JPH0245717B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides corrosion protection facilities that supply direct current between a conduit buried underground and a cast iron electrode buried deep underground as an anode. This article relates to maintenance and management methods for underground structures to prevent corrosion of conduits.

Conventionally, when two or more corrosion protection facilities are operated at the same time, one worker has been assigned to each corrosion protection facility to measure the effectiveness of each corrosion protection facility. This worker conducts and interrupts the current supplied between the conduit and the electrode of each corrosion protection facility, and another worker changes the pipe-to-ground potential of the conduit at a point away from the corrosion protection facility. Measured. From the measurement results of the pipe-to-ground potential, the contribution of each corrosion prevention facility at the measurement point was determined.

In other words, when corrosion protection is being performed normally at the center position between two corrosion protection facilities installed at a distance in the axial direction of the conduit, the pipe-to-ground potential of one corrosion protection facility and the other corrosion protection facility are different. The tube-to-ground potential is almost the same. If the electrically insulating coating of the conduit is damaged between these two corrosion protection facilities or elsewhere, a low ground condition,
In other words, a state occurs in which the electrical resistance between the pipe and the soil decreases, and a difference occurs in the pipe-to-ground potential between each corrosion protection facility. Such a low ground, ie, the potential to the pipe ground due to the corrosion protection facility near the location where the electrically insulating coating layer of the pipe is damaged, is reduced. In other words, it can be seen that the effect of the contribution of the corrosion protection facility becomes smaller and damaged areas occur. In addition, when measuring the pipe-to-ground potential at multiple locations between two corrosion-protection facilities, if the contribution from each corrosion-protection facility to the pipe-to-ground potential changes rapidly between the two measurement points, It can be seen that a low ground condition occurs in the vicinity. Therefore, by periodically measuring the degree to which each corrosion protection facility contributes to the pipe-to-ground potential at the measurement point, that is, the effect of each corrosion protection facility contributing to the pipe-to-ground potential, it is possible to determine the state of low grounding. If such a low ground condition occurs, take measures such as repairing the damaged electrically insulating coating layer. In this way, underground structures are maintained and managed to prevent conduit corrosion.

With such conventional methods, when two or more corrosion protection facilities are in a conductive state at the same time, it may not only be unclear which corrosion protection facility is contributing at the measurement point, but also the effectiveness value of each corrosion protection facility may be In order to accurately understand the results, long-term measurements were required. As a result, the workers were extremely fatigued. Furthermore, there was a waste of having to assign workers to each anti-corrosion facility.

The purpose of the present invention is to solve the shortcomings of the conventional technology, and to maintain underground structures in which the effectiveness of each of a plurality of corrosion protection facilities can be easily measured and analyzed, and each corrosion protection facility can be efficiently controlled. The purpose is to provide a management method.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a simplified cross-sectional view of one embodiment of the invention. A metal conduit 2 for gas or the like is buried underground 1. In order to prevent this conduit 2 from being corroded, anti-corrosion facilities 3, 4 are provided.
Corrosion protection facilities 3, 4 are provided along the conduit 2, for example, in number 10.
Located at Km intervals.

The corrosion protection facility 3 has an external power source 5 that supplies direct current.
and an electrode 7 connected to the positive terminal 6 of the external power source 5
and a switch 8 interposed between the terminal 6 and the electrode 7.
, a connecting line 9 connecting the terminal 6 and the electrode 7 , and a connecting line 11 connecting the negative terminal 10 of the external power source 5 and the conduit 2 . Corrosion prevention facility 4 and corrosion prevention facility 3
It has the same configuration as the external power supply 12 and the switch 13.
and an electrode 14. The electrodes 7 and 14 are made of cast iron, for example, and are buried, for example, about 70 meters underground.

The pipe-to-ground potential measuring device 15 is moved along the conduit 2 in which the anti-corrosion facilities 3 and 4 are provided. The pipe-to-ground potential measuring device 15 includes a potentiometer 16, a connecting wire 17 connecting the conduit 2 and the potentiometer 16, a saturated copper sulfate electrode 18 for measuring the underground potential, and the potentiometer 1.
6 and a connection line 19 connecting the electrode 18 to the electrode 18 .
The pipe-to-ground potential measuring device 15 is installed by a worker so that it can be operated at any point where the pipe-to-ground potential of the conduit 2 is to be measured.

A timer (not shown) or the like is connected to the switches 8 and 13, and the currents of the external power supplies 5 and 12 are automatically turned on and off, respectively. The conduction/cutoff interval of the switches 8 and 13 is determined by the corrosion protection facility 3,
4, each uniquely predetermined by.

