JPH062347A - Anticorrosion method of water supply pipe line and device - Google Patents

Abstract

PURPOSE:To easily prevent a water supply pipe line from corrosion by bubbling nitrogen gas into water before it is supplied to the water supply pipe line of steel pipes. CONSTITUTION:City water is supplied to a water storage tank installed at a basement of a building from a city water pipe 2 through a stop cock 3 and a water meter 4 and, at the same time, it is pumped up to a high placed tank 6 by a pump 5. Nitrogen gas obtained through a nitrogen gas generator 7 is introduced to positions under the surfaces of the waters of the water storage tank 1 and high placed tank 6 through a gas releasing means 8. Dissolved oxygen in the water is nearly and completely mixed with nitrogen gas bubbles, and an amount of dissolved oxygen in the water is decreased. According to the constitution, the formation of iron (11) hydroxide is suppressed, and the corrosion of a water supply pipe line of steel pipes is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anticorrosion method and apparatus for water supply lines.

[0002]

2. Description of the Related Art When a water leak in a water supply line in an existing building occurs, the question of whether the responsibility of the leak lies with the building designer, manager or builder, or with the pipe manufacturer or builder. Of course, repairing is often not easy.

In particular, when corrosion is the cause, not only a part of repair but also a situation where full repair is required occurs. Therefore, corrosion of the water supply pipe should be prevented as much as possible.

It has been proposed to use a material having excellent corrosion resistance, for example, a stainless steel pipe, but this is also limited to a semi-permanent facility, a special building, or a specific pipeline position,
It is rare to take safety measures such as using stainless steel pipes for all water supply pipes for general buildings, considering the useful life and economy of the building.

On the other hand, with the recent increase in the height and complexity of buildings, the members (water receiving tank, high-position tank, vertical pipe, horizontal pipe, etc.) that form a water channel from the viewpoint of pressure resistance, strength, workability, weldability, etc. (Joints, valves, etc.) also depend on steel in many cases, and it is unavoidable to use steel pipes or steel plates as materials for the water supply channel.

In order to prevent corrosion of the steel used in such a water supply channel, it has been customary to use a steel material having an anticorrosion coating (for example, a resin-coated steel sheet or a hot-dip galvanized steel sheet). In addition, sacrificial anodes are used to prevent corrosion in water tanks.

[0007]

Even when a steel material having an anticorrosion coating is used as a water supply conduit material, it is difficult to completely and permanently perform the anticorrosion function.

For example, even when a hot-dip galvanized steel sheet is used, corrosion may be promoted due to a difference in ionization potential at a portion joined to another metal member such as a valve body, and crevice corrosion cannot be completely prevented. Corrosion may be accelerated if zinc elutes and the base metal steel is exposed. Further, the galvanized layer on the inner surface of the pipe may be destroyed by welding, screwing, or working.

[0009] Even in a material in which a surface of a hot-dip galvanized steel sheet is further coated with resin, the resin may be decomposed, or swelling or cracking may occur depending on the use environment, and in this case, there is a similar problem.

Although the anticorrosion method using a sacrificial anode has been generalized for water tanks such as water heaters, it is difficult to apply it to a general water supply pipeline system because of the existence of water flow and the installation situation of electrodes. It is impossible because it is.

The present invention prevents the corrosion of steel occurring in the water supply line
It is intended to prevent the corrosion easily by removing the cause of the corrosion.

[0012]

According to the present invention, in a building provided with a water supply pipe made of steel pipe, nitrogen gas is bubbled through the water before being supplied to the water supply pipe. To provide anti-corrosion methods. Nitrogen gas bubbling is conveniently performed in a water receiving tank installed upstream of the water supply pipeline. The nitrogen gas is sufficient if it is separated from air using a hollow fiber membrane.

The present invention also provides a building water supply facility in which water is supplied from a water receiving tank to various parts of the building through a steel water supply pipe, and the water receiving tank is constructed as a closed container which is isolated from the atmosphere. Provided is a corrosion preventive device for a water supply pipe, characterized in that a porous tube connected to a nitrogen gas source is installed below the water surface of the water receiving tank, and an exhaust gas pipe communicating from the space inside the water receiving tank to the atmospheric pressure atmosphere is provided.

