JP2597654B2 - Valve seat leak detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention relates to a valve seat leak detecting device that measures noise generated when a fluid leaks from a valve seat to detect the presence or absence of a leak. .

(Prior Art) Many valves are provided in a thermal power plant, a nuclear power plant, and the like for process control, isolation, and the like.

Among these valves, for example, a drain valve or the like existing in a main steam system or a bleeding system which is a high-temperature and high-pressure steam system is fully opened at the time of startup to discharge the drain of the steam piping line to a load of about 5 to 15%. During normal operation, no drain occurs and the steam is in a fully closed state in order to prevent unnecessary loss of heat energy of the steam.

However, when these valves are used for a long period of time, they may be damaged due to erosion of the valve seat portion or biting of foreign matter during opening / closing operations, and may cause leakage. Once a leak has occurred, the high-speed steam flow tends to spread the scar in a blink of an hour and cause a greater amount of leaks, from the standpoint of thermal efficiency and maintenance.
Early detection of valve leaks has become an important research topic.

Recently, acoustic emission (Ac) using piezoelectric ceramics etc. for the seats of these valves
Research has been actively conducted to detect a leak when the valve is fully closed or to detect an erroneous operation when the valve is fully closed using an oustic emission (AE sensor) sensor (for example, Japanese Patent Application Laid-Open No. Sho 62). -80535).

FIG. 3 shows an example of the configuration of a valve seat leak detection device using an AE sensor that is generally considered at present.
Denotes a target valve for detecting a leak, 2 denotes a working fluid such as steam or water, 3 denotes an AE sensor, 4 denotes an amplifier, 5 denotes a signal processing unit, 6 denotes a signal determination unit, and 7 denotes a display unit.

In the valve seat leak detection device having such a configuration,
If the working fluid 2 leaks when the valve 1 is fully closed, the sound of the working fluid flowing, the cavitation sound, or the vibration of the pipes and valves accompanying the flow is generated. These sounds and vibrations are used as the AE signal. AE sensor 3 detects.

This signal is continuous but the signal level is low,
After being amplified by the amplifier 4, it is input to the signal processing unit 5. As a processing method in the signal processing unit 5, a method of obtaining an effective value, a method of performing frequency analysis using a spectrum analyzer, and the like are general.

The signal from the signal processing unit 5 is output to the signal determination unit 6. In this determination unit, the signal from the signal processing unit 5 is detected and compared with an effective value level when no leak occurs from the valve or a threshold value having a predetermined margin in the frequency analysis result. When the signal level exceeds this threshold, it is determined that a leak has occurred.

In addition, the display unit 7 displays the blinking of the warning lamp 7a, the effective value or the frequency analysis value based on the diagnosis result, the display of the estimated leak amount, and the like.

(Problems to be Solved by the Invention) In such a valve seat leak detecting device, there is no particular problem with the leak monitoring during normal operation, that is, when the valve is fully closed. For example, a drain valve such as a main steam system or a bleed air system is used. As described above, the valve that automatically opens when the load decreases has the following problems.

When the load drops and the drain valve opens, the valve seat leak detection device indicates that a leak has occurred, but the operator considers the drain valve opening interlock condition such as load, and this It is necessary to determine whether the problem is caused by the automatic opening of the drain valve.

Generally, the load that the drain valve opens is 5 to 15%, but since this load varies depending on the drain valve, the operator must have a good understanding of the many drain valves and their open load conditions.

In particular, recent thermal power plants are operated for load adjustment, and DSS (Daily Start Stop) operation or midnight minimum load operation frequently occurs. Thought,
Some countermeasures are needed to reduce the burden on operators.

The present invention provides a drain valve provided with a valve seat leak detecting device using an AE sensor, in a load operation in which the drain valve is automatically opened, by giving the open state of the drain valve to the valve seat leak detecting device, It is an object of the present invention to provide a valve seat leak detecting device that does not give erroneous information to a plant operator.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the valve seat leak detection device of the present invention is installed in each of a plurality of valves that automatically open and close according to the load on the plant. A plurality of AE sensors, a leak occurrence determination unit that receives detection signals of these AE sensors and determines whether or not a leak has occurred in each valve seat, and whether or not each of the valves is fully closed based on a load signal of the plant. A valve opening degree determination unit that determines whether the determination result of the valve opening degree determination unit and the determination result of the leak occurrence determination unit is input,
A display judging unit for inputting a judgment result of the leak occurrence judging unit to a display unit when it is judged that at least one of the valves is fully closed and that a leak has occurred. Information is provided only during the validity period.

