Gasdicht

Gasdicht, or gas-tight, describes a state in which a container, joint, or enclosure prevents the passage of gas under specified conditions of pressure, temperature, and time. It is a key property in engineering where containment of gases, avoidance of contamination, or preservation of inert atmospheres is required. A gas-tight closure must resist both leakage and permeation, depending on gas type and service conditions.

Achieving gas-tightness involves selecting appropriate materials and joining methods, such as welded or brazed metal seams, precision machined closures with gaskets or O-rings, and elastomeric or polymeric seals. The surface finish, tolerances, and proper assembly are critical, as microscopic defects can become leakage paths. Material compatibility with the gas, chemical resistance, temperature limits, and mechanical loads all influence whether a seal remains gas-tight.

Testing and verification are essential. Common methods include helium leak testing, pressure decay tests, and vacuum decay tests. Leak rates are specified in units such as mbar·L/s or Pa·m^3/s and are matched to the application's safety and performance requirements. Permeation, the slow diffusion of gas through materials, is also considered, especially for long-term containment at elevated temperatures or with highly permeable polymers.

Applications include chemical processing vessels, glove boxes and inert atmosphere enclosures, pharmaceutical packaging, gas transport systems, and safety equipment. While “gas-tight” implies very low leakage, it is usually defined for particular conditions and time scales; no containment is absolutely gas-tight under all circumstances.