[0014]

Function: Corrosion of steel in the water supply line is caused by the coexistence of water and oxygen. Although the theory of corrosion has been studied academically, in model terms, part of water dissociates in water and hydrogen ions H ⁺ and hydroxide ions OH ⁻ exist, but part of iron is It elutes as cations, the iron base material is negatively charged and binds to hydrogen ions, and the iron surface is covered with a hydrogen film. On the other hand, the eluted ferrous ion (Fe ²⁺ ) combines with OH ⁻ to form ferrous hydroxide Fe (OH) ₂ and becomes stable on the surface of iron.

In a kind of equilibrium state covered with this hydrogen film and ferrous hydroxide film, the progress of corrosion almost stops, but when oxygen coexists there, hydrogen on the iron surface reacts with oxygen. And the equilibrium is lost due to binding, and ferrous hydroxide also reacts with oxygen as shown in the following formula to form ferric hydroxide and precipitate, so the elution of iron ions begins and corrosion occurs. It will proceed.

4Fe (OH) ₂ + O ₂ + 2H ₂ O = 4Fe (OH) ₃

In general fresh water, the type and amount of dissolved gas, p
Corrosion shows various behaviors due to factors such as H value, temperature, flow velocity, and water quality, but it is undoubted that the coexistence of oxygen in water accelerates the corrosion of steel. The same is true for coated steels.

Water placed under atmospheric pressure dissolves air, oxygen and nitrogen, but their solubilities are temperature dependent, and the dissolved amount increases as the temperature decreases. For example, at 20 ° C., it is said that about 23 ppm of air, about 15 ppm of nitrogen, and 9 ppm of oxygen are dissolved under atmospheric pressure.
The solubility of nitrogen and oxygen is related to the partial pressure of nitrogen and the partial pressure of oxygen in the air.

According to the present invention, when nitrogen gas is bubbled into water and a large number of nitrogen gas bubbles are introduced into the water, at the interface where the water and the nitrogen gas bubbles contact, the gas phase having substantially zero oxygen partial pressure or extremely low contact with water. Therefore, the phenomenon that dissolved oxygen in water shifts to the gas phase occurs. For this reason,
If a large number of nitrogen gas bubbles are continuously generated in the water and the bubbles are continuously removed, the dissolved oxygen in the water is almost completely transferred into the bubbles and the dissolved oxygen amount in the water can be reduced. .

If nitrogen gas bubbles are introduced into the water before being supplied to the water supply line to reduce the amount of dissolved oxygen, the progress of corrosion of steel in the water supply line is prevented. If a nitrogen generator using a hollow fiber membrane is used, nitrogen gas can be continuously supplied using air as a raw material.

[0021]

EXAMPLE FIG. 1 shows a typical water supply route for a middle-rise building. The water tank 1 is installed in the basement of the building. City water is supplied to the water receiving tank 1 from a city water pipe 2 through a water stopcock 3 and a water meter 4. The water received in the water receiving tank 1 is pumped up to the elevated tank 6 by the pump 5, and is sent from this elevated tank 6 to the water supply position on each floor.

In the water supply path of such a building, according to the present invention, a large number of nitrogen gas bubbles are continuously introduced into the water in the water receiving tank 1. Although the details will be shown later, in FIG. 1, reference numeral 7 denotes a nitrogen gas generating device using air as a raw material, and the nitrogen gas obtained by the nitrogen gas generating means 7 is stored under the water surface of the water receiving tank 1 and the elevated tank 6. It is introduced into the position via the gas releasing means 8.

FIG. 2 shows an example of a water supply route in a high-rise building using the intermediate tank 9, and in FIG. 2A, the water tank 1
In this example, the pumps 5 and 5'are used to pump water from the high tank 6 to the intermediate tank 9 and water is supplied to the upper floor zone from the high tank 6 and to the lower floor zone from the intermediate tank 9.

FIG. 2B shows an example in which water is pumped from the water receiving tank 1 to the intermediate tank 9 by the pump 5 and a part of water is pumped from the intermediate tank 9 to the elevated tank 6 by the pump 5 ″, and in FIG. 2C, the water receiving tank. Pumping water from 1 to the elevated tank 6 by the pump 5, and then from this elevated tank 6 to the intermediate tank 9
2A shows an example in which a part of water is dropped, and both are the same as FIG. 2A in that water is supplied from the high tank 6 to the upper floor zone and from the intermediate tank 9 to the lower floor zone.

