificial anode and a pump device having the anticorrosion system will be described below with reference to the drawings. FIG. 1 is a diagram showing a seawater desalination system 80, and FIG. 1A is a block diagram of an embodiment of the seawater desalination system 80. FIG.1 (b) is the X section enlarged view of Fig.1 (a). The seawater desalination system 80 includes a seawater intake pump 30 as a pump device.

  In the seawater desalination system 80, the seawater 5 is guided to the suction tank 42 provided near the coast 40 through the water conduit 41. The main part including the suction part of the pump device 30 is immersed in the suction tank 42. A discharge pipe 43 is connected to the discharge side of the pump device 30, and the discharge pipe 43 is led to a two-layer filter 44 that filters foreign matters such as sand in the seawater sucked by the pump device 30.

  The seawater 5 filtered by the two-layer filter 44 is guided to the filtered seawater tank 45. And it is supplied to the security filter 47 by the pump 46 provided in the filtration seawater tank 45. Seawater from which foreign matters such as iron particles have been removed by the safety filter 47 is sent to a high-pressure pump 49 to which a power recovery turbine 50 is connected. Seawater pressurized by the high-pressure pump 49 is supplied to the RO membrane (reverse osmosis membrane) module 52 via the pipe 48, salt is removed, and the fresh water is stored in the production water tank 54 via the pipe 53. . On the other hand, the concentrated water concentrated by reducing the water content in the RO membrane module 52 is guided from the pipe 51 to the power recovery turbine 50 and recovered as part of the power for driving the high-pressure pump 49. The concentrated water that has been recovered in power and brought to a low pressure is sent out of the seawater desalination system 80 through the pipe 55.

  Here, as will be described in detail later, the inner and outer surfaces of the pumping pipe of the pump device 30 are immersed in seawater. The inner surfaces of the high pressure pump 49 and the pump 46 are in contact with seawater. Therefore, it is in an environment where corrosion is likely to occur. Furthermore, a metal pipe is used for a pipe portion downstream from the high-pressure pump 49, and seawater flows at an internal pressure of 5 MPa or more. In these metal pipes, corrosion phenomena that depend on the salt concentration occur over time, especially in the flanges that are pipe joints and in the welds where the surface texture and surface roughness are uneven, the corrosion rate is high. May develop. In order to prevent the occurrence of these corrosions, the anticorrosion system 70 according to the present invention is required.

  The seawater intake pump which is the pump device 30 is a vertical shaft pump in this embodiment, and a suction bell mouth 34 is attached to the tip. A pump casing 33 is flange-connected to the suction bell mouth 34, and the pump casing 33 is flange-connected to the guide vane 32 on the downstream side. A pumping pipe (column pipe) 31 is flanged by a flange 35 further downstream of the guide vane 32. A flange 39 for fixing the seawater intake pump 30 is attached to an intermediate portion in the axial direction of the pumping pipe 31, and the flange 39 is fixed to a base plate 42 a that covers the upper portion of the suction tank 42. The suction bell mouth 34, the pump casing 33, the guide vane 32, and the pumping pipe 31 constitute a casing.

  On the other hand, inside the casing, the rotating shaft 36 extends in the vertical direction, and an impeller 38 is attached to the lowermost end portion of the rotating shaft 36 and is fixed to the rotating shaft 36 with an impeller nut or the like. On the inner peripheral side of the guide vane 32, a guide vane inner wall portion 37 having a smaller diameter as it goes downstream is disposed in order to form a guide vane channel. The measuring unit 20 includes a sacrificial anode 3 and a heating / cooling unit 11. Details of the anticorrosion system 70 provided in the seawater intake pump 30 will be described later.

  Next, the polarization curve, which is an important indicator regarding the consumption amount of the sacrificial anode, will be described. Below, the result of having measured the polarization curve about some of the structural materials used as the said sacrificial anode and cathode is shown. The potential and current density of the metal in the sea water are determined by a specific polarization curve. When two kinds of metals come into contact with each other in seawater, an electric potential at the intersection of the two kinds of polarization curves (a hybrid electric potential) is generated, and an anticorrosion current flows at a current density at the intersection. The polarization of the metal is caused by an electrochemical reaction at the interface between the electrolyte and the metal. Since this electrochemical reaction depends on temperature, the polarization curve also depends on temperature. In other words, it is possible to design an optimal cathodic protection system while taking other influences into account using temperature as a control parameter.

  2 to 5 show the results of measuring polarization characteristics of each material. In measuring the polarization characteristics, artificial seawater (Aquamarine manufactured by Yashima Pharmaceutical) was used as seawater. The test conditions were adjusted so that dissolved oxygen was saturated with air, the flow rate V of seawater was V = 0 (m / s), and the pH was 8.2. The electrical conductivity EC was EC = 5 (S / m).

