Lukkegrad

Lukkegrad is a term used in Scandinavian engineering to denote the degree of closure of a sealing interface, such as a valve, gasket, door seal, or other closure mechanism. It is a dimensionless quantity, often expressed as a percentage, that characterizes how effectively a closure prevents leakage under specified conditions.

Definition and calculation

Lukkegrad describes how completely a seal or closure is closed relative to an intended or reference state. In many contexts it is defined in relation to a reference leakage rate at a standard test condition. A common way to express it is lukkegrad = (1 − Q_actual / Q_ref) × 100%, where Q represents a leak rate. Values near 100% indicate near-complete closure, while lower values indicate higher leakage. Practically, engineers specify target lukkegrad values for components such as shut-off valves or high-performance gaskets, with demands often reaching 99.9% or higher in critical equipment.

Measurement methods

Determination of lukkegrad relies on leakage testing under controlled conditions. Methods include pressure decay tests, helium or gas leak testing with mass spectrometry, bubble tests for larger leaks, and flow-based assays. Tests are conducted at defined pressures, temperatures, and test fluids to ensure repeatability and comparability across components and manufacturers.

Applications

Lukkegrad is used in valve design, gasket specification, and door or hatch sealing across industries such as oil and gas, chemical processing, HVAC, automotive, and electronics. It provides a concise metric for comparing seal performance and for validating compliance with safety and quality standards.

See also

Sealing, gasket, valve shut-off standards, leak testing.