CKH664H/CKH664Y Pneumatic Welded Exhaust Check Valve

The CKH664H/CKH664Y pneumatic welded exhaust check valve is used in the extraction system of power plants or thermal power plants, or in non corrosive medium pipelines such as water, to prevent the sudden decrease in pressure inside the turbine during turbine stage load, and the back flow of steam from the extraction pipes and heaters into the turbine, causing the turbine to break and damage the turbine generator. It also prevents the heater system pipeline from leaking and causing water to close tightly from the extraction, Ensure that in the event of excessive water level in the feed water heater, the pneumatic components receive a liquid back flow signal and quickly isolate the turbine to provide maximum protection to the turbine or extraction system. Its function is to prevent the sudden decrease in internal pressure of the steam turbine during sudden load rejection, and the back flow of steam from the extraction pipe and various heat exchangers into the steam turbine, causing the high-speed rotating steam turbine blades to suddenly reverse and run at over 3000 revolutions per minute, resulting in the malignant accident of breaking the steam turbine blades and damaging the steam turbine generator. It also prevents the leakage of the heater system pipeline from causing water to enter the steam turbine through the extraction pipe and cause water hammer accidents.
Working principle and purpose:
When the air source enters the upper cylinder, the air source drives the piston to rotate the shaft and drive the valve disc, that is, the valve disc opens, and the medium passes through the valve. When the air enters the lower cylinder, the air source drives the piston to rotate the shaft and drive the valve disc, that is, the valve disc closes, and the medium stops passing through the valve. The CKH664H/CKH664Y pneumatic welding extraction check valve is used on non corrosive medium pipelines such as steam and water in the extraction system of power plants or thermal power plants, or other systems, to prevent the sudden decrease in pressure inside the turbine during sudden load rejection, and the back flow of steam from the extraction pipes and heaters into the turbine, causing the turbine blades to break and damaging the turbine generator, And prevent the leakage of the heater system pipeline from causing water to enter the turbine through the extraction pipeline and cause water hammer accidents, in order to protect the safe operation of the turbine. As a device to prevent reverse flow of the medium, this valve can quickly and tightly close within 0.5 seconds, ensuring that in the event of excessive water level in the feed water heater, pneumatic components receive a liquid reverse flow signal and quickly isolate the turbine, providing maximum protection to the turbine or extraction system.

Product features:

1. The design and manufacturing acceptance standards adopt ANSIB16.34, E101 or JB/T3595, and the strength and sealing performance fully meet the requirements of the standards. The valve in vacuum state undergoes vacuum testing, and the overall service life meets the user’s requirements.
2. For different temperatures, the main material is made of carbon steel or high-temperature steel, and the sealing surface is welded with hard alloy.
3. The valve disc is designed to be connected to the valve stem through a movable rocker, which can self align with the sealing surface of the valve, ensuring that the sealing surface matches.
4. The sealing surface of the valve seat is inclined at a certain angle to reduce closing time, reduce impact, and protect the safety of the equipment and pipeline.
5. The valve is equipped with a damping hammer, which can balance the power moment of the closing part and prevent the occurrence of hammer failure.
6. The inner chamber of the valve body adopts a streamlined design, which has a large flow capacity and reduces valve resistance.
7. The actuator is a spring return type cylinder or hydraulic cylinder, and is relatively independent of the valve closing part action. The actuator failure does not affect the closing part action.
8. The inner wall of the hydraulic cylinder ring is coated with a wear-resistant and corrosion-resistant layer, which can increase service life, reduce action resistance, and make the valve flexible and reliable.
9. The closing part is equipped with a limit mechanism to prevent damage caused by over opening.
10. The actuator is equipped with valve switch position signal output and on-site indication of valve opening position.
11. Targeted design can also be carried out according to specific user requirements.

Execution standards:
Design and manufacturing standards: ASME/ANSIB16.34, E101, JB/T3595
Structural length standards: JB/T3595, ASME/ANSIB16.10, GB/T12221
Welding end or flange standards: GB/T12224, ASME/ANSIB16.25, GB/T9113, JB/T79~JB/T82
Test acceptance standards: JB/T9092, JB/T3595, ASME/ANSIB16.34, E101

Main parts material:

Product external size and weight

Operation of check valve:
The operation of check valves should avoid the following situations:

1. Excessive impact pressure caused by the closure of the check valve.
2. The valve closing component quickly oscillates.

To avoid excessive shock pressure caused by closing the check valve, the valve must close quickly. To prevent the formation of excessive back flow velocity. The back flow velocity is the reason for the formation of shock pressure, so the closing speed of the check valve should be correctly matched with the attenuation velocity of the downstream medium.
However, the attenuation rate of the downstream medium may vary greatly in liquid systems. For example, if a liquid system uses a set of parallel pumps and one of them suddenly fails, the check valve at the outlet of the failed pump must be closed almost simultaneously. In addition, if there is only one pump in the liquid system and this pump suddenly fails, such as if the delivery pipe is long and the back pressure and pumping head at the outlet end are low, it is better to close the check valve with a smaller speed.
If the moving parts of the check valve wear out too quickly, it can lead to premature failure of the valve. To prevent this situation from happening, it is necessary to avoid the rapid oscillation action of the closing component. This rapid oscillation action of the closing component can be avoided by selecting a valve that forces the closing component to stably respond to the medium velocity that stops flowing.
This ideal situation is not often obtainable. For example, if the velocity variation range of the downstream medium is large. The minimum flow rate is not enough to force the closing component to stop steadily. In this case, the movement of the closing member can be within a certain range of its movement stroke
Use dampers inside the enclosure to suppress it. If the medium is pulsating flow, the check valve should be placed as far away from the pulsating source as possible. The rapid oscillation of the closing component may also be caused by extreme medium disturbance. In cases where this occurs, check valves should be installed.In the place where the disturbance of the medium is minimal.
Therefore, the first step in choosing a check valve is to understand the operating conditions under which the check valve is located.

Installation precautions for check valves:
The installation of check valves should pay attention to the following matters:

1. Do not let the check valve bear weight in the pipeline. Large check valves should be supported independently to prevent them from being affected by the pressure generated by the pipeline system.
2. During installation, pay attention to the direction of medium flow, which should be consistent with the arrow direction indicated on the valve body.
3. Lift type vertical disc check valves should be installed on vertical pipelines.
4. The lifting type horizontal disc check valve should be installed on the horizontal pipeline.