In the operation of large steam turbine units, the emergency shutdown system (ETS) is a key protection system to ensure the safety of the unit. When the unit encounters an emergency situation that endangers the safety of the unit, such as overspeed, bearing failure, low lubricating oil pressure, etc., the ETS system must be able to quickly and reliably perform shutdown operations to prevent equipment damage and casualties. Among them, the overspeed protection solenoid valve 4WE6D-L6X/EG220NZ5L (Over-speed Protection Control valve, OPC) is an important actuator of the ETS system. Its rapid response characteristics are directly related to the timeliness and effectiveness of the emergency shutdown action.

1. Structure and working principle of OPC solenoid valve

The 4WE6D-L6X/EG220NZ5L OPC solenoid valve is a two-position four-way solenoid reversing valve, and its core components include electromagnets, valve cores, valve bodies and oil circuits. The valve adopts a two-stage valve structure, consisting of a pilot stage and a main stage, which can realize rapid switching of the oil circuit, thereby controlling the closing of the main steam valve and the speed regulating valve.

When the turbine speed exceeds the set value (such as 103% rated speed) or an emergency such as decoupling occurs, the ETS system issues a shutdown command, and the electromagnet of the OPC solenoid valve 4WE6D-L6X/EG220NZ5L loses power instantly. At this time, the pilot stage valve core moves rapidly under the action of the spring force to open the unloading oil circuit. Under the action of the hydraulic pressure, the main stage valve core quickly closes the main oil circuit, cuts off the control oil source of the main steam valve and the speed regulating valve, and realizes the rapid closure of the steam valve, thereby causing the turbine unit to shut down urgently.

2. Analysis of the rapid response mechanism

The rapid response characteristics of the OPC solenoid valve 4WE6D-L6X/EG220NZ5L are mainly reflected in the following aspects:

• Secondary valve structure: The solenoid valve adopts a secondary valve structure. The action of the pilot stage valve core drives the main stage valve core, which greatly shortens the switching time of the oil circuit and realizes a rapid response of milliseconds.
• Electromagnet loses power quickly: When the ETS system issues a shutdown command, the electromagnet loses power instantly, eliminating the restraint of the electromagnetic force on the valve core, allowing the valve core to move quickly under the action of the spring force, thereby realizing the rapid switching of the oil circuit.
• Large flow unloading oil circuit: The unloading oil circuit opened by the pilot stage valve core has a large flow capacity, which can quickly release the hydraulic oil in the control chamber of the main stage valve core and accelerate the action speed of the main stage valve core.
• These design features enable the OPC solenoid valve to complete the switching of the oil circuit in a very short time, ensuring the timeliness of the emergency shutdown action and effectively preventing the occurrence of dangerous situations such as overspeed of the steam turbine unit.

3. The impact of fast response characteristics on emergency shutdown protection

The impact of the fast response characteristics of the OPC solenoid valve 4WE6D-L6X/EG220NZ5L on the emergency shutdown protection of the steam turbine is mainly reflected in the following aspects:

• Shorten the shutdown time: Fast oil circuit switching can quickly close the main steam valve and the speed regulating valve, shorten the shutdown time of the steam turbine unit, and reduce the risk of overspeed of the unit.
• Reduce impact load: Rapid valve closing can effectively reduce the impact load generated during the unit shutdown process and reduce damage to the unit equipment.
• Improve protection reliability: The rapid response characteristics reduce the delay of protection action, improve the reliability of emergency shutdown protection, and enhance the safety factor of the unit.

4. Improvement of system reliability

In order to further improve the reliability of the ETS system, the OPC solenoid valve 4WE6D-L6X/EG220NZ5L usually adopts a dual-channel design, that is, each protection circuit is equipped with two OPC solenoid valves to form a redundant configuration. When one of the solenoid valves fails, the other solenoid valve can still work normally to ensure the reliable execution of the emergency shutdown action.

In addition, the ETS system is also equipped with an online test function, which can regularly test the OPC solenoid valve 4WE6D-L6X/EG220NZ5L during the operation of the unit to verify the reliability of its action without affecting the normal operation of the steam turbine unit. This online test function can detect potential faults in a timely manner and improve the availability of the ETS system.

In practical applications, the fast response characteristics of the ETS system OPC solenoid valve 4WE6D-L6X/EG220NZ5L play a key role in preventing the steam turbine unit from overspeeding. The OPC solenoid valve quickly acts within milliseconds to close the main steam valve and the speed regulating valve, effectively preventing the unit from overspeeding, avoiding equipment damage and casualties. In addition, in the EH oil system, the solenoid valve is a key hydraulic control component, and its fast action is crucial to ensure the rapid establishment and maintenance of oil pressure during emergency shutdown.

When looking for high-quality, reliable Solenoid Valves, YOYIK is undoubtedly a choice worth considering. The company specializes in providing a variety of power equipment including steam turbine accessories, and has won wide acclaim for its high-quality products and services. For more information or inquiries, please contact the customer service below:
E-mail: sales@yoyik.com
Tel: +86-838-2226655
Whatsapp: +86-13618105229

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