German WALTHER-PRAEZISION valves WALTHER-PRAEZISION models WALTHER-PRAEZISION prices

WALTHER-PRAEZISION valves are an important component of the safety system for thermal power plant units. They are critical safety devices that ensure the safe operation of extraction turbine units and prevent steam backflow in extraction pipelines, which can cause turbine overspeed accidents. To this end, Article 8110 of the "Twenty-Five Key Requirements for Preventing Major Accidents in Power Production" issued by the State Power Corporation specifically emphasizes that "the adjustable extraction check valves of extraction units must be tight, with reliable interlock actions, and fast-closing extraction stop valves must be installed to prevent overspeed caused by extraction backflow." Currently, the safety measure adopted by extraction turbine units to prevent overspeed due to steam backflow is the installation of check valves on the extraction pipelines. However, the currently applied extraction check valves have defects such as slow closing response, incomplete sealing, poor reliability, and inability to effectively prevent steam backflow. These defects have previously caused several major accidents involving serious overspeed due to extraction backflow, posing significant hidden dangers to production safety. Therefore, it is highly necessary to install a new type of faster and more reliable quick-closing valve on this pipeline to effectively prevent accidents and substantially improve the safety performance of the unit.

WALTHER-PRAEZISION Valve Structure

Consists of four parts: hydraulic actuator, mechanical conversion mechanism, triple-offset butterfly valve, and electrical control system. 1) Hydraulic Actuator The hydraulic actuator consists of an integrated hydraulic control system, including a power oil source, accumulator, control valve block, and hydraulic cylinder. The output of the actuator's hydraulic cylinder is linear motion. The cylinder piston is connected via threads to the rack of the mechanical conversion mechanism. 2. Mechanical Conversion Mechanism The mechanical conversion mechanism consists of a rack and a gear transmission mechanism. It converts the linear output of the hydraulic cylinder into angular output. The mechanical conversion mechanism is connected to the valve body via a flange. Its gears are directly connected to the drive of the butterfly valve, driving the valve disc to perform various actions, thereby enabling the actuator to control the butterfly valve and achieve functions such as quick closing. 3) Valve The valve offers excellent tightness, zero leakage, no sticking, long service life, and low torque. To ensure the safety and reliability of valve operation, the valve paired with the electro-hydraulic control quick-shutoff device should be a high-quality triple-offset metal-sealed butterfly valve. Various imported and domestic valves are available. 4) Electrical Control System The electrical control part consists of an operation unit, controller, and display and alarm unit. The operation unit supports automatic, manual, remote, and local operation modes. In automatic mode, it receives protection signals such as turbine main steam valve closure or oil circuit breaker tripping to implement quick closing of the valve. Manual remote operation can be performed from the control room to implement quick closing, normal opening and closing, and valve activity testing. A manual local operation mode with the same functions as manual remote operation is provided to facilitate adjustment tests and emergency handling in accident situations. The controller receives information from the operation unit, performs logical judgments, outputs function commands, and controls solenoid valves to achieve various control functions. The solenoid valves are normally de-energized and operate when energized. The controller also receives system oil pressure signals to control the start and stop of the oil pump, maintaining constant pressure in the oil system. The display and alarm unit provides status indications for valve "Open," "Close," "Activity Test," and "Quick Close." It also monitors and alarms for faults such as low oil system pressure, low oil tank level, low accumulator gas pressure, and motor overheating.

WALTHER-PRAEZISION Valve Functions

1) Slow Opening/Closing When PLC receives a slow opening/closing signal, it sends pulse commands to the stepper motor, causing the motor to rotate in the corresponding direction. This directs high-pressure oil into the right or left side of the double-acting cylinder, driving the gears and valve to move in the opening or closing direction. Upon receiving signals for the fully open or fully closed positions, PLC continues to send commands for a period to ensure the valve reaches the fully open or fully closed position. 2) Position Holding When PLC does not receive any commands, the motor, pump, and gears remain stationary. Since the hydraulic components in the equipment are leak-free, the valve holds its position in this state. 3) Quick Closing When PLC receives a quick-close signal, PLC energizes the quick-close solenoid valve. The two chambers of the double-acting cylinder communicate to relieve oil pressure. Under the action of the quick-close spring, the valve rapidly moves to the fully closed position. 4) Cushioning To reduce impact during the quick-closing process, variable throttling cushioning is added to the double-acting cylinder when the valve closes to 10% of its stroke. 5) Status Display and Alarm Displays working statuses such as valve "Open," "Close," and "Quick Close." It also monitors and alarms for faults such as "Actuator Error" and "Valve Opening/Closing Time Too Long." Working Principle: The electro-hydraulic control quick-shutoff valve consists of an electrical control device, actuator, and valve. Control signals are output as control commands by the controller, and the hydraulic actuator drives the valve action to achieve various control functions.

WALTHER-PRAEZISION Valve Working Principle

The electro-hydraulic control quick-shutoff valve consists of an electrical control device, actuator, and valve. Control signals are output as control commands by the controller, and the hydraulic actuator drives the valve action to achieve various control functions.

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