Page 185 - Know and Understand Centrifugal Pumps

Know and Understand Centrifugal Pumps

The labyrinth seal
The word labyrinth means ‘a tortured pathway’. In the Dark Ages,
elaborate gardens, stone walls and an artificial lake with a drawbridge
would lead up to the main gate of a King’s Castle. This was the
labyrinth. An attackmg army would have to march through the garden,
around the stone walls and swim the lake containing ferocious
crocodiles, to attack the castle. All the while, the King’s soldiers were
shooting arrows at the attacking army as they marched back and forth
and swam the croc-infested lake.
As a bearing shaft seal mounted into modern industrial pumps, the
labyrinth seal is composed of a rotary unit that spins with the shaft and
a stationary unit mounted into the bore of the bearing housing around
the shaft. Labyrinth seals are considered ‘non-contact’ seals. The rotary
and stationary units do not actually touch each other. However, they
are in very close proximity. Its operating principal utilizes centrifugal
canals or grooves with openings to an external gravity drainage.
The dual purpose of the labyrinth seal is to prevent external
contaminants, like dust and water, from entering into the bearing
housing, while it maintains the lubricating grease or oil inside the
bearings. If a dust particle or drop of water tries to enter into the
bearings through the seal, it is caught into the labyrinth of centrifugal
spirals and ushered toward the external drainage. If the bearing
lubricant tries to exit the housing through the seal, it is trapped into it’s
own labyrinth and returned toward the oil sump.

BEARING

OUTER RACE
LTATlONARY ELEMENT
OF LAB SEAL
INNER RACE

SEALS
! !
I I-SHA-AFT
! !
I I
I I
INNER RACE

OUTER RACE
BEARING

Figure 11-4
_. - ~~

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