231-800BK bearing: complete specifications & equivalents
The 231-800BK is a ISO 15 radial bearing sized 800 x 1280 x 375 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 800 mm |
| Outer diameter D | 1280 mm |
| Width B | 375 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 16000 kN |
| Basic static load rating C0 | 31000 kN |
| Fatigue load limit Pu | 1780 kN |
| Limiting speed (mechanical) | 180 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 1830000 g |
| Manufacturer designation | NTN 231/800BK |
| 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 | 31.496 in |
|---|---|
| Outer diameter D | 50.394 in |
| Width B | 14.764 in |
| ISO bore code | 31 |
| Radial section height (D−d)/2 | 240 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) | 34 of 36 |
| Bore above smallest 23100-series size | 700 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 231-800B | 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 231-800B — 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 231-800BK model number is decoded
In NTN Ball and Roller Bearings CAT.No.2203E, 231/800BK denotes the 800 mm bore spherical roller bearing (16000 kN C / 31000 kN C0) in the 23100 series, the self-aligning choice for heavy combined load. Numbering ties 231/800BK to its envelope and execution: same-number EA versus EM or plain variants share the 800 mm bore but differ in cage and sometimes mass, so they are quoted as separate articles. At 16000 kN C and 1830000 g mass the 23100 series part is built for shock and vibration; the 375 mm-wide ring needs square abutments to keep both rows equally loaded. Catalogue mass 1830000 g (1830.00 kg) for the 800×1280×375 mm execution includes the basic cage and both roller rows; shaft and housing shoulders must support that ring squarely. Check the self-aligning movement after fitting: the housing should pivot freely around the sphered outer raceway; a pinched outer ring removes the alignment capacity the bearing was selected for.
Typical equipment & failure modes
Common applications
- cement-rotary-kiln support and trunnion rolls
- large SAG/ball-mill trunnion and pinion shafts
- heavy vibrating screens and grizzly feeders
- offshore and marine propulsion shaftlines
Known failure patterns
- raceway spalling at the roller ends when misalignment or deflection concentrates the line contact
- cage damage when a mounting force is applied through the roller set instead of the ring face
- sliding wear and heat when relubrication intervals ignore the groove (D1/W33) supply path
- false brinelling on stopped machines exposed to screen or crusher vibration
- brinelling from static overload or a hammer blow during sleeve mounting
Selection pitfalls — read before you substitute
- At 800 mm bore 231/800BK 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.
- The 1:12 tapered bore is the only difference from the cylindrical-bore 231/800B: 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 800 mm shaft; a sleeve sized to bore alone ignores thread, width and the oil-injection option on large K30 seats.
- The D1/W33 groove only helps if the housing has a matching grease passage; mounting a grooved 231/800BK in a solid block with no port wastes the feature and leaves the centre rows under-lubricated.
- Open spherical rollers swallow dust in mining duty; specify labyrinth or taconite seals externally, or the 180 r/min grease rating is lost to abrasive wear long before fatigue.
- The 16000/31000 kN ratings, 1780 kN Pu and 1830000 g mass are NTN Ball and Roller Bearings CAT.No.2203E values for 231/800BK (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 231/800BK?
231/800BK is an NTN double-row spherical roller bearing to ISO 15: 800 mm bore, 1280 mm OD and 375 mm width (31.496 × 50.394 × 14.764 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 16000 kN, C0 31000 kN, Pu 1780 kN, grease limiting speed 180 r/min, oil 240 r/min, mass about 1830000 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. 231/800BK 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 231/800B.
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. 231/800BK is the basic execution.
What do D1 and W33 mean on 231/800BK?
231/800BK 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 231/800BK 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 — 16000 kN C / 31000 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.