SKFNJ2218Single Row Cylindrical Roller Bearing, 90 x 160 x 40 mm, NJ Design — One Flanged Inner Ring, One-Direction Axial Location

Product Description

What this part is

An SKF single row cylindrical roller bearing, 90 mm bore, 160 mm outside diameter, 40 mm wide. Cylindrical rollers contact the raceway along a line rather than at a point, which is why this bearing type carries far more radial load than a ball bearing of the same envelope. It is the workhorse of gearboxes, electric motors, rolling mills and any shaft where radial load is the dominant problem.

Decoding the designation — NJ is not NU

The two letters in front of the number describe the flange arrangement, and that determines what the bearing does axially. It is the most important thing on this page.

NJ: two flanges on the outer ring and one integral flange on the inner ring. The rollers are trapped against that single inner flange, so the bearing can take a modest thrust load in one direction and locate the shaft that way.

NU: two flanges on the outer ring, with a plain inner ring. The inner ring and shaft can float axially through the bearing. This is the free-end bearing.

NUP: an NJ plus a loose retaining ring on the other side of the inner ring, giving two-direction axial location.

A typical shaft uses one located bearing and one free bearing, so that thermal growth has somewhere to go. Fit an NJ where the drawing calls for an NU and you have created a second located position — the shaft can no longer expand, and the axial load it generates as it heats has nowhere to go but into the roller ends and the flanges. That failure looks like heavy wear on the roller ends and the inner flange face, and it is entirely a design-substitution error, not a bearing defect.

NJ2218 and NJ218 are different bearings

These two designations are one character apart. Both are 90 mm bore and 160 mm outside diameter. NJ2218 is 40 mm wide; NJ218 is 30 mm wide. The 22-series prefix denotes the wider dimension series with a correspondingly higher load rating, and the published load ratings for the two differ substantially, so a specification worked out for one will be wrong for the other. This listing is the 40 mm wide NJ2218.

Published ratings

Bore (d): 90 mm.

Outside Diameter (D): 160 mm.

Width (B): 40 mm.

Dynamic Radial Load Rating C: 280 kN (62,947 lbf), per bearing.

Static Radial Load Rating C0: 315 kN (70,815 lbf), per bearing.

Reference Speed: 4,500 r/min.

Internal Clearance: CN.

Tolerance Class: Normal.

Number of Rows: 1.

Rolling Elements: cylindrical rollers.

Axial Location: one direction (NJ design).

Performance Class: SKF Explorer.

Why the static rating sits above the dynamic rating:
C0 of 315 kN against C of 280 kN is SKF’s own published pair for this bearing. The dynamic rating is a rolling-fatigue figure: the load the bearing sustains for a defined life while each roller cycles in and out of the loaded zone. The static rating is a permanent-deformation limit on a stationary bearing, where the loaded rollers press into the raceway along their full contact line at once. On a wide-section cylindrical roller bearing the long line contact resists indentation more readily than it resists fatigue cycling, which puts the static figure ahead.

Cage suffixes and what they buy you

The NJ 2218 is catalogued by SKF in several cage variants, and the suffix matters when running near the speed limit or in a high-temperature installation. The load ratings are identical across the cage variants; the speed ceiling is not.

ECP: glass-fibre reinforced polyamide 6,6 cage. Light, quiet, low friction, with a service-temperature ceiling, and degraded by some synthetic oils and by oil oxidation products. Limiting speed 5,000 r/min.

ECM / ECML: machined brass cage. Heavier and dearer, but tolerant of high temperature, oil-mist and jet lubrication, shock load and aggressive lubricants. ML denotes the brass cage centred on the inner ring. Limiting speed 7,500 r/min.

EC: SKF’s optimised internal design, giving a higher load rating and better roller-end and flange lubrication than the older non-EC build.

Reference Speed is 4,500 r/min across the variants, and it is the thermally-derived figure that governs ordinary continuous duty.

Quantity and configuration

Unit Quantity: 1 Pc. A complete, one-piece bearing — both rings, rollers and cage, in the plain NJ2218 designation. The load ratings above are per bearing. Cylindrical roller bearings are separable in the sense that the inner ring can usually be drawn out of the outer ring and roller set, which is a mounting convenience on a blind installation: the inner ring goes onto the shaft and the outer ring into the housing separately, and the two are then brought together.

Interchange guidance

Search forms include NJ2218, NJ-2218, NJ 2218, NJ2218E, NJ 2218 ECP, NJ 2218 ECM, NJ 2218 ECML, NJ2218ECJ. Same-envelope alternatives at 90 × 160 × 40 mm: FAG NJ2218-E-XL-TVP2 and NJ2218-E-M1; NSK, NTN and Koyo NJ2218; and NU2218 or NUP2218 where a different axial arrangement is what the shaft needs — NU2218 E and its variants share the same boundary dimensions. The 30 mm wide NJ218 family is a different bearing and sits outside this envelope.