The pressure resistance limit of a vacuum integrated valve is determined by a combination of factors, including material properties, structural design, manufacturing process, sealing method, operating environment, and working medium. These factors are interconnected, and a deficiency in any one of them can become a bottleneck limiting pressure resistance.
Material properties are the physical basis of pressure resistance. Vacuum integrated valves require high-strength, high-toughness, and corrosion-resistant materials, such as stainless steel, aluminum alloys, or special alloys. These materials must have a uniform microstructure to avoid stress concentration caused by internal defects (such as pores and inclusions). For example, stainless steel, due to the chromium content forming a dense oxide film, effectively resists corrosive gas corrosion; while aluminum alloys, although slightly lower in strength, can have their fatigue resistance improved through heat treatment, making them suitable for weight-sensitive vacuum systems. Material selection must comprehensively consider mechanical properties and chemical stability to ensure long-term stable operation under high-pressure environments.
Structural design directly affects the valve's pressure-bearing capacity. A reasonable structure needs to balance strength and lightweight requirements; for example, using a thin-walled cylindrical or spherical design can distribute pressure loads and reduce local stress concentration. The connection method between the valve body and valve cover (e.g., flange connection, welding) must be selected according to the pressure rating.
High-pressure valves typically use integral forging or high-strength bolt connections to avoid fatigue cracking at welded joints. Furthermore, the internal flow channel design of the valve must be smooth and free of dead corners to prevent the formation of eddies in localized high-pressure gas, which can exacerbate wear or cause vibration.
The precision of the manufacturing process determines the actual performance of the theoretical design. During processing, the dimensional tolerances and surface roughness of each component of the valve body must be strictly controlled. For example, the sealing surfaces of the valve seat and valve disc need to be ground or polished to achieve a mirror finish to reduce micro-leakage under high pressure; welded joints require high-precision processes such as vacuum electron beam welding or laser welding to avoid porosity or cracks in the weld area. Heat treatment is equally crucial; quenching and tempering processes can eliminate processing stress, improve the material's creep resistance, and ensure that the valve does not deform under long-term high pressure.
The sealing method is a key factor in pressure resistance. Vacuum integrated valves typically employ either metal or rubber seals: metal seals (such as hard alloy weld necks) achieve zero leakage through plastic deformation, suitable for ultra-high vacuum or high-temperature environments, but require high-precision machining; rubber seals (such as fluororubber O-rings) rely on elastic deformation to fill gaps, offering lower cost, but their pressure resistance is limited by the material's elastic limit. The sealing structure design must consider the pressure direction: unidirectional pressure valves can use self-tightening seals, utilizing media pressure to enhance the sealing effect; bidirectional pressure valves require symmetrically arranged sealing structures to ensure balanced force on both sides.
The operating environment poses additional challenges to pressure resistance. Temperature fluctuations cause thermal expansion and contraction of materials, leading to seal failure or structural deformation. For example, at high temperatures, rubber seals may age faster, while creep effects must be considered for metal materials; at low temperatures, material brittleness increases, requiring protection against impact loads that could cause fracture. Furthermore, corrosive media (such as acidic gases and halogens) can erode the sealing surface or valve body material, necessitating surface coatings or the selection of corrosion-resistant alloys to improve durability.
The characteristics of the working medium directly affect valve selection. The molecular weight, viscosity, and compressibility of the gaseous medium determine the pressure transmission efficiency: light gases (such as hydrogen) are prone to leakage and require a higher sealing rating; heavy gases (such as sulfur hexafluoride) require consideration of flow resistance. If the medium contains particulate matter or droplets, a filter must be installed at the valve inlet to prevent impurities from clogging or abrading the sealing surface, which would reduce pressure resistance.
The pressure resistance limit of a vacuum integrated valve is the result of the combined effects of multiple factors, including materials, design, process, sealing, environment, and medium. In practical applications, the design rationality must be verified through simulation analysis and type testing, and strict manufacturing and testing standards must be established to ensure the valve operates safely and reliably under extreme conditions.