  FIG. 2 is a graph obtained by logarithmically approximating the cathode polarization characteristics of stainless steel SUS316L, and is a result of measurement using seawater temperature as a parameter. Stainless steel SUS316L is a material conventionally used in the pumping pipe 31 and the like of the seawater intake pump 30 shown in FIG. 1 and was tested as a metal candidate for corrosion protection. From the potential of the pipe made of stainless steel SUS316L using the cathodic protection system and the potential of the sacrificial anode attached to the pipe, the current between the pipe and the sacrificial anode is determined by the cathode polarization curve shown in FIG. It is obtained from the intersection of polarization curves.

The cathode polarization of stainless steel SUS316L has a slight difference in polarization voltage due to the difference in seawater temperature up to a current density of about 10 ¹ (μA / cm ² ), but the current density is 10 ¹ to 10 ² (μA / cm ^2). ) Increases in temperature dependence, and the amount of change in the polarization voltage also increases. When the current density exceeds 10 ² (μA / cm ² ), the temperature dependence of the polarization voltage remains, but the amount of change is relatively small.

FIG. 3 shows a result of testing the duplex stainless steel S31803, which is another candidate material for the piping material, in the same manner as in FIG. Seawater temperature was used as a parameter. Duplex stainless steel S31803 is increasingly used as a material for seawater pumps that require more corrosion resistance. In FIG. 3 as well, the polarization voltage becomes highly temperature-dependent between current densities of 10 ¹ to 10 ² (μA / cm ² ), and the amount of change in the polarization voltage is large. Moreover, in any of FIG. 2 and FIG. 3, when the seawater temperature is 40 ° C. between a current density of 10 ¹ to 10 ² (μA / cm ² ) with a large change in the polarization voltage, the polarization voltage becomes the largest. . In other words, the current density is the smallest under the same voltage condition.

  FIG. 4 shows a graph in which the anodic polarization characteristics are logarithmically approximated for a zinc alloy that is a candidate material for a sacrificial anode. It is the result of having tested seawater temperature as a parameter. The test conditions are the same as in the cathode polarization characteristics test. As the zinc alloy, ZAP-A (EL) (hereinafter referred to as a zinc alloy) manufactured by Sumitomo Mitsui Metals Copper Alloy was used. This zinc alloy has a composition obtained by adding aluminum as an alloy element to pure zinc.

  In FIG. 4, when compared at the same potential, the current density is lowest when the seawater temperature is 40 ° C., and when the seawater temperature is 30 to 50 ° C., compared to the case where the seawater temperature is 20 to 25 ° C., The current density is greatly reduced. Therefore, in the case of a sacrificial anode made of zinc alloy, it can be seen that there is a possibility that the life of the sacrificial anode can be extended if the seawater temperature in contact with the sacrificial anode is 30 to 50 ° C. Furthermore, the longest life can be expected at 40 ° C.

  FIG. 5 shows a logarithmic approximation of the anodic polarization characteristics of carbon steel as another candidate material for the sacrificial anode. The seawater temperature is shown as a parameter. The test conditions are the same as in the test of FIG. SS400 was used as carbon steel. In the case of the carbon steel shown in FIG. 5, unlike the case of the zinc alloy shown in FIG. 4, when compared with the same potential, the carbon steel has a lower current density as the seawater temperature with which the carbon steel is in contact is lower. Yes. Therefore, when carbon steel is used for the sacrificial anode, a long life can be expected by making the temperature of seawater in contact with the carbon steel as low as possible.

  Next, referring to the above results, a specific method for obtaining a change in generated current density due to seawater temperature in an example in which SUS316L, which is austenitic stainless steel, is used as a cathode material and a zinc alloy is used as a sacrificial anode is shown in FIG. Will be described. FIG. 6 is obtained by combining FIG. 2 and FIG. In order to avoid complication of the figure, a logarithmic approximation curve 100 of cathode polarization of stainless steel SUS316L at 25 ° C. and a logarithmic approximation curve 101 of anodic polarization of zinc alloy at 25 ° C. are shown as representatives.

The potential and current density when SUS316L and zinc alloy are short-circuited in seawater under the conditions of seawater temperature 25 ° C. and sacrificial anode (zinc alloy) temperature 25 ° C. are −1.074 V and 97.0 μA / cm from the intersection of the figure. ² Similarly, when the intersection of the zinc alloy with the logarithmic approximate curve of anodic polarization at 20 ° C., 30 ° C., 40 ° C., and 50 ° C. is obtained, the position of the black circle described on the cathode curve 100 is obtained. From the intersection of both curves at each temperature, the potential and current density at each temperature are obtained.

Here, if an approximate expression is used, the potential and current density at the time of anticorrosion can be estimated quickly by calculation. For example, the intersection of the cathode curve 100 and the anode curve 101 at 25 ° C. is approximated by the following equation 1 for the cathode curve 100 and the following equation 2 for the anode curve 101. By solving these two equations as simultaneous equations, the potential and current density at the intersection can be obtained.

