NU31-500-ECMA-HB1 bearing: complete specifications & equivalents
The NU31-500-ECMA-HB1 is a ISO 15 radial bearing sized 500 x 830 x 264 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 500 mm |
| Outer diameter D | 830 mm |
| Width B | 264 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | brass |
| Basic dynamic load rating C | 6440 kN |
| Basic static load rating C0 | 12000 kN |
| Fatigue load limit Pu | 880 kN |
| Reference speed (thermal) | 600 rpm |
| Limiting speed (mechanical) | 1000 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 595000 g |
| Manufacturer designation | SKF NU 31/500 ECMA/HB1 |
| 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 & NU3100-series range
| Bore d | 19.685 in |
|---|---|
| Outer diameter D | 32.677 in |
| Width B | 10.394 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 165 mm |
| Smallest bore in NU3100-series | 280 mm |
| Largest outer diameter in NU3100-series | 870 mm |
| Width range across NU3100-series | 146–272 mm |
| Bore position in NU3100-series (smallest first) | 8 of 9 |
| Bore above smallest NU3100-series size | 220 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the NU31-500-ECMA-HB1 model number is decoded
SKF NU 31/500 ECMA/HB1 is a single-row caged cylindrical roller bearing sized 500×830×264 mm — a dimension series 31 (compact OD, wide), listed in SKF catalogue PUB BU/P1 17000 ch. 6.1. Reading the NU prefix: 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. This makes the execution non-locating: the inner ring assembly can float axially in both directions and the bearing cannot support axial load. The plain designation (no cage suffix) identifies the basic execution supplied with a standard pressed-steel cage. The one-piece machined brass cage is reflected in the published speeds and temperature limits. Selection arithmetic: C0/C ≈ 1.86 (12000 against 6440 kN), and the Pu figure 880 kN is the fatigue load-limit floor for the SKF life equation; the catalogue lists 600 r/min thermal reference speed and 1,000 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
- roller-end scoring from inadequate oil flow in the roller-raceway contact
- edge-loading fatigue after shaft deflection beyond the 3–4 minute alignment limit
- false brinelling on standby machines exposed to external vibration
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 31 (compact OD, wide) envelope is shared with the N/NU/NJ/NUP executions of 31/500, but flange configuration and axial-locating behaviour differ — quote the full SKF NU 31/500 ECMA/HB1 and do not substitute rib styles without checking the shaft locating scheme.
- Shaft and housing fillets must clear the bearing chamfers; an oversized radius tilts the 264 mm-wide ring and concentrates load.
- Press-fit force goes through ring faces only; driving a ring home through the rollers brinells the 830 mm raceway.
- The 6440/12000 kN ratings are SKF catalogue 17000 (2018) values for the ECMA/HB1 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 NU31-500-ECMA-HB1?
SKF NU 31/500 ECMA/HB1 is a single-row caged cylindrical roller bearing with 500 mm bore, 830 mm OD and 264 mm width per ISO 15. SKF lists C 6440 kN, C0 12000 kN, Pu 880 kN, reference speed 600 r/min and limiting speed 1,000 r/min, mass about 595000 g.
What does the NU designation and ECMA/HB1 suffix mean?
The plain designation (no cage suffix) identifies the basic execution supplied with a standard pressed-steel cage. 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 NU31-500-ECMA-HB1 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 NU31-500-ECMA-HB1 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.