Labyrinth seal

The labyrinth seal ( clearance seal ) is a non-contact shaft seal. The sealing effect based on fluid dynamic effects due to the extension of the gap to be sealed. Characterized the flow resistance is increased. Complete sealing is not possible. The lengthening is usually through a mesh (technical term " interlacing " ) reaches of the form elements on the shaft and the stationary housing part.

Use

The use of this type of seal is limited to extreme operating conditions such as high engine speeds, pressures and temperatures, otherwise - for example, only at high pressures and temperatures - even considerably favorable seal types, such as graphite gaskets (so-called graphite - packs) for the superheated steam range, may be used. Labyrinth seals are technically very complicated to manufacture and assemble, and correspondingly expensive. They are widely used as a shaft seal in gas turbine construction, such as in jet engines and increase the efficiency of steam turbines in power plants designed often particularly complex.

A particular application of so-called labyrinth seals are motor spindles and capable of depending on the design up to several 100,000 min -1 ( rpm). In these spindle motors, the design of the labyrinth seal serves as a fluid bearing (liquid storage ) or hydrostatic bearings or hydrodynamic bearing. A key advantage is the extremely low friction, makes such high speeds possible.

Variants

Labyrinth seals are designed as smooth gap maze or a stumbling covenant maze. Due to the high flow resistance in the long gap, only a small, tolerable amount of fluid (leakage mass flow) can escape through the labyrinth seal. An absolute tightness is not possible with this non-contact design. For hazardous and toxic substances more complex mazes are necessary, in the direction of flow acting in the labyrinth pressure loss of the medium to be compressed is to achieve a 100% seal with a barrier fluid as repealed eg nitrogen. Additionally, the use of barrier media prevents the penetration of foreign matter.

Special variant of the labyrinth seals are sealing air seals.