2 is the same as that of FIG. 1 in that nitrogen gas bubbles are introduced into the water of the water receiving tank 1, the intermediate tank 9 and the elevated tank 6.

FIG. 3 shows an example of a water supply path in a high-rise building provided with the pressure reducing valve 10. In FIG. 3A, the pressure reducing valve 10 is installed in the main falling water pipe, and in B, the pressure reducing valve 10 is installed in the branch pipes on the lower floors.
Further, C shows an example in which the pressure reducing valve 10 is provided in the lower group, and in each case, the pumping pressure to the elevated tank 6 is relaxed by the operation of these pressure reducing valves 10. Also in such a water supply line, in the present invention, nitrogen gas bubbles are introduced into the water in the water receiving tank 1 and the elevated tank 6 in the same manner as described above.

4 and 5 show an example of the present invention in which nitrogen gas bubbles are introduced into the water in the water receiving tank 1. Water tank 1
Is configured as a closed container by attaching the lid 12. Reference numeral 13 is a water receiving inlet to the water receiving tank, and 14 is a water feeding outlet from the water receiving tank. From this water inlet 13 to the water outlet 1
A partition wall 15 is provided in the tank so that water flows unidirectionally in a zigzag manner up to No. 4. This partition wall 15
As shown in the plane of FIG. 5, a large number of sheets are arranged side by side with a predetermined gap alternately with the front wall or the rear wall,
As a result, water flows in a zigzag shape in the direction of the arrow shown.

In this way, a unidirectional water passage is formed in the water receiving tank 1, and the porous tube 16 is arranged at the bottom of the passage so as to cross the passage. Then, the porous tube 16 is connected to a nitrogen gas generator 17 provided outside the tank.

In the illustrated example, a plurality of porous tubes 16 are arranged at the bottom of the tank at a position where the flow of water in the water channel is reversed, and each porous tube 16 is used as a single nitrogen gas generator 17 with a gas pipe 18. Connected. As a result, by driving the nitrogen gas generator 17, nitrogen gas is ejected from the pores of each porous tube 16 to form fine nitrogen gas bubbles in water.

Therefore, from the water inlet 15 to the water outlet 1
During the process up to 4, the water in the tank was given multiple opportunities to contact with the nitrogen gas bubbles, and the oxygen dissolved in the water migrated into the nitrogen gas bubbles due to the partial pressure difference, and the water was discharged through the water outlet 14. Almost no dissolved oxygen exists at the time of exit.

On the other hand, the gas bubbles that have absorbed the oxygen gas in the process of rising in water are discharged from the space 19 in the tank on the water surface to the outside of the system through the exhaust gas pipeline 20. This exhaust gas line 2
0 communicates with the atmosphere via the check valve 21. Check valve 2
1 prevents the atmospheric air from entering the water receiving tank 1 while the apparatus is at rest.

An overflow pipe 23 is attached to take out an overflow when the amount of water received in the water receiving tank 1 exceeds the amount of water to be sent. In the facility of the present invention, an overflow tank 24 is attached to the overflow pipe 23. .

The overflow tank 24 comprises a closed container, and the overflow port 2
5 is installed at a predetermined height so that water can be stored in the overflow tank 24 and the overflow pipe 23 and the overflow port 25 do not communicate with each other through the space above the water surface. 26 is attached. A gas pipe 27 is connected to the overflow tank 24 from the nitrogen gas generator 17, and nitrogen gas is also introduced into the overflow tank 24. Reference numeral 28 denotes a water supply pipe, which is supplied by a control valve 29 so that water is always stored in the overflow tank 24 even when there is no overflow from the water receiving tank 1.

With this configuration, the atmosphere is prevented from entering the water receiving tank 1 through the overflow pipe 23.
As a result, oxygen is prevented from being dissolved in the water in the water receiving tank 1. Also, the mixed gas of nitrogen and oxygen generated in the tank 1 is prevented from leaking outside through the overflow pipe.

FIG. 6 shows details of the porous tube 16 arranged at the bottom of the water receiving tank 1. One end of the porous ceramic tube 30 is closed with a closing member 31,
The other end is closed by the gas header 32. Closure member 3
1 and the gas header 32 are fixed to each other by a frame 33. When nitrogen gas is introduced from the gas supply port 34 provided in the gas header 32, the ceramic pipe 3
Nitrogen gas is jetted entirely from the peripheral surface through the porous wall of 0.

