JPS6334492A - Leakage detection for condensate heat exchanger - Google Patents

Abstract

PURPOSE:To improve the efficiency of detection of a leak hole, by a method wherein seawater in a pipe is discharged and the inside of the pipe is pressurized or evacuated while air noise which is generated at the leak hole is detected by an acoustic wave sensor scanning the upper and side parts of a main body. CONSTITUTION:When seawater in a heat exchanging pipe 7 is discharged and high-pressure air is supplied into the pipe 7, the air leaks through the leak hole of the pipe and ultrasonic waves are generated. An ultrasonic wave sensor 24 is provided on a condensate heat exchanger 2 to scan reciprocally arrow sign directions in a diagram and detect the lengthwise and widthwise distances of the condensate heat exchanger 2 in which the leak hole is positioned. The side part of the condensate heat exchanger 2 is scanned with another ultrasonic wave sensor 29 in the same manner to detect the lengthwise distance and the distance in height of the condensate heat exchanger 2 in which the leak hole is positioned. According to these method, the heat exchanging pipe having the leak hole may be detected efficiently in a short period of time.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a condenser equipped with a large number of heat exchange pipes used for condensing steam from a turbine of a nuclear power plant. In particular, the present invention relates to a method for quickly detecting a leak in a condenser pipe.

``Conventional technologyj'' Large condensing heat exchangers used in nuclear power plants use seawater to exchange heat from the steam coming out of the turbine, so some parts of the heat exchange pipes If a damaged part such as a hole or crack occurs in the heat exchanger, seawater will leak from the damaged part of the heat exchanger, causing an increase in the conductivity and chlorine concentration of the condensate.

This will lead to problems such as corrosion of various pipes and an increase in activated products such as Mn and Co contained in seawater, which will hinder reactor operation. It is necessary to stop.

The conventional method for detecting leaks in condensing heat exchangers is to gradually drain the seawater in the heat exchange pipes of the condensing heat exchanger during periodic inspections of the reactor, and to check the high temperature of the condensing heat exchanger using a conductive needle, etc. Roughly locate the broken pipe in the horizontal direction. The heat exchange pipes in the vicinity were detected one by one using a detection method such as the eddy current method or the water manometer method.

``Problems to be Solved by the Invention'' In the conventional leak detection method described above, if the damaged part of the heat exchange pipe, that is, the leak hole, does not have a certain size, the height direction during seawater drainage will increase. The problem is that it cannot be detected. Furthermore, the number of heat exchange pipes in the condensate heat exchanger is approximately 7,000, and it is necessary to perform leak detection on many of the heat exchange pipes, which requires a large amount of work and labor. There are problems such as increased time and radiation exposure.

"Means for Solving Problems" In the present invention, during periodic inspection of a nuclear reactor, the seawater in the heat exchange pipe of the condensing heat exchanger is drained, and the inside of the heat exchange pipe is pressurized or depressurized. Ultrasonic waves generated by air leakage or suction at the leak hole of the heat exchange pipe are detected by an ultrasonic sensor that scans the top and one side of the condensate heat exchanger in a direction perpendicular to the heat exchange pipe. This allows leak holes in heat exchange pipes to be detected.

"Example" An embodiment of the present invention will be described below based on the drawings.

In FIGS. 1 and 2, one system of low pressure turbine 1
It has two systems of condensate heat exchangers 2 for each water system (
A conductivity level of 4.5 is provided in each of the paths (as shown in the figure). When there are three condensate heat exchangers 2 in a nuclear reactor, a total of six condensate heat exchangers 2 each having the above-mentioned conductivity of 4.5 are arranged.

If seawater leaks during reactor operation, it is possible to easily determine which condensate heat exchanger 2 is leaking from the electrical conductivity of each water system, which is 4.5. As a result, the determined leakage of the condensate heat exchanger 2 is inspected as described below.

A plurality of heat exchange pipes 7 are provided in the main body 6 of the condensate heat exchanger 2.
are installed horizontally, and each end thereof is electrically connected to a hollow connection 'B8.9 formed at the front and rear of the main body 6, respectively.

A seawater supply pipe 12 is connected to the connection part 8 through a valve 11, and a discharge pipe 14 is connected to the connection part 9 through a valve 13. An air pipe 16 is connected to the supply pipe 12 via a valve 15 .

In the support mechanism 17 shown in FIGS. 3 and 4, both ends of a guide shaft 21 are fixed to arm portions 18a and 19b of a pair of brackets 18 and 19, respectively. Further, both ends of a feed screw 22 are pivotally attached to the arm portions 18a and 19b, respectively.

The gear fixed to one end of the feed screw 22 and the gear fixed to the output shaft of the motor 23 fixed to the arm 18a of the bracket 18 are in mesh with each other, and are rotated forward and backward by the feed screw 22. It has become so.

A movable member 25 to which an ultrasonic sensor 24 is fixed at the bottom
is loosely fitted to the guide shaft 21, and the feed screw 2
2, and reciprocates between both brackets 18 and 19 by forward and reverse rotation of the feed screw 22.

