Labyrinth seal
The labyrinth seal (also gap seal) is a non-contact shaft seal . The sealing effect is based on the extension of the flow path through the gap to be sealed, which significantly increases the flow resistance. The path lengthening is usually achieved by interlocking (technical term "intermeshing") of the form elements on the shaft and the fixed housing part.
use
Labyrinth seals are used as standard in almost all types of wheel set drives in rail vehicles . The decisive advantage here is that this type of seal is wear-free.
Special designs are limited to extreme operating conditions such as high speeds , pressures and temperatures , otherwise - e.g. B. only at high pressures and temperatures - also much cheaper types of seals, z. B. graphite seals (so-called graphite packings) for the superheated steam area can be used. Labyrinth seals are technically very complex to manufacture and assemble and are correspondingly expensive. They are widely used as shaft seals in gas turbine construction , e.g. B. in jet engines and to increase the efficiency of steam turbines in power plants are often designed particularly complex.
One particular application of so-called labyrinth seals are motor spindles , which depending on the design up to several 100,000 min -1 reach (revolutions per minute). In these spindle motors, the design of the labyrinth seal also serves as a fluid bearing (liquid bearing) or hydrostatic bearing or hydrodynamic bearing . A decisive advantage is the extremely low friction that makes such high speeds possible.
variants
Labyrinth seals are designed as a smooth gap labyrinth or as a trip hazard labyrinth. 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. Absolute tightness is not possible with this non-contact construction. More complex labyrinths are required for dangerous and toxic substances. The pressure loss of the medium to be compressed acting in the direction of flow in the labyrinth is required to achieve 100% tightness with a barrier medium such as e.g. B. canceled nitrogen. In addition, the use of barrier media prevents foreign matter from entering.
Sealing air seals are a special variant of the labyrinth seals .
Individual evidence
- ^ Wilhelm Gentsch : Dampfturbinen , BoD - Books on Demand, August 2011, ISBN 978-3-86444-114-1 . P. 291 ff.