FIG. 7 shows a gas generator 1 used in the present invention.
7 shows details of No. 7. A large number of hollow fiber membranes 35 are arranged in a container 38 with one end opened to the gas supply header 36 and the other end opened to the gas discharge header 37. Also, almost the entire length of the group of hollow fiber membranes 35 is exposed in the internal space surrounded by the partition plates 39 and 40, and this internal space communicates with the exhaust gas pipe 41.

When compressed air is introduced into the supply header 36 and sent into the hollow fiber membrane 35, oxygen gas or CO ₂ gas having a high permeation rate selectively permeates the hollow fiber membrane 35,
Exhaust header 3 without permeating nitrogen gas with a slow permeation rate
It flows to the 7 side. Although various hollow fiber membranes 35 have been developed, a composite membrane obtained by laminating a silicone polymer on a polyolefin porous hollow fiber is available on the market. Nitrogen gas can be separated.

The separated nitrogen gas is pressure-fed to the water receiving tank 1, the porous tube 16 provided at the bottom of the high tank 6 and the intermediate tank 9, and the overflow tank 24 as described above, to remove the dissolved oxygen in the water. The other oxygen-enriched gas is introduced into the air conditioner to increase the oxygen concentration in the room air, and is optionally stored and used for indoor discharge or other purposes.

[0039]

As described above, according to the present invention,
It is very effective in avoiding or reducing the extremely troublesome trouble of corrosion of the water supply line of the existing building. In particular, the fact that the corrosion of the water supply pipe has been achieved with harmless nitrogen gas and with a simple facility is advantageous in terms of both safety and economy, and the water supply pipe in the building after it has been constructed once has been achieved. It can make a great contribution to prolonging the life of the road.

The effect of the present invention as described above is also exerted on a water supply pipe using a steel pipe or a steel plate coated with an anticorrosion coating.

[Brief description of drawings]

FIG. 1 is a diagram showing a water supply system for explaining a method of preventing corrosion of a water supply pipe of the present invention.

FIG. 2 is a diagram showing a water supply system of a high-rise building for explaining the anticorrosion method of the present invention.

FIG. 3 is a diagram showing a water supply system of a high-rise building for explaining the anticorrosion method of the present invention.

FIG. 4 is a schematic cross-sectional view showing an example of a water tank for carrying out corrosion protection according to the present invention.

5 is a plan view of the inside of the water receiving tank of FIG. 4. FIG.

FIG. 6 is a schematic cross-sectional view showing an example of a porous tube used in the present invention.

FIG. 7 is a schematic cross-sectional view showing an example of a nitrogen gas generator used in the present invention.

[Explanation of symbols]

 1 Water Tank 5 Pumping Pump 6 High Tank 13 Water Inlet 14 Water Outlet 15 Partition Wall 16 Porous Tube 17 Nitrogen Gas Generator 18 Gas Pipe 20 Exhaust Gas Pipeline 24 Overflow Tank 30 Porous Ceramics Pipe 35 Hollow Fiber Membrane

Claims (6)

[Claims] 1. A method for preventing corrosion of a water supply pipe in a building having a water supply pipe made of steel, wherein nitrogen gas is bubbled through the water before being supplied to the water supply pipe. 2. The method for preventing corrosion of a water supply line according to claim 1, wherein the bubbling of nitrogen gas is performed in a water receiving tank installed upstream of the water supply line. 3. The method for preventing corrosion of a water supply line according to claim 1, wherein the nitrogen gas is separated from air by using a hollow fiber membrane. 4. In a water supply facility of a building in which water is supplied from a water receiving tank to various places in the building through a steel water supply pipe, the water receiving tank is constructed as a closed container that is shielded from the atmosphere, and An anticorrosion device for a water supply line, characterized in that a porous tube connected to a nitrogen gas source is installed below the surface of the water, and an exhaust gas line that communicates from the space inside the water receiving tank to the atmosphere is provided. 5. A partition wall is provided inside the water receiving tank so that a unidirectional water channel is formed between the water receiving inlet to the water receiving tank and the water sending outlet from the water receiving tank. The corrosion prevention device according to claim 4, wherein the porous tube is arranged so as to cross the water channel. 6. The anticorrosion device according to claim 4, wherein the water receiving tank is provided with a water-tight overflow port, and the water-sealing portion is filled with nitrogen gas.