A pair of guide rollers 26, 27 are each pivotally supported on opposing sides of both brackets 18, 19, and a similar pair of guide rollers 26, 27 is also provided at the bottom of the bracket 18, 19.
8 are each pivotally supported. Said guide roller 26.
28 and guide rollers 27, 28 to the condensing heat exchanger 2.
The ultrasonic sensor 24 is moved a certain distance from the top of the main body 6 by pressing the support mechanism 17 in the front-back direction (left-right direction in FIG. 1) while in contact with both corners of the top of the main body 6. is moved forward and backward.

The condensing heat exchanger 2 condenses steam from the turbine 1 using seawater supplied into the heat exchange pipe 7 through the supply pipe 12 and the discharge pipe 14 .

At this time, both valves 11, 12 are in an open state and valve 15 is in a closed state. When a leak in a certain condensing heat exchanger 2 is determined based on the electrical conductivity of 4.5, the seawater in the supply pipe 12, discharge pipe 14, and heat exchange pipe 7 is drained, and both valves 11 and 12 are closed. Obstructed. In this state, the valve 15 is opened and high pressure air is supplied into the heat exchange pipe 7. Due to this air supply, the air leaks forcefully from the leak hole of the heat exchange pipe 7, and generates ultrasonic waves.

Next, the support mechanism 17 is placed on one end of the upper part of the condensate heat exchanger 2, and the ultrasonic sensor 24 is caused to reciprocate. Further, each time the ultrasonic sensor 24 is moved in the direction of the arrow at an appropriate interval as shown in FIG. 1, the ultrasonic sensor 24 is reciprocated to scan the upper part of the support mechanism 17. This scanning of the ultrasonic sensor 24 detects the distance in the longitudinal direction and the distance in the width direction of the condensing heat exchanger 2 where the leak hole is located.

A support mechanism (not shown) similar to the support mechanism 17 described above is applied to the side of the condensate heat exchanger 2, and the ultrasonic sensor 2
9 is moved at appropriate intervals in the front-rear direction of the condensing heat exchanger 2 and reciprocated in the up-down direction, as shown in FIG. By scanning this ultrasonic sensor 29, the position in the longitudinal direction and the height direction of the condensing heat exchanger 2 where the leak hole is located are detected.

After the approximate position of the leak hole is detected in this way, by inspecting a small number of heat exchange pipes 7 in the vicinity,
The heat exchange pipe 7 having a leak hole in the condensate heat exchanger 2 can be detected in a short time.

In the above embodiment, the case where the inside of the heat exchange pipe 7 is pressurized is described, but the position of the ultrasonic wave generated by the air sucked from the leak hole by reducing the pressure inside the heat exchange pipe 7 is detected. Even if the heat exchange pipe 7 is used, it is possible to detect the leak hole in the heat exchange pipe 7 in the same manner as described above.

"Effects of the Invention" As explained above, according to the present invention, seawater in the heat exchange pipe of a condensing heat exchanger is drained, and the heat exchange pipe is pressurized or depressurized. The ultrasonic waves generated by air leakage or suction at the leak holes are detected by ultrasonic sensors that are scanned in a direction perpendicular to the heat exchange pipes at the top and one side of the condensate heat exchanger. It is possible to efficiently detect a heat exchange pipe having a heat exchange pipe within a short time.

[Brief explanation of the drawing]

Fig. 1 is a side view of a condensing heat exchanger to which the leak detection method for a condensing heat exchanger of the present invention is applied and its related parts, Fig. 2 is a longitudinal sectional view of the condensing heat exchanger, and Fig. 3 4 is a plan view of the support mechanism of the ultrasonic sensor, and FIG. 4 is a front view of the support mechanism. 1... Turbine, 2... Condensate heat exchanger, 4.5
...Conductivity level, 6...Main body, 7...
... Heat exchange pipe, 12 ... Supply pipe, 14
...Exhaust pipe, 16...Air pipe,
17... Support mechanism, 24.29... Ultrasonic sensor.

Claims (1)

[Claims] A main body to which steam discharged from the turbine is supplied, a plurality of heat exchange pipes installed horizontally in parallel within the main body, a supply pipe that supplies seawater for cooling to each of the heat exchange pipes, and a heat exchanger. In a condensate heat exchange system having a discharge pipe for discharging seawater after cooling from a service pipe, the seawater in the supply pipe, discharge pipe, and heat exchange pipe is removed, and appropriate places in the supply pipe and discharge pipe are blocked. In this state, the heat exchange pipe is depressurized or pressurized, and an ultrasonic sensor is scanned at appropriate intervals in a direction perpendicular to the heat exchange pipe on the top and one side of the main body to detect damage to the pipe. A leak detection method for a condensing heat exchanger, characterized in that a heat exchange pipe in a leak state is detected by measuring ultrasonic waves emitted by air leaking or being sucked in a condensing heat exchanger.