In modern power generator units, steam turbines are controlled by digital electro-hydraulic control system, known as DEH system. The impulse starting of steam turbine, synchronization and grid connection with load are all realized by controlling the valve opening. YOYIK now introduce you the 9 most commonly used valves in the steam turbine DEH system and their applications.
The quick close solenoid valve cuts off the safety oil supply with electricity, so as to close the valve. It is an important equipment to ensure the safe operation of the extraction unit and prevent the steam turbine overspeed accident caused by the backflow of steam in the extraction pipe.
The shut-off valve is an auxiliary means for quick closing of the actuator. When the actuator loses the safety oil, the shut-off valve can quickly cut off the high pressure fire-resistant oil inlet of the actuator to prevent the system oil pressure from dropping due to the transient oil consumption of the actuator.
Servo valve is an important component of steam turbine DEH system. It amplifies and converts the electrical signal of DEH valve position into hydraulic signal, pushes the actuator slide valve to move, changes the opening of the control valve, changes the steam inlet volume of the unit, makes the speed (or load) of the unit reach the set value of the operator, and the system reaches a new balance state.
The trip solenoid valve receives DEH or ETS trip signal, loses power and trips the unit.
The test solenoid valve is used to remotely close the reheat steam valve. When the valve is energized, it opens the oil return channel and cuts off the high-pressure oil supply.
Stop valves are widely used in steam turbine control, such as actuator manifold block, pump outlet control block, accumulator manifold block, etc. Close the stop valve to block the oil circuit of the system to make online maintenance or replacement of some hydraulic spare parts.
The unloading valve is used for emergency shutdown. When emergency shutdown is required, the needle valve of the unloading valve can be pulled out locally to realize shutdown.
AST solenoid valve is an important component of turbine emergency shutdown protection. During normal operation, the AST solenoid valve is energized and closed, thus closing the oil drain channel on the AST header, so that the oil pressure in the lower chamber of all actuator pistons can be established. When a certain parameter of the turbine reaches the shutdown value, the AST solenoid valve will be opened after power loss, the safety oil will be drained, and all steam valves of the turbine will be closed quickly to shut down the turbine.
OPC solenoid valve is the overspeed protection control solenoid valve. It is closed in normal operation, which closes the oil drain channel of OPC main pipe, so that the lower chamber of the actuator piston of the regulating steam valve and reheat regulating steam valve can establish oil pressure. Once the OPC control board acts, the OPC solenoid valve will be energized and opened to drain the oil in the OPC main pipe. In this way, the unloading valve on the corresponding actuator will be opened quickly, so that the regulating steam valve and reheat regulating steam valve can be closed quickly.
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