(Example) Hereinafter, an example of the present invention is described with reference to drawings. 1 and 2, the same elements as those of the prior art are denoted by the same reference numerals.

FIG. 2 shows an embodiment of the valve seat leak detecting device according to the present invention, and FIG. 1 shows the basic configuration thereof.

In this embodiment, a second signal judgment unit 8 is provided, and a condition switch 14 which is turned on / off by the output of the second signal judgment unit 8 is provided between the first signal judgment unit 6 and the display unit 7. It is interposed.

In FIG. 2, although not shown, detection signals from the AE sensor 3 attached to each detection target valve 1 as shown in FIG. 1 are input to the corresponding amplifiers 4A, 4B, and 4C, respectively. Each of the amplified signals is input to the signal processing unit 5 via the signal selector 20 and then to the first signal determination unit 6 to determine whether or not a valve seat leak has occurred for each detection target valve 1. . Further, the determination result of the occurrence of the valve seat leak is input to the signal collecting unit 21, and the condition switch 14
Is output to the display unit 7 when is turned on.

The second signal determination unit 8 receives a load signal 18 or the like as a signal indicating the valve opening state and determines whether each of the detection target valves 1 is fully closed. The determination result of each detection target valve 1 of the unit and the determination result of the leak detection of the corresponding detection target valve 1 from the first signal determination unit 6 are input, and it is determined that any one of the valves 1 is fully closed and a leak has occurred. And a display determination unit that turns on the condition switch 14 when determined.

In the present embodiment, as shown in FIG. 2, the valve opening degree determining section is constituted by a load condition determining section 11 for determining whether or not each detection target valve 1 is fully closed based on the load signal 18.
In addition, the display determination unit compares the determination result of each detection target valve 1 of whether or not the valve is fully closed by the load condition determination unit 11 and the determination result of the leak occurrence of the corresponding detection target valve 1 from the first signal determination unit 6. AND circuits 13A, 13B, and 13C as input signals, and a signal collecting unit 19 that receives output signals of these AND circuits 13A, 13B, and 13C, and turns on the condition switch 14 when any of the ANDs is established. It is composed of

In addition, as shown in FIG. 1, the valve opening degree determination unit is configured to output a signal from a full opening position detection limit switch 15 or an actual opening degree detector such as a differential transformer, which indicates the actual opening state of the detection target valve 1.
The actual opening degree condition determining unit 9 that determines whether or not the valve is fully closed based on the load signal 18 and the opening request condition determining unit 10 that determines whether or not the valve is fully closed based on the detection target valve 1. Any one of the load condition determination units 11 for determining whether or not the vehicle is fully closed, or an OR circuit 12 for inputting a result of the determination may be configured. Each of these judging units 9 to 11 receives signals 16 to 18 indicating the valve opening degree state and outputs an ON signal only in the fully closed state.

However, in an actual power plant, the case where the valve seat leak detection device targets one drain valve 1 is rare, and generally targets several to several tens of valves. Each of these valves 1 is fully open below a predetermined load. For example, when a signal 16 from a limit switch 15 or the like or an opening request signal 17 is adopted as a signal indicating a valve opening state, a valve seat is not provided. The input signal to the leak detector will also increase in proportion to this.

Also, the place where the drain valve 1 is installed is the site of the power plant, whereas the valve seat leak detection device is generally installed in the central operation room. Connecting a cable between them requires a great deal of labor and cost.

Furthermore, even if signals from the limit switch 15 and the like can be extracted from a panel or the like in the central control room via a cable, the core of the cable must be at least as many as the number of valves to be detected, which is quite complicated. System.

In contrast, a load signal is used as a signal indicating the valve opening state.
In the case of employing 18, the input signal of the valve opening degree determination unit may be only this signal, and even if a large number of valves are connected, a system can be constructed without being affected by them.

