JPH11218002A - Steam leakage detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To early detect steam leakage by discharging leaking steam by detection pipes leading steam to a flange part having a possibility of generating steam leakage and detecting a change in humidity by a humidity sensor installed at the outside of a heat insulating material. SOLUTION: Steam of a high temperature and high pressure flows from a main steam entrance 150 to a compartment 50 in which upper and lower flanges 122, 124 are fastened with many bolts 126 and nuts 128. When a heat expansion difference is generated between the compartment 50 and the bolts 126 due to the starting and stopping of a turbine, steam sometimes leaks from a flange joining surface. One end of each detection pipes 602, 604 is provided at a location where the pipes 602, 604 are capable of detecting this leakage and the other end is connected with a sensor box 640. When steam leakage is generated, steam flows into the sensor box 640 via the detection pipes 602, 604, power supply voltage is supplied from a humidity indicator and a humidity sensor 610 outputting a change in resistance detects power supply voltage. The other end of the sensor box 640 is released to the atmosphere, and is capable of easily detecting flow of steam and steam leakage from the inside of a heat insulating material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steam leak detecting device for detecting a steam leak from an object to be fastened such as a casing of a steam turbine or a flange or a lid of a steam pipe.

[0002]

2. Description of the Related Art When the fastening force of an object to be fastened such as a flange or a lid of a vehicle room or a valve room of a steam turbine or the like is excessive, not only the stress of a bolt is increased, but also relaxation is caused due to exposure to high temperature. Then, the fastening force is weakened, and steam leakage from the flange or the lid occurs. On the other hand, if it is too small, the fastening strength of the bolt becomes insufficient, which causes steam leakage. Monitoring of this steam leak is important to prevent turbine travel before it occurs.
There is a steam leak detection device described in JP-A-8-303208. The conventional example measures by bringing a sensor close to the vicinity where leaked steam flows out to the surroundings, the present invention provides a detection tube for guiding steam near the occurrence of steam leakage, and discharges the leaked steam through the detection tube,
A humidity change is detected by a humidity sensor provided outside the heat insulating material.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to detect steam leakage from an object to be fastened, such as a flange or a lid of a vehicle room such as a steam turbine or a valve room, or a lid at an early stage. It is known that the bolt fastening force causes relaxation in a device exposed to a high temperature. When relaxation occurs, the fastening force is weakened, and steam leakage from the flange or the lid may occur.

[0004] It is an object of the present invention to provide means for early detection of steam leakage from a flange or a lid. The inspection target of steam leak is covered with heat insulating material because of high temperature and high pressure.
That is, it is difficult to detect when the leak starts. Therefore, it is important to detect the humidity near the location where the leak occurs. However, this type of sensor usually has a heat-resistant temperature of 200 ° C. or less, and it is necessary to consider the heat resistance of the sensor.

[0005]

The present invention employs the following means to solve the above-mentioned problems. That is, by a detection pipe that guides steam to a flange portion where steam leak may occur so that a humidity sensor whose resistance or capacitance changes depending on humidity can be used as a steam leak detection device.
The leaked steam was discharged, and the humidity change was detected by a humidity sensor installed outside the heat insulating material.

Further, the temperature of the steam leaked by the detection tube is cooled to a temperature lower than the heat resistant temperature of the humidity sensor. A conversion means for converting a change in resistance or capacitance of the humidity sensor into a voltage change, a linearizer for receiving an output of the conversion means and outputting a signal proportional to humidity, and a means for measuring an output of the linearizer from a central control room Are provided.

That is, the leaked steam is discharged by a detection pipe for guiding the steam to a flange portion where a steam leak is likely to occur, and the humidity change is detected by a humidity sensor installed outside the heat insulating material. Leaks can be detected. Also, the humidity can be accurately measured by cooling the temperature of the steam leaked by the detection tube to a temperature lower than the allowable temperature limit of the humidity sensor.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A description will be given of a steam leak detector for a steam turbine or the like according to an embodiment of the present invention.

FIG. 1 is a schematic diagram showing the measurement principle of the steam leak detector according to the present invention.

High-temperature, high-pressure steam is sent from a boiler (not shown), and flows into a vehicle compartment 50 from a main steam inlet 150. The upper and lower flanges 122 and 124 of the casing 500 are tightened by a number of bolts 126 and nuts 128.

With such a structure, a thermal expansion difference occurs between the vehicle compartment and the bolt due to the start / stop of the turbine, or relaxation occurs in the bolt due to a high temperature. If the tightening force is reduced, high-pressure steam is generated in the vehicle interior, so that steam may leak from the joint surface of the flange.

