JPS6249086A - Method and device for testing steam valve - Google Patents

Abstract

PURPOSE:To prevent a drain from reversely flowing into a piping and a valve casing and being suddenly cooled, by preliminarily slightly opening a drain valve in testing a closing operation of a steam valve. CONSTITUTION:A plurality of steam pipings A and B for supplying a high- pressure high-temperature steam to a common steam turbine T are provided, and steam valves 1a, 1b, 2a and 2b are provided in the steam pipings. A steam prime mover plant includes the steam valves, drain pipings 6a and 6b and drain valves 4a and 4b located on the downstream side of the steam valves. In testing a closing operation of the steam valves during operation of the steam prime mover plant, the drain valves 4a and 4b are preliminarily slightly opened. Accordingly, when a drain staying in the drain pipings 6a and 6b is eliminated, and any one of the steam valves is closed, the drain in the drain pipings is prevented from reversely flowing.

Description

Detailed Description of the Invention [Field of Application of the Invention] The present invention provides steam valves (for example, reheat blocking valves, intermediate blocking valves, etc.) provided in multiple lines of steam supply piping, The present invention relates to a method for individually testing valve closing during operation, and an apparatus therefor.

[Background of the invention]

Figure 2 shows two systems of steam piping A for the steam turbine T.
, B is a steam supply system diagram for one row of a steam motor plant that supplies high-temperature, high-pressure steam.

The steam pipe AK is provided with a reheat pain relief valve 1a on the upstream side and an intermediate blocking valve 2a on the downstream side thereof.

Further, the 7 steam pipes B are provided with a reheat 1 stop valve 1b on the 1 upstream side and an intermediate stop valve 2b on the downstream side thereof.

A drain pipe 6 is provided on the upstream side of the reheat blocking valves 1a and lb.
a is connected, drain wiring f18a, Ft and drain valve 4
It is connected to the condenser via b.

Further, a drain pipe 6b is connected to the downstream side of the intermediate check valves 2a and 2b, and a drain pipe 8b and a drain valve 4 are connected to each other.
It is connected to the condenser via b. .

The intermediate check valves 2a and 2bld are periodically (eg, once every week) subjected to a valve opening/closing test (valve test). This valve test is used to periodically confirm that the intermediate check valve is fully functional by opening and closing the intermediate check valve using a test device, regardless of the control (opening/closing) signal to the intermediate check valve during turbine load operation. be.

Main steam valves when a steam turbine is provided with multiple systems of steam supply piping (in this example, intermediate check valves 2a, 2
b, and a mutual common main pipe 6a in the drain system provided in the reheat blocking valves 1a, lb).

When drain valves 4a and 4b are installed in 6b, since the drain piping is relatively long, some of the steam condenses and becomes drain due to the heat radiation from the drain piping, and the drain valve of the drain system Also, condensate accumulates on the upstream side during turbine operation. In this state, when a fully closed operation test is performed on one of the multiple steam valves (intermediate check valve 2a or 2b), the steam pressure on the downstream side of the intermediate check valve fluctuates, and the steam pressure on the downstream side of the other intermediate check valve fluctuates. A pressure difference occurs between the valve and the valve, and the condensate that accumulates during turbine operation flows back to the VJ check valve side where the valve test was performed. Due to this drain flowing backwards,
Pipes and valve casings that are at a high temperature are rapidly cooled and excessive thermal stress is generated, and at the same time, there is a danger that cracks may occur due to repeated thermal shocks caused by drain attacks.

FIG. 3 is an explanatory diagram of the above-mentioned problem. Parts D and D' surrounded by chain lines represent parts where drain accumulates.

PI represented by the symbol of a pressure gauge, PfrPz
, P; indicates the pressure at each location.

Now, assume that one side of the two intermediate check valves 2a and 2b is closed for a valve test while the turbine T, 2aQ, is in operation.

With this operation, the relationship between the pressure P after the reheat blocking valve 1a and the pressure P after the reheat blocking valve 1b becomes p,>p'.

Moreover, the pressure P2 after the intermediate block-*2a becomes approximately equal to the internal pressure P3 of the steam turbine T. Here, by performing the valve test, the intermediate check valve 2a is fully closed. Up until now, steam was flowing through the intermediate check valve 2a and the other intermediate check valve 2b at a flow rate of approximately 100,000 yen. This is because the inflowing steam flows to the intermediate check valve 2b side which is in the fully open state.

The pressure P(after this intermediate check valve 2b) becomes higher than P2.

Due to the pressure path p1) p'H, the drain accumulated in the D section V flows back toward the intermediate check valve 2b on the side where the valve test is not performed, as shown by the arrow A.

Furthermore, due to the pressure difference P:>p2, the drain accumulated in the D portion flows backward toward the intermediate check valve 2a on the side where the valve test is being performed, as indicated by the arrow.

This backflow of condensate rapidly cools the main steam valves and piping, which are at a high temperature, creating excessive thermal stress, and there is a danger that repeated thermal shock may cause cracks, leading to steam leakage. Ta.

In order to prevent the above-mentioned problems, the equity
The device described in No.

The above-mentioned known technology is a method for preventing drain flow (reverse flow) into the intermediate check valve, which is at a high temperature during the valve test of the intermediate check valve, to prevent accidents when cracks occur. The feature of this drain prevention device is that if the drain piping on the downstream side of multiple series of steam valves is made into a common main pipe and a stop valve is provided, it will prevent water flow during turbine operation during a valve test. Since accumulated drain flows backward, a check valve was provided in each drain pipe in order to prevent this drain from flowing backward.

2 However, this backflow prevention function does not prevent drain backflow in the upstream side of the check valve installed in the drain piping, that is, in the range from the main valve (intermediate check valve) to the backflow valve. There is a problem in that a drain attack occurs due to the pressure difference during the 3-sho test.

[Purpose of the invention]

The purpose of the present invention is to prevent cracks that occur due to repeated thermal shocks by rapidly cooling the condensate accumulated during normal operation of the intermediate check valve by flowing back into the piping and valve gauging. An object of the present invention is to provide a method and device for testing an intermediate check valve.

[Summary of the invention]

First, the basic principle of the method of the present invention created to achieve the above object will be briefly described.

The key point of the present invention is to discharge the condensate accumulated in parts D and D' to the condenser in advance, as described above, before starting the valve test. If you drain the drain in advance,
Naturally, the risk of drain backflow is eliminated.

In order to achieve the above objective (prevention of drain backflow) based on the above principle, the steam valve test method of the present invention is to provide multiple lines of steam piping for supplying high-pressure and high-temperature steam to the same steam turbine. In addition, a steam tank is provided in the middle of each of the steam piping of the plurality of series, and a drain pipe and a drain valve are provided downstream of the steam valve. In the method of individually testing valve closing during operation, before closing any one of the steam valves listed in @, the drain valve is slightly opened and the drain accumulated in the drain piping is checked. It is characterized in that when the steam valve is discharged and any one of the steam valves is closed, the drain in the drain pipe is prevented from flowing backward.

Since the above valve test is performed while the turbine T is in operation, high-temperature and high-pressure steam is flowing through the steam supply piping of the turbine. Therefore, the opening degree of the fifi drain valve must be slightly open.

Furthermore, when carrying out the method of the invention described above, it is not possible to visually confirm whether or not draining of the drain in the drain pipe has been completed. Therefore, in order to easily confirm the completion of drain discharge and to easily carry out the method of the invention described above, the steam valve testing device of the present invention is designed to provide multiple series of steam valves that supply high-pressure and high-temperature steam to the same steam turbine. In a steam power plant, in which steam piping is provided, steam valves are provided in the middle of each of the plurality of steam piping lines, and drain piping and drain valves are provided downstream of the steam valves.

The present invention is characterized in that a thermometer for detecting the temperature of the fluid in the drain pipe is provided immediately upstream of the drain valve.

[Embodiments of the invention]

FIG. 1 is a flowchart showing an interlock in one embodiment of the method of the present invention.

