Inner Eccentric Bushing for Nordberg 4ft Cone Crusher

Symons 4ft Inner Eccentric Bushing: 2214-4481 Replacement

The Inner Eccentric Bushing (P/N: 2214-4481) serves as the primary sacrificial interface between the stationary main shaft and the rotating eccentric assembly in Symons 4ft cone crushers. Unlike modern hydraulic crushers, the Symons design relies on a long, cylindrical main shaft. This bushing must endure constant radial rubbing speeds and high compressive loads, necessitating a material with exceptional lubricity and thermal conductivity.

We manufacture this component using ASTM B505 C93700 High-Leaded Tin Bronze via a Centrifugal Casting process. This manufacturing technique spins the molten alloy at high G-forces, forcing oxides and impurities to the inner diameter (which are subsequently machined away). The result is a dense, non-porous grain structure that offers 25% higher fatigue resistance compared to standard sand-cast crusher spares found in the aftermarket.

Metallurgy: The C93700 Advantage

For Symons crushers, standard bronze is insufficient. We utilize Alloy C93700 (SAE 64) specifically for its high lead content. The microstructure consists of copper-tin solid solution alpha dendrites with distinct, isolated lead pools.

• Emergency Lubrication: In the event of an oil pump failure or momentary film rupture, the 10% lead content smears across the main shaft surface. This prevents the bronze from welding to the steel shaft, saving your main shaft from catastrophic scoring.
• Embeddability: The material hardness (60-80 HBW) allows abrasive silica fines (that bypass the seals) to embed into the soft bronze matrix rather than grinding the shaft.

Field Diagnosis: When to Replace

Proper diagnosis extends the life of your crushing circuit. Maintenance teams should inspect the inner eccentric bushing for the following failure modes:

1. The “Hourglass” Wear Pattern
Measure the internal diameter (ID) at the top, middle, and bottom. If the top and bottom measurements exceed the middle measurement by more than 0.25mm, the bushing has “bell-mouthed.” This causes the eccentric to wobble, leading to uneven crushing and potential gear misalignment.

2. Thermal Discoloration
A healthy bushing bore should be matte grey or bronze. If you observe “Blueing” or “Blackening” zones, the operating temperature has exceeded 180°C locally. This indicates oil starvation or excessive clamping force. The bushing must be replaced as its metallurgical structure has been compromised.

Installation: Cryogenic Fit and Locking

Installation of the 2214-4481 bushing requires precise thermal management to ensure it locks correctly into the eccentric casting.

1. Cleanliness: The eccentric bore must be degreased and free of old locking compound.
2. Freezing: Use Dry Ice or Liquid Nitrogen to cool the bushing to -50°C. Do not rely solely on a hydraulic press, as “shaving” bronze during insertion creates stress risers.
3. Locking Compound: Unlike some modern designs, Symons bushings often require a backing material or locking compound (epoxy) to fill the void between the bushing OD and eccentric ID. This prevents the bushing from spinning under load.
4. Alignment: Ensure the oil feed holes in the bushing align perfectly with the eccentric oil galleries before the temperature equalizes.

Compatibility

This part is a direct dimensional replacement for:

• Symons / Nordberg 4 Ft Standard Cone Crusher
• Symons / Nordberg 4 Ft Short Head Cone Crusher
• Supported OEM Ref: 2214-4481

Quality Assurance

Our crusher part suppliers protocol ensures every unit meets OEM standards:

• Spectrometer Analysis: Verifies Sn (9-11%) and Pb (9-11%) content.
• Ultrasonic Testing (UT): Ensures zero sub-surface porosity in the casting.
• Dimensional Report: Full CMM data provided for concentricity and perpendicularity.

[Expert Note] When replacing the Inner Eccentric Bushing, always inspect the Main Shaft for “steps” or ridges. Installing a new bushing on a worn shaft will lead to rapid failure (less than 200 hours). If the shaft wear exceeds 0.15mm, it must be re-machined or replaced to ensure the longevity of your new bronze component.