One end of each of the detection tubes 600 and 602 is provided at a position where the leak can be detected, and the other end is connected to the sensor box 640. When a steam leak occurs, the steam flows into the sensor box via the detection tube, and the humidity sensor 610 detects the leak. The humidity sensor 610 receives a power supply voltage from the hygrometer and outputs a change in resistance. The other end of the sensor box is open to the atmosphere to facilitate steam flow. With such a configuration, when a steam leak occurs, the steam leak can be detected from inside the heat insulating material 604.

FIGS. 2A and 2B show a general configuration example of a humidity sensor. A water-resistant insulating layer of silicon nitride and a comb-shaped electrode with a gap of 10 microns are formed on the silicon crystal.
An organic polymer moisture-sensitive film is formed thereon.

FIG. 3 shows the resistance value of the sensor with respect to humidity, which changes exponentially with respect to relative humidity. Because of such characteristics, when steam leaks, it is easy to determine. The hygrometer 630 supplies a power supply voltage for the sensor, a linearizer for linearly converting a nonlinear change in impedance with respect to humidity, a signal-to-noise ratio, so-called S /
Normal means consisting of an amplifier for increasing the N ratio.

FIG. 4 shows an application example of FIG. Detection tube 60
0, 602 has one end at a position where this leak can be detected,
A discharge pump 656 is provided at the other end of the sensor box 640. Further, cooling units A and B are installed in front of the sensor box 640.

[0016] With such a configuration, when a steam leak occurs, the discharge pump 656 operates through the detection tube.
The steam flows into the sensor box via the cooling units A and B before the sensor box 640. Therefore, the leaked steam becomes cooled steam and is detected without damaging the humidity sensor 610.

The humidity sensor 610 is supplied with a power supply voltage from a hygrometer and outputs a resistance change. Discharge pump 6
The other end of 56 is open to the atmosphere to facilitate steam flow. With such a configuration, when a steam leak occurs, the steam leak can be detected from inside the heat insulating material 604. In such a configuration, the discharge pump 656 is connected to the sensor box 640.
May be installed in front of.

It is also effective to operate the discharge pump 656 periodically. In this operation, the discharge pump 656 is started by remote control from the control room, and after a certain period of operation, air from the detection pipe is discharged to the sensor box, and if there is a steam leak, it is detected by the sensor. Since the vapor leak can be sufficiently detected in several tens of seconds to several minutes, the discharge pump may be stopped after the lapse of the time.

If such a detection method is adopted, it is possible to periodically detect leakage. In addition, if the operation time of the discharge pump is limited to a time necessary and sufficient for the detection time of the steam leak, even if high-temperature steam leaks, the discharge pump will be stopped in a short time, and the steam sensor that is weak to high temperature will also fail. The function can be maintained without doing.

[0020]

According to the method and apparatus for detecting a steam leak of the present invention, the power generation system can be operated while periodically measuring from the control room, so that the steam leak can be detected at an early stage and not only can the energy efficiency be kept high, but also a serious accident can be prevented. It can be prevented beforehand.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a steam leak detection device according to the present invention.

FIGS. 2A and 2B are a plan view and a cross-sectional view illustrating an example of a humidity sensor used in the present invention.

FIG. 3 is a diagram illustrating an example of electrical characteristics of a humidity sensor used in the present invention.

FIG. 4 is a cross-sectional view illustrating a method and apparatus for detecting a steam leak according to the present invention.

[Explanation of symbols]

20 ... sensor, 40 ... measuring pin, 42 ... measuring seat, 60 ...
Nut, 80 ... bolt, 100 ... upper flange, 102 ...
Lower flange, 120: measuring ring, 122: sensor holder.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takeshi Onoda 3-1-1, Sachimachi, Hitachi-City, Ibaraki Pref. Hitachi, Ltd. Hitachi Plant Co., Ltd. No. 1 Inside Hitachi, Ltd. Hitachi Plant

Claims (4)

[Claims] In a steam pressure vessel, a steam detection tube (600) is provided.
A steam leak detecting device for detecting a steam leak from a change in an electric signal of a humidity sensor whose impedance changes depending on humidity and humidity. 2. In a steam pressure vessel having a plurality of bolts, a steam sensor 600, 602, a humidity sensor 610 whose resistance changes according to humidity, a hygrometer 620 for converting a resistance change of the humidity sensor into a voltage change, a detection tube. A steam leak detection device comprising a cooling unit in a part of the steam leak detector. 3. In a steam pressure vessel having a plurality of bolts, a steam sensor 600, 602, a humidity sensor 610 whose capacitance changes according to humidity, and a hygrometer 620 for converting a resistance change of the humidity sensor into a voltage change. A steam leak detection device, comprising: 4. In a steam pressure vessel having a plurality of bolts, a humidity sensor 610 whose capacitance changes according to humidity with a steam detection tube 600, 602, a hygrometer 620 which converts a resistance change of the humidity sensor into a voltage change, A steam leak detection device comprising a cooling unit provided in a part of a detection tube.