JPS62247103A - Valve close operation test control device of bleed air check valve - Google Patents

Abstract

PURPOSE:To prevent a supply bleed air flow from being lowered from its lower limit by detecting the supply bleed air flow to a feed water pump driving turbine reduced by actuation in the valve closing direction, in a bleed air check valve closing operation test and releasing a valve closing operation test signal when said flow reaches a specified one. CONSTITUTION:A bleed air check valve 7 which is arranged on a bleed air pipe from a turbine to a feed water driving turbine is opened and closed by performing feed and discharge control of a compressed air supplied through an air-relay dump valve 32 with the help of a three-way solenoid valve 31. In the case where operation of said three-way solenoid valve 31 is tested with a valve close operation test control device 30, a lower limit bleed air flow signal from a flow set device 39 is compared with a flow signal from a flow detecting device 20 with the help of a comparator 34 and a valve closing operation test release signal is made to generate when said flow signal is less than that of a lower limit bleed air flow. And said release signal is held in a holding circuit 40, and a valve closing operation test signal is made to release in a wipe-out circuit 38 with the help of the held release signal.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a control device for a bleed check valve having a drive cylinder for a thermal power plant, and particularly for a bleed check valve provided on a bleed pipe to a feed water pump drive turbine. The present invention relates to a valve closing operation test control device for a bleed check valve that can suitably control the check valve and improve the reliability of a power generation plant.

[Conventional technology]

Conventionally, the closing operation test of the bleed check valve was usually carried out every month when the thermal power plant was operating under high load. However, recently, thermal power plants are often operated in a low load range due to electricity demand, and when a valve closing operation test of the bleed air check valve installed on the bleed air pipe to the feed water pump drive turbine was conducted. In this case, there is a concern that the amount of extracted air supplied to the feed water pump drive turbine will be insufficient, leading to a boiler trip, so it is no longer possible to conduct a valve closing operation test in a low load range, which was the original purpose of the valve closing operation test. A situation has arisen in which tests to prevent shaft seizure of bleed check valves are being restricted. Regarding this, JP-A-60-14
As stated in Publication No. 003, the timing when the valve closing operation test can be performed is set at high load of the plant (condition of low load signal NOT).
There is a way to avoid the dangers such as pump trips caused by bleed check valve tests by limiting the number of valve tests to bleed check valves, but this restricts the ability of operators to test valves at any time.

[Problem that the invention seeks to solve]

There are pneumatic and hydraulic types of bleed check valves depending on the driving source, and the pneumatic type will be explained below as an example.

If a valve closing signal is issued for some reason in the 100% turbine load range, the bleed check valve discharges the air in the cylinder installed in the bleed check valve to the atmosphere, and uses the spring force built into the cylinder to release the air inside the cylinder installed in the bleed check valve. Therefore, cylinders and built-in springs are often designed so that the valve can be closed from a fully closed state to an intermediate opening (approximately 50%). (compresses the built-in spring) Therefore, when the load is low and a valve closing signal is generated due to a drop in steam pressure flowing inside the bleed check foot, the valve closing ability increases relatively and becomes close to fully open. . However, the purpose of the valve operation test is to prevent seizure of the valve stem and keep the valve in a normal state at all times, so there is no need to close the valve excessively, and the water pump drive turbine can operate stably. As long as the valve test is performed within the range that ensures the amount of steam available, there is no need to restrict the valve closing test in the low load range.

An object of the present invention is to enable a valve closing operation test of a bleed air check valve without reducing the bleed air amount supplied to the water supply pump drive turbine below the lower limit bleed air amount even in a wide load range from low load to high load. .

[Means for solving problems]

The purpose of the above is to close the bleed check valve with a driving cylinder when the amount of steam supplied to the feed water pump drive turbine reaches the lower limit bleed air amount of the feed water pump drive turbine, or when the bleed check valve is closed. This is achieved by canceling the valve closing operation test signal and restoring the bleed check valve to the fully open side when the valve opening reaches a specified opening set to the lower limit bleed air amount equivalent opening or higher.

[Effect]

A flow rate detector installed on the air extraction pipe to the water supply pump drive turbine detects the amount of extracted air supplied to the water supply pump drive turbine, which decreases due to the operation in the valve closing direction during the extraction check valve closing operation test, and measures the current amount. When the lower limit bleed air amount of the water supply pump drive turbine is reached at the load, the valve closing operation test signal is released and the bleed forced closure check valve is restored to the fully open side. It becomes possible to perform a valve closing operation test of the bleed check valve without causing any trouble to the water pump drive turbine. Also.

The above valve closing test signal is canceled when the valve opening, which decreases due to the operation in the valve closing direction during the bleed check valve operation test, is determined by the opening meter installed on the bleed check valve. It is also possible to perform the operation at the time when the specified opening is reached, which is set in advance so that the opening is activated before the corresponding opening is reached.

〔Example〕

An embodiment of the present invention will be described with reference to FIGS. 1 and 3.

