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KR-102962345-B1 - Control valve capable of valve test to prevent valve stick phenomenon

KR102962345B1KR 102962345 B1KR102962345 B1KR 102962345B1KR-102962345-B1

Abstract

The present invention relates to a control valve capable of valve testing to prevent valve sticking. The control valve capable of valve testing to prevent valve sticking according to the present invention is characterized in that the rated flow coefficient (Rated Cv) does not increase or decrease at an opening rate of 0% to a first value and at an opening rate of 2% to 100%, and the rated flow coefficient (Rated Cv) increases or decreases at an opening rate of the first value to the second value.

Inventors

  • 오흥일

Assignees

  • 한국전력기술 주식회사

Dates

Publication Date
20260507
Application Date
20231019

Claims (9)

  1. In a control valve for controlling fluid flow, The rated flow coefficient (Rated Cv) does not increase or decrease at an opening rate of 0% to the first value and at an opening rate of the second value to 100%, and At the opening rates of the first and second values above, the rated flow coefficient (Rated Cv) increases or decreases, and A control valve capable of valve testing to prevent valve sticking, characterized in that the rated flow coefficient (Rated Cv) increases from 0 to 100 at the opening rate of the first value to the second value.
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  3. In paragraph 1, A control valve capable of valve testing to prevent valve sticking, characterized in that the first value is 5% and the second value is 95%.
  4. In paragraph 1, A cage having a fluid movement space inside and a plurality of fluid movement holes on the outside; A sheet supporting the cage at the bottom of the cage; A control valve capable of valve testing to prevent valve sticking, characterized by including a plug that opens and closes the fluid movement space of the cage while sliding up and down.
  5. In paragraph 4, When the opening rate is 0%, the above plug moves to the maximum in the downward direction, and A control valve capable of valve testing to prevent valve sticking, characterized in that the plug moves maximally in the upward direction when the opening rate is 100%.
  6. In paragraph 5, A control valve capable of valve testing for preventing valve sticking, characterized in that the plug does not open or close the fluid transfer hole provided in the cage at an opening rate of 0% to a first value and at an opening rate of 2% to 100%.
  7. In paragraph 5, The above cage includes a row in which a plurality of fluid transfer holes are arranged in a parallel direction, and A control valve capable of valve testing to prevent valve sticking, characterized in that the cage above is provided with a plurality of rows.
  8. In Paragraph 7, When the plug slides up and down to open and close the fluid movement space of the cage, At an opening rate of 0% to a first value, the plug does not come into contact with the bottom row of the plurality of rows provided in the cage, and A control valve capable of valve testing to prevent valve sticking, characterized in that at an opening rate of 2 to 100%, the plug does not come into contact with the uppermost row among a plurality of rows provided in the cage.
  9. In paragraph 1, At the opening rates of the first and second values above, the rated flow coefficient (Rated Cv) is, A control valve capable of valve testing to prevent valve sticking, characterized by increasing or decreasing while having QUICK OPEN flow characteristics, LINEAR flow characteristics, or EQUAL PERCENTAGE flow characteristics.

Description

Control valve capable of valve test to prevent valve stick phenomenon The present invention relates to a control valve capable of performing valve testing to prevent valve sticking, and more specifically, to a control valve capable of performing valve testing to prevent valve sticking without affecting the flow of process fluid, wherein the rated flow coefficient (Rated Cv) is formed to be 0 to 100 at an opening rate in the range of 5% to 95%. A steam bypass system is installed in the power plant to enable the boiler and turbine to be operated independently by bypassing the high-temperature and high-pressure steam produced in the boiler without passing it through the steam turbine during the start, stop, and emergency operation of the power plant. Steam bypass systems are classified into high-pressure steam bypass systems (HPB), intermediate-pressure steam bypass systems (IPB), and low-pressure steam bypass systems (LPB). The steam bypass system includes control valves comprising a pressure control valve (PCV), a steam shut-off valve (FV1), a temperature control valve (TCV), and a spray water shut-off valve (FV2), and the valves described above can be applied to the high-pressure steam bypass system (HPB), the medium-pressure steam bypass system (IPB), and the low-pressure steam bypass system (LPB). The high pressure steam bypass system (HPB) is installed in the high pressure steam line and lowers the temperature of the high pressure steam to a temperature that the cold reheat steam line can accept, thereby allowing the high pressure steam to bypass the cold reheat steam line without passing through the high pressure steam turbine. An intermediate pressure steam bypass system (IPB) is installed between a hot reheat steam line and a condenser, and by lowering the enthalpy of the hot reheat steam to a level that the condenser can accept, the hot reheat steam can be bypassed to the condenser without passing through an intermediate pressure steam turbine. A low pressure steam bypass system (LPB) is installed between a low pressure steam line and a condenser, and by lowering the enthalpy of the low pressure steam to a level that the condenser can accept, the low pressure steam can be bypassed to the condenser without passing through a low pressure steam turbine. When the power plant reaches full output (100% output) after the startup process, the operating state of the control valve of the steam bypass system may be as shown in Table 1. Unless the steam turbine is stopped in an emergency or the power plant is stopped, the operating state of Table 1 may be maintained for a long period. control valveSteam shut-off valve (FV1)Pressure regulating valve (PCV)Water spray shut-off valve (FV2)Temperature control valve (TCV)High-pressure steam bypass system (HPB)100% OPENED100% CLOSED100% OPENED100% CLOSEDMedium pressure steam bypass system (IPB)100% OPENED100% CLOSED100% OPENED100% CLOSEDLow-pressure steam bypass system (LPB)100% OPENED100% CLOSED100% OPENED100% CLOSED However, if the operating conditions of Table 1 persist for a long period, a sticking phenomenon may occur in the control valves constituting the steam bypass system. The sticking phenomenon of the control valve refers to a phenomenon in which the seat, cage, and plug, which directly control the flow rate inside the control valve, become obstructed by each other. Referring to Fig. 1, the control valve that has a sticking phenomenon does not open immediately when it receives an opening command, but when the opening command becomes larger, the control valve opens wide. Since such sticking of control valves can adversely affect the operation of a reliable power plant's steam bypass system, valve tests are performed periodically to prevent sticking. During the valve test, the control valve included in the steam bypass system may be operated for a short period of time as shown in Table 2. control valveSteam shut-off valve (FV1)Pressure regulating valve (PCV)Water spray shut-off valve (FV2)Temperature control valve (TCV)High pressure steam bypass system (HPB), medium pressure steam bypass system (IPB), low pressure steam bypass system (LPB)100% OPENED → 95% OPENED → 100% OPENED 100% CLOSED → 95% CLOSED → 100% CLOSED100% OPENED → 95% OPENED → 100% OPENED 100% CLOSED → 95% CLOSED → 100% CLOSED However, if the operating state of the control valve is changed for valve testing in this way, the following problems may occur. When the steam shut-off valve (FV1) is in a 95% OPENED (5% CLOSE) state, the steam flow rate that can be supplied to the pressure regulating valve (PCV) through the steam shut-off valve (FV1) is reduced compared to when the steam shut-off valve (FV1) is 100% OPENED. In other words, there is a problem in that stable steam pressure control through the pressure regulating valve (PCV) may become difficult when the steam shut-off valve (FV1) is in a 95% OPENED (5% CLOSED) state. When the pressure control valve (PCV) is in a 95% closed (5% open) state,