Vacuum glass is a specialized glazing structure made by sealing two or more panes of glass and creating a vacuum cavity between them. The pressure inside the vacuum cavity is generally maintained at no more than 1 Pa, and in practical applications, the vacuum level can typically be controlled at around 0.1 Pa to 0.01 Pa or lower.
Because the vacuum cavity is exposed to atmospheric pressure from the outside, the glass must be designed to withstand the resulting pressure difference. To maintain a stable gap between the glass panes, small support pillars are placed inside the vacuum cavity.
The arrangement and spacing of these support pillars depend on factors such as the glass thickness, pillar type, material, shape, dimensions, structural loading conditions, and relevant mechanical properties.
In general, support pillars are designed to be as small as practical. A typical diameter is around 0.3–0.5 mm, with a height of approximately 0.1–0.4 mm and a spacing of about 20–60 mm. This helps reduce heat transfer through the pillars while also minimizing their visual impact.
1. Factors Affecting the Pressure Resistance of Vacuum Glass
The structure of vacuum glass is designed to withstand the pressure difference between the vacuum cavity and the surrounding atmosphere. Its actual pressure resistance depends on several factors.
1. Glass Thickness
Glass thickness is an important factor in the structural performance of vacuum glazing. In general, thicker glass provides greater resistance to pressure and external loads.
The appropriate glass thickness needs to be determined according to the size of the glazing unit, its installation conditions, and the loads expected in the application.
2. Support Pillars
Small support pillars are normally arranged between the glass panes in vacuum glass to prevent the panes from being pushed together by atmospheric pressure.
The number, spacing, strength, material, and geometry of the support pillars all affect the structural performance of the vacuum glazing system.
The pillars need to provide sufficient support while remaining as small and inconspicuous as possible. Their arrangement is therefore an important part of vacuum glass design.
3. Vacuum Level
The higher the vacuum level, the greater the pressure difference between the inside of the cavity and the surrounding atmosphere.
This means that a higher vacuum places greater requirements on the glass panes and the internal support structure. The vacuum level therefore needs to be considered together with the glass thickness, cavity design, support pillars, and overall dimensions of the glazing unit.
4. Glass Size
The dimensions of the glass unit also affect its pressure resistance.
For larger vacuum glass panels, the atmospheric pressure is distributed over a larger surface area. The design and arrangement of the support pillars therefore become increasingly important to distribute the load and maintain the required cavity spacing.
2. Pressure Limitations in Practical Applications
In architectural applications, vacuum glass is commonly used in windows, curtain walls, and other building glazing systems. The glazing design needs to take into account the environmental loads expected at the installation location.
These may include:
- Wind loads
- Snow loads
- Temperature variations
- The dimensions and installation conditions of the glazing unit
The pressure resistance of vacuum glass should therefore not be determined by vacuum level alone. The overall glazing structure, including the glass thickness, support pillars, panel dimensions, and installation conditions, must be considered as a complete system. For architectural glazing, applicable glass load-resistance standards should also be considered during structural design.
For applications involving unusual pressure conditions, such as underwater environments or high-pressure chambers, vacuum glass requires a specialized structural design. Depending on the application, this may involve increasing the glass thickness or modifying the support structure to achieve the required pressure resistance.
Conclusion
The pressure resistance of vacuum glass is determined by more than its vacuum level. Glass thickness, support pillar design, vacuum level, panel size, and application conditions all influence the structural performance of the glazing unit.
A well-designed vacuum glazing system uses an appropriate combination of these factors to maintain the vacuum cavity while withstanding the pressure difference between the cavity and the surrounding environment.
For architectural applications, vacuum glass is therefore designed according to the specific requirements of the project rather than according to a single universal pressure rating. Check our architectural vacuum glass solutions for window and curtain wall projects.