JP3470417B2 - How to operate the bleed check valve - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for operating an extraction check valve incorporated in an extraction system of a steam turbine.

[0002]

2. Description of the Related Art FIG. 2 is a basic system diagram of an extraction system of a steam turbine, showing a system for supplying high pressure steam to two high pressure heaters. The high-pressure steam of the steam turbine 1 is branched after passing through the extraction check valve 2 to the first high-pressure heater 6 via the electric first extraction stop valve 4 and the electric second extraction stop valve 5. It is sent to the second high-voltage heater 7 via. The bleed check valve 2 is of a type that opens or closes by supplying or stopping air by the solenoid valve 3.

3A and 3B show the basic structure of the bleed check valve 2. FIG. 3A is a sectional view of the valve body, and FIG. 3B is a sectional view of an air cylinder for opening and closing the valve. As shown in (a), the valve body 13 supported by the arm 14 is incorporated inside the valve box 11. The arm 14 is connected to a lever 15 via a spindle (not shown) and a clutch shaft (not shown), and is further connected to a piston rod 19 of the air cylinder by a connecting fitting 20 shown in (b). When no air pressure is applied to the cylinder 16, the extension force of the spring 17 incorporated with the upper end as a fulcrum pushes down the piston 18 to the lower end, and accordingly the piston rod 1
As 9 moves downward, the arm 14 and the valve body 13 are pushed to the lower left in the drawing of (a), the pressure of the steam flow is overcome, the valve body 13 contacts the valve seat 12, and the valve is closed. The Rukoto. When air pressure is applied to the cylinder 16, a force opposite to the extension force of the spring 17 is applied to the piston 18, the piston rod 19 is lifted upward, and the connection with the lever 15 is released by a clutch mechanism (not shown). Since the force of closing the valve body 13 by the spring 17 is removed, the force of closing the valve is only the weight of the arm 14 and the valve body 13 and becomes a so-called free check valve state. That is, in this case, the valve is opened when the pressure of the steam flow becomes equal to or more than the force of closing due to the self weight. Needless to say, when the flow of the steam flow is in the opposite direction, the pressure of the steam flow also works in the direction to close the valve and there is no force to open the valve, so the valve is kept in the closed state. , Backflow of steam flow is blocked.

Therefore, in the conventional apparatus, the free check valve is set in the normal operation, and when the bleed air is not supplied, the air pressure supply to the cylinder 16 is stopped and the valve body 13 is closed by the spring 17. Is taken.
FIG. 4 is a basic configuration diagram of an interlock that has been conventionally used. In the basic configuration of this interlock, when the electric first bleed stop valve 4 and the second bleed stop valve 5 shown in FIG. 2 are both closed, the bleed is performed. The solenoid valve 3 for air pressure driving of the check valve is closed, the supply of air pressure to the cylinder 16 of the extraction check valve is stopped, and the valve body 13 is closed by the spring 17. During normal operation other than these states, the solenoid valve 3 for driving the air pressure is in the open state, the air pressure is supplied to the cylinder 16, and the extraction check valve is held in the free check valve state.

[0005]

In this type of bleed check valve, the valve closing moment is the moment around the rotation center of the arm 14 due to the closing force of the spring 17 and the weight of the arm 14 and the valve body 13. , The arm 14 and the valve body 1 in the above-described free check valve state.
3 is the moment around the center of rotation of the arm 14 due to its own weight. On the other hand, the valve opening moment is the moment around the rotation center of the arm 14 that the static pressure Ps of the steam flow exerts on the valve body in the fully closed state, and the rotation pressure of the arm 14 that the dynamic pressure Pd of the steam flow exerts on the valve body in the fully open state. It is the moment around the center. Therefore, the valve element in the fully closed state has a static pressure Ps.
When the valve opening moment due to Vd exceeds the valve closing moment, the valve opening angle is opened, and the valve opening angle due to the dynamic pressure Pd and the valve closing moment are held at a valve opening angle that balances them. When the flow velocity of the vapor flow is q, the specific weight is γ, and the gravitational acceleration is g, the dynamic pressure Pd is expressed by the following equation.