In the anti-corrosion facility 3, the switch 8 repeats the conduction/cutoff state at time intervals T1 and T2, so that the current from the external power source 5 flows through the conduit 2 and the electrode 7 as shown in the waveform diagram of FIG. 2a. , supplied. In addition, in the corrosion protection facility 4, the switch 13 repeats the conduction and cutoff states at times T3 and T4, respectively, so that the current from the external power supply 12 is
Conduit 2 and electrode 14 are supplied as shown in the waveform diagram of FIG. 2b. At this time, the pipe-to-ground potential is measured by the pipe-to-ground potential measuring device 15 at measurement points that are, for example, 10 to 20 km away from the corrosion protection facilities 3 and 4 of the conduit 2. As shown in the waveform diagram in Figure 2c,
In the corrosion protection facilities 3 and 4, from time t3 to t4 when current is being supplied from the external power supplies 5 and 12, the potentiometer 16 indicates the pipe-to-ground potential V1. In the corrosion protection facility 3, the current from the external power source 5 is connected to the switch 8.
During the time t2-t3 when the voltage is not supplied due to the interruption of the voltage, the potentiometer 16 indicates that the tube-to-ground potential is smaller in absolute value by the potential difference V2. Also, in the corrosion protection facility 4, the time t1 to t2 when the current from the external power source 12 is not supplied due to the cutoff of the switch 13.
When , the potentiometer 16 indicates that the tube-to-ground potential is a potential difference V
3 indicates that the absolute value is smaller. In this way, the conduction/cutoff interval T1 of each switch 8, 13,
Since T2; T3 and T4 are respectively determined, the effect of each corrosion protection facility 3, 4 at the measurement point can be accurately measured as a change in the respective pipe-to-ground potential.

When the pipe-to-ground potential of the conduit 2 is a negative value and the absolute value is larger than 850 mV, for example, when the conduit 2 is made of steel, ionization of iron is suppressed, so the conduit 2 is protected against corrosion. Therefore, as a comprehensive effect of the corrosion prevention facilities 3 and 4, the pipe-to-ground potential V1-V2 is set to, for example, about -850 mV regardless of the measurement point of the pipe 2.
The voltages of the external power supplies 5 and 12 of the corrosion protection facilities 3 and 4 are respectively controlled. For example, when the measurement point is equidistant from the corrosion prevention facilities 3 and 4, the voltages of the external power supplies 5 and 12 of the corrosion prevention facilities 3 and 4 are set so that the ratio of the difference in pipe-to-ground potential is V2/V3=1. each controlled. As a result, the conduit 2 is protected from corrosion, and the amount of consumption of the electrodes 7 and 14 buried deep underground can be minimized. That is, in order to make the pipe-to-ground potential of the conduit 2 negative, suppress ionization, and prevent corrosion, the electrode 7 buried deep underground,
14 is given a positive potential. The electrodes 7 and 14 are ionized and consumed, but by controlling the above-mentioned ratio to be constant, the consumption amounts in the electrodes 7 and 14 can be made almost the same. Furthermore, when it is detected that a low ground condition has occurred in the conduit 2, measures can be taken, for example, by repairing the damaged part of the electrode insulating coating layer of the conduit 2 with an electrical insulating material. Electrodes 7, 14
consumption can be reduced.

In the above-mentioned embodiment, the conduction of the switches 8 and 13 is
Although the sum of the cutoff intervals, that is, one period of the conduction and cutoff intervals, is determined to be the same time, in other embodiments of the present invention, the conduction and cutoff intervals of the switches 8 and 13 are determined to be equal.
The time ratio of interruption may be the same, but each corrosion protection facility 3, 4 may have its own conduction/interruption cycle that is different.

In the above embodiment, the method for maintaining and managing the two anti-corrosion facilities 3 and 4 in the conduit 2 was described.
According to the present invention, the effect of three or more corrosion prevention facilities can be easily measured as a change in the pipe-to-ground potential. Therefore, it is possible to prevent corrosion of the conduit 2 and extend the life of the electrode buried deep underground.

As described above, according to the present invention, the effects of a plurality of corrosion prevention facilities can be easily measured and analyzed, and the corrosion prevention facilities can be controlled to protect conduits from corrosion and extend the life of electrodes.

[Brief explanation of drawings]

FIG. 1 is a sectional view of one embodiment of the present invention, and FIG. 2 is a waveform diagram for explaining the operation of the corrosion protection facilities 3, 4 and the pipe-to-ground potential measuring device 15 shown in FIG. 1... Underground, 2... Conduit, 3, 4... Corrosion protection facility, 5, 12... External power supply, 7, 14... Electrode,
8, 13...Switch, 15...Tube-to-ground potential measuring device, 16...Potentiometer.

Claims (1)

[Claims] 1. Corrosion of the conduit is prevented by a corrosion protection facility that supplies direct current between the conduit buried underground and a cast iron electrode buried deep underground as an anode. In the method for maintenance and management of underground underground facilities, each of the plurality of corrosion protection facilities has a different ratio of conduction time to cutoff time between the conduit and the electrode, or Measure the pipe-to-ground potential at any point on the pipe using a switch having a cut-off period, and measure the pipe-to-ground potential of each corrosion prevention facility based on the change in pipe-to-ground potential measured in response to conduction/cutoff of each of the switches. A method for maintaining and managing underground objects, comprising controlling a DC voltage supplied between a conduit and an electrode so that the potential of the pipe to the ground at a measurement point becomes a desired value.