JP5197390B2 - Seal structure and sealing method - Google Patents

Description

  The present invention relates to a seal structure and a sealing method for suppressing gas leakage using a plurality of valves.

  In the combined cycle power plant, the gate valve is switched (open / closed) in accordance with the combustion mode of the gas turbine for the purpose of air purging of the fuel gas, supplying purge air to the fuel gas line (full open) and shutting off the fuel gas ( Fully closed) (see Patent Document 1). Generally, in these important process lines, it is important to maintain / check the stable sealing performance of the valve over a long period of time. Therefore, the gate valve generally has a double block / bleed system configuration. It has been. Here, the double block bleed system is a small-diameter valve (bleed valve) for external discharge in the middle (cavity line) between two series of partition valves. A system configuration that can confirm the presence or absence of valve seat leak.

JP 2002-213208 A

  In the operation so far, for stable plant operation, whenever a leak from the bleed line is confirmed, the plant must be stopped, and the seat performance of the gate valve must be restored (valve disassembly / reassembly). It was an impediment to continued driving.

  The present invention has been made based on such circumstances, and it is an object of the present invention to prevent or suppress seat leakage regardless of the seat performance of the gate valve in the double block / bleed configuration.

  In order to achieve the above object, one aspect of the seal structure according to the present invention is a first gate valve connected to a downstream end of a high-pressure gas pipe in which a gas having a pressure higher than atmospheric pressure exists. A cavity pipe connected to the downstream end of the first gate valve, a second gate valve connected to the downstream side of the cavity pipe, and a tip branched to the atmosphere and opened to the atmosphere Vent pipe, a relief valve connected to the vent pipe, an air pipe connected to one of the cavity pipe and the vent pipe and capable of supplying compressed air into the cavity pipe, and the air pipe The difference between the pressure in the cavity pipe and the pressure in the high-pressure gas pipe is within a predetermined range with the control valve disposed in the middle, the first and second gate valves, and the relief valve closed. It characterized in that it has control means for adjusting the opening of the regulating valve so that the.

  Another aspect of the seal structure according to the present invention includes a first gate valve connected to an end of a high-pressure gas pipe in which a gas having a pressure higher than atmospheric pressure exists, and the first gate valve A cavity pipe connected to the side opposite to the high-pressure gas pipe of the gate valve, and a second gate valve connected to the end of the cavity pipe opposite to the first gate valve and capable of adjusting the opening. An air supply pipe connected to the opposite side of the second gate valve to the cavity pipe and capable of supplying compressed air; a vent pipe branched from the cavity pipe and having a tip open to the atmosphere; and the vent pipe The relief valve connected to the first valve, and the first gate valve and the relief valve are closed so that the difference between the pressure in the cavity pipe and the pressure in the high-pressure gas pipe falls within a predetermined range. Adjust the opening of the second gate valve Characterized in that it has control means for the.

  One aspect of the sealing method according to the present invention is a method in which a first gate valve is connected to a downstream end of a high-pressure gas pipe in which a gas having a pressure higher than atmospheric pressure exists, and the first partition A cavity pipe is connected to the downstream end of the valve, a second gate valve is connected to the downstream side of the cavity pipe, a vent pipe whose tip is opened to the atmosphere is branched from the cavity pipe, and is connected to the vent pipe. Connecting the relief valve, connecting an air pipe to the cavity pipe, arranging a control valve in the middle of the air pipe, and closing the first and second gate valves and the relief valve, the air pipe Compressed air is supplied into the cavity pipe via the control valve, and the opening of the control valve is adjusted so that the difference between the pressure in the cavity pipe and the pressure in the high-pressure gas pipe falls within a predetermined range. Adjusting, Sealing method for the butterflies.

  In another aspect of the sealing method according to the present invention, a first partition valve is connected to an end of a high-pressure gas pipe in which a gas having a pressure higher than atmospheric pressure exists, and the first partition A cavity pipe is connected to the opposite side of the valve to the high-pressure gas pipe, and a second gate valve capable of adjusting the opening is connected to the end of the cavity pipe opposite to the first gate valve; An air supply pipe is connected to the side opposite to the cavity pipe of the gate valve of No. 2, a vent pipe whose tip is open to the atmosphere is branched from the cavity pipe, a relief valve is connected to the vent pipe, and the first pipe With the gate valve and the relief valve closed, compressed air is supplied into the cavity pipe through the air supply pipe and the second gate valve, and the pressure in the cavity pipe and the pressure in the high-pressure gas pipe are supplied. The difference between Adjusting the degree of opening of the second gate valve to enter the 囲内, characterized by.

