VV valve pneumatic actuator control system with early warning function and control method

Abstract

The invention discloses a VV valve pneumatic actuating mechanism control system with an early warning function and a control method. In the prior art, an alarm monitoring function is not provided, abnormal conditions on site cannot be found in time, a standby air storage tank or an air cylinder spring is adopted to open a valve, and the safety performance is poor. The method comprises the following steps that a gas flow meter is installed on a pipeline of a control system outside a control box body, the gas flow meter monitors gas of a control loop, signals are sent to a DEH system, under the normal operation state of a unit, a pneumatic valve is kept closed, no gas flows in the control loop, and when gas leakage exists in a certain connector or pipeline, the DEH system is started; the measured value of the gas flow meter immediately changes remarkably, and the DEH system receives and judges the measured value and then sends out alarm information to remind operation and maintenance personnel to check and process the measured value; the pressure transmitter monitors the air pressure of a driving instrument of the airlock valve, and a signal is sent to the DEH system. The control system and the control method are used for the VV valve pneumatic actuating mechanism with the early warning function.

Description

technical field [0001] The invention relates to the technical field of thermal power plant equipment, in particular to a VV valve pneumatic actuator control system and a control method with an early warning function. Background technique [0002] The 1036MW ultra-supercritical unit designed based on Hitachi technology does not have a high-pressure cylinder exhaust check valve, but a ventilation valve, referred to as a VV valve, is connected to the steam guide pipe behind the No. 4 high-pressure regulating valve of the steam turbine. The condenser, when the turbine trips the high-pressure regulating steam valve, is interlocked to open the VV valve. On the one hand, the steam backflow of the reheater system is used to cool the high-pressure cylinder and its blades at all levels to prevent the high-pressure cylinder blades from overheating. The high-pressure cylinder and the cold re-steam are returned to the condenser, which greatly reduces the axial thrust of the turbine and t...

AI Technical Summary

Problems solved by technology

[0003] However, in practice, it has been found that the design of many VV valve control systems is unreasonable, and there have been many cases of abnormal shutdown of the unit due to mis-opening of the VV valve. The mis-opening of the VV valve caused damage to the thrust bearing and condenser of the turbine Impact damage poses a potential threat to the safety of the steam turbine, and also causes huge economic losses to the thermal power plant;

[0004] Due to the high temperature of the working environment and the large vibration of the pipeline in the existing VV valve pneumatic actuator, the control accessories on the cylinder, the gas source pipeline, the instrument joint, etc. are prone to loose air leakage. If it is not found in time, the air leakage will increase. The system will lose pressure, which will cause non-shutdown accidents; in addition, the existing schemes all use a gas storage tank with a check valve to provide a backup working gas source, and the check valve is difficult to judge whether it is normal. In extreme cases, the instrument gas will be lost source and the one-way valve has been damaged, the failure to open the valve in time will cause irreparable damage to the high-pressure cylinder during shutdown; therefore, the prior art has the following disadvantages:

[0005] (1) The existing technology has no alarm monitoring function, and cannot detect abnormal conditions on site in time, resulting in non-stop accidents of steam turbines;

[0006] (2) The existing technology only uses a spare gas storage tank or cylinder spring to open the valve, which has poor safety performance and will cause damage to the steam turbine in extreme cases

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