1 Model Information & Technical Parameters

Model：RNU 204 ECP

Dimensions

Nominal raceway bore Fw：26.5 mm

Outer diameter D：47 mm

Width B：14 mm

Performance Data

Basic dynamic load rating Cr：28.5 kN

Basic static load rating C0r：22 kN

Reference speed：17000 r/min

Limiting speed：19000 r/min

Technical Attributes

Supply form: Outer ring + roller cage assembly (without inner ring)

Number of roller rows: Single row

Structure type: RNU (NU variant, inner ring omitted)

Axial characteristic: Bidirectional axial floating (floating bearing, no axial locating capability, cannot sustain axial load)

Outer ring feature: Without snap groove

Cage: P glass fiber reinforced PA66, roller centered window cage

Outer ring flanges: 2

Coating: None

Seal: Open type, no seal

Pre-grease: None

Logistics & Industry Codes

Net weight：0.082 kg

Indicative carbon footprint：0.21 kg CO₂e

eClass code：23-05-09-01

UNSPSC code：31171505

Suffix Explanation

RNU: NU-type cylindrical roller bearing without separate inner ring; hardened shaft journal acts as inner raceway;

EC: Optimized internal geometry, modified roller end profile to reduce edge stress, improve load capacity and fatigue life;

P: Glass fiber reinforced PA66 window cage, roller-guided, lightweight, low friction for continuous medium-high speed operation.

Important reminder: This bearing is supplied without inner ring. Shaft journal surface must be quenched and precision ground, meeting bearing raceway standards on hardness, roughness and tolerance, otherwise premature scuffing and spalling will occur. The bearing only supports radial loads and cannot bear axial force. Normally paired with NJ/NUP locating bearings as floating end to compensate shaft thermal expansion. Open design requires housing sealing against dust and moisture. Continuous operating temperature of PA66 cage ranges -40～+120℃; avoid high temperature and strong polar solvents.

2 Structure & Operating Characteristics

Japan NMT RNU 204 ECP single row cylindrical roller bearing without inner ring is a derivative of NU design. Eliminating separate inner ring allows larger shaft diameter and greatly improves shaft bending stiffness. Double integral outer ring flanges restrain rollers; EC crowned roller profile equalizes contact stress and suppresses edge loading. Matched glass fiber reinforced PA66 roller-centered cage delivers low frictional heat and stable high-speed rotation.

Typical shaft layout: One end fitted with NUP/NJ bearing for axial location; the opposite end adopts RNU bearing as floating support to absorb axial thermal elongation and eliminate additional preload caused by temperature rise. Separable construction simplifies assembly, yet demands far higher machining precision on shaft journal compared to standard NU 204 ECP with complete inner ring.

3 Core Performance Advantages

1. RNU inner-ring-free design enables larger shaft diameter to boost shaft strength and rigidity, saving radial installation space.

2. EC optimized roller geometry balances contact stress, cuts thermal generation and extends bearing fatigue service life.

3. Glass fiber reinforced PA66 cage features light weight, good impact toughness and low centrifugal force, suitable for sustained medium-high speed operation.

4. Double outer ring flanges stabilize roller guidance, offering excellent pure radial load capacity and good shock resistance.

5. Permits free bidirectional axial movement of shaft, perfectly compensating thermal elongation and preventing shaft system seizure.

6. Coating-free open design compatible with mineral grease, circulating mineral oil and synthetic lubricants.

4 Typical Application Fields

4.1 Gear Transmission Equipment

Compact gear reducers, small gearbox floating support

4.2 Fluid Power Equipment

Centrifugal fans, blowers, small air compressor floating end support

4.3 Light Conveying Machinery

Conveyor rollers, chain drive units, packaging machinery transmission shafts

4.4 General Power Machinery

Medium-small electric motors, small machine tool transmission shaft floating support

5 Assembly Specifications & Usage Guidelines

5.1 Assembly Environment & Operation Standards

Maintain clean assembly area free of metal chips. Apply pressing load only to outer ring end face; never strike roller assembly directly. Rotate outer ring manually after assembly to verify smooth rotation without sticking or abnormal noise. Strictly check shaft journal hardness, roundness and surface roughness; never use on unhardened shafts.

5.2 Selection Guidance

Need enlarged shaft diameter and axial thermal compensation → RNU 204 ECP

Shaft journal cannot be hardened, complete raceway assembly required → Standard NU 204 ECP

Axial positioning and axial load support required → NJ204, NUP204 series bearings

5.3 Lubrication Maintenance Instruction

No pre-filled lubricant on delivery; fully apply grease on rollers and shaft raceway during assembly. Circulating oil lubrication recommended for high-speed conditions. Establish regular regreasing cycle according to load and rotating speed; dry friction operation is prohibited.

5.4 Environmental Application Notes

No anti-rust coating. Apply anti-rust oil and seal for long-term storage. Strengthen housing sealing under dusty and humid conditions. If continuous temperature exceeds 120℃, switch to machined brass cage version.

6 Fault Identification

Common failure modes: shaft journal scuffing, roller end pitting, outer ring raceway fatigue spalling, cage wear & cracking. Shut down for overhaul once extensive journal abrasion, cracked cage or roller pitting appears.