  According to the present invention, it is possible to prevent or suppress seat leakage regardless of the seat performance of the gate valve in the double block / bleed configuration.

1 is a schematic system diagram showing a first embodiment of a seal structure according to the present invention. The schematic system diagram which shows 2nd Embodiment of the seal structure which concerns on this invention. The schematic system diagram which shows 3rd Embodiment of the seal structure which concerns on this invention. The schematic system diagram which shows 4th Embodiment of the seal structure which concerns on this invention. The schematic system diagram which shows 5th Embodiment of the seal structure which concerns on this invention.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a double block / bleed seal structure according to the present invention will be described below with reference to the drawings. Here, the same or similar parts are denoted by common reference numerals, and redundant description is omitted.

[First Embodiment]
FIG. 1 is a schematic system diagram showing a first embodiment of a seal structure according to the present invention. For example, in a combined cycle power plant, this seal structure switches the gate valve in accordance with the combustion mode of the gas turbine in order to air purge the fuel gas, and supplies the purge gas to the fuel gas line and shuts off the fuel gas. It is used as a seal structure of the gate valve.

  In FIG. 1, one end of the high-pressure gas pipe 1 is connected to the first gate valve 2, and the other end of the high-pressure gas pipe 1 (the right side in FIG. 1) is connected to a gas turbine combustor (not shown). One end of the cavity pipe 3 is connected to the opposite side of the high pressure gas pipe 1 of the first gate valve 2, and the second gate valve 4 is connected to the other end of the cavity pipe 3. The opposite side (the left side in FIG. 1) of the cavity piping 3 of the second gate valve 4 is connected to a compressed air supply source (not shown).

  A vent pipe 5 branches from the cavity pipe 3, and the vent pipe 5 is opened to the atmosphere via a relief valve 6. Furthermore, one end of an air pipe 7 is connected to the cavity pipe 3, and the other end of the air pipe 7 is connected to a compressed air supply source (not shown) via a control valve 8.

  A first pressure gauge 10 is attached to measure the gas pressure Pg in the high-pressure gas pipe 1, and a second pressure gauge 11 is attached to measure the cavity pressure Pc in the cavity pipe 3.

  In the above configuration, when performing air purge of the high-pressure gas pipe 1 that is a fuel gas line, the relief valve 6 and the control valve 8 are closed, the first gate valve 2 and the second gate valve 4 are opened, Compressed air is fed into the high-pressure gas pipe 1 through the gate valve 4 and the first gate valve 2.

  When the combined cycle power plant is operating and fuel is being sent to the combustor through the corresponding fuel line, the first gate valve 2, the second gate valve 4, the relief valve 6, and the control valve 8 are normally closed. ing. At this time, the fuel gas having a pressure higher than the atmospheric pressure and a temperature higher than the environmental temperature stays in the high-pressure gas pipe 2. At this time, the cavity pipe 3 has an atmospheric temperature or an intermediate temperature between the atmospheric pressure or the high-pressure gas pipe 2 and the atmospheric temperature at a cavity pressure Pc that is about the middle of the atmospheric pressure or the gas pressure Pg in the high-pressure gas pipe 2. The air of the temperature is stagnant.

  Leakage of the first gate valve 2 may occur due to deterioration of the seal portion of the first gate valve 2 due to long-term operation. The occurrence of this leakage can be determined, for example, because the output of the second pressure gauge 3 that detects the pressure in the cavity pipe 3 is higher than before the occurrence of the leakage. When leakage occurs in this way, the control valve 8 is opened and compressed air is introduced from the air pipe 7 into the cavity pipe 3. At that time, the control is performed so that the gas pressure Pg in the high-pressure gas pipe 1 measured by the first pressure gauge 10 and the cavity pressure Pc in the cavity pipe 3 measured by the second pressure gauge 11 are substantially equal. The opening degree of the control valve 8 is controlled by the device 12. Specifically, for example, control is performed so that the difference between the gas pressure Pg and the cavity pressure Pc is smaller than a predetermined value.

  According to this embodiment, since the gas pressure Pg and the cavity pressure Pc are maintained to be substantially equal to each other, even if the seal of the first gate valve 2 is deteriorated, the fuel gas in the high-pressure gas pipe 1 Can be prevented from leaking into the atmosphere. Therefore, unlike the prior art, it is not necessary to stop the plant and restore the seat performance (valve disassembly / reassembly) of the gate valve every time a seal failure of the gate valve occurs.

[Second Embodiment]
FIG. 2 is a schematic system diagram showing a second embodiment of the seal structure according to the present invention. The embodiment shown in FIG. 2 is different from the first embodiment shown in FIG. 1 in that a flow meter 14 is attached to the vent pipe 5.