  As an approximation method, in addition to logarithmic approximation, methods such as linear approximation, polynomial approximation, and exponential approximation can be used. Further, by using these approximate expressions, the potential distribution and the current density distribution can be obtained by simulation and designed by known means such as a finite element method and a boundary element method. Note that the polarization curve may be used without approximation, and in that case, the potential and current density during corrosion prevention can be estimated with high accuracy.

  Here, in the sacrificial anode type cathodic protection system, a current is generated using a potential difference in the electrolyte between the metal member to be protected and the sacrificial anode as a driving force. The electrolyte may be fresh water, brackish water, saline, salt water, etc. in addition to seawater. Generally, when classified by sodium chloride concentration, less than 0.05% is fresh water, 0.05% or more and less than 0.35% is brackish water, 0.35% or more and less than 0.5% is saline, and 0.5% or more is salt water. It is called. The sodium chloride concentration in seawater is about 0.24% to 2.96%, and there are differences in concentration depending on the sea area. On the other hand, an aqueous solution containing any ionic species can be applied as the electrolyte.

  2 to 6, the current density generated in the sacrificial anode is obtained under the condition that the seawater temperature and the temperature of the sacrificial anode and the cathode material as the structural material are all the same. In the present invention, in order to suppress the consumption amount of the sacrificial anode, only the temperature of the sacrificial anode can be adjusted. Below, the test result at the time of changing the temperature of a sacrificial anode with respect to seawater temperature is demonstrated.

  FIG. 7 is a schematic diagram showing a test apparatus for an anticorrosion system simulating a seawater intake pump. FIG. 7A is a diagram of the first test apparatus 61, and FIG. 7B is a diagram of the second test apparatus 62. In both the test apparatuses 61 and 62, the surfaces of both the simulated pipe 1 and the sacrificial anode 3 that are cathode materials are in contact with the artificial seawater 6.

  That is, in the first test apparatus 61, the container 21 in which the artificial seawater 6 is stored in a predetermined amount is installed in the water bath 8 in which the water 7 is accommodated. In the container 21, a specimen of the pipe simulating member 1 is suspended by using the cable 15e as a supporting means. Similarly, the sacrificial anode 3 is suspended in the container 21 using the cable 15f as a supporting means. A heating / cooling section 11 is attached to one surface of the sacrificial anode 3 via a heat conductive sheet 10. The heating / cooling unit 11 is connected to the control unit 13 by a cable 15b. A temperature detector 12a is attached to the sacrificial anode, and temperature information detected by the temperature detector 12a is input to the control unit 13 via the cable 15c. The control unit 13 is connected to the power source 14 by a cable 15a. The piping simulation member 1 and the sacrificial anode 3 are connected by cables 15e and 15f through a non-resistance ammeter 9.

  The second test apparatus 62 includes the same components as the first test apparatus 61, and further includes a second temperature detector 12b. The second temperature detector 12 b detects the temperature of the artificial seawater 6, and the temperature information detected by the second temperature detector is input to the control unit 13 using the cable 15.

  In the test apparatuses 61 and 62, the simulated pipe 1 and the sacrificial anode 3 are electrically connected using the non-resistance ammeter 9 and the cables 15e and 15f. Can be fixed with a conductive bolt 4, or the simulated pipe 1 and the sacrificial anode 3 can be directly brought into contact with each other. With these configurations, the sacrificial anode 3 can make the simulated piping 1 lower than the immersion potential of the simulated piping material itself.

  In the first and second test devices 61 and 62, the temperature control device 17 is provided so that the temperature of the portion of the sacrificial anode 3 in contact with the artificial seawater 6 can be controlled. The temperature control device 17 includes a measurement unit 20 attached to the sacrificial anode 3 and a control unit 16 disposed in a portion simulating the seawater intake pump installation unit. The measurement unit 20 includes a heating / cooling unit 11 and temperature detectors 12 a and 12 b, and the control unit 16 includes a control unit 13 and a power source 14.

  The heating / cooling unit 11 was installed in a place where it was in thermal contact with the sacrificial anode 3 using a heating wire sealed so as not to touch the artificial seawater 6 directly. The heating / cooling unit 11 may be a Peltier element or a heat exchanger. In order to reduce the thermal resistance between the heating / cooling section 11 and the sacrificial anode 3, it is preferable to bond with a heat conductive sheet 10 as shown in the figure. Alternatively, heat conductive grease may be used.

  Thermocouples with sheaths were used for the temperature detectors 12a and 12b. Various methods such as a thermocouple without a sheath and a resistance thermometer can be used instead of the sheathed thermocouple. Temperature information measured by the temperature detectors 12a and 12b was input to the control unit 13, and the surface temperature of the sacrificial anode 3 was controlled to a predetermined temperature by feedback control.

