Labyrinth Oil Seal ring alternative

[KMP04]

Hi, I have a large 3ft diameter turbine bearing that has a damaged non-contact mechanical Labyrinth seal that uses multiple brass rings in the assembly. My machine shop is proposing to replace the lab seal with a 1 piece aluminum housing out of 6061-T6 with the grooves cut directly into the assembly.

Is there any reason why I should not pursue this alternative, replacing brass rings with aluminum?

Spec: 3ft dia. carbon steel shaft rotates at 60rpm, splash lubricated plain bearing. Steel hardness is 166 Brinell. considering replacing with 6061-T6 with a hardness of 95 Brinell... Labryinth radial clearance is 2.5mil.

Any feedback or references who repair Labyrinth seals will help.

Thanks Kevin

 

[JJPellin]

I am not sure if I understand the configuration you are describing. We don’t have any laby bearing housing seals quite this large. But the general trend in our plant is opposite of the direction you are proposing. We have found that we tend to have chronic oil leaks with fixed, non-contacting multiple tooth laby seals on bearing housings. We have converted a number of these to more complex designs with floating brass rings captured in grooves within the laby seal. These are often designed with the option of injecting purge air between the rings. These floating brass rings are designed with much tighter clearances than the fixed laby seals can be. Because they float, a 10” seal on the drive turbine for our main air blower might have a diametral clearance of only 0.004” to 0.006”. A fixed laby in the same housing might have a clearance of 0.010” per side.

Over the years, we have developed a lower tolerance for chronic oil leaks. I would not want to go back to fixed laby seals in these applications if it meant a drippy seal and an oily deck. I would be curious why you are considering this. Is the machine shop just hoping to save a buck or make their machining job easier? If so, I would be inclined to tell them to stick with the original design unless there was a valid engineering reason to change. We have purchased some of these specialized seals with floating brass rings from Bearings Plus, Inc. in Houston. They might be able to go this large.


Johnny Pellin

 

[KMP04]

Thanks for the comment JP. Actually, this damaged laby seal was only discovered during bearing dis-assembly, there was no issues raised with leaking seals. The only difference in the seal design is changing of ring materials...Aluminum vs. Brass. My concern is protecting the condition of the shaft without comprimising ring performance/service life.