  In the second embodiment, as in the first embodiment, when the combined cycle power plant is operating, when the fuel is being sent to the combustor through the corresponding fuel line, the first gate valve 2 is usually used. The second gate valve 4, the relief valve 6, and the control valve 8 are closed. At this time, the cavity pipe 3 has an ambient temperature or an intermediate temperature between the atmospheric pressure or the high-pressure gas pipe 2 and the ambient temperature at a cavity pressure Pc which is about the middle between the atmospheric pressure or the gas pressure Pg in the high-pressure gas pipe 2 and the atmospheric pressure. The air is stagnating.

  When leakage of the first gate valve 2 occurs due to a decrease in the performance of the seal portion of the first gate valve 2, in this embodiment, the occurrence of this leak can be determined by an increase in the output of the flow meter 14. That is, when the output of the flow meter 14 exceeds a predetermined value, it is determined that the leakage of the first gate valve 2 is considerably large, and thereafter, as in the first embodiment, the gas in the high-pressure gas pipe 1 is determined. The opening degree of the control valve 8 is controlled by the control device 12 so that the pressure Pg and the cavity pressure Pc in the cavity pipe 3 are substantially equal.

  According to this embodiment, the same effect as that of the first embodiment can be obtained, and a decrease in the sealing performance of the first gate valve 1 can be determined from the output of the flow meter 14, more reliably, Gas leakage can be suppressed.

[Third Embodiment]
FIG. 3 is a schematic system diagram showing a third embodiment of the seal structure according to the present invention. In the embodiment shown in FIG. 3, the concentration meter 16 that measures the gas concentration in the vent pipe 5 (the ratio of the fuel gas mixed in the air) is attached to the vent pipe 5. Different from the first embodiment.

  In the third embodiment, as in the first and second embodiments, when fuel is being sent to the combustor through the corresponding fuel line during the combined cycle power plant operation, the first The gate valve 2, the second gate valve 4, the relief valve 6 and the control valve 8 are closed. At this time, the cavity pipe 3 has an ambient temperature or an intermediate temperature between the atmospheric pressure or the high-pressure gas pipe 2 and the ambient temperature at a cavity pressure Pc which is about the middle between the atmospheric pressure or the gas pressure Pg in the high-pressure gas pipe 2 and the atmospheric pressure. The air is stagnating.

  When leakage of the first gate valve 2 occurs due to a decrease in the performance of the seal portion of the first gate valve 2, in this embodiment, the occurrence of this leak can be determined by an increase in the output of the densitometer 16. That is, when the output of the densitometer 16 exceeds a predetermined value, it is determined that the leakage of the first gate valve 2 is considerably large, and thereafter, the first pressure is the same as in the first and second embodiments. The control device 12 controls the control valve 8 so that the gas pressure Pg in the high-pressure gas pipe 1 measured by the meter 10 and the cavity pressure Pc in the cavity pipe 3 measured by the second pressure gauge 11 are substantially equal. Control the opening.

  According to this embodiment, the same effect as that of the first embodiment can be obtained, and the decrease in the sealing performance of the first gate valve 1 can be determined by the output of the densitometer 16, more reliably, Gas leakage can be suppressed.

[Fourth Embodiment]
FIG. 4 is a schematic system diagram showing a fourth embodiment of the seal structure according to the present invention. The embodiment shown in FIG. 4 is different from the first embodiment shown in FIG. 1 in that a thermometer 18 for measuring the gas temperature in the vent pipe 5 is attached to the vent pipe 5.

  In the fourth embodiment, as in the first to third embodiments, when the combined cycle power plant is operating, when the fuel is sent to the combustor through the corresponding fuel line, the first The gate valve 2, the second gate valve 4, the relief valve 6 and the control valve 8 are closed. At this time, the cavity pipe 3 has an ambient temperature or an intermediate temperature between the atmospheric pressure or the high-pressure gas pipe 2 and the ambient temperature at a cavity pressure Pc which is about the middle between the atmospheric pressure or the gas pressure Pg in the high-pressure gas pipe 2 and the atmospheric pressure. The air is stagnating.

  When leakage of the first gate valve 2 occurs due to a decrease in the performance of the seal portion of the first gate valve 2, in this embodiment, the occurrence of this leak can be determined by the increase in the output of the thermometer 18. That is, when the output of the thermometer 18 exceeds a predetermined value, it is determined that the leakage of the first gate valve 2 is considerably large, and thereafter, the first pressure is the same as in the first and second embodiments. The control device 12 controls the control valve 8 so that the gas pressure Pg in the high-pressure gas pipe 1 measured by the meter 10 and the cavity pressure Pc in the cavity pipe 3 measured by the second pressure gauge 11 are substantially equal. Control the opening.

