231-900BK bearing: complete specifications & equivalents
The 231-900BK is a ISO 15 radial bearing sized 900 x 1420 x 412 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 900 mm |
| Outer diameter D | 1420 mm |
| Width B | 412 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 18700 kN |
| Basic static load rating C0 | 38000 kN |
| Fatigue load limit Pu | 2030 kN |
| Limiting speed (mechanical) | 150 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 2420000 g |
| Manufacturer designation | NTN 231/900BK |
| Standard | ISO 15 |
| Catalog version | NTN Ball and Roller Bearings CAT.No.2203E |
| Last verified | 2026-10-01 |
Source: catalog reference (NTN Ball and Roller Bearings CAT.No.2203E) · extracted 2026-10-01
Parameters extracted from the official NTN Ball and Roller Bearings catalogue (NTN Ball and Roller Bearings CAT.No.2203E); NTN® is a trademark of NTN Corporation, used here for identification only — mpnbase is not an authorized NTN distributor. Boundary dimensions are ISO 15 interchangeable; current production values may differ, verify at ntnglobal.com.
Dimensions in inches & 23100-series range
| Bore d | 35.433 in |
|---|---|
| Outer diameter D | 55.906 in |
| Width B | 16.22 in |
| ISO bore code | 31 |
| Radial section height (D−d)/2 | 260 mm |
| Smallest bore in 23100-series | 100 mm |
| Largest outer diameter in 23100-series | 1420 mm |
| Width range across 23100-series | 52–412 mm |
| Bore position in 23100-series (smallest first) | 36 of 36 |
| Bore above smallest 23100-series size | 800 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 231-900B | NTN | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same NTN 23100-series envelope, cage and ratings; this is the tapered-bore execution (K, 1:12) of the cylindrical-bore 231-900B — mounting (adapter/withdrawal sleeve or tapered seat, drive-up) differs. Verify shaft arrangement. |
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 231-900BK model number is decoded
231/900BK is an NTN double-row spherical roller bearing: two rows of symmetric rollers on a sphered outer raceway, 900×1420×412 mm to ISO 15, with pressed-steel cage (standard execution). The leading digits are the ISO 15 dimension series (23100 series); the bore code resolves to 900 mm (two-digit code ×5, with the 00–03 exception table), and 1420 mm OD / 412 mm width follow the general plan. Two symmetric roller rows share the load: C 18700 kN, C0 38000 kN (C0/C ≈ 2.03), with useful axial capacity in either direction alongside the dominant radial load. Pu 2030 kN against C0 38000 kN anchors the contamination derating; for dirty mining duty the adjusted life of 231/900BK moves with cleanliness far more than with small C variations. On vibrating-duty shafts verify the radial clearance class and cage choice at order time; the open 231/900BK leaves sealing and the C3/C4 clearance decision to the application drawing.
Typical equipment & failure modes
Common applications
- heavy vibrating screens and grizzly feeders
- offshore and marine propulsion shaftlines
- large wind-turbine main-shaft arrangements
- steel-mill and heavy crusher main shafts
Known failure patterns
- lubricant starvation at the centre rib area when the D1/W33 groove is not connected to a relubrication supply
- machined EM cage wear from inadequate oil film at the cage-guiding surfaces
- sliding wear and heat when relubrication intervals ignore the groove (D1/W33) supply path
- fretting corrosion between adapter sleeve and tapered bore when the drive-up is insufficient
- false brinelling on stopped machines exposed to screen or crusher vibration
Selection pitfalls — read before you substitute
- At 900 mm bore 231/900BK is normally mounted on adapter/withdrawal sleeves with hydraulic assistance; follow the NTN drive-up angle or oil-injection procedure — manual nut tightening cannot set the multi-tonne seating correctly.
- Never substitute 231/900BK by envelope alone: the 38000 kN C0 and 2030 kN Pu are specific to the NTN basic execution, and vibrating duty depends heavily on cage identity.
- Minimum load must be maintained even at rest under vibration: an unloaded 231/900BK on a stopped screen false-brinells; parking brakes and shaker isolation both matter.
- The 1:12 tapered bore is the only difference from the cylindrical-bore 231/900B: envelopes and ratings match, but drive-up tooling, sleeve and seat do not — never mix the two mounting methods.
- Adapter-sleeve mounting requires the correct sleeve series and locknut for the 900 mm shaft; a sleeve sized to bore alone ignores thread, width and the oil-injection option on large K30 seats.
- The 18700/38000 kN ratings, 2030 kN Pu and 2420000 g mass are NTN Ball and Roller Bearings CAT.No.2203E values for 231/900BK (basic); another maker's same-envelope part revises internal geometry, so re-verify ratings and cage before substitution on vibrating or rated drives.
Frequently asked questions
What are the dimensions and catalogue data of 231/900BK?
231/900BK is an NTN double-row spherical roller bearing to ISO 15: 900 mm bore, 1420 mm OD and 412 mm width (35.433 × 55.906 × 16.22 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 18700 kN, C0 38000 kN, Pu 2030 kN, grease limiting speed 150 r/min, oil 200 r/min, mass about 2420000 g. It is open, with pressed-steel cage (standard execution) and a 1:12 tapered bore.
What is the difference between the K/K30 tapered bore and the cylindrical bore versions?
K denotes a 1:12 tapered bore. 231/900BK mounts on an adapter sleeve (or tapered shaft seat) and is driven up to the specified residual clearance; its cylindrical-bore counterpart in the same envelope and ratings is 231/900B.
What do EA and EM mean on NTN spherical roller bearings?
EA is the NTN standard-capacity/high-capacity execution with a pressed sheet-steel window cage; EM is the high-capacity execution with a one-piece machined brass cage. Both use the optimised symmetric-roller design, but cage identity changes mass, speed behaviour and suitability for duties like vibrating screens, so they are separate order numbers. 231/900BK is the basic execution.
What do D1 and W33 mean on 231/900BK?
231/900BK is listed without a D1/W33 outer-ring groove in 2203E; lubrication is supplied from the ring sides. D1 (NTN spelling) and W33 add the annular groove plus holes and are ordered as distinct suffixed executions of the same envelope.
How much misalignment and axial load can 231/900BK take?
The sphered outer raceway compensates static and dynamic misalignment in the order of 1–2° (verify the exact 2203E figure for the 23100 series); beyond that, load concentrates on one roller row. Load is predominantly radial with a moderate axial share in either direction — 18700 kN C / 38000 kN C0 — but sustained pure axial load is not recommended because it unloads one row.
Reviewed & verified by the MPN Base engineering desk against source catalog NTN Ball and Roller Bearings CAT.No.2203E on 2026-10-01. Read our editorial & correction policy.