Although different production departments have different requirements for stainless steel valves, sealing is the most basic and most important performance. Most valve failures are caused by seal damage. The sealing performance is a comprehensive performance involving many factors, and measures must be taken in each link to be effectively improved.

The valve stem seal is the most difficult valve seal, because the valve stem and the valve body have relative movement. The valve stem seal can be divided into two types: packing seal and bellows seal. Packing seal can meet the requirements of high temperature and high pressure, and with the continuous development of the sealing structure and packing, the reliability of the seal has also been continuously improved. Traditional packing seals are compressed from the outside. The main disadvantages are uneven compression force, high friction, and serious wear. Using internal compression and two-way compression, these shortcomings have been largely overcome, and the reliability of the packing seal has been greatly improved. Another better way is to place the packing in the processed In the groove, the sealing effect is also very good. However, no matter how perfect the packing seal is, it cannot completely eradicate the leakage problem. The bellows seal completely eliminates the possibility of medium leakage through the valve stem. Therefore, stainless steel valves used to control highly toxic and highly corrosive media often use bellows to seal.

However, the pressure resistance of the bellows itself is limited, and the uneven wall thickness or tiny welding defects in the forming process of the bellows may cause it to break. To improve the pressure resistance of the bellows, the bellows can be strengthened. When the sealing requirements are extremely high, the bellows-packing double sealing structure can be used. For valve seat seals, there are multiple forms such as cone seals, spherical seals, plane seals and knife edge seals. Among them, the width of the sealing band and the angle of the sealing surface are very critical parameters, which have a great influence on the sealing quality. Cone seals are generally suitable for stop valves with smaller nominal diameters, while flat seals are suitable for valves with larger nominal diameters. In addition to the sealing structure, the leakage rate of the sealing surface is also related to the nature of the medium, the temperature, and the pressure difference between the two sides of the sealing surface. Therefore, these factors must be considered when selecting the sealing surface structure.