  According to this embodiment, the same effect as that of the first embodiment can be obtained, and a decrease in the sealing performance of the first gate valve 1 can be determined from the output of the thermometer 18, and more reliably, Gas leakage can be suppressed.

[Fifth Embodiment]
FIG. 5 is a schematic system diagram showing a fifth embodiment of the seal structure according to the present invention. In the embodiment shown in FIG. 5, there is nothing corresponding to the air pipe 7 and the control valve 8 of the first embodiment (FIG. 1). The second gate valve 4a is not a simple on-off valve but a valve whose opening degree can be adjusted.

  In the fifth embodiment, when the air purge of the high-pressure gas pipe 1 which is a fuel gas line is performed, the relief valve 6 is closed and the first gate valve 2 and the second gate valve are closed as in the first embodiment. The valve 4 is opened, and compressed air is fed into the high-pressure gas pipe 1 through the second gate valve 4 a and the first gate valve 2.

  In addition, when the combined cycle power plant is in operation and the fuel is being sent to the combustor through the corresponding fuel line, the first gate valve 2 and the second gate valve 4a are normally closed. At this time, the cavity pipe 3 has an ambient temperature or an intermediate temperature between the atmospheric pressure or the high-pressure gas pipe 1 and the ambient temperature at a cavity pressure Pc that is about the middle between the atmospheric pressure or the gas pressure Pg in the high-pressure gas pipe 1 and the atmospheric pressure. The air is stagnating.

  In the present embodiment, when the leakage of the first gate valve 2 occurs due to the deterioration of the performance of the seal portion of the first gate valve 2, in this embodiment, the second gate valve 4a is opened and compressed air is supplied into the cavity pipe 3. To do. And the opening degree of the 2nd gate valve 4a is controlled by the control apparatus 12 so that the gas pressure Pg in the high pressure gas piping 1 and the cavity pressure Pc in the cavity piping 3 may become substantially equal.

  According to this embodiment, the same effect as that of the first embodiment can be obtained, and the air pipe 7 and the regulating valve 8 in the first embodiment can be omitted, so that the structure can be simplified.

[Other Embodiments]
Each embodiment described above is merely an example, and the present invention is not limited thereto. For example, the features of the embodiments can be combined.

  For example, the flow meter 14 of the second embodiment, the concentration meter 16 of the third embodiment, and the thermometer 18 of the fourth embodiment can be added to the configuration of the fifth embodiment.

  Further, the flow meter 14 of the second embodiment, the concentration meter 16 of the third embodiment, and the thermometer 18 of the fourth embodiment are all attached to the vent pipe 5, but these are all cavities. It may be attached to the pipe 3.

  In addition, in the first to fourth embodiments, one end of the air pipe 7 is connected to the cavity pipe 3, but the air pipe 7 may be connected to the vent pipe 5.

  Moreover, in the said embodiment, although the example of the seal structure in the fuel gas line of a combined cycle power plant was shown, this invention is not limited to application to this fuel gas line, and also to this plant It is not limited to the application of.

1: High pressure gas piping 2: First gate valve 3: Cavity piping 4, 4a: Second gate valve 5: Vent piping 6: Relief valve 7: Air piping 8: Control valve 10: First pressure gauge 11: Second pressure gauge 12: control device

Claims (10)

