Make Severe Service Flow Control Easy

The role and operation method of the inlet valve

Verspec Valve 1197

effect:

As an accident valve and an overhaul valve, the inlet valve usually has only two working states, fully open or fully closed, and cannot be used to adjust the flow. The main valve is not allowed to be opened in the case of moving water, its function is:
(1) As a backup protection for the overspeed of the unit. When the load rejection of the unit coincides with the governor failure and cannot operate, the main valve can be quickly closed under dynamic water conditions to cut off the water flow and prevent the unit from running out of speed to exceed the allowable value. , To avoid the expansion of accidents.
(2) Reduce the water leakage of the unit during shutdown and shorten the time required for startup when it is turned on. The water guiding mechanism of the turbine is often not closed tightly, and there is a large amount of water leakage after shutdown. This not only wastes water energy, but also leaks in the gap due to water leakage. Cause cavitation damage. According to statistics, the general guide vane leakage is 2% to 3% of the maximum flow of the turbine, and it can reach 5% in serious cases. Some small-scale units with high water head even cannot be shut down due to excessive water leakage. When the unit is shut down for a long time, closing its water inlet valve can greatly reduce water leakage.
The unit is shut down for a short time, and the inlet valve is generally not closed. Because this will release the water in the penstock, it needs to be refilled before the next start, which not only prolongs the start-up time of the unit, but also makes the unit unable to keep standby at any time, and loses the advantages of flexibility and quick mobility of hydropower station operation. . At this time, open the water inlet valve to make the penstock in a state of waiting for water filling, which saves startup time. For medium and high head power stations with long pressure pipes, this function of the inlet valve is more obvious.
(3) Provide safe working conditions for unit maintenance. When the power station uses a pressure pipe to divert water for several units to generate electricity, an inlet valve must be installed in front of each unit. When a unit is overhauled, closing the water inlet valve of the unit will not affect the normal operation of other units.

Operation method:

In medium and small hydropower stations, there are three ways to operate the inlet valve: manual operation, electric operation and hydraulic operation.
Generally, the inlet valve of the micro unit is manually operated. The inlet valve of a small unit generally adopts electric operation, and the electric operating mechanism is also equipped with a manual operating mechanism to ensure the reliable operation of the inlet valve. The water inlet valve is opened and closed by the electric motor or the manual operation handle through the speed change mechanism (that is, the reduction box), the screw, the nut and the rotating arm.
For large diameter inlet valves that require a large operating torque, hydraulic operation is adopted to ensure the closing speed of the inlet valve.
Regardless of the type and operation mode of the main valve, the valve should be opened only after three basic conditions: the water pressure on the upper and lower sides of the inlet valve are basically equal, the sealing device exits the working position, and the lock spindle exits. Still water open). The water inlet valve is not allowed to be opened under dynamic water conditions, because this increases the operating torque and is not required for operation. When shutting down in normal operation, it should meet the following two conditions: the water turbine guide vane is completely closed and the lock spindle is withdrawn before the water inlet valve can be closed (static water shutdown). In the event of an accident, after the water inlet valve receives the accident closing signal, it can be closed without fully closing the guide vanes of the turbine (moving water shut down) only when the lock spindle is withdrawn. When the water inlet valve reaches the fully open or fully closed position, the lock spindle must be put in again.
The working state of the inlet valve has only two positions, fully open and fully closed, and the inlet valve cannot stay in a certain position in the middle to operate, that is, it cannot be used to replace the guide vane to adjust the flow.


Company Profile

2005——Start to produce ceramic lined valve series.

2006——Start to produce rubber seat dome valve, knife gate valve and pinch valves.

2010——Joint venture start to produce Teflon plastic lined valve series.

2016——VerSpec US warehouse operated in Akensas.

2018——VerSpec Korea branch operated in Cheonnam.

2019——VerSpec India and VerSpec Mexico start operating.

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Tel: +86-577-57666870  
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E-mail: info@verspec.com

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