Long-life multi-stage ferrofluid seals incorporating a ferrofluid reservoir
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United States of America Patent
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Sep 12, 1989
Grant Date -
N/A
app pub date -
Nov 4, 1988
filing date -
Nov 4, 1988
priority date (Note) -
Expired
status (Latency Note)
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Abstract
A multi-stage ferrofluid seal incorporates a ferrofluid reservoir for extending seal life. The reservoir is located between seal stages and contains a quantity of ferrofluid sufficient to replace ferrofluid in the seal stages which is lost due to evaporation or contamination. The seal is designed to withstand a pressure drop between a high pressure area and a low pressure area and the location of the reservoir is selected so that the pressure capacity of the seal stages between the low pressure area and the reservoir is sufficient to withstand the entire pressure drop. The pressure capacity of the seal stages between the high pressure area and the reservoir is less than the entire pressure drop. Failure of the seal stages between the reservoir and low pressure area causes failure of the seal stages between the reservoir and the high pressure area. The total failure of all of the seal stages allows fluid to flow through the seal which fluid sweeps ferrofluid from the reservoir into the seal stages between the reservoir and low pressure area. This latter ferrofluid replenishes the ferrofluid in the failed seal stages and restores pressure capacity of the seal. A preferred embodiment is described which utilizes a single pole piece to define the seal stages and the reservoir.
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