  The temperature information was visualized and displayed by a display device attached to an image processing device (not shown) provided in the control unit 16. This temperature information was used to monitor the surface temperature of the sacrificial anode 3. In addition, after recording temperature information in a recording device, it was made possible to output it as information. The temperature detector 12 was disposed on the surface where the sacrificial anode 3 was in contact with the artificial seawater 6 so that the temperature of the portion where the sacrificial anode 3 was in contact with the artificial seawater 6 could be measured. In this case, the area of the temperature detectors 12a and 12b is made as small as possible.

  The control unit 13 controls the output of the heating / cooling unit 11 based on information from the temperature detectors 12a and 12b. The power source 14 supplies power to the sacrificial anode 3 and the control unit 13. The control unit 13 and the power source 14 are preferably installed in a part away from the sacrificial anode 3 like the test devices 61 and 62, and are provided in a place where the artificial seawater 6 is not directly touched.

  FIG. 8 is a flowchart showing a procedure for controlling the temperature control device 17 when performing the anticorrosion test using the first test device 61. In the first test apparatus 61, the first temperature detector 12 a that measures the temperature of the sacrificial anode 3 is installed in a portion where the sacrificial anode 3 is in contact with the artificial seawater 6.

In step S110, the minimum value of the test range determined in advance according to the material of the sacrificial anode 3 to be used (when heating means is used as the heating / cooling section 11) or the maximum value (when cooling means is used as the heating / cooling section 11) ) the set temperature T ₀ to be, input from the controller 13. Next, using the first temperature detector 12a attached to a portion sacrificial anode 3 is in contact with the sea water, to measure the temperature T ₁ of the sacrificial anode (step S120). The control unit 13 controls the temperature using the heating / cooling unit 13 so that the deviation between the two temperatures T ₀ and T ₁ is reduced (step S130). Subsequently, the temperature T ₁ ′ of the sacrificial anode is measured using the first temperature detector 12a (step S140). The set temperatures T ₀ and T ₁ ′ are compared in step S150. If the difference between the two temperatures T ₀ and T ₁ ′ is within the allowable temperature range, the flow is terminated and the process proceeds to the next temperature measurement point. If the temperature difference is outside the allowable temperature range, the process returns to step S120. When measurement is completed at all measurement points, the test is terminated.

In the second test apparatus 62 shown in FIG. 7B, in addition to the configuration of the first test apparatus shown in FIG. 7A, a _second seawater temperature T ₂ in the vicinity of the sacrificial anode 3 is measured. The temperature detector 12b was installed. The same thing as the 1st temperature detector 12a was used for the 2nd temperature detector 12b. The temperature signals detected by the two temperature detectors 12 a and 12 b were input to the control unit 13. In the test using the second test apparatus 62, the controller 13 controlled the temperature of the sacrificial anode 3 so that the difference (absolute value) in the detected temperature was within a predetermined range.

FIG. 9 is a flowchart showing a test method using the second test apparatus 62. That is, in step S210, the seawater temperature _{T 2} and to any of 25,30,40,50 ° C., heated as the minimum value (heating and cooling unit 11 of the previously obtained test range according to the material of the sacrificial anode 3 to be used A difference ΔT from the temperature T _{1 which} is a maximum value (when a cooling means is used as the heating / cooling section 11) or a maximum value (when using the means) is input from the control section 13. Next, to measure the sea water temperature T ₂ using the second temperature detector 12b for measuring the sea water temperature T ₂ in the vicinity of the sacrificial anode 3 (step S220).

Using a first temperature detector 12a which sacrificial anode 3 is mounted on the portion in contact with the sea water, to detect the temperature T ₁ of the sacrificial anode (step S230). The control unit 13 uses the heating / cooling unit to control the temperature so that the temperature difference ΔT between the _two temperatures T ₂ and T ₁ approaches a predetermined value (step S240). Subsequently, the temperature T ₁ ′ of the sacrificial anode 3 is measured using the first temperature detector 12a (step S250).

The temperature _{T 1} 'of the sea water temperature _{T 2} and the sacrificial anode second temperature detector 12b detects, compared at step S260. If the difference between the _two temperatures T ₂ and T ₁ ′ is within an allowable range of a predetermined temperature difference ΔT, the flow ends, and the process proceeds to a temperature measurement point where the next temperature difference ΔT is obtained. If the difference between the _two temperatures T ₂ and T ₁ ′ is outside the set temperature allowable temperature range, the process returns to step S230. When measurement is completed at all measurement points (step S260), the test is terminated.

  Results of testing using stainless steel SUS316L and duplex stainless steel S31803 as cathode piping members, zinc alloy and structural carbon steel SS400 as sacrificial anode materials using the two test apparatuses and two test methods described above Is described below.

(A series)
This is a case where stainless steel SUS316L is used for the simulated piping 1 serving as the cathode material, and zinc alloy is used for the sacrificial anode 3. Using a first test device 61 and the first test method, the seawater temperature _{T 2} was varied between 25 to 50 ° C., the temperature _{T 1} of the sacrificial anode 3 is varied between 20 to 50 ° C.. The simulated pipe 1 and the sacrificial anode 3 were connected with a non-resistance ammeter, and the current density flowing between the simulated pipe 1 and the sacrificial anode 3 was measured. In the following series of tests, seawater internal pumps in consideration of the case where the temperature rise by power supplied from the impeller, the seawater temperature T ₂ has been tested also rise to 50 ° C..

