JPS6217084B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a turbine bypass valve erosion prevention device for a turbine bypass system of a turbine plant, and particularly to a turbine bypass valve corrosion prevention device for preventing erosion of the bypass valve valve stem due to backflow of wet steam. This invention relates to a bypass valve erosion prevention device.

[Technical background of the invention]

As a conventional turbine bypass valve corrosion prevention device, there is one shown in Japanese Patent Publication No. 13161/1983, and an application of this device to a nuclear power turbine plant will be explained with reference to FIG.

FIG. 1 is a system diagram showing a conventional turbine bypass valve corrosion prevention device, which includes a nuclear reactor 1, a main steam pipe 3 that sends steam generated in the reactor 1 to a high-pressure turbine 2, and A main steam stop valve 4 and a main steam control valve 5 provided in the middle, a high pressure exhaust pipe 7 that sends the steam that has worked in the high pressure turbine 2 to the low pressure turbine 6, and a moisture control valve provided in the middle of the high pressure exhaust pipe 7. A separator 8, an intermediate steam stop valve 9, a generator 10 coupled to the turbine shaft, and a condenser 11 that condenses the steam that has done work in the low-pressure turbine 6.
, a water supply pipe 13 that supplies the condensate to the reactor 1 by a water supply pump 12, and a bypass inlet pipe 1 that branches from the main steam pipe 3 and sends main steam to a bypass valve 14.
5, a bypass outlet pipe 16 for sending the steam that has passed through the turbine bypass valve 14 to the condenser 11, a bypass valve valve stem 17, and a bypass valve stem 17 for preventing steam from leaking from the valve stem 17 to the outside. a first leak circuit 19 equipped with a check valve 18 that opens from 17 toward the high-pressure exhaust pipe 7; a second leak circuit 20 connected to the condenser 11; and a third leak circuit 20 connected to the steam generator 21.
A leak circuit 22 is provided.

During normal operation of the turbine, the bypass valve 14 is closed and the slightly moist saturated steam generated in the reactor 1 is passed from the main steam pipe 3 to the high pressure turbine 2.
Steam flows into the high-pressure turbine 2 through a main steam stop valve 4 provided to shut off steam flowing into the high-pressure turbine 2 and a main steam control valve 5 provided to adjust the amount of steam flowing into the high-pressure turbine 2 . High pressure turbine 2
The steam that has done work passes through the high-pressure exhaust pipe 7 and enters the moisture separator 8 to remove moisture, and then flows into the low-pressure turbine 6 through the intermediate steam stop valve 9. The steam that has done work in the low-pressure turbine 6 enters the condenser 11 and becomes condensed water, which is then supplied to the nuclear reactor 1 through the water supply pipe 13 by the water supply pump 12.

Note that the turbine bypass valve 14 needs to be opened in the following two cases.

First, the first case is when the nuclear reactor 1 is started. The reactor 1 cannot be started unless there is a system to release the steam generated in the reactor 1. For this reason, the turbine bypass valve 14 is opened until the reactor 1 is started and steam is sent to the high-pressure turbine 2 and low-pressure turbine 6, and the steam generated in the reactor 1 is released to the condenser 11. and main steam control valve 5
As the bypass valve 14 is opened, the bypass valve 14 is closed.

The second case is when the main steam stop valve 4 or the main steam control valve 5 suddenly closes during normal operation of the turbine. In particular, in a boiling water reactor, it is necessary to keep the pressure of steam generated in the reactor 1 constant due to its nature, but during normal operation the turbine bypass valve 1
If the main steam stop valve 4 or the main steam control valve 5 suddenly closes while the turbine bypass valve 4 is closed, the steam pressure generated in the reactor 1 will rise rapidly.
4 is opened to suppress the pressure rise.

Next, the turbine bypass valve 1 in the above two cases
4 opens, the high-pressure steam that has entered around the valve stem 17 opens the check valve 20 and leaks through the first leak circuit 19 to the high-pressure exhaust pipe 7 whose pressure is slightly lower. Further leaking steam leaks to the condenser 11 through the second leak circuit 20.

Further, the third leak circuit 22 includes a steam generator 2
To supply steam that is not contaminated with radioactivity and has a pressure slightly higher than that of the condenser 11 generated in step 1 and lower than atmospheric pressure. This steam leaks to the condenser 11 through the second leak circuit 20, and is completely sealed to prevent radioactively contaminated steam from leaking to the outside. When the turbine bypass valve 14 is closed during normal operation of the turbine,
Since the first leak circuit 19 is provided with the check valve 18, steam does not flow back from the high-pressure exhaust pipe 7 through the first leak circuit 19 to the turbine bypass valve 14 side.

[Problems with background technology]

However, in the conventional turbine bypass valve erosion prevention device described above, since the check valve 18 is closed during normal operation, steam that remains for a long time becomes a drain. As a result, the check valve 18 becomes stuck, the first leak circuit 19 is blocked, and the leak circuit is not sufficiently secured, and the pressure balance in the second leak circuit 20 and the third leak circuit 22 is broken, resulting in radioactivity. The drawback was that contaminated steam leaked out.

[Purpose of the invention]

The present invention eliminates the drawbacks of the conventional system described above, and by providing a leak circuit with an orifice attached to the turbine bypass system,
It is an object of the present invention to provide a turbine bypass valve corrosion prevention device that prevents corrosion of a turbine bypass valve valve stem and also completely seals internal steam.

[Summary of the invention]

According to the present invention, the above-mentioned object is a turbine bypass valve corrosion prevention device having a leak circuit for guiding leaked steam from a turbine bypass valve valve stem of a turbine bypass system of a turbine plant to a condenser. This is achieved by providing a leak circuit with an orifice to prevent steam from flowing back into the bypass valve even when the turbine bypass valve is fully closed during normal operation.

[Embodiments of the invention]

The present invention will be explained below with reference to embodiments shown in the drawings. Note that the same components as those of the conventional device described above are denoted by the same reference numerals in the drawings, and the explanation thereof will be omitted.

FIG. 2 is a system diagram showing a state in which an embodiment of the turbine bypass valve erosion prevention device of the present invention is applied to a nuclear power turbine plant. A first leak circuit 19 is provided.

Therefore, when the bypass valve 14 is closed during normal operation of the turbine, the moist saturated steam does not flow back into the turbine bypass valve 14. Therefore, no erosion of the bypass valve stem 17 occurs.

Next, in the two cases where the turbine bypass valve 14 opens, when the turbine bypass valve 14 opens,
The high-pressure steam that has entered the area around the valve stem 17 is
First leak circuit 19 with orifice 23 attached
leaks to the condenser 11 through the Further leaking steam passes through the second leak circuit 20 to the condenser 1
Leak to 1. Normally, the amount of leakage from around the valve stem 17 is large in the first leakage circuit 19 from which high-pressure steam leaks, and the amount in the second leakage circuit 20 is considerably smaller than the amount in the first leakage circuit 19. It's getting bigger. This first leak circuit 19 is connected directly to the condenser 1
If connected to 1, the specific volume of steam will become excessive, and the 1st
The volumetric flow rate through the leakage circuit 19 increases. Then, the flow velocity becomes excessive, or the cross-sectional area of the circuit becomes large in order to slow down the flow velocity. In order to suppress this, the first leak circuit 19 provided with the orifice 23 increases the pressure of the leaking steam up to the point before the orifice 22 of the first leak circuit 19, thereby reducing the specific volume of the steam. Note that the flow rate of steam passing through the first leak circuit 19 is determined by the internal pressure of the turbine bypass valve 14 and the diameter of the valve rod 17, so the pressure in front of the orifice 23 is determined by the size of the orifice 23. Can be set arbitrarily. Therefore, it is also possible to provide exactly the same sealing conditions as in the conventional system in which the first leak circuit 19 is connected to the high-pressure exhaust pipe 7.

Furthermore, when the turbine bypass valve 14 opens,
Since this is when a large amount of steam is dumped into the condenser 11, heat recovery is not affected even if the first leak circuit 19 is not connected to the high pressure exhaust pipe 7. On the contrary, steam does not flow back from the high-pressure exhaust pipe 7 through the first leak circuit 19, and thermal efficiency is improved.

〔Effect of the invention〕

As explained above, the turbine bypass valve corrosion prevention device according to the present invention has a leak circuit for guiding leaked steam from a turbine bypass valve valve stem of a turbine bypass system of a turbine plant to a condenser. In the prevention device, the leak circuit is equipped with an orifice, so when the turbine bypass valve is closed, the valve stem is not exposed to moist steam from the high-pressure exhaust pipe, and the valve stem is prevented from being exposed to moist steam from the high-pressure exhaust pipe. Erosion of the rod is prevented. Further, there are excellent effects such as no reduction in sealing performance against leakage from the valve stem when the turbine bypass valve is open.

[Brief explanation of the drawing]

Figure 1 is a system diagram showing a conventional turbine bypass valve erosion prevention device for a nuclear turbine plant;
The figure is a system diagram showing an embodiment of the turbine bypass valve corrosion prevention device of the present invention in a nuclear power turbine plant. DESCRIPTION OF SYMBOLS 1...Nuclear reactor, 2...High pressure turbine, 3...Main steam pipe, 4...Main steam stop valve, 5...Main steam control valve, 6...
Low pressure turbine, 7... High pressure exhaust pipe, 8... Moisture separator, 9... Intermediate steam stop valve, 10... Generator, 11...
Condenser, 12... Water supply pump, 13... Water supply pipe, 14
... bypass valve, 15 ... bypass inlet pipe, 16 ... bypass outlet pipe, 17 ... bus pass valve valve stem, 18 ... half check valve, 19 ... first leak circuit, 20 ... second leak circuit, 21 ... steam generator, 22...Third leak circuit, 23...Orifice.

Claims (1)

[Claims] 1. A turbine bypass valve corrosion prevention device having a leak circuit for guiding leaked steam from a turbine bypass valve stem of a turbine bypass system of a turbine plant to a condenser, the leak circuit having an orifice attached to the leak circuit. A turbine bypass valve erosion prevention device characterized by comprising: