Labyrinth Seal Design & Technology
Labyrinth seals are made with a standard inner ring made from mild steel, and an outer ring formed from Aluminum. GD AI Si 12 Special materials on request.
Production Process for Labyrinth Seals
Labyrinth Seals, formerly named Leidenfrost Seals or Mini mace, are produced in the following way: The totally turned steel inner ring is surrounded with molded aluminum. This configuration is turned and milled as per the desired Type "L" or "M" and then radial pressure is applied while the seal is turning. Thus radial expansion of the soft aluminum ring is created which results in creating a labyrinth gap between inner and outer ring.
This production process guarantees the absolute identity of the profiles of inner and outer ring. Both rings are inseparable and not to be disassembled. We use different profiles for different seal sizes with at least three peaks.
Labyrinth Seal: Sealing Principle
The basic principle of a Labyrinth Seal is based on the geometric shape of the labyrinth seals which causes some turns of the contaminant on its way to penetrate the seal. The major factor for the efficiency of a non-contact seal is the centrifugal force caused by rotation and applied to the contaminant to throw it radially away before penetrating the seal.
At higher peripheral speed an air barrier is built inside the seal keeping different types of contamination (e.g. dust or liquids) out.
There is no chance for a labyrinth Seal to protect against higher liquid levels and against a pressure gradient between both sides of the seals. Pressure gradients may be reduced but not be sealed.
Axial and Radial clearance The catalog information on axial end play means the total axial movement of the seals inner and outer ring in relation to each other; from one end position to the other. Normally the seals should be installed in flush position - thus the axial allowance would be half the value in either direction. Axial and radial clearance are almost of the same size. They interfere each other. You will find the real clearance for a certain size on the data sheets when clicking "product selection".
Speed Limit GMN Labyrinth seals are pressed onto the shaft with a certain press fit. Due to centrifugal forces the inner ring could lift off of the shaft. The diagram below shows the speed limit depending on the size.
Examples how to optimize the sealing efficiency:
Problem: Liquid splash directly on to the sealing gap
Solution: You should place a disc in front of the seal rotating with the shaft. Care should be taken that there is enough distance between the seal and the disc to allow for free flow back of infiltrating liquid without backup in front of the seal.
Problem: Large quantities of liquids facing the seal.
- Please prepare drain areas or drain holes in front of the seal to avoid liquid backup.
- Use of the "M"-Type seal with sufficiently dimensioned drain groove and drain hole.
- The grooves of the "M"-Type seal may be used to improve the seal efficiency by using an air porche system to blow penetrating liquid out of the system.
Problem: Very large amount of liquids - pressure gradient.
Solution: You should try to prepare enough space for the sealing assembly, to allow using two labyrinth seals side by side with a parallel spacer of at least 0.5 mm width in between. Thus penetrating liquids may calm down and may be drained back by an annular groove and an a drain hole placed in between the two seals.