  Table 2 summarizes the test results. In Table 2, “X” indicates that the operating temperature of the sacrificial anode 3 is not suitable, “◯” indicates that the operating temperature of the sacrificial anode 3 is appropriate, and “◎” indicates the sacrificial anode 3. This shows that the operating temperature is particularly effective. The appropriate / inappropriate operating temperature of the sacrificial anode 3 was determined to be the range in which the current density was reduced when the temperature T1 of the sacrificial anode 3 was changed between 20 and 50 ° C.

As shown in Table 1, in the range of test numbers A1～A20, when the temperature _{T 1} of the sacrificial anode 3 is below a by 50 ° C. at 30 ° C. or higher, the temperature _{T 1} of the sacrificial anode 3 is 20 ° C. or 25 ° C. Compared to the case, the current density between the simulated pipe 1 of the stainless steel SUS316L and the sacrificial anode was reduced. The combination of the present cathode material and anode material, when the temperature control of the temperature T ₁ of the sacrificial anode 3 to a temperature higher than the predetermined temperature, it has been found that can be expected to extend the life of the sacrificial anode 3.

(B series)
This is a case where stainless steel SUS316L is used for the simulated piping 1 serving as the cathode material, and structural carbon steel SS400 is used for the sacrificial anode. Using the second test device 62 and the second test method, the seawater temperature T ₂ was varied between 25 to 50 ° C., the temperature T ₁ of the sacrificial anode 3, using a Peltier element as the cooling means 10 Vary between 50 ° C. Here, based on the first temperature detector 12a, a temperature signal by the second temperature detector 12b detects that detects seawater temperature T ₂ for detecting the temperature T ₁ of the sacrificial anode 3, the temperature T of the sacrificial anode 3 ₁ was temperature controlled to be lower than the sea water temperature T _2. Further, the simulated pipe 1 and the sacrificial anode 3 were connected by a non-resistance ammeter, and the current density flowing between the simulated pipe 1 and the sacrificial anode 3 was measured.

The test results are summarized in Table 4. In Table 4, “x” indicates that the operating temperature of the sacrificial anode 3 is not suitable, “◯” indicates that the operating temperature of the sacrificial anode 3 is appropriate, and “◎” indicates the sacrificial anode 3. This shows that the operating temperature is particularly effective. Note that “−” indicates that the test was not performed because it was predicted that no effect could be obtained. Suitable / unsuitable operating temperature of the sacrificial anode 3, based on the current density at the temperature T ₁ of the sea water temperature T ₂ and the sacrificial anode 3 are identical, and suitable if lower than the current density it It was judged.

As shown in Table 3, in Test No. B1～B18, when the temperature _{T 1} of the sacrificial anode 3 is lower than the temperature _{T 2} of the seawater, than the temperature _{T 1} of the sacrificial anode 3 is equal to the temperature _{T 2} of the seawater The current density between the simulated pipe 1 of the stainless steel SUS316L and the sacrificial anode 3 was reduced. The combination of the present cathode material and anode material, when the temperature controlled to a temperature T ₁ of the sacrificial anode 3 is lower than the temperature T ₂ of the seawater, the life of the sacrificial anode 3 has been found to be expected.

(C series)
This is a case where duplex stainless steel S31803 is used for the simulated pipe 1 serving as the cathode material, and zinc alloy is used for the sacrificial anode. Using a first test device 61 and the first test method, the seawater temperature _{T 2} was varied between 25 to 50 ° C., the temperature _{T 1} of the sacrificial anode 3, was varied between 20 to 50 ° C. . The simulated pipe 1 and the sacrificial anode 3 were connected with a non-resistance ammeter, and the current density flowing between the simulated pipe 1 and the sacrificial anode 3 was measured.

  The test results are summarized in Table 6. In Table 6, “x” indicates that the operating temperature of the sacrificial anode 3 is not suitable, “◯” indicates that the operating temperature of the sacrificial anode 3 is appropriate, and “◎” indicates the sacrificial anode 3. This shows that the operating temperature is particularly effective.

As shown in Table 1, in the range of test numbers C1 to C20, when the temperature _{T 1} of the sacrificial anode 3 is below a by 50 ° C. at 30 ° C. or higher, the temperature _{T 1} of the sacrificial anode 3 is 20 ° C. or 25 ° C. Compared to the case, the current density between the simulated piping 1 of the duplex stainless steel S31803 and the sacrificial anode 3 was reduced. The combination of the present cathode material and anode material, the predetermined temperature T ₁ of the sacrificial anode 3 temperature, when the temperature controlled to a temperature higher than, for example, 30 ° C., were found to be expected to extend the life of the sacrificial anode 3.