[0006]

## EQU1 ## Pd = γ × q ² / (2g) (1) That is, when the flow rate is relatively large and the flow velocity q is high, the dynamic pressure Pd is high and the valve opening angle is large, but the flow rate is relatively high. If it is relatively small, the flow velocity q becomes slow, and the valve opening angle also becomes small. When the flow rate becomes excessively small, the valve opening moment due to the dynamic pressure Pd falls below the valve closing moment to close the valve, and the static pressure Ps rises again with the closing of the valve, and the valve opens again repeatedly. It will be. This phenomenon is called a chattering phenomenon, which leads to damage or wear of the valve seat 12 and the spindle, generation of abnormal noise and vibration, and therefore it is necessary to avoid use in such an unstable region.

In the conventional operation method of the extraction check valve,
Since the interlock shown in FIG. 4 is used, smooth operation can be obtained during normal steam supply or when the steam supply is completely stopped. However, when the electrically driven first bleed stop valve and the second bleed stop valve move from the open state to the closed state according to the operating condition, the bleed check valve is closed due to the interlock, but the two bleed stop valves are closed. Since the flow rate of steam decreases as the valve moves to the closed state, the bleed check valve in the closed state transiently causes chattering during this period.

As a method of avoiding such chattering phenomenon, the swing body portion including the valve body 13 and the arm 14 is made lighter to reduce the valve closing moment, or a counterweight is attached to the swing body. Although structural measures such as reducing the valve closing moment can be considered, it is not technically easy and costly. If a bleed check valve with a relatively small diameter is selected and used, it is possible to avoid the occurrence of chattering, but pressure loss increases during normal operation, This causes basic problems such as difficulty in dealing with patterns.

The present invention has been made in consideration of these problems, and in the extraction check valve 2 incorporated in the extraction system of the steam turbine as described above, the occurrence of chattering is avoided and the valve seat 12 is provided. Another object of the present invention is to provide a method for operating a bleed check valve that can prevent damage or wear of a spindle, the occurrence of abnormal noise or vibration, and operate stably for a long period of time.

[0010]

In order to achieve the above object, in the present invention, high-pressure steam is fed from a steam turbine to a parallel connection body of a plurality of high-pressure heaters in which electric bleed stop valves are connected in series in a preceding stage. In the extraction check valve that is opened and closed by the air pressure installed in the supply pipe, the operating condition of the steam turbine is such that all the electric extraction stop valves are in the closed state, and at least one of these extraction stop valves is Only when one is in the open state, an interlock for closing the bleed check valve is added to operate the bleed check valve.

Further, the operating conditions of the steam turbine in which all of the above extraction stop valves are in the closed state are: (1) Turbine startup conditions leading to high pressure heater operation after steam turbine startup (2) Steam after high pressure heater shutdown Turbine stop condition leading to turbine stop (3) Steam turbine trip condition (4) High pressure heater water level abnormal condition (5) At least one of the five operating conditions of the emergency operation switch shall be selected.

[0012]

In order to shut off the supply of high-pressure steam to the high-pressure heater under operating conditions such as when the steam turbine is started, stopped, or abnormal, such as the above conditions (1) to (5), A measure is taken to move and hold the electrically connected bleed stop valves connected in series to the closed state. However, when the electric bleed stop valve is changed from the fully open state to the closed state, the flow rate of steam supplied transiently decreases. Therefore, when the bleed check valve is closed, a chattering phenomenon occurs.

Therefore, as described above, these (1)
Under the conditions of (5) to (5), add an interlock that closes the bleed check valve only when at least one of these bleed check valves is in the open state, and opens it in other cases. If it is operated, the conditions (1) to (5) will be met, and all bleed stop valves will be closed.
Even if the flow rate is transiently reduced, unlike the conventional example, the bleed check valve is held in the free check valve state, so that the chattering phenomenon is avoided. In addition,
Under normal operating conditions that do not satisfy the conditions of (1) to (5), the extraction check valve is held in the open state, that is, the state of the free check valve, and is used as a regular extraction check valve.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an interlock diagram of a bleed check valve which is included in the method of operating a bleed check valve according to the present invention. As shown in the basic system diagram of FIG. 2, this interlock branches the high-pressure steam of the steam turbine after passing through the extraction check valve, and then branches the high-pressure steam through the first electrically-operated extraction check valve.
The interlock is applied to the extraction check valve of the extraction system of the steam turbine that supplies two high pressure heaters to the high pressure heater and the second high pressure heater via the electric second extraction stop valve.

In the present interlock, in order to shut off the high-pressure steam supplied to the two high-pressure heaters, a condition is issued in which the first bleed stop valve and the second bleed stop valve are moved to the closed state and held. That is, (1) when the valve operation signal is transmitted when the turbine is started after the steam turbine is started and the high pressure heater is activated (2) When the valve operation signal is transmitted when the turbine is stopped after the high pressure heater is stopped and the turbine is stopped (3) steam At the time of transmitting the turbine trip signal (4) At the time of transmitting the water level abnormality signal of the high-pressure heater (5) Either of the five conditions at the time of operation of the emergency operation switch, and at least the first bleed stop valve and the second bleed stop valve Only when one of the bleed check valves is open, the pneumatically operated solenoid valve to the cylinder that operates the bleed check valve is closed, and the bleed check valve is fully closed. There it is always fully opened electromagnetic valve pneumatically actuated to cylinder operating the bleed check valve, the this by bleed check valve is held in a state of free check valve fully opened.

If the bleed check valve is operated by incorporating this interlock, the bleed check valve is always free when the flow rate becomes a minute flow which may cause a chattering phenomenon if the bleed check valve is closed. Since it is held in the stop valve state,
There is no risk of chattering. Therefore, if the bleed check valve is operated by incorporating this interlock, the chattering phenomenon that leads to damage or wear of the valve seat or the spindle, abnormal noise or vibration can be avoided, and stable operation can be achieved for a long period of time.

[0017]

As described above, according to the present invention, the steam turbine is installed in the pipe for supplying high-pressure steam to the parallel connection body of a plurality of high-pressure heaters in which the electric extraction stop valves are connected in series in the preceding stage. In a bleed check valve that is opened and closed by air pressure, the operating conditions of the steam turbine are, for example, (1) Conditions for starting the high-pressure heater after starting the steam turbine and conditions for starting the turbine (2) After stopping the high-pressure heater and stopping the steam turbine Turbine stop condition (3) Steam turbine trip condition (4) High-pressure heater water level abnormal condition (5) Emergency operation switch operating condition Is also in a condition to be closed, and only when at least one of these bleed stop valves is in the open state, an interlock for closing the bleed check valve is added to open the bleed check valve. In the fully closed state, when there is a possibility of a minute flow rate that causes chattering, the bleed check valve is kept in the free check valve state. The chattering phenomenon, which leads to damage or wear of the valve seat and spindle, abnormal noise and vibration, is avoided, and it is possible to obtain a method of operating the bleed check valve that can operate stably for a long period of time.

[Brief description of drawings]

FIG. 1 is a basic configuration diagram of an interlock of a bleed check valve showing an embodiment of a method of operating a bleed check valve according to the present invention.

[Fig. 2] Basic system diagram of steam turbine extraction system

FIG. 3 is a basic configuration diagram of an extraction check valve, (a) is a cross-sectional view of a valve body, and (b) is a cross-sectional view of an air cylinder for opening and closing the valve.

FIG. 4 is a basic configuration diagram of an interlock in a conventional operation method of a bleed check valve.

[Explanation of symbols]

1 steam turbine 2 Bleed check valve 3 Solenoid valve (for bleed check valve operation) 4 First bleed stop valve 5 Second bleed stop valve 6 First high pressure heater 7 Second high pressure heater 11 valve box 12 seat 13 valve 14 arms 15 lever 16 cylinders 17 spring 18 pistons 19 piston rod 20 connection fittings

Claims (2)

(57) [Claims] 1. A bleed check valve installed in a pipe for supplying high-pressure steam to a parallel connection body of a plurality of high-pressure heaters in which an electric bleed stop valve is connected in series to a preceding stage from a steam turbine, by applying air pressure. In the case where the closing spring force acts to close it, and the closing spring force is released by removing the air pressure to open it, the steam turbine operating condition is the extraction stop connected in series to the high pressure heaters. Only when all of the valves are in the closed state and at least one of the bleed stop valves is in the open state, an air pressure is applied to add an interlock for closing the bleed check valve to operate. A method for operating a bleed check valve, comprising: 2. The conditions under which all of the extraction stop valves are closed are: (1) Turbine startup conditions leading to high pressure heater operation after steam turbine startup (2) Steam turbine shutdown after high pressure heater operation stopped Turbine stop condition (3) Steam turbine trip condition (4) High pressure heater water level abnormal condition (5) Emergency operation switch operating condition At least one of the five conditions is included, and the extraction air according to claim 1 How to operate the check valve.