The bleed check valves 7 and 8 with drive cylinders are installed on the bleed line from the turbine 1 to the feed water pump driven turbine 3.
I! ! During normal operation, air is supplied through the air relay dump valve 32, as shown in FIG. Pressurized air is introduced into the air cylinder 27 through the air supply pipe 33 via the three-way solenoid valve 31, and the spring 25 is compressed by the piston 26, and the lever 24 and spindle 2
3 and arm 22 to hold the valve body 21 in the valve opening direction.

When a turbine trip occurs, the hydraulic pressure supplied to the near relay dump valve 32 is removed, the supply air supplied to the near relay dump valve 32 is cut off, and the air pressure between the air cylinder 27 and the near relay dump valve 32 is removed. The air is released to the atmosphere, and the bleed check valve 7 moves in the valve closing direction by the force of the spring 25.

If the valve closing operation test signal is issued, the air supply pipe 3
The three-way solenoid valve 31 provided on the air cylinder 27 and the three-way solenoid valve 31 is energized and switched to the direction of releasing the air between the air cylinder 27 and the three-way solenoid valve 31 to the atmosphere, and the bleed check valve 7 is moved to the valve closed position by the force of the spring 25. Become. Further, regarding the bleed check valve 8, the three-way solenoid valve is energized by the deaerator water level and becomes the valve closed position. (
(Figure 1 only shows the opening/closing control system for the bleed check valve 7, and the bleed check valve 8 is omitted.) The configuration up to this point is basically the same as the conventional one, but the conventional technology The difference is that, as shown in Fig. 1, the flow rate is reduced by the valve closing direction operation during the bleed check valve closing test using the flow rate detector 20 installed on the supply bleed piping 10 to the water supply pump drive turbine 3. The supplied bleed air amount is detected and the flow rate is determined to be the lower limit bleed air amount of the water supply pump driving turbine at the current load, or if an opening detector is installed on the bleed check valve, the valve opening is set to the specified opening equivalent to the above lower limit bleed air amount or more. This is because a valve closing operation test control device 30 is provided which cancels the valve closing operation test signal and restores the bleed check valve 7 to the fully open side when the valve closing operation test signal reaches this point.

Next, the functions and control operations of the constituent instruments will be explained.

The valve closing operation test control device 130 includes a flow rate setting device 39 that sets the lower limit bleed air amount based on the load signal S2, and a flow rate setting device 3.
The lower limit bleed air amount signal from 9 is compared with the flow rate signal S1 from the flow rate detector 20, and if the flow rate signal S0 is smaller than the lower limit bleed air amount, a valve closing operation test release signal is issued, and if it is larger, a valve operation test is performed. A signal comparator 34 that does not emit a release signal, an OR circuit 35 that holds this valve closing test solution signal when a valve closing test release signal is issued, and a wipeout circuit 36 (including an external signal) When present, the wipeout circuit 36 output signal will no longer be emitted)
a hold circuit 40 having a hold circuit 40, a wipeout circuit 38 that releases the valve closing test signal S3 by the valve closing test release signal held in the hold circuit 40, and a hold circuit when the valve closing test signal S3 no longer exists. 40
It is composed of a NOT circuit 37 which gives a signal to the wipeout circuit 36 of the valve closing operation test and cancels the valve closing operation test release signal.

When the valve closing operation test signal S3 is issued, the signal comparator 34 does not issue the valve closing operation test release signal because the flow rate of extracted air to the water supply pump driving turbine 3 is the normal flow rate before the test, and the hold circuit is also activated. Since this signal also does not exist in the wipeout circuit 38, the valve closing operation test signal S3 is transmitted to the three-way solenoid valve 31 without being canceled by the wipeout circuit 38, energizing the three-way solenoid valve 31, and causing the air cylinder 27 to close. Switch the air to the atmosphere open side. With this switching, the air in the air cylinder 27 disappears, and the force of the spring 25 causes the bleed check valve 7 to operate in the closing direction. If the above-mentioned valve closing operation test is performed in a high load zone and the flow rate signal S1 of the flow rate detector 20 does not reach the lower limit of the bleed air amount of the water supply pump drive turbine 3 even if the bleed air check valve closes, the signal comparator Since the valve closing operation test release signal is not issued from 34, the opening/closing operation of the bleed air check valve is always performed depending on whether the valve closing operation test signal S3 is issued or not.

However, the flow rate signal S of the flow rate detector 20 is
1 reaches the lower limit bleed air amount set by the load signal S2 in the flow rate setting device 39, a valve closing operation test release signal is issued from the signal comparator 34, and this signal is held in the hold circuit 40. At the same time, the valve closing operation test signal S3 is transmitted to the wipeout circuit 38 via the hold circuit 40.
is released and the signal to the three-way solenoid valve 31 is made into a non-excitation signal.

