Gate valves and globe valves are required to have an upper sealing device, mainly based on the following considerations:

1、To prevent media leakage and packing protection

Prevent media leakage: gate valve and stop valve in the closed state, the valve stem in the static position. Without an upper sealing device, the medium may penetrate upward along the gap between the valve stem and the valve body, resulting in leakage of the medium. The upper sealing device can effectively prevent the leakage of the medium and ensure the working performance and safety of the valve.

Packing protection: Packing boxes are usually sealed with flexible materials such as asbestos, polytetrafluoroethylene, etc., and long-term contact media are vulnerable to erosion, aging and damage. The upper sealing device can prevent the medium from entering the stuffing box, play a protective role on the stuffing, and extend the service life of the stuffing.

2、Environmental safety and energy saving

Environmental safety: For some toxic, harmful, flammable, explosive or valuable media, preventing its leakage is not only a guarantee for the safety of the working environment, but also a necessary measure to avoid environmental pollution. The upper sealing device can prevent medium leakage at the first line of defense, that is, the match between the valve stem and the valve body, providing a reliable guarantee for the sealing of the valve.

Energy saving: To prevent media leakage can also avoid waste of resources, in line with the environmental protection concept of energy saving and emission reduction.

3、Easy valve maintenance and packing replacement

Online replacement of packing: When the packing needs to be replaced, if there is no upper sealing device, the medium in the pipeline where the valve is located must be emptied first, so that the pressure on both sides of the valve can be balanced before operation. This will lead to production interruption in some continuous production processes, resulting in greater economic losses. With the upper sealing device, when replacing the packing, just close the valve, the upper sealing device can form a seal at the valve stem to prevent the medium from leaking, and there is no need to empty the medium in the pipeline, which can realize online replacement of the packing, greatly improving the maintenance efficiency and reducing the production downtime.

Valve stem inspection and maintenance convenience: the existence of the upper sealing device makes it unnecessary to worry about media leakage when conducting daily inspection, lubrication or maintenance of the valve stem, and maintenance personnel can operate the valve stem more easily and carry out necessary inspection and maintenance work to ensure the normal operation of the valve stem.

4、Improve valve reliability

Double seal protection: the upper seal device and the main seal of the valve (such as the seal between the gate and the seat) together constitute a double seal structure. When the main seal is slightly leaked due to wear, impurities and other reasons, the upper sealing device can be used as a supplementary sealing line to continue to ensure the sealing performance of the valve to a certain extent, and improve the overall sealing reliability of the valve.

5、Adapt to changes in working conditions

Working condition adaptability: In some working conditions, the valve may be affected by frequent fluctuations in temperature, pressure and other parameters, or parts deformation after long-term operation. The upper sealing device can adapt to these changes to a certain extent, and always maintains a good sealing state through its own elastic deformation or fine tuning to ensure the stable operation of the valve under different working conditions.

6、Comply with standard specifications

Industry general requirements: In the relevant standard specifications for valve design and manufacturing, such as API 600, GB/T 12234, etc., it is clearly stipulated that gate valves and globe valves should be equipped with sealing devices. This is a general requirement in the industry, and also an important guarantee to ensure the quality and performance of the valve.

In summary, the gate valve and globe valve are required to have an upper sealing device in order to ensure the sealing performance of the valve, protect the filler, ensure environmental safety, facilitate valve maintenance and replacement of the filler, improve the reliability of the valve and adapt to changes in working conditions.