A hydro turbine thrust bearing may show a hotter pad, an uneven temperature pattern, or Babbitt wear at an outage. Those signs deserve investigation, but none identifies a root cause on its own. Here is what to check before deciding whether a replacement thrust pad is needed.
In a vertical turbine-generator, the thrust bearing carries axial load. It may sit near the generator rotor, while guide bearings control radial shaft position. Confirm the bearing station before ordering. For oil-film basics, see our tilting pad thrust bearing guide.
When Is a Rising Thrust Bearing Temperature a Warning?
Start with the trend, not a temperature copied from another plant. Compare thrust pad metal temperatures at the same operating condition and sensor location. Record load, speed, oil temperature, cooling-water conditions, and whether the change followed a start, stop, reversal, or maintenance work. One pad rising while others remain steady can be more informative than a single absolute reading, provided the sensors are comparable.
Pad metal and oil-bath temperatures measure different things. A warm oil bath may point toward a cooling or circulation problem; a local hot pad also raises questions about load sharing, oil delivery, the runner surface, or the sensor itself. Sensor depth and position matter: temperatures vary across the face of a thrust shoe. Check the instrument and its history before treating one reading as proof of Babbitt damage.
There is no universal alarm temperature for every hydro generator thrust bearing. Use the unit’s OEM limits and plant procedure. If an alarm or rapid rise occurs, follow those instructions and keep the readings and event sequence for inspection.
Why Can Thrust Pads Wipe or Wear Unevenly?
During normal operation, an oil film separates the thrust runner from the pads. At low speed, start-up, shutdown, or inadequate oil supply, that film can become too thin. On units equipped with a high-pressure oil lift system, its purpose includes protecting these surfaces while a full running film has not formed. A fault in that system is one possible lead, not a diagnosis for every unit: some hydro generators operate without it.
Other leads include restricted oil flow, contaminated oil, reduced cooling, uneven pad loading, a damaged runner, or worn support parts. Oil deposits and electrical pitting are separate possibilities. A wiped area, scoring, or uneven wear shows where to look, but similar marks can have different causes. Replacing a pad without correcting the cause can expose the new part to the same conditions.
The U.S. Bureau of Reclamation’s hydro maintenance guidance describes how high-pressure lift protects the runner and Babbitt face during low-speed operation and why bearing insulation matters. The applicable machine design must still govern the investigation.
What Should Be Recorded During a Shutdown Inspection?
Before cleaning removed parts, photograph each pad in its installed position and mark the direction of rotation. Record which face carried the load, each pad’s temperature history, and the location and extent of wiping, scoring, embedded debris, cracks, or exposed backing. Inspect the Babbitt-to-backing condition according to the approved procedure. A clean-looking face alone does not establish that the pad or its bond is sound.
Look beyond the running face. The pivot or support contact, leveling components where fitted, oil feed paths, and high-pressure lift ports can reveal problems that a photograph of the Babbitt misses. Check the mating thrust runner for scoring, surface damage, and relevant fit or geometry issues. Preserve oil samples and operating records if available. The site engineer should connect these findings with lubrication, cooling, loading, and alignment data before approving the remedy.
Record dimensions against the approved drawing rather than copying the profile of a worn pad. If the runner or support arrangement will be restored, the replacement specification must reflect the approved final assembly. The owner or bearing designer determines whether a part can remain in service, be repaired, or must be replaced; JEDBUSHING can review the manufacturing requirements for a new component.
Send Your Thrust Pad Drawing for a Replacement Quote
JEDBUSHING manufactures custom Babbitt-lined thrust bearing components for hydropower unit replacements, based on agreed drawings or verified replacement data.
For a useful quotation, send your drawing and project details: unit and bearing station, drawing revision, pad quantity and position, backing and Babbitt specifications, lining thickness, finished geometry, pivot details, oil holes or lift features, sensor provisions, and required inspection. Include photos of the damaged pad and runner, plus any approved changes to the mating parts. If only an old pad is available, identify the dimensions that still need verification. We can then review what is needed to manufacture the replacement.
FAQ
Are main-thrust and counter-thrust pads interchangeable?
Do not assume so. The two sides may have different loading, support geometry, oil features, or part numbers. Match the exact face and drawing revision before ordering.
Can a temperature sensor hole be added to a replacement pad?
Only after the responsible designer approves its location, depth, and effect on the pad. Send the approved sensor drawing with the part specification; copying a hole from another machine could change the intended measurement or geometry.
Can solid bronze replace a specified Babbitt-lined thrust pad?
Not as a like-for-like substitution. The facing material, backing, oil film, temperature behavior, and runner must be assessed together. Use the approved original construction unless the equipment designer authorizes a redesigned bearing.