A first gate valve connected to a downstream end of a high-pressure gas pipe in which a gas having a pressure higher than atmospheric pressure exists;
A cavity pipe connected to the downstream end of the first gate valve;
A second gate valve connected to the downstream side of the cavity pipe;
A vent pipe branched from the cavity pipe and having a tip opened to the atmosphere;
A relief valve connected to the vent pipe;
An air pipe connected to either the cavity pipe or the vent pipe and capable of supplying compressed air into the cavity pipe;
A control valve disposed in the middle of the air pipe;
The opening degree of the control valve is such that the difference between the pressure in the cavity pipe and the pressure in the high-pressure gas pipe falls within a predetermined range with the first and second gate valves and the relief valve closed. Control means for adjusting,
A seal structure characterized by comprising: A flow rate detector for detecting a flow rate of gas discharged from the relief valve through the vent pipe;
After the first and second gate valves and the relief valve are closed and compressed air is not supplied into the cavity pipe, the gas flow rate measured by the flow rate detector exceeds a predetermined value, Control means for starting supply of compressed air into the cavity pipe and opening adjustment of the control valve;
The seal structure according to claim 1, comprising: The high-pressure gas present in the high-pressure gas pipe is a different gas other than air,
A concentration detector for detecting the concentration of the different gas in the cavity pipe or the vent pipe;
When the first and second gate valves and the relief valve are closed and compressed air is not supplied into the cavity piping, the concentration of the different gas measured by the concentration detector exceeds a predetermined value. Later, control means for starting the supply of compressed air into the cavity pipe and the opening adjustment of the control valve,
The seal structure according to claim 1, comprising: The temperature of the high-pressure gas present in the high-pressure gas pipe is different from the environmental temperature,
A temperature detector for detecting the temperature in the pipe on the upstream side of the relief valve of the cavity pipe or the vent pipe; and
In a state where the first and second gate valves and the relief valve are closed and compressed air is not supplied into the cavity pipe, the temperature measured by the temperature detector is higher than the environmental temperature. Control means for starting supply of compressed air into the cavity pipe and adjustment of the opening of the control valve after exceeding a predetermined value in a direction close to the temperature of the gas;
The seal structure according to claim 1, comprising: A first gate valve connected to an end of a high-pressure gas pipe in which a gas having a pressure higher than atmospheric pressure exists;
A cavity pipe connected to the opposite side of the high pressure gas pipe of the first gate valve;
A second gate valve connected to the end of the cavity pipe opposite to the first gate valve and capable of adjusting the opening;
An air supply pipe connected to the opposite side to the cavity pipe of the second gate valve and capable of supplying compressed air;
A vent pipe branched from the cavity pipe and having a tip opened to the atmosphere;
A relief valve connected to the vent pipe;
The degree of opening of the second gate valve is such that the difference between the pressure in the cavity pipe and the pressure in the high-pressure gas pipe falls within a predetermined range with the first gate valve and the relief valve closed. Control means for adjusting,
A seal structure characterized by comprising: A flow rate detector for detecting a flow rate of gas discharged from the relief valve through the vent pipe;
In the state where the first and second gate valves and the relief valve are closed, the opening degree adjustment of the second gate valve is started after the gas flow rate measured by the flow rate detector exceeds a predetermined value. Control means;
The seal structure according to claim 5, comprising: The high-pressure gas present in the high-pressure gas pipe is a different gas other than air,
A concentration detector for detecting the concentration of the different gas in the cavity pipe or the vent pipe;
After the first and second gate valves and the relief valve are closed, the degree of opening of the second gate valve is adjusted after the concentration of the different gas measured by the concentration detector exceeds a predetermined value. Control means to start,
The seal structure according to claim 5, comprising: The temperature of the high-pressure gas present in the high-pressure gas pipe is different from the environmental temperature,
A temperature detector for detecting the temperature in the pipe on the upstream side of the relief valve of the cavity pipe or the vent pipe; and
In a state where the first and second gate valves and the relief valve are closed, the temperature measured by the temperature detector is a predetermined value set in advance in a direction closer to the temperature of the high-pressure gas than the environmental temperature. Control means for starting the opening adjustment of the second gate valve after exceeding
The seal structure according to claim 5, comprising: A first gate valve is connected to the downstream end of the high-pressure gas pipe in which a gas having a pressure higher than atmospheric pressure exists;
Connecting a cavity pipe to the downstream end of the first gate valve;
Connecting a second gate valve downstream of the cavity pipe;
The vent pipe whose tip is opened to the atmosphere is branched from the cavity pipe,
Connect a relief valve to the vent pipe,
An air pipe is connected to the cavity pipe;
A control valve is arranged in the middle of the air pipe,
With the first and second gate valves and the relief valve closed, compressed air is supplied into the cavity pipe through the air pipe and the control valve, and the pressure in the cavity pipe and the high-pressure gas pipe are supplied. And adjusting the opening of the control valve so that the difference from the internal pressure falls within a predetermined range. A first gate valve is connected to the end of the high-pressure gas pipe in which a gas having a pressure higher than atmospheric pressure exists;
Connecting a cavity pipe to the opposite side of the high pressure gas pipe of the first gate valve;
A second gate valve capable of adjusting an opening degree is connected to an end of the cavity pipe opposite to the first gate valve;
An air supply pipe is connected to the opposite side of the cavity pipe of the second gate valve;
The vent pipe whose tip is opened to the atmosphere is branched from the cavity pipe,
Connect a relief valve to the vent pipe,
With the first gate valve and the relief valve closed, compressed air is supplied into the cavity pipe through the air supply pipe and the second gate valve, and the pressure in the cavity pipe and the high-pressure gas are supplied. A sealing method, characterized in that the opening of the second gate valve is adjusted so that a difference from the pressure in the pipe falls within a predetermined range.

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