(D series)
This is a case where duplex stainless steel S30803 is used for the simulated piping 1 serving as the cathode material, and structural carbon steel SS400 is used for the sacrificial anode. Using the second test device 62 and the second test method, the seawater temperature _{T 2} was varied between 10 to 50 ° C., the temperature _{T 1} of the sacrificial anode 3 is varied between 20 to 50 ° C.. The temperature T ₁ of the sacrificial anode 3 was changed between 10 to 50 ° C. using a cooling means. Here, based on the first temperature detector 12a, a temperature signal by the second temperature detector 12b detects that detects seawater temperature T ₂ for detecting the temperature T ₁ of the sacrificial anode 3, the temperature T of the sacrificial anode 3 ₁ was temperature controlled to be lower than the sea water temperature T _2. The simulated pipe 1 and the sacrificial anode 3 were connected with a non-resistance ammeter, and the current density flowing between the simulated pipe 1 and the sacrificial anode 3 was measured.

  The test results are summarized in Table 8. In Table 8, “X” indicates that the operating temperature of the sacrificial anode 3 is not suitable, “◯” indicates that the operating temperature of the sacrificial anode 3 is appropriate, and “◎” indicates the sacrificial anode 3. This shows that the operating temperature is particularly effective. “-” Indicates that the test was not performed because it was predicted that no effect could be obtained.

As shown in Table 7, in Test No. D1～D18, when the temperature _{T 1} of the sacrificial anode 3 is lower than the sea water temperature _{T 2} than if the temperature _{T 1} of the sacrificial anode 3 is equal to the seawater temperature _{T 2,} two The current density between the phase stainless steel S31803 and the sacrificial anode 3 is small. In the combination of the present cathode material and the anode material, it was found that the life of the sacrificial anode 3 can be expected to be increased by controlling the temperature T ₁ of the sacrificial anode 3 to a temperature lower than the seawater temperature T ₂ . In particular, when the temperature of the sacrificial anode was lowered to 10 ° C., the current density became the smallest, and the most preferable result was obtained for extending the life of the sacrificial anode 3.

  The test devices 61 and 62 using the simulated pipe 1 can be applied to the anticorrosion system of the pump device 30 as they are. As for the temperature control method, if the seawater temperature is measured instead of the artificial seawater temperature, the temperature of the sacrificial anode 3 can be set, corrected, and used for optimum temperature control.

  FIG. 10 shows an anticorrosion system in consideration of application to the actual pump device 30 reflecting the combination test result of the simulated pipe 1 and the sacrificial anode using the first and second test apparatuses 61 and 62 described above. . FIG. 10 is a front sectional view of the third test apparatus 63 of the anticorrosion system divertable to an actual machine.

FIG. 11 is a flowchart showing a test method using the test apparatus 63. First, the case where the sacrificial anode 3 shown in FIG. 11A is cooled will be described. That is, in step S310, the minimum value T _max and the maximum value T _min of the test range obtained in advance according to the material of the sacrificial anode 3 to be used are set and input from the control unit 13. Thereafter, the temperature control loop is started. The number of loops is counted as the nth, and the initial value is set to n = 0 (step S320). First, to detect the current _{i 0} at the current detector 9 detects the temperature _{T 0} of the sacrificial anode 3 at a first temperature detector 12a (step S330). Next, (step S340) a sacrificial anode on cooling in the heating and cooling unit 11, n + 1 th, i.e. enters the first loop (step S350), detects a current _{i 1} by the current detector 9, a first detecting the sacrificial anode temperature _{T 1} of at a temperature detector 12a (step S360). i ₀ and i ₁ are compared (step S370). If i ₁ is small, T ₁ and T _min are compared (step S380). If T ₁ is higher, cooling is performed again by the heating / cooling unit 11 (step S340). , after heating at a heating and cooling unit 11 for the lower the better of T ₁ returns to a predetermined temperature range (step S390), each (n + 1) th, i.e. enters the second loop (step S350), the temperature control similar Repeat. Further, by comparing the _{i 1} and _{i 0} (step S400), if the difference between them is in the allowable temperature range is determined that the current value becomes minimum, to maintain the temperature _{T 1} of the sacrificial anode 3 (step S410), End the temperature control flow and move to the next temperature measurement point. If i ₁ is large, it is determined that the cooling is excessive, and after heating by the heating / cooling unit 11 (step S390), the n + 1th, that is, the second loop is entered (step S350), and the temperature control is similarly repeated. When measurement is completed at all measurement points, the test is terminated.
When the sacrificial anode 3 shown in FIG. 11B is heated, the heating and cooling in the description of FIG. However, in step S381, compares the _{T n} and _{T max,} heated by the heating and cooling unit 11 the lower the better of _{T n} (S341), - heating because the higher the direction of _{T n} return to a predetermined temperature range After cooling by the cooling unit 11 (step S391), each enters the (n + 1) th loop (step S350), and the temperature control is similarly repeated.

