JPS619137A - Underwater motor pump - Google Patents

Abstract

PURPOSE:To prevent an underwater motor pump from corroding by grounding the pump by two grounding rods, forming one of the rods of a material having a lower potential than that of the other rod, thereby corroding the rod of the low potential. CONSTITUTION:An underwater motor pump 1 mounted in a liquid 7 for supplying and exhausting the liquid 7 such as contaminants, drain water, civil water is connected through a lower cable 9 with the first grounding rod 12, and connected throgh lead wirings 19 with the second grounding rod 18 buried directly under a water storage tank. In this case, the material of the second rod 18 is selected from a material having lower potential than the pump 1 such as zinc, aluminum or magnesium. Thus, since the rod 18 performs as the grounding and sacrificing anode, if can prevent the pump 1 from corroding.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a submersible motor pump that prevents abnormal corrosion in water.

[Technical background of the invention and its problems]

Sewage and filth from buildings, department stores, housing complexes, etc.

Submersible motor pumps (hereinafter simply referred to as pumps) are used in various places for drainage and water supply. All of these pumps are connected via power cables to the ground terminal of the switchboard that operates them, and from this point to a ground rod buried underground. Also, due to its purpose, this pump is installed in a tank made of concrete or other material to collect sewage and wastewater.

Immersed in tap water, etc. For this reason, the outer surface of the pump is painted with highly water-resistant epoxy paint or tar epoxy paint to prevent the aforementioned sewage, waste water, tap water, etc. from coming into contact with the pump material, thereby preventing corrosion. . However, during transport and installation of the pump, or during subsequent inspection work, the paint film may be damaged and the base material may be exposed. In particular, the lower part, which touches the floor, is at greater risk of damage to the paint film and exposure of the base material than other parts due to movement during installation. On the other hand, the pump body is the power cable and the ground terminal of the power distribution board.

It is connected to a grounding rod buried underground via a lead wire.

These situations will be explained using, as an example, a pump used in a tap water storage tank in a housing complex. As shown in FIG. 2, the pump 1 is installed on the floor of a water tank consisting of a water tank 2 and a power supply room 3. The water tank and power supply room are separated by a concrete wall 4,
A part of the upper part through which the pipe 5 connected to the pump 1 passes is open.

Tap water 7 sucked in from the casing 6 of the pump 1 is supplied to water tanks on the rooftops of each building through piping. The water tank is filled with tap water 7, and since the pump 1 is immersed in this tap water 7, it is coated with a paint having excellent water resistance as described above. Further, a power distribution board 8 is installed in the power supply room 3, from which a power cable 9 for the pump 1 is connected to the pump 1 in the water tank through the same route as the piping. Naturally, the switchboard has a grounding terminal section 10, which is connected via a lead wire 11 to a copper grounding rod 12 buried underground, so that the pump 1 and the grounding rod 12 are indirectly connected. This grounding rod 12 is usually made of steel, which has a higher potential than the material of the pump 1 body (steel). Initially, the pump 1 is carried in and installed through the manhole 13 at the top of the water tank, but the handling at that time and subsequent It is expected that the paint film on the outside of the pump 1 will be damaged during periodic inspections, etc. If it is damaged, the base material will be exposed, and as shown in Figure 3, the paint film on the pump 1 will be damaged. The membrane damaged part (base exposed part) 14 is electrically connected to the grounding rod 12 via the tap water 7 and the underground 15.Then, due to the difference in the materials of the two underwater, the lead wire 11 and the power supply are connected from the grounding rod 12 to the lead wire 11 and the power supply. The electric current indicated by the arrow 16 via the cable 9 forms an electric circuit that returns from the damaged paint film part 14 of the pump 1 to the grounding rod 12 via the tap water 7 and the underground 15.
This is an enlarged view showing the flow of current between the pump l and the grounding rod 12, and the switchboard 8, piping 5, etc. are omitted. The concrete wall 4 absorbs water and becomes conductive, and the ground also has conductivity, so the pump 1 and the ground rod 12 are electrically connected via the tap water 7 and the ground 15, and the pump has a low potential. The current shown by the arrow 17 that has passed from the grounding rod 12 through the power cable 9 flows out from the paint film damaged portion 14 of No. 1 into the tap water 7.

Due to the current indicated by the arrow 17, the paint film damaged portion 14 exhibits a much larger amount of corrosion than that caused by mere immersion in water, and may corrode in a short period of time, sometimes penetrating the paint film. A sample simulating the paint film damage part 14 is immersed in a water tank, and the ground rod 12 is
The table below shows an example of the results of measuring the current from the
85III in a year! I+ also erodes, and about 20% of simple corrosion
It can be as much as 0 times.

As shown above, corrosion caused by the current shown by the arrow 16 from the grounding rod 12 is a phenomenon that reduces the reliability of equipment with damaged coatings 14 and exposed substrates, and when the exposed area is small, The electric current concentrated on the exposed parts causes local corrosion (pitting corrosion), which may even cause an accident in which it penetrates the substrate in a short period of time, causing the equipment to lose its functionality. Once an accident occurs with equipment installed in a water tank or the like, the water in the tank must be drained and emptied in order to inspect it or to transport the equipment in and out.

It is also predicted that water will need to be cut off for a period of time, which will require enormous amounts of time and expense, and will cause significant damage.

One way to prevent such corrosion is to increase the thickness of the frame of the pump 1, but since the amount of corrosion caused by battery action is extremely large, it takes a lot of weight, cost, and This is a major disadvantage in terms of manufacturing.
Commercialization becomes difficult.

Also, since corrosion due to battery action occurs because of a potential difference, it is conceivable to use a material that has a potential similar to that of grounding copper, such as copper, but this is a manufacturing problem.

Due to strength, cost, etc., this application is difficult.

[Object of the present invention]

The present invention improves the above-mentioned drawbacks by burying a metal grounding rod with a lower potential than copper in the lower part of the water tank, in addition to the grounding rod directly below the switchboard, and connecting this to the terminal part of the submersible motor pump. It is an object of the present invention to provide a submersible motor pump that prevents corrosion by causing current flowing into the liquid from a damaged part to flow in the opposite direction.

[Summary of the invention]

The present invention provides a submersible motor pump used for supplying and draining sewage, waste water, tap water, etc., in which the submersible motor pump is grounded to two buried grounding rods via power cable lines or lead wires, respectively, and the first grounding is connected to the submersible motor pump. This submersible motor pump is characterized in that the material of the second ground rod has a lower potential than the material of the rod. As a result, the second grounding rod corrodes,
Instead, it prevents corrosion of the submersible motor pump.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings. However, the same parts as in the prior art will be designated by the same reference numerals and detailed explanation will be omitted.

FIG. 1 is a state diagram showing the current flowing between the submersible motor pump in the water tank and the ground rod at the bottom of the water tank, showing one embodiment of the present invention. A second grounding rod 18 having a lower potential than the iron of which the pump 1 is made is buried in the second grounding rod 18 , and its lead wire 19 is connected to the terminal portion 20 of the pump 1 .

The material of the second grounding rod 18 is zinc or aluminum.

Any material having a lower potential than the pump 1, such as magnesium, may be used. Alternatively, the material may be a steel rod whose surface is coated with the above-mentioned metal. The shape thereof is not particularly rod-like, but may be plate-like, and the essential condition is that it is buried underground at the bottom of the water tank, and that its lead wire 19 is connected to the terminal section of the pump. Incidentally, the construction of the second grounding rod 18 can be carried out at the time when the grounding rod 12 of the switchboard 8 is buried at the time of construction of the water tank, and no special work is required. Furthermore, there is a lead connecting the terminal section of the pump 1 and the second grounding rod 18. line 1
9 is a lead wire 19 that is branched from a part of the power cable 9 because it is difficult to prepare extra when manufacturing the pump.
You can also connect to

If the ground rod 12, pump 1, and second ground rod 18 are electrically connected through the tap water 1 in this way, water will flow out into the liquid (tap water) from the damaged paint film 14 as shown in FIG. The current flow is in the opposite direction to the current indicated by arrow 17, and flows from the liquid into the damaged paint film portion 14 like the current indicated by arrow 22 shown in FIG. That is, since the second grounding rod 18 has a low potential with respect to either the bomber or the grounding rod 12, the direction from the second grounding rod 18 to the arrow 2
1 flows into the ground rod 12 through the ground, and a current flows into the damaged paint film portion 14 through the ground and the tap water 7, as shown by arrow 22. If this flow is displayed in each component, it will look like this:
This means that when three different materials form an electric circuit with lead wires and electrolyte (water or underground), they are connected as long as the material with the lowest potential exists. This is the same as the current acting on the other two materials.That is, during the period when the second grounding rod 18 made of the material with the lowest equipotential of zinc, aluminum, or magnesium is present, the second grounding rod 18 is lower than the pump 1.
8 becomes a low potential, no current flows from the paint film damaged area 14 into the tap water 7, and conversely, the current 22 flows from the tap water 7 into the paint film damaged area 14, preventing corrosion of the paint film damaged area 14. be done. Instead, corrosion of the second grounding rod 18 progresses. Therefore, the second grounding rod 18 is replaced or replenished periodically. In this way, the second grounding rod 18 has two functions: grounding and sacrificial anode.

In the present invention, the second grounding rod 18 is provided directly below the water tank, but if the material of the first grounding rod 12 is simply selected to be a material with a lower potential than, for example, iron, which is the constituent material of the bomb 1. , which has the same effect as the second grounding rod 8 and can prevent corrosion of the damaged part 14 of the paint film. However, with this method, the first grounding rod 12
As the corrosion progresses, the first grounding rod 12 becomes smaller and eventually becomes completely corroded and worn out. In this case, the pump 1 or the switchboard 8 cannot be grounded and cannot be used. In this way, by using the second grounding rod 18, corrosion of the paint film damaged part 14 can be prevented,
Electric shock accidents from the pump 1 can be prevented. Furthermore, if a large number of ground rods 18 are buried, corrosion of the equipment can be prevented for a very long period of time.

Although the submersible motor pump installed and used in a tap water storage tank has been explained here as an example, the same effect can be obtained even if it is used in equipment installed underwater for sewage, drainage, etc.

〔Effect of the invention〕

As explained above, according to the present invention, the submersible motor pump is grounded by two grounding rods, and the material of the second grounding rod is made to have a lower potential than the material of the first grounding rod. Corrosion and instead prevents corrosion of submersible motor pumps.

[Brief explanation of drawings]

FIG. 1 is a state diagram of the current flowing between a submersible motor pump and a grounding rod showing an embodiment of the present invention, and FIG. 2 is a layout diagram of a submersible motor pump and a grounding rod installed in a conventional water storage tank. FIG. 3 is a state diagram of current flowing between a conventional submersible motor pump and a ground rod. 1... Submersible motor pump, 7... Tap water. 9...Power cable, 11.19...Lead wire. 12.18...Ground rod, 14...Damaged part of paint film. 15... Underground. Agent Patent Attorney Nori Chika
Yu (1 idiot) Figure 1

Claims (1)

[Claims] In a submersible motor pump used for supplying and draining sewage, wastewater, tap water, etc., the submersible motor pump is grounded to two buried grounding rods via power cable lines or lead wires, respectively, and the material of the first grounding rod is A submersible motor pump characterized in that the material of the second grounding rod has a lower potential.