C30-900-KMB bearing: complete specifications & equivalents
The C30-900-KMB is a ISO 15 radial bearing sized 900 x 1280 x 280 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 900 mm |
| Outer diameter D | 1280 mm |
| Width B | 280 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | brass |
| Basic dynamic load rating C | 12700 kN |
| Basic static load rating C0 | 26500 kN |
| Fatigue load limit Pu | 1530 kN |
| Reference speed (thermal) | 300 rpm |
| Limiting speed (mechanical) | 400 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 1200000 g |
| Manufacturer designation | C 30/900 KMB |
| Standard | ISO 15 |
| Catalog version | SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 10.1 CARB toroidal roller bearings |
| Last verified | 2026-09-27 |
Source: catalog reference (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 10.1 CARB toroidal roller bearings) · extracted 2026-09-27
Parameters extracted from the official SKF Rolling Bearings catalogue (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 10.1 CARB toroidal roller bearings); SKF® and SKF Explorer® are trademarks of AB SKF, used here for identification only — mpnbase is not an authorized SKF distributor. Boundary dimensions are ISO 15 interchangeable; current production values may differ, verify at skf.com.
Dimensions in inches & C3000-series range
| Bore d | 35.433 in |
|---|---|
| Outer diameter D | 50.394 in |
| Width B | 11.024 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 190 mm |
| Smallest bore in C3000-series | 120 mm |
| Largest outer diameter in C3000-series | 1420 mm |
| Width range across C3000-series | 46–308 mm |
| Bore position in C3000-series (smallest first) | 31 of 33 |
| Bore above smallest C3000-series size | 780 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| C30-900-MB | SKF | full Dimensions and internal design equivalent — standard interchange. | Same 900×1280×280 mm ISO 15 envelope and equivalent catalogue C/C0; C 30/900 MB is the cylindrical-bore MB inner-ring-guided brass-caged execution of this size — boundary dimensions interchangeable, only mounting and cage execution differ. |
Interchange levels: full standard interchange · partial verify parameters · verify manual confirmation required. Links resolve to the equivalent model's specification page where available.
How the C30-900-KMB model number is decoded
For long shafts that grow thermally, SKF supplies C 30/900 KMB: the toroidal rollers allow the 900 mm inner ring to displace axially without induced thrust, while still accommodating shaft deflection like a spherical bearing. Reading the code: C marks the CARB toroidal family, the first two digits (30) identify the ISO dimension series and the last two (900 mm (slash-size)) encode the 900 mm bore; suffixes describe bore and execution. The KMB suffix is a machined two-piece brass cage guided on the inner ring, the standard choice for wide, large-bore CARB sizes where a polymer cage would run beyond its temperature or load limit. Float capacity is a selection criterion: the catalogue lists the permissible axial displacement (s) for the 280 mm wide set; size the free-end housing so thermal growth stays within it, not just inside the overall width. Open executions accept relubrication — route it through the outer-ring groove on sizes that have one and purge stale grease at service intervals. Grease through the annular groove features where provided; on open executions feed lubricant past the long roller set at assembly, since the 280 mm wide cavity does not fill itself.
Typical equipment & failure modes
Common applications
- paper machine drying cylinders and calender rolls with long, thermally expanding shafts
- continuous-caster guide rolls and slab-caster segments under heat growth
- vibrating screen exciters fitted with the VE240 tolerance execution
- long fan and kiln main shafts where the free end must float without thrust load
Known failure patterns
- roller-end and flange smearing after lubricant starvation at the long roller contacts
- thermal preloading when a shaft is located at both ends and growth has nowhere to go
- PA66 cage (TN9) softening when the sustained temperature passes the polymer limit
- condensation pitting in machines that run intermittently in humid environments
- abrasive paste forming as dust bypasses the housing seals into the open washer set
Selection pitfalls — read before you substitute
- At 900 mm bore the 1200 kg mass and 280 mm width make seating geometry dominant: sphered-washer seats and oil flow must be verified in place, not just on the drawing.
- Envelope-identical spherical roller bearings (same ISO 15 d×D×B) are not drop-in equivalents — they locate the shaft axially, while C 30/900 KMB must float; the two are designed to be used as a pair.
- Never use C 30/900 KMB as the locating bearing: it carries no axial load by design — the arrangement needs a separate locating spherical, tapered or angular bearing facing the thrust.
- Do not block the axial displacement in the drawing: housing covers, labyrinth rings and snap rings must leave the catalogue float (s) free, or the bearing silently becomes a poorly located fixed bearing.
- Tapered-bore K executions mount on adapter sleeves (1:12) and K30 on withdrawal sleeves (1:30) — the 900 mm bore changes the sleeve family, and the drive-up procedure differs accordingly.
- The 12700/26500 kN ratings and 1200000 g mass are SKF catalogue values transcribed from ch. 10.1 of PUB BU/P1 17000 (PDF table page 868); mounting data — axial displacement (s) and seating details — appears in the running text because the structured record carries the boundary envelope only.
Frequently asked questions
What fails first on a misapplied CARB bearing?
Blocking the designed axial float — clamping the free end or locating both shaft ends — turns thermal growth into edge loading and spalls the toroidal raceways. Cage damage and ordinary fatigue follow overload or dry running.
Which dimensions does the C 30/900 KMB have?
A C 30/900 KMB measures 900 mm bore × 1280 mm outside diameter × 280 mm width (35.433 × 50.394 × 11.024 in). From SKF catalogue PUB BU/P1 17000: dynamic C 12700 kN, static C0 26500 kN, fatigue limit Pu 1530 kN, reference speed 300 r/min, limiting speed 400 r/min, mass about 1200000 g.
What does C 30/900 KMB mean in SKF part numbering?
C marks CARB; 30 the dimension series; the size code gives 900 mm bore; KMB is the execution (tapered 1:12 bore for adapter (H) sleeve mounting, machined inner-ring-guided brass cage (MB)). The envelope follows ISO 15 and matches spherical roller bearing outlines, but the functions differ.
Why is C 30/900 KMB used opposite a spherical roller bearing?
The spherical bearing locates the shaft and takes thrust; the CARB bearing at the other end self-aligns but floats, absorbing thermal expansion without inducing axial load. The pair is standard on paper machine drying cylinders and long caster rolls.
Reviewed & verified by the MPN Base engineering desk against source catalog SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 10.1 CARB toroidal roller bearings on 2026-09-27. Read our editorial & correction policy.