  The material of the simulated pipe 1 was stainless steel SUS316L, and the sacrificial anode 3 was a zinc alloy (test number E1). The temperature of the sacrificial anode 3 is controlled using the heating / cooling unit 11 so that the current value detected by the non-resistance ammeter 9 that measures the current value of the sacrificial anode 3 and the simulated pipe 1 becomes smaller. In the temperature range of the artificial seawater 6 of 25 ° C. to 50 ° C., the current density becomes smaller when the temperature of the sacrificial anode 3 becomes 30 ° C. to 50 ° C. When the temperature of the sacrificial anode 3 is 40 ° C., the current density shows the minimum value.

  The material of the simulated pipe 1 was stainless steel SUS316L, and the sacrificial anode 3 was carbon steel (test number E2). Other configurations are the same as those of the test number E1. In the temperature range of the artificial seawater 6 of 25 ° C. to 50 ° C., the current density becomes smaller when the temperature of the sacrificial anode 3 is set lower than the temperature of the artificial seawater 6. When the temperature of the sacrificial anode 3 is 10 ° C., the current density shows the minimum value.

Two materials of stainless steel SUS316L and cast iron FC200 were used as the material of the simulated pipe 1, and the sacrificial anode 3 was made of a zinc alloy (test number E3). Contact the stainless steel with a clearance jig. A clearance was provided. Furthermore, an external power source type anticorrosion using a platinum electrode was combined. Stainless steel and carbon steel were electrically connected in parallel to the external power supply, and both were subject to corrosion protection. The surface current of the cast iron FC200 is controlled to be 5 to 100 μA / cm ² to suppress the overall corrosion. The crevice corrosion is suppressed by controlling the current density of the crevice part of stainless steel SUS316L to be 5 to 100 μA / cm ² .

  The case where the anticorrosion system which concerns on this invention is applied to the pump apparatus 30 shown in FIG. 1 is demonstrated below. This is a case where the first test apparatus 61 is applied to an actual machine. As shown in FIG. 1B, the surfaces of both the column pipe 31 and the sacrificial anode 3 that are cathode materials are in contact with seawater. Further, the column pipe 31 and the sacrificial anode 3 are fixed with conductive bolts 4 at portions not in contact with seawater. The sacrificial anode 3 makes the column pipe 31 lower than the immersion potential of the column pipe material itself.

  In order to control the temperature of the portion of the sacrificial anode 3 in contact with the seawater, a temperature control device having a measuring unit 20 attached to the sacrificial anode 3 and a control unit 16 disposed in the seawater intake pump installation unit is provided. The measurement unit 20 includes a heating / cooling unit 11 and a temperature detector 12, and the control unit 16 includes a control unit 13 and a power source 14. A characteristic feature of this embodiment is that it has a current detector 22 for measuring a current value in an electrical conduction portion between the column pipe 31 and the sacrificial anode 3.

  In the seawater intake pump 30, the sacrificial anode 3 is disposed on the outer peripheral surface portion of the column pipe 31. The sacrificial anode 3 is electrically connected to the column pipe 31 by the conductive fixture 4 and fixed. A heating / cooling unit 11 is disposed via a heat conductive sheet 10 in close contact with the sacrificial anode 3.

  Further, a temperature detector 12 is disposed on the side surface of the sacrificial anode 3. The heating / cooling unit 11 and the temperature detector 12 are connected to the control unit 13 by cables 15b and 15c, respectively. The cables 15b and 15c have functions of signal transmission / reception and power supply. The control unit 13 is connected to the power source 14 by a cable 15a. The heating / cooling unit 11, the temperature detector 12, the control unit 13, the power source 14, and the cables 15a to 15c are collectively referred to as a temperature control device.

  The sacrificial anode 3 and the measuring unit 20 are also installed on the inner surface of the column pipe 31. At this time, in order not to affect the flow in the pump 30 and to prevent the measuring unit 20 including the sacrificial anode 3 from falling off, a recess is provided on the inner surface of the column pipe 31 and the measuring unit including the sacrificial anode 3 inside thereof. 20 is disposed. Furthermore, in order not to waste the space of the recess, the surface of the sacrificial anode 3 and the inner wall surface of the column pipe 31 are on the same plane.

  Alternatively, instead of providing a recess on the inner peripheral surface of the column pipe 31, a hole is formed in the column pipe 31 to form an opening. A flange may be disposed in the opening, and the flange and the measurement unit 20 may be integrated. In this case, the column pipe 31, the flange, and the sacrificial anode 3 are electrically connected. It is also possible to adopt an external power supply type anti-corrosion method in which electrodes are provided on the outer peripheral surface portion and the inner peripheral surface portion of the column pipe 31 and a voltage is applied between the column pipe 31 and the electrode. In this case, the column pipe 31 and the electrode are insulated.

  Although the present invention has been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention described in the claims. .