In step E, when a test command for the main steam valve (in this example, one of the intermediate check valves 2a, 2b or the reheat stop valves 1a, lb) is issued, the valve test in step G) M
Before starting, be sure to check whether the drain valve is slightly opened (Step F). If the drain valve is not slightly open at this time, the valve test cannot be performed. If the drain valve is confirmed to be slightly open, a valve test of the main steam valve is carried out, and the drain valve, which is slightly open as a result of the valve test, is returned to the fully closed state (step H). By conducting a valve test according to this series of interlocks, all condensate accumulated in the drain piping is discharged to the condenser side, eliminating thermal shock inside the drain piping and causing cracks in the valve casing and piping. cracks) can be prevented from occurring.

FIG. 4 is an explanatory diagram of an improved embodiment of the above embodiment, and is a system diagram depicting one embodiment of the apparatus of the present invention configured to carry out the method of this embodiment.

On the immediate upstream side of each of the drain valves 4a and 4b.

A thermometer 7a detects the temperature of the fluid in the drain pipe.

7b is provided.

During normal operation, some of the steam condensed at ↓ due to the heat dissipation of the drain pipe of the low-gamma product is converted into a drain, and drain valve 4a.

This collected drain is collected on the upstream side of 4b, but the temperature of this collected drain is low. By slightly opening the drain valve, the drain is discharged to the condenser together with a portion of the steam, so that a portion of the high-temperature, high-pressure steam flows into the upstream side of the drain valve. If this high-temperature, high-pressure steam stays in this location, it will cool down and become a drain, but as mentioned above, when the drain valve is slightly open, it is flowing slightly, so it is in a high α and high pressure state. be. When the thermometers 7a and 7b detect that this high-temperature, high-pressure steam has flowed upstream to the immediate vicinity of the drain valve, it can be determined that "drain discharge is complete."

In this embodiment, the permission condition for starting the valve test is that the indicated temperatures of the first thermometers 7a and 7b are respectively higher than preset temperatures. Due to this.

It becomes a more reliable interlock, and it becomes possible to completely eliminate thermal shock caused by drain attack.

〔Effect of the invention〕

As detailed above, 1. According to the steam valve testing method of the present invention, the valve test can be performed without the risk of drain backflow, and the advantage is that cracks caused by drain backflow can be prevented. It has many practical effects and greatly contributes to improving the reliability and durability of steam power plants.

Furthermore, according to the steam valve testing device of the present invention, the above testing method can be easily and reliably carried out, and its effects can be fully exhibited.

[Brief explanation of the drawing]

FIG. 1 is an interlock flow diagram in one embodiment of the test method of the present invention. FIG. 2 is an example of a high-pressure steam supply system diagram for a steam turbine. FIG. 3 is an explanatory diagram of the drain backflow phenomenon in the valve test. FIG. 4 is a system diagram of one embodiment of the present invention's steam valve testing device. la, lb... reheat blocking valve, 2a, 2b...
・Intermediate blocking valve, 4a, 4b...Drain valve, 5a, 5b
...Balance pipe, 6a, 6b...Drain pipe, 7a
, 7b...Thermometer, 8a, 8b...Drain piping, T
...Steam turbine.

Claims (1)

[Claims] 1. A plurality of lines of steam piping for supplying high-pressure and high-temperature steam to the same steam turbine are provided, and a steam valve is provided in the middle of each of the plurality of lines of steam piping, and In a method of individually closing the steam valves of a steam power plant provided with drain piping and drain valves on the downstream side while the steam power plant is in operation, one of the steam valves is closed. Before doing so, slightly open the drain valve and drain the drain that has accumulated in the drain pipe.
A method for testing a steam valve, characterized in that when any one of the steam valves is closed, there is no possibility that the drain in the drain pipe will flow backwards. 2. The drain valve is provided with a temperature sensor immediately upstream thereof, and the completion of drain discharge is determined based on the rising state of the temperature of the thermometer. A method for testing a steam valve as described in paragraph 1. 3. Provide multiple lines of steam piping that supply high-pressure, high-temperature steam to the same steam turbine, and provide steam valves in the middle of each of the multiple lines of steam piping, and provide drain piping and drain piping downstream of the steam valves. A steam valve testing device characterized in that, in a steam motor plant equipped with a drain valve, a sensor for detecting the temperature of fluid in a drain pipe is provided immediately upstream of the drain valve.