Glossary

EN 13555 is a European standard titled “Flanges and their joints — Gasket parameters and test procedures relevant to the design rules for gasketed circular flange connections.” Its main job is to define which gasket “design constants” you need and how to test for them, so you can do a proper engineering calculation of a bolted flange joint’s tightness and integrity using EN 1591-1.

In practical terms, EN 13555 tells a lab or gasket manufacturer how to generate repeatable data for things like compression behavior, gasket stiffness, creep/relaxation behavior (how much sealing stress you lose over time), and leakage performance under controlled conditions—then how to evaluate/report the results.

It’s also important what it’s not: EN 13555’s procedures are commonly framed as being suitable for type testing of gasket materials/constructs (to create engineering data), not routine production quality control on every batch.

A common detail you’ll see referenced in EN 13555-based leakage datasets is the use of helium as a test gas, often at a defined pressure (frequently cited as 40 bar in standardized testing contexts), because helium makes leakage measurement sensitive and consistent.