NU18-900-ECMA bearing: complete specifications & equivalents
The NU18-900-ECMA is a ISO 15 radial bearing sized 900 x 1090 x 85 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 | 1090 mm |
| Width B | 85 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | brass |
| Basic dynamic load rating C | 1980 kN |
| Basic static load rating C0 | 4900 kN |
| Fatigue load limit Pu | 240 kN |
| Reference speed (thermal) | 450 rpm |
| Limiting speed (mechanical) | 600 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 169000 g |
| Manufacturer designation | SKF NU 18/900 ECMA |
| Standard | ISO 15 |
| Catalog version | SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 6.1 single-row cylindrical roller bearings |
| Last verified | 2026-09-26 |
Source: catalog reference (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 6.1 single-row cylindrical roller bearings) · extracted 2026-09-26
Parameters extracted from the official SKF Rolling Bearings catalogue (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 6.1 single-row cylindrical 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 & NU1800-series range
| Bore d | 35.433 in |
|---|---|
| Outer diameter D | 42.913 in |
| Width B | 3.346 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 95 mm |
| Smallest bore in NU1800-series | 380 mm |
| Largest outer diameter in NU1800-series | 1090 mm |
| Width range across NU1800-series | 46–85 mm |
| Bore position in NU1800-series (smallest first) | 6 of 6 |
| Bore above smallest NU1800-series size | 520 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the NU18-900-ECMA model number is decoded
For a 900 mm shaft, SKF lists NU18-900-ECMA as single-row caged cylindrical roller: 1090 mm OD, 85 mm wide, Pu 240 kN, the catalogue lists 450 r/min thermal reference speed and 600 r/min mechanical limiting speed. The NU configuration means two integral flanges on the outer ring and no flanges on the inner ring, so the inner ring together with the roller set is separable; functionally the bearing is non-locating: the inner ring assembly can float axially in both directions and the bearing cannot support axial load. The ECMA suffix denotes the E-design execution with a one-piece machined brass cage for higher-temperature and higher-speed continuous duty. Selection arithmetic: C0/C ≈ 2.47 (4900 against 1980 kN), and the Pu figure 240 kN is the fatigue load-limit floor for the SKF life equation; the catalogue lists 450 r/min thermal reference speed and 600 r/min mechanical limiting speed. Assembly note: fit the inner ring and roller assembly onto the shaft and the outer ring into the housing independently; thermal expansion is absorbed by axial float, so do not trap the inner ring between shaft shoulders. Heat steel rings inductively to max 120 °C.
Typical equipment & failure modes
Common applications
- large rolling-mill drive trains
- marine propulsion line shafts
- heavy turbogenerator rotor supports
- mining hoist and winder shafts
Known failure patterns
- inner-ring raceway spalling from overload or contamination in the line-contact hertz zone
- outer-ring raceway fatigue after extended service at loads above the catalogue L10 rating
- cage pocket wear from roller skew at light load
- polymer cage cracking or softening after sustained running above 120 °C or with incompatible lubricant
- surface distress (micro-pitting) when the EHL film falls below the composite roughness at high specific load
- edge-loading fatigue after shaft deflection beyond the 3–4 minute alignment limit
- smearing (microwelding) on roller surfaces during skid starts with insufficient minimum load
Selection pitfalls — read before you substitute
- Do not use a NU bearing where axial load must be carried — the design carries radial load only
- The dimension series 18 (ultra-slim section for large shafts) envelope is shared with the N/NU/NJ/NUP executions of 18/900, but flange configuration and axial-locating behaviour differ — quote the full SKF NU 18/900 ECMA and do not substitute rib styles without checking the shaft locating scheme.
- Press-fit force goes through ring faces only; driving a ring home through the rollers brinells the 1090 mm raceway.
- Catalogue reference and limiting speeds are different criteria: observe the mechanical ceiling even when thermal calculations allow more.
- The 1980/4900 kN ratings are SKF catalogue 17000 (2018) values for the ECMA execution; re-verify against the current catalogue for critical drives and keep the catalogue version with the specification.
Frequently asked questions
What are the dimensions and catalogue data of NU18-900-ECMA?
SKF NU 18/900 ECMA is a single-row caged cylindrical roller bearing with 900 mm bore, 1090 mm OD and 85 mm width per ISO 15. SKF lists C 1980 kN, C0 4900 kN, Pu 240 kN, reference speed 450 r/min and limiting speed 600 r/min, mass about 169000 g.
What does the NU designation and ECMA suffix mean?
The ECMA suffix denotes the E-design execution with a one-piece machined brass cage for higher-temperature and higher-speed continuous duty. Structurally this execution has two integral flanges on the outer ring and no flanges on the inner ring, so the inner ring together with the roller set is separable.
Can NU18-900-ECMA take axial load and locate the shaft?
No — the inner ring has no flanges, so the NU bearing is non-locating and carries radial load only; use NJ (one direction), NUP (both directions) or a paired thrust bearing for axial duty.
How does NU18-900-ECMA compare with the other executions in the same envelope?
The N/NU/NJ/NUP executions share the ISO 15 envelope and load ratings but differ in flange arrangement and axial-locating behaviour; quote the exact order number.
What limits the service life of this bearing most often?
Line-contact fatigue above the L10 rating, cage wear at light loads and high temperatures, and edge loading from misalignment beyond about 3–4 minutes of arc are the typical failure drivers.
Reviewed & verified by the MPN Base engineering desk against source catalog SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 6.1 single-row cylindrical roller bearings on 2026-09-26. Read our editorial & correction policy.