The load value at which each drain valve 1 to be detected is changed from the fully closed state to the open state is set in the load condition determination unit 11, where α ₁ , α ₂ , and α ₃ (α ₁ > α ₂ > α ₃ ), respectively. And

 Next, the operation of the present embodiment will be described.

When the load of the plant alpha ₁ or more, the degree of opening of the drain valve 1 in the load condition determination unit 11 is determined to be fully closed, the respective AND circuits 13A, 13B, signal ON is output to 13C.

In addition, each of the AND circuits 13A, 13B, and 13C receives, from the first signal determination unit 6, a determination result of the presence / absence of a leak for the corresponding valve 1, and for each of the valves 1, there is no sheet leak. In this case, the first signal determination unit 6
Signals are turned off, and the AND circuits 13A, 13B,
The logical product of 13C does not hold.

However, when a seat leak has occurred in any one of the valves 1, any one of the AND circuits 13A, 13B, and 13C is established, and the signal collecting unit 19 turns on the condition switch 14. I do. Thus, the display unit 7 inputs the valve seat leak occurrence information from the signal collecting unit 21, blinks the warning light 7a corresponding to the valve, and displays the estimated leak amount and the like on the diagnosis result display unit 7b.

Similarly, when the load becomes ₂ or more, or alpha ₃ or more alpha, corresponding opening of the drain valve 1 is determined to conditionally fully closed, the output signal from the AE sensor 3 attached to the valve 1 Means that the valve seat leak is detected.

Conversely, when the load is less than α ₁ , α ₂ , α ₃ , the corresponding drain valve 1 is opened, and the output signal level from the AE sensor 3 is regarded as having a valve seat leak, but the fully closed condition is satisfied. The condition switch 14 is turned off,
The display unit 7 does not provide erroneous information with a leak. Therefore, unnecessary confusion is not given to the operator.

As described above, according to the present embodiment, regardless of the number of drain valves, one representative signal, for example, a load signal can represent the degree of opening of the drain valve, thereby simplifying the system. it can.

Further, regardless of the number of the drain valves, the display of the determination information of the non-valve seat leak detection target can be prevented with one condition switch, and the configuration of the system can be simplified.

[Effects of the Invention] As described above, according to the present invention, in a valve seat leak detection device for a control valve typified by a drain valve or the like of a power plant, the opening degree state of a valve targeted by the detection device By inputting a load signal for determining the value and determining that the valve seat leak detection result is appropriate, it is possible to prevent unnecessary output of an alarm signal when the plant is under a low load.

Therefore, the power plant operator can concentrate on the very complicated and cautious start-up operation without being confused by the erroneous signal from the valve seat leak detection device.

[Brief description of the drawings]

FIG. 1 is a system diagram showing a basic configuration of a valve seat leak detecting device according to the present invention, FIG. 2 is a system diagram showing an embodiment in which a signal representative of a valve opening state is a load signal of a plant, and FIG. It is a system diagram of the conventional valve seat leak detecting device. DESCRIPTION OF SYMBOLS 1 ... Valve 2 ... Working fluid 3 ... AE sensor 4, 4A, 4B, 4C ... Amplifier 5 ... Signal processing unit 6 ... Signal determination unit (first signal determination unit) 7 ... Display unit 8 ... Second signal judging unit 9 Actual opening degree condition judging unit 10 Opening requirement condition judging unit 11 Load condition judging unit 12 OR circuit 13A, 13B, 13C AND circuit 14 …… Condition switch 15 …… Limit switch 16-18 …… Signal 19, 21 …… Signal aggregation section 20 …… Signal selector

Claims (1)

(57) [Claims] 1. A plurality of AE sensors respectively installed in a plurality of valves which automatically open and close according to a load of a plant, and detection signals of these AE sensors are inputted to determine whether or not a leak occurs in a valve seat. A leak occurrence determining unit for determining
A valve opening degree determination unit that determines whether or not each of the valves is fully closed based on a load signal of a plant, and a determination result of the valve opening degree determination unit and a determination result of the leak occurrence determination unit, and the valve And a display determining unit for inputting a determination result of the leak occurrence determining unit to a display unit when it is determined that at least one of them is fully closed and a leak has occurred.