DESCRIPTION OF SYMBOLS 1 ... Corrosion prevention object simulation member (pipe simulation member), 3 ... Sacrificial anode, 4 ... Conductive fixing tool, 5 ... Seawater, 6 ... Artificial seawater, 7 ... Water, 8 ... Water bath, 9 ... Non-resistance ammeter, 10 ... heat conduction sheet, 11 ... heating / cooling unit, 12, 12a, 12b ... temperature detector, 13 ... control unit, 14 ... power supply, 15a-15f ... cable, 16 ... control unit, 17 ... temperature control device, 20 ... Measuring unit, 21 ... container, 22 ... current detector, 30 ... seawater intake pump (pump device), 31 ... column pipe, 32 ... guide vane, 33 ... impeller casing, 34 ... suction bell mouth, 35 ... flange, 36 DESCRIPTION OF SYMBOLS ... Rotating shaft, 37 ... Guide vane inner wall part, 38 ... Impeller (impeller), 39 ... Installation part, 40 ... Beach, 41 ... Water conduit, 42 ... Suction tank, 42a ... Base plate, 43 ... Discharge piping, 44 ... Double-layer filter, 45 ... filtered seawater , 46 ... pump, 47 ... security filter, 48 ... piping, 49 ... high pressure pump, 50 ... power recovery turbine, 51 ... piping, 52 ... RO membrane module, 53 ... piping, 54 ... production tank, 55 ... concentrated water piping, DESCRIPTION OF SYMBOLS 61 ... 1st test apparatus, 62 ... 2nd test apparatus, 63 ... 3rd test apparatus, 70 ... Corrosion prevention system, 80 ... Seawater desalination system, 100 ... Cathode polarization curve, 101 ... Anode polarization curve.

Claims (9)

  A corrosion-controllable metal member, a temperature-controllable sacrificial anode electrically connected to the metal member, and a temperature control device for controlling the temperature of the sacrificial anode, An anticorrosion system characterized in that a sacrificial anode is arranged in an electrolyte.   The sacrificial anode has a heating / cooling unit that at least heats or cools the sacrificial anode, and a first temperature detector for measuring the temperature of the sacrificial anode is attached to the sacrificial anode. 2. The cathodic protection system according to claim 1, wherein the sacrificial anode temperature is controlled using a heating / cooling unit of the sacrificial anode based on a temperature measured by one temperature detector.   The sacrificial anode has at least a heating / cooling section for heating or cooling the sacrificial anode, a first temperature detector for measuring the temperature of the sacrificial anode is attached to the sacrificial anode, and a temperature of the electrolyte is measured. 2 temperature detectors are arranged in the electrolyte, and the temperature control device controls the heating so that the temperature difference measured by the first temperature detector and the second temperature detector falls within a predetermined range. The cathodic protection system according to claim 1, wherein the temperature of the sacrificial anode is controlled using a cooling unit.   The sacrificial anode has a heating / cooling unit that at least heats or cools the sacrificial anode, and a first temperature detector for measuring the temperature of the sacrificial anode is attached to the sacrificial anode, and the sacrificial anode is disposed between the sacrificial anode and the metal member. A current detector for measuring a current value flowing through the first temperature detector, and storing a relationship of an allowable range of a detected current of the current detector with respect to a detected temperature of the first temperature detector; 2. The apparatus according to claim 1, wherein the apparatus controls the heating / cooling unit using the relationship between the detected temperature and the detected current so that a current value measured by the current detector falls within an allowable range. Electric corrosion protection system.   The electrolyte is seawater, the material of the metal member to be protected against corrosion is stainless steel, the material of the sacrificial anode is a zinc alloy, and the temperature of the sacrificial anode is 30 ° C. or higher and 50 ° C. or lower. The cathodic protection system according to any one of claims 1 to 4.   The electrolyte is seawater, the material of the metal member to be protected against corrosion is stainless steel, the material of the sacrificial anode is carbon steel, and the temperature control device is configured so that the sacrificial anode is at a lower temperature than the metal member. The cathodic protection system according to any one of claims 1 to 4, wherein the heating / cooling unit is temperature-controlled.   5. The pump device having the cathodic protection system according to any one of claims 1 to 4, wherein the metal member to be protected is a casing of the pump device, and the casing is immersed in an electrolyte in the casing. A pump apparatus having an anticorrosion system, wherein the sacrificial anode is attached in a conductive state.   The electrolyte is seawater, the casing is made of stainless steel, the sacrificial anode is made of a zinc alloy, and the temperature control device sets the temperature of the sacrificial anode to 30 ° C. or more and 50 ° C. or less. 8. The pump device having the cathodic protection system according to claim 7, wherein the pump device is controlled.   The electrolyte is seawater, the casing is made of stainless steel, the sacrificial anode is made of carbon steel, and the temperature control device is configured so that the temperature of the sacrificial anode is lower than the temperature of the casing. 8. The pump apparatus having the cathodic protection system according to claim 7, wherein the temperature of the sacrificial anode is controlled.

Images