Thrust bearing installation discipline splits by load regime: tilting-pad hydrodynamic units for turbomachinery routinely operate above 4 MPa continuous load with sliding speeds of 160 m/s and higher when the oil supply is correctly conditioned [S1]. The pad tilting action is what allows that speed-load combination without boundary-contact failure, which is why the same physical thrust bearing cannot be installed like a radial journal.
For vertical hydro-generating sets, the China water-resources standard SL 668-2014 codifies the install and adjustment procedure, covering thrust and guide bearing alignment on vertical units, with reversible units, horizontal machines, and pump motors referenced for analogous application [S2]. Field crews routinely treat SL 668-2014 as a defunct record [S3] but the install principles — leveling, runner-lift adjustment, pad clearance, oil-bath commissioning — remain the de facto reference. Cross-checking pad geometry against the roller bearing installation procedure clarifies which steps are bearing-class specific and which are mechanical-assembly common sense.
Thrust Bearing Class and Mounting Family
Tilting-pad thrust bearings are the dominant high-load class for compressors, steam turbines, integrally geared compressors, expanders, and turbo gearboxes, with common pad-face material pairs of steel/babbitt, steel/bronze, bronze/babbitt, CuCr/babbitt, and CuCr/AlSn40, and PEEK as an alternate polymer [S1]. The hydrodynamic film forms only when the rotating collar pulls oil into the converging wedge; if the unit is dry-installed or rotated without oil, the babbitt face welds within seconds. By contrast, an angular-contact ball bearing handles thrust via rolling-element contact pressure, not a fluid film, so its install procedure (mounting force, abutment orientation, preload) is fundamentally different even though both carry axial load.
For hydro sets under SL 668-2014, the install family is the Kingsbury-style or spring-supported thrust head with guide bearings (upper and lower) controlling radial shaft position, and the procedure covers alignment of the thrust collar, runner lift, and the bearing-housing leveling sequence [S2][S3]. When the rotor is lowered, the thrust collar must engage its pads in a controlled, oil-flooded condition; sliding surfaces on babbitt-faced pads are typically held to flatness within a few hundredths of a millimetre and the pad pivot point must be free of burrs. Skipping the oil-prime step is the single most common cause of pad scoring on commissioning day.
Pre-Install Inspection and Surface Tolerances
Before any thrust bearing is set, three things must be physically verified on the receiving inspection: shaft collar runout, housing bore perpendicularity to the shaft axis, and the pad/pivot contact surface finish. MIBA's published performance numbers — >4 MPa continuous load, ≥160 m/s sliding speed — are only repeatable when collar roundness and surface finish stay inside the OEM's tolerance window, because the hydrodynamic wedge breaks down first on the high-spot [S1]. A practical check: dial-indicator the thrust collar face for axial runout as it is slowly rotated by hand; readings above the OEM limit mean remachining or re-chroming before the bearing is mounted, not after.
Pad and runner components need a solvent wash, a clean-room dry, and a white-glove visual for score lines deeper than the lay of the original surface; any scratch that catches a fingernail across the babbitt is grounds to re-babbitt, not to install and hope. Lift the pads with clean, lint-free tools — bare fingers deposit chlorides that pit babbitt during the first heat cycle. The same cleanliness logic that protects a ceramic bearing from raceway spalling applies here, with the added twist that the failure mode is a wiped pad rather than a spalled race.
Alignment, Leveling, and Lift Adjustment
SL 668-2014 governs the install sequence on hydro sets: level the thrust bearing housing with a precision level, then set the shaft plumb, then set the guide bearing clearances to the design values, then set the runner lift within the specified range [S2][S3]. The level-instrument tolerance is typically in the 0.02–0.05 mm/m range; readings outside that window create a rotating bent, which loads one pad harder than the rest and shortens babbitt life by an order of magnitude.
For turbomachinery tilting-pad units, the install-side equivalent is not leveling but the shaft-centerline alignment to the driver/coupling, the axial position of the rotor relative to the thrust bearing centerline, and the freedom of each pad to pivot on its pivot without bind [S1]. With appropriate oil supply, bearing loads of >4 MPa are achievable for continuous operation [S1] — that "appropriate oil supply" is not a footnote, it is the controlling parameter: oil viscosity, inlet temperature, flow rate per pad, and oil cleanliness (typically ISO 4406 18/16/13 or better for new turbomachinery).
Lubrication Prime, Running-In, and Acceptance
Prime the bearing with oil before the shaft ever rotates. Flood the pad face until oil weeps evenly across all pads, then rotate the shaft by hand for at least one full revolution to confirm there is no metal-to-metal contact. The first powered run-in should be on uncoupled drive, short duration (typically 5–15 minutes), with bearing temperature, oil inlet/outlet temperature, and vibration logged every minute. Acceptance for a tilting-pad thrust bearing typically requires: stable pad temperature within 10–15 °C of oil-inlet after warm-up, no pad temperature spread greater than ~5 °C between pads, and vibration below the ISO 10816-3 zone A/B boundary for the machine class. [S1]
For hydro-generator units, the equivalent acceptance under SL 668-2014 is the runout and clearance check after the runner is lifted to design height and the bearing is oil-flooded, followed by a turning-gear rotation and a low-speed no-load spin before synchronization [S2][S3]. If any pad temperature is a sustained outlier, the standard corrective path is to recheck leveling and pad-pivot freedom — not to push the machine through to full load. For radial-bearing work on the same shaft train, the techniques differ; see the linear guide and crossed-roller guide references for the parallel rolling-element install logic.
Common Failure Modes Linked to Installation Error
Four failure patterns dominate the field, and three of them trace back to install steps. (1) Babbitt wipe on first rotation: oil was not primed, or the pad pivot is bound — both are 100% install-side fixes. (2) Pad temperature split greater than ~5 °C across pads: housing is not level, or one pad is sitting on a high-spot on the shaft collar — re-level and recheck runout. (3) Rapid oil-temperature rise and metal-flush alarms: oil flow is restricted or the inlet temperature is wrong for the viscosity grade selected — verify the oil spec matches the OEM table, not the warehouse shelf. (4) Pad face grooving or circumferential scoring: contamination in the oil or particulate left in the housing during install — flush, filter, and replace oil before re-running. [S1]
A fifth, less common failure is pad-pivot fretting, which shows up as a hot pad that cools only when the machine is stopped and restarted cold — that one is almost always a pad-replacement job, not a re-leveling job, because the pivot pin has been work-hardened and lost its clearance. Long-term operating economics on these failure classes are covered in the Roller Bearing TCO breakdown, and the wider rolling-element type map is in Roller bearing types and classifications; both are useful framing if a site mixes tilting-pad and rolling-element bearings on the same train.
Sourcing, Standards, and Specification Discipline
For high-speed turbomachinery, the OEM data sheet is the controlling document; published performance figures like >4 MPa continuous load at ≥160 m/s sliding speed only hold inside that OEM's tolerance window, with that OEM's oil spec, on that OEM's pad material [S1]. For hydro sets, SL 668-2014 is the install-process reference for thrust and guide bearings on vertical units, with reversible units, horizontal machines, and pump motors in scope by analogy [S2]. Some listing sites already mark the standard as superseded [S3], but the install content remains the field reference until an explicit replacement is published — when that happens, audit the revisions before quoting the standard number on a new data sheet.
Two trackable signals to watch: any replacement or amendment to SL 668-2014 issued by the China water-resources authority, and any tilt-pad OEM datasheet revision that re-states the continuous-load envelope or the oil cleanliness target. Both change the install acceptance criteria, and both are likely to be reflected first in the thrust bearing reference page rather than in the underlying standard library.