Symons 4.25ft Inner Eccentric Bushing | 2214-3930 | C93700

Symons 4.25ft Inner Eccentric Bushing: 2214-3930 Replacement

The Inner Eccentric Bushing (P/N: 2214-3930) is the primary bearing surface that supports the radial load of the Main Shaft in Symons 4.25ft cone crushers. Unlike modern hydraulic crushers that use spider bearings, the Symons design relies on this long, cylindrical bushing to maintain the eccentric throw. Given the low-pressure lubrication system typical of these legacy machines, the bushing material must possess exceptional self-lubricating properties to prevent catastrophic seizure.

We manufