JP3363767B2 - Method and apparatus for electrolytic protection and sterilization of water pipes - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and a device for preventing electrical corrosion of a water pipe such as a water pipe, a hot water pipe and the like, while preventing corrosion of the metal on the inner surface of the pipe. Regarding

[0002]

2. Description of the Related Art Iron pipes are usually used for water supply pipes, hot water supply pipes, and the like in view of cost and quality. There is a problem that rust is generated on the inner surface of the iron pipe with time, the water distribution becomes reddish, and the odor and taste of the water distribution are changed. This is the so-called red water problem. In this red water phenomenon, not only the turbidity of the distribution water, but also the mixing of metal components of the distribution pipe into the distribution water, the adhesion of scale mainly consisting of rust on the inner surface of the pipe, and the further growth of microorganisms on this scale. Water quality deterioration factors occur simultaneously or over time.

Various measures have been taken in the past for the problem of red water. For example, membrane degassing method or vacuum degassing method to reduce the oxygen concentration in the distribution water, calcium injection method or rust preventive agent injection method that forms a film on the inner surface of the pipe with calcium compound or rust preventive agent to obtain anticorrosion effect. There are chemical mixing method, magnetic method, etc. These conventional anticorrosion methods, for example, in the degassing method, there is a problem that the running cost for degassing increases, in the drug mixing method, the cost for using the drug every several months increases, also, There was no decisive means because there was a problem of water pollution caused by the drug.

Therefore, as a second best measure, a method of repairing the inner surface of the pipe by lining it with a resin has been most popular, though the cost is high. However, even if the pipe is lined, it is inevitable that the metal is exposed at the pipe connection portion, and pinholes and cracks also occur with time in the lining layer. As a result, even if the pipe is lined, the exposed portion is unavoidably generated, so rust is generated from such exposed portion, and the local rust gradually spreads, causing a red water problem. Not a few such cases have occurred.

Further, as a method of preventing corrosion of the water distribution pipe, an electrolytic protection method has been conventionally proposed. As is well known, the occurrence of rust in the water distribution pipe is caused locally by the inner surface of the pipe and water distribution (electrolyte).
The cause is that a battery action occurs due to the potential difference between That is, an electric current flows from the metal on the inner surface of the pipe to the water distribution (electrolyte), the metal is ionized and begins to melt in the water distribution, resulting in rust. Such a phenomenon occurs separately at a plurality of local points on the inner surface of the pipe, and rust or corrosion occurs as a whole. Therefore, in the cathodic protection method, conversely, a current (referred to as an anticorrosion current) is supplied from the water distribution (electrolyte) to the metal on the inner surface of the pipe with a constant applied voltage to prevent the metal from being ionized and the occurrence of rust. However, the actual water pipe is a wide range of equipment, and according to the conventional knowledge about the cathodic protection method,
The effective range of cathodic protection is narrow, and if it is installed in a wide range of actual water distribution facilities, the cost will be high, so it has not been put into practical use at present.

[0006]

The object of the present invention has been made in view of the above-mentioned conventional circumstances, and it is economically distributed by expanding the effective range of the cathodic protection method which has been considered to be impractical. An object of the present invention is to provide a method and apparatus for cathodic sterilization that not only protects water pipes but also improves water quality.

[0007]

[Means for Solving the Problems] The inventors of the present invention have found that the problems can be solved by intensively examining the following items after intensively conducting experiments for solving the above problems. Came to.

(I) The voltage is raised to the limit where over-corrosion does not occur in the vicinity of the anode, and the reaching distance of the anti-corrosion current is lengthened.

(Ii) A small amount of calcium or magnesium present in water is deposited as an electrolytic coating on the metal surface in the pipe by applying an anticorrosion current. The deposited layer is a dense layer of calcium carbonate and magnesium hydroxide. Yes, it has electrical insulation. Focusing on this, as soon as possible after the start of anticorrosion, and as far as possible from the anode,
Explore the way electrolytic coatings prevail.

As a result of intensive examination of these items, if the output current into the water supply in the water distribution pipe is controlled to a constant value,
It has been found that, depending on the growth of the electrolytic coating on the inner surface of the water pipe, the voltage can be automatically increased to extend the corrosion protection range further. Also, since the constant current value has an optimum value depending on the condition of the water distribution system such as the form of the water distribution circuit to be applied and the water quality, it is necessary to have a function to easily set the level of the constant current control value. ,found. It was also found that the general bacteria in the water can be drastically reduced or extinguished by passing an anticorrosive current through the water.

Based on these findings, the present invention has conventionally been thought to be impossible to economically perform galvanic protection of water pipes, whereas an economical cathodic sterilization method and device have been realized. Is.

Namely, claim 1 of the present invention, there is provided a cathodic protection method of sterilizing a water pipe to achieve anticorrosion of the water distribution pipe surface and distribution water sterilization simultaneously exposing the anode inside the water pipe in the water distribution In addition to the above, a cathode is provided on the outer surface of the water pipe separated from the anode, and a predetermined constant current is supplied over time in the water distribution regardless of the fluctuation of the applied voltage .

According to a second aspect of the present invention, in the method for cathodic sterilizing a water pipe according to the first aspect, the predetermined constant current is applied to the inner surface of the water pipe to form an electrolytic coating layer over time. It is characterized in that it is realized by increasing the voltage in proportion to the growth.

According to a third aspect of the present invention, in the method for cathodic sterilization of a water pipe according to the first or second aspect, an aqueous solution of magnesium hydroxide and calcium carbonate having a predetermined concentration is added to the water in the water pipe. It is characterized in that it is added at the same time as the supply of a constant current to promote the growth of the electrolytic coating layer formed on the inner surface of the water distribution pipe with time, and to expand the anticorrosion range of the coating layer.

According to a fourth aspect of the present invention, an anode is attached to a joint portion of a water distribution pipe so as to be exposed in a space inside the pipe, a cathode connected to a desired outer surface of the water distribution pipe, the anode and the cathode. And a constant current supply device which is connected to and supplies a constant current between the anode and the cathode irrespective of the fluctuation of the applied voltage .

[0016] According to a fifth aspect of the present invention, in the apparatus of the fourth aspect of the present invention, in the apparatus of the fourth aspect, the constant current supply device comprises an electrolytic coating layer formed on the inner surface of the water pipe over time. It is characterized by having a constant current output characteristic of increasing the voltage in proportion to the growth.

[0016] According to a sixth aspect of the present invention, there is provided an electrical corrosion sterilization apparatus for a water distribution pipe according to the fourth or fifth aspect, further comprising an annular support for inserting and sandwiching the joint in the water distribution pipe. The anode is attached to the central space of the annular support with a part thereof exposed, and the inner diameter of the annular support is set smaller than the inner diameter of the water distribution pipe.

According to a seventh aspect of the present invention, in the apparatus for electrical corrosion protection of a water distribution pipe according to the sixth aspect, the annular support is formed thick and a storage space is formed in the thick portion.
The constant current supply device is housed in this housing space, and the cathode is connected to the outer surface of the annular support, whereby the device is unitized.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to these embodiments.

(First Embodiment) FIG. 1 is an explanatory view of a schematic configuration of a method for cathodic sterilization of a water pipe according to the present invention. In this method, a constant current supply device 2 having a power supply connection terminal 1 is used. The anode 3 is attached to the tip of the constant current output line of the constant current supply device 2, and the anode 3 is connected to the water pipe 5.
The cathode 4 is attached to the outer surface 5b of the water distribution pipe 5 and the cathode 4 is connected to the input line of the constant current supply device 2. The electric circuit is configured as described above, the constant current supply device 2 is turned on, and a constant low current is caused to flow in the water distribution in the water distribution pipe 5 from the anode 3 to the cathode 4. The direction of this current (anticorrosion current) is from the metal to the water distribution based on the corrosion current that naturally occurs in a normal water distribution pipe, that is, the potential difference between the metal (iron) inside the water distribution pipe and the water distribution (electrolyte). This is in the opposite direction to the current that occurs, and this normal reverse current prevents metal ionization and avoids corrosion protection.

The constant current supply device 2 has means for controlling the current to a constant value and means for setting the constant current to an optimum current value, and has the circuit configuration shown in FIG. This circuit is composed of the anode 3 and the cathode 4 which are loads.
It is a constant current power supply device of the type that constantly draws current from the water distribution between and. The principle of this circuit is that the drain current I ₀ and the source current I _S of the FET (field effect transistor) 12 are
, And TR transistor 13 is merely used for current boost. Further, by switching the rotary switch 14 to the standard resistance 15, the output constant current I ₀ can be designated by the following equation.

[0022]

## EQU1 ## I ₀ = V _i / R _i (i = 1, 2, 3, 4, 5) In FIG. 2, the anode 3 is formed in a ring shape, and the connecting portion of the water pipe 5 is connected to the anode 3. It is attached to the inner periphery of a resinous annular support (which can also serve as packing) 6 to be inserted into and is exposed to water distribution. The inner diameter of the ring-shaped anode 3 is smaller than the inner diameter of the water distribution pipe 5. As a result, the flow of the distribution water passing through the anode 3 becomes turbulent. When turbulent flow occurs here, in order to grow the electrolytic coating layer on the inner surface of the water distribution pipe, if magnesium hydroxide or calcium carbonate is added to the water distribution from this location or its vicinity, they will be mixed into the water distribution. Will be promoted.

(Second Embodiment) FIG. 3 is a partial cross-sectional view showing an example of the case where the cathodic sterilization apparatus according to the present invention is unitized. In this unit, each component is incorporated in an annular support 6 which is formed thick. The support 6 is made of a composite hard synthetic resin, and has an outer shape that can be mounted in the middle of the pipe to be protected by a flange or by screwing. The anode 3 is attached to the inner surface of the support 6 so that a part of the anode 3 is exposed in water distribution. A storage space 6a is formed in the thick portion of the support 6, and the compact constant-current supply device 2 described above is stored in the space 6a. Is exposed on the outer peripheral surface of. Also, the cathode 4
Is connected to the support 6 in the vicinity of the bolt hole 6b.
Although the anode 3 is exposed in a plate shape on the outer periphery of the cross section of the flow path, it may be a wire shape exposed in the water distribution channel. Further, the material is preferably platinum-coated titanium or platinum-coated niobium.

(Embodiment 3) The cathodic sterilization apparatus for water pipes having the structure shown in FIG. 4 replaces the flange type anode in the apparatus shown in FIGS. 2 and 3 and further reduces the construction cost. This device has been developed and adopted as an anode with a screw-in mounting structure that can be easily mounted even in a narrow space.

In the figure, 21 is a screw-in type fitting, 22 is an iron outer frame pipe, and 23 is a plastic insertion pipe made of high performance polyethylene or the like. Reference numeral 24 denotes an anode, which is composed of a wire made of niobium or titanium coated with platinum. The anode 24 is embedded in the insertion pipe 23. The inner diameter of the insertion pipe 23 is adjusted to the diameter of the water pipe to be attached. The outer frame pipe 22 is fitted on the outer circumference of the inner pipe 23. Outer threads are formed on both ends of the outer circumference of the outer frame pipe 22, and the outer threads are utilized to facilitate the fixing of the screw-in type fitting 21.

An inner screw terminal 25 made of brass is connected to the open end of the anode 24, and a positive lead wire from a power source is connected thereto. On the other hand, a screw 26 was screwed into the iron outer frame pipe 22, and a negative lead wire from the power source was connected to the screw 26. As the power source, an AC power source converted into a DC voltage of 15 V by a converter was used. From this power source, a current was made to flow through the positive and negative lead wires described above through the constant current system shown in FIG. This completes the assembly of the device.

As an application of this, a converter and a constant current system are incorporated on the outer periphery of the insertion pipe 23 to realize integration of a compact anode and control system. AC100V or a battery is used as a power source in this case.

[0028]

Example Regarding the JIS 25A water distribution pipe 5, several kinds of tests were conducted as follows.

(I) Lining steel pipe, (ii) White gas pipe (new), (iii) White gas pipe Used for 15 years with red rust rising like a bump.

The pipe lengths are 5 m, 10 m and 15 m,
20m and 30m for lined steel pipes
The ones were also selected for the test.

5 m from the discharge valve of the water supply pump, the rusted pipe used for 15 years was used as it was, the above-mentioned unit of FIG. 3 was incorporated in the tip, and the test pipe was connected to the end of the unit for the test. .

The pump is operated only during the day (the discharge amount is about 2,0
The pump was stopped at night and on holidays, but the unit was energized and the anticorrosion current was continuously applied while the water was still filled.

(I) Lining The lining of the steel pipe measuring portion was peeled off with a diameter of 5 mmφ, and the rusting condition of the portion was observed and the potential of the portion was measured.

In a comparatively short time, the defective portion at a distance of about 30 m from the anode was -750 at (anode voltage 10 to 20 V).
Corresponding to ~ -900 mV / Ag / AgCl, the anticorrosion potential was sufficiently reached, and no rusting was observed.

(Ii) White gas tube (new) Initially, it reached the anticorrosion zone for only a few meters, but the one tested by adding magnesium hydroxide and calcium carbonate aqueous solution to water electrolyzes in several months. It was revealed that the coating was formed in the tube of 13 to 15 m and the corrosion could be prevented up to around 15 m.

(Iii) White gas pipe (used for 15 years) Since red rust elutes in the pipe after 15 years and the circulating water becomes red turbid, the circulating water was frequently replaced. The anticorrosive area reached a relatively long distance compared to the case of (ii), and the natural electrolytic coating formation (due to a trace amount of Mg ⁺⁺ and Ca ⁺⁺ inclusions in the feed water) was also performed relatively quickly. 10 to 15 in 12 to 18 months
It progressed to m.

In the process of inspecting the water quality in order to measure the change in the elution amount of iron, general bacteria were detected in the water sample immediately before the unit was energized. Especially in the case of (iii), in the sample one month after the unit was energized, the number of general bacteria was initially 3,000 / l but was reduced to 18 / l.

As a result of further tests, a correlation between a range for completely eliminating general bacteria and conditions was found by the voltage applied to the anode 3 and the length of the water distribution pipe, and water supply for a high-rise building as shown in FIG. The sterilization system was established.

In the figure, in the system in which the water receiving layer 31 receives water from a water supply source pipe such as a water supply, pumps water from the pump 32 to the elevated water tank 33, and supplies water from the elevated water tank 33 to each use end, the anode A To S.

That is, the pump 3 adjacent to the water receiving layer 31
By installing an anode for each of the two discharge ports, one each for the entrance and exit of the elevated water tank 33, and one each for the branch pipe (length 5 to 40 m) to the water use end, the inside of the water distribution pipe can be protected. This rusting system has established the technology to eliminate general sterilization that simultaneously parasitizes and propagates in the water supply system.

[0041]

EFFECTS OF THE INVENTION Unlike conventional wisdom, water distribution pipes such as a water supply pipe and a hot water supply pipe are electrically connected in a wide range from the anode to a side of 10 to 15 m with a bare pipe and to the anode with a side of about 30 m with a lining pipe. We have established a technology that can prevent corrosion. This makes it possible to realize economical and permanent measures to prevent red water in distribution pipes.

At the same time, according to the present invention, without a drug,
It was shown as a side effect that general sterilization that is parasitic on the water supply system can also be performed. In particular, the condominium system shown in FIG. 5 can eliminate the general bacteria in the water taken from the tap.

Further, the water treated by the current supply to the water distribution pipe by this device has a higher penetration force to the dirt, slime, scales and other deposits adhering to the inner surface of the water distribution pipe as compared with normal water. It has been found to be enhanced, which enhances the cleaning power to wash off the deposits. This is considered to be because a weak current flows through the water in the water distribution pipe, whereby the water clusters are subdivided and the water with the smaller clusters easily enters the deposit.

The above-described sterilizing effect and osmotic force enhancing effect which can be obtained by the device of the present invention are obtained even when a non-metal water distribution pipe such as a resin pipe is connected to the tip of a local metal water distribution pipe around the anode. It has also been found to extend to this non-metallic water pipe and its downstream pipelines.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a schematic configuration of a method for cathodic sterilization of a water distribution pipe according to the present invention.

FIG. 2 is a circuit diagram showing an example of a constant current supply device used in the present invention.

FIG. 3 is a partial cross-sectional side view showing a schematic configuration of a cathodic sterilization device for a water distribution pipe according to the present invention.

FIG. 4 is a side view, partially in cross-section, showing another configuration in which the cathodic sterilization device for water pipes according to the present invention is made compact.

FIG. 5 is a configuration diagram of a water supply system anticorrosion sterilization system in an apartment house constructed by the device of the present invention.

[Explanation of symbols]

1 Power Supply Connection Terminal 2 Constant Current Supply Device 3 Anode 4 Cathode 5 Water Distribution Pipe 6 Annular Support 21 Threaded Fixture 22 Iron Outer Frame Pipe 23 Plastic Insertion Pipe 24 Anode (Platinum Coated Niobium or Titanium Wire) 25 Inner screw terminal 26 made of brass 26 Screw

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI F16L 58/00 F16L 58/00 (56) References JP-A-2-133588 (JP, A) JP-A-3-253588 (JP , A) JP 63-166983 (JP, A) JP 51-44310 (JP, A) JP 49-51650 (JP, A) JP 8-134671 (JP, A) JP 1-268889 (JP, A) JP 38-24222 (JP, B1) Piping Technology, Japan, Nippon Kogyo Shuppan, November 1996, Vol. 38, No. 13, P.I. 55-58 Growth of calcareous film by electro-coating, Proc. Of 42nd Symposium on Corrosion and Corrosion Protection, Japan, Japan Corrosion and Protection Association, September 14, 1995, pp. 549-552 (58) Fields investigated (Int. Cl. ⁷ , DB name) C23F 13 / 00,15 / 00,11 / 18 C02F 1/46 C02F 5/00 610 F16L 58/00

Claims (7)

(57) [Claims] 1. A cathodic protection method of sterilizing a water pipe to achieve anticorrosion of the water distribution pipe surface and distribution water sterilization simultaneously, provided with so as to be exposed in the distribution of the anode inside the water pipe, from the anode A cathode is provided on the outer surface of the water distribution pipes that are separated from each other, and a predetermined constant current is applied to the water over time to change the applied voltage.
A method for catalyzing sterilization of water distribution pipes, which is supplied regardless of the method. 2. The predetermined constant current is realized by increasing the voltage in proportion to the growth of an electrolytic coating layer formed on the inner surface of the water distribution pipe over time. The method for cathodic sterilization of a water pipe according to. 3. An electrolytic coating formed on the inner surface of the water pipe over time by adding an aqueous solution of magnesium hydroxide and calcium carbonate having a predetermined concentration to the water distribution pipe at the same time as the supply of the constant current. 3. The method for cathodic sterilization of a water pipe according to claim 1 or 2, wherein the layer growth is promoted and the corrosion protection range of the coating layer is expanded. 4. An anode attached to a joint portion of a water pipe so as to be exposed in a space inside the pipe, a cathode connected to a desired outer surface of the water pipe, and an anode and a cathode connected to the anode and the cathode. A constant current is applied between the
And a constant current supply device for supplying without supplying a constant current. 5. The constant current supply device has a constant current output characteristic of increasing a voltage in proportion to the growth of an electrolytic coating layer formed over time on the inner surface of the water distribution pipe. 4. An electric corrosion preventive sterilizer for water pipes according to item 4. 6. An annular support for inserting and sandwiching it in a joint portion of the water distribution pipe, wherein the anode is attached to the central space of the annular support with a part of the anode exposed. The cathodic sterilization apparatus for a water distribution pipe according to claim 4 or 5, wherein an inner diameter of the body is set smaller than an inner diameter of the water distribution pipe. 7. The annular support is formed thick, and a storage space is formed in the thick portion, the constant current supply device is stored in the storage space, and the outer surface of the annular support is provided with the constant current supply device. The cathodic sterilization device for water pipes according to claim 6, wherein the device is unitized by connecting a cathode.