Function of double seal rail valve


The function of the double seal guide rail valve is described in the following six aspects:
Online maintenance function, fire protection function and sealing, double shut-off and release function, cavity pressure relief function, unique pipeline decompression function, internal leakage inspection function.
1. Online maintenance function

When the soft seal on the disc is damaged for some reason and causes internal leakage or the manipulator (actuator) fails, the valve can be replaced or repaired without removing the valve from the pipeline, and the manipulator can also be repaired in the pipeline. Carry out without pressure. When the sealing part of the gate valve or ball valve is damaged, the valve must be removed from the pipeline to be repaired or replaced, or even the valve is directly scrapped.
2. Fireproof function and tightness
The medium in the oil and gas storage and transportation system is flammable and explosive. Fire prevention is a key issue in the design and selection of oil and gas storage and transportation devices. The device not only requires good sealing performance, but also has a certain sealing performance in the event of a fire on site. The sealing form of the double-seal guide rail valve adopts a combination of soft and hard seals, including valve discs, end covers, chassis and other structures. The soft seal can ensure zero leakage under normal operating conditions. When a fire breaks out on site, the soft seal may be damaged. At this time, the hard seal will act as the main seal to prevent a large amount of leakage of the medium. In comparison, the gate valve adopts hard seal, which has better fire protection function, but the sealing performance is not easy to guarantee, and it is difficult to guarantee zero leakage in long-term use; the ball valve adopts soft seal, which has a long service life, but does not have fire protection function.

3. Double shut-off and discharge function
Two isolation valves (gate valve or ball valve) are used to isolate the medium, and a discharge valve is installed between the two isolation valves. When internal leakage occurs in the isolation valve, the leaked medium will go out through the discharge valve, so that there will be no damage. Blending of two media.If the double-seal guide rail valve is used, only one valve is needed to realize the above functions, and there is a discharge medium at the bottom of the double-seal guide rail valve.
4. Pressure relief function in the cavity
The API I6 D specification stipulates that “for all double-sealed valves, when used in liquid media, they must have a differential pressure relief function”, and the differential pressure of the discharge is generated due to changes in ambient temperature. In the normally closed state, the pressure in the cavity of the double-sealed valve will increase rapidly due to the increase in temperature. If the pressure difference is not released in time, it will have a serious impact on the operation of the valve. Manually operated double seal rail valves generally have the following two pressure relief systems.
(1) Manual pressure relief system The manual pressure relief system is usually a needle valve mounted on the end cap.When the medium is a liquid that can be discharged into the atmosphere in a small amount, this pressure relief system can be equipped
(2) Differential thermal pressure relief system The differential thermal pressure relief system is a piping system with a check valve. In this system, the needle valve I is normally closed and the needle valve is normally open. When the medium is a liquid that cannot be discharged into the atmosphere, this kind of pressure relief system (usually to the upstream pipeline) must be equipped. The differential thermal pressure relief system does not require human control and only needs to manually open the needle when detecting internal leakage.
5. Unique pipeline decompression function
Pipeline decompression is an important consideration in the design of manifolds in storage tank farms, that is, when the valve in front of the tank is closed, the pipe network is still full of medium: as the ambient temperature rises, the pressure of the medium in the pipe network will increase rapidly Large; when the temperature difference changes greatly, the increased pressure will exceed the bearing capacity of the pipeline, which will easily cause pipeline leakage. Therefore, the pipeline should be equipped with decompression equipment and pipeline decompression design. Connect the pipeline decompression between the upstream and downstream of the main shut-off valve System, the system consists of two shut-off valves (gate valve, ball valve or globe valve) and a pressure reducing valve between the two shut-off valves. The main cut-off valve adopts the pipeline design principle of double-sealed guide rail valve, and the decompression system is attached to the main cut-off valve. Its design structure is simple, it takes up little space and is low in cost.
6. Check the inner leakage function
When the ordinary valve is in the closed state, it is difficult to detect its sealing effect, but the detection of the double-sealed guide rail valve is very easy. Just open the needle valve connected to the end cover of the pressure relief system in the closed state. If there is internal leakage, the medium will flow out through the needle valve. If the medium is not allowed to be discharged to the atmosphere, a pressure gauge can be connected to the needle valve, and whether there is internal leakage can be judged by observing the change of the gauge pressure.

The above six points are the functions of the double seal guide rail valve shared with you today. These six functions: On-line maintenance function, fire protection function and sealing, double shut-off and release function, middle cavity pressure relief function, unique pipeline decompression function, internal leakage inspection function, all areDouble seal rail valveThe more prominent functional features, get it quickly~

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