Labyrinth Seals: Non-Contact Sealing for Shafts and Bearings. A labyrinth seal forces a leaking fluid through interlocking teeth and chambers, dropping pressure in stages so leakage falls to an acceptable level rather than being eliminated outright. Because the rotor and stator never touch, labyrinth seals avoid the friction, heat and wear that limit contact seals, making them the standard choice wherever shaft speeds are high, seal life must be long, and a small, controlled leak is acceptable.
A labyrinth seal consists of thin radial fins, or teeth, machined onto the rotating shaft or the stationary housing, facing a surface on the opposite member with a small radial clearance. Each tooth forces fluid through a narrow gap into a slightly larger chamber, where it expands and loses velocity and pressure, converting pressure energy into turbulent heat. Repeating this cycle across many teeth drops the pressure differential in small increments, so the flow escaping the last tooth is only a fraction of what a single orifice of the same clearance would pass.
Leakage is never fully stopped, since the seal relies on a running clearance rather than a rubbing interface. Design leakage rates are set by tooth count, radial clearance, chamber geometry and pressure differential, and are accepted as a controlled, predictable loss rather than a fault condition.
With no rubbing contact, labyrinth seals generate negligible frictional heat and consume little to no shaft power, an advantage on large turbomachinery where seal drag would otherwise be a measurable efficiency loss. There is no wear-driven end of life in normal operation, so service life tracks the machine's mechanical condition rather than a wear surface. This makes labyrinth seals well suited to:
The trade-off: clearance-based sealing is leakier than a properly functioning contact seal, and performance is sensitive to rotor position, thermal growth and any rub event that alters the running clearance.
Labyrinth seals are the default internal seal on steam and gas turbines, controlling leakage between stages and at shaft end glands, tolerating high speeds and hot, dirty process gas that would foul a contact seal. In centrifugal compressors, labyrinth seals, sometimes paired with dry gas seals, are used at balance drums and interstage locations to manage recirculation and axial thrust.
A second major use is as a bearing isolator: a compact labyrinth device fitted at the bearing housing end cap, in place of a conventional lip seal. Its job is to keep dust, wash-down water and moisture out of the housing while keeping lubricant in, not to contain a pressurized fluid. Many isolators pair a labyrinth path with a rotating O-ring or a drainage groove that channels moisture back out before it reaches the bearing.
The choice between a labyrinth seal and a contact seal such as a mechanical seal or gland packing comes down to acceptable leakage versus tolerable wear, friction and maintenance.
| Characteristic | Labyrinth seal | Mechanical seal | Gland packing |
|---|---|---|---|
| Contact type | Non-contact, running clearance | Contacting faces, or non-contact for gas seals | Contacting, compressed rings |
| Leakage | Low but non-zero, by design | Very low to near-zero when healthy | Controlled drip, by design |
| Wear / life limit | None normally | Face wear, spring fatigue | Ring wear, sleeve wear |
| Speed suitability | Very high | High, with proper flush | Low to moderate |
| Power loss | Negligible | Moderate, face friction | Moderate to significant |
| Typical duty | Turbine/compressor stages, bearing isolators | Pump and mixer shaft seals | Legacy pumps, valves |
Selecting a labyrinth seal involves several variables:
Because labyrinth seals have no wear component to inspect on a fixed interval, condition monitoring relies on indirect indicators: a rising leakage rate, a drop in stage efficiency, bearing contamination, or vibration severity readings consistent with a rotor rub. Tracking these trends beats a calendar-based replacement policy, since the seal does not degrade on a predictable schedule the way a packing set or seal face does. Logging leakage, lubricant condition and rub events against the asset in a CMMS lets a reliability team catch a slow clearance drift before it causes a bearing failure. Book a Fabrico demo to see this history tracked against the asset record.
No. They restrict leakage to a low, predictable rate by dropping pressure across a series of clearances, not by achieving zero leakage. Some flow always passes through the clearance.
They generate minimal friction and heat, with no face or packing wear, so they operate reliably at speeds and temperatures that would destroy a contact seal.
A bearing isolator is a compact labyrinth device fitted at a bearing housing end cap. It keeps contamination out and lubricant in, rather than containing pressurized process fluid, and typically replaces a lip seal.
Yes, though not by wear the way a contact seal wears. A rotor rub from misalignment or thermal growth can open the clearance or damage teeth, and erosion from an abrasive fluid can enlarge the gap, raising leakage above design.
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