Accordingly, the three-way solenoid valve 31 is switched to the side that communicates with the air cylinder 27 and the near redundant valve 32, and the bleed air check valve 7 is operated to the fully open side. Due to this operation to the fully open side, the flow rate of air extracted to the feed water pump drive turbine is restored to the normal amount of air extracted, and the signal comparator 34 no longer issues a valve closing operation test release signal, but this signal is held in the hold circuit 40. Therefore, the valve closing operation test release signal is transmitted to the wipeout circuit 38, and then the valve closing operation test signal S3 is canceled and the three-way solenoid valve 31 is maintained in a non-excited state.

The valve closing test release signal held in the hold circuit 40 is released by issuing a signal from the NOT circuit 37 to the wipeout circuit 36 when the valve closing test signal S no longer exists. With this valve closing operation test control device, it is possible to perform a valve closing operation test of the bleed air check valve in a wide load range from low load to high load without causing any trouble to the feed water pump drive turbine. It becomes possible to reliably prevent the stop valve from being forcibly closed and inoperable.

The above describes the valve closing operation test control device for the bleed check valve 7, but the flow rate detector 2 also applies to the bleed check valve 8.
By installing a device similar to the one described above using the 0, the valve closing operation test of the bleed check valve can be carried out in a wide load range from low to high loads without causing any trouble to the water pump drive turbine. It becomes possible to reliably prevent the forced closing and inoperation of the bleed air check valve.

FIG. 2 shows an embodiment, and the same parts as in FIG. 1 are indicated by the same reference numerals.The difference from FIG. Furthermore, an opening setting device 39' is provided to set the load (corresponding to the lower limit extraction amount of the water supply pump driving turbine by No. 6 S2) to the specified opening of 2. The signal of these opening detectors 50 and the opening setting device 39' is introduced into the signal comparator 34 to compare both signals, and if the signal from the opening degree detector 50 is small, the signal comparator 34 issues a valve closing operation test release signal.

The point is that the valve closing operation test release signal is not issued when the value is large. With this device, substantially the same effects as in the first embodiment can be obtained.

The above describes the bleed air check valve 7, but the bleed air check valve 8 is also equipped with an opening detector and an opening setting device. The specified opening equivalent to the lower limit bleed air amount of the drive turbine and the opening equivalent to the bleed air amount supplied to the deaerator 2 are added together, and compared with the signal of the opening degree detector using a signal comparator. Accordingly, in one or more first embodiments that can obtain the same effect as the first embodiment in claim 1, the flow rate is detected by the flow rate detector 20 on the bleed air pipe, and the flow rate signal S2 is The signal comparator 34 compared the signal from the flow rate setter 39, which sets the lower limit bleed air amount depending on the load, and issued a valve closing operation test release signal, but a margin was added to the lower limit bleed air amount of the water pump drive turbine. The above device can be substituted by providing a flow rate switch which issues a valve closing operation test cancellation signal when the bleed air amount is reached.

In other embodiments, an opening detector 50 is installed on the bleed check valve.
The opening signal is compared with the valve opening signal from the opening setting device 39', which is set to a specified opening equal to or higher than the lower limit bleed air amount depending on the load, and the signal comparator 34 cancels the valve closing operation test. However, it is possible to replace the above device by installing a limit switch at a valve opening that is the specified opening plus a margin and issuing a valve closing operation test release signal when this opening is reached. can.

〔Effect of the invention〕

According to the present invention, it is possible to always operate the feedwater pump drive turbine normally in a wide load range from low load to high load, so it is possible to avoid dangers such as boiler trips caused by insufficient water supply to the boiler, and to avoid emergency situations. Since it is possible to reliably prevent the bleed check valve from closing and inoperating when the bleed check valve is closed, it is possible to reliably prevent turbine overspeed, etc., and to provide an extremely reliable thermal power plant.

[Brief explanation of drawings]

Fig. 1 is a system diagram for opening/closing control of a bleed check valve showing one embodiment of the present invention, and Fig. 2 is a system diagram for opening/closing control of a bleed check valve showing another embodiment of the present invention. FIG. 3 is a system diagram for explaining the present invention in detail. 3... Water supply pump driving turbine, 7.8... Air extraction forced closing inverse ratio valve, 20... Flow rate detector, 30... Valve closing operation test signal control device, 34... Signal comparator, 36
... Wipeout circuit, 38 ... Wipeout circuit, 39 ... Flow rate setting device, 40 ... Hold circuit, 5
0...Opening degree detector.

Claims (1)

[Claims] 1. In a control device that closes when necessary an bleed check valve having a drive cylinder provided in an bleed pipe connected from a steam turbine to a feedwater pump drive turbine, when the feedwater pump drive turbine is in operation and the water supply If the amount of bleed air flowing into the pump drive turbine is greater than the minimum flow rate that allows the feedwater pump drive turbine to operate normally at each load of the steam turbine, the valve closing signal issued for the closing operation test of the bleed check valve is canceled. By operating the bleed air check valve in the closing direction in response to the valve closing signal for the valve closing operation test, the amount of bleed air flowing into the water pump driving turbine during operation of the water pump driving turbine increases as described above. A valve closing operation test control device for a bleed check valve, characterized in that when a lower limit bleed air amount is reached, a valve closing signal is canceled and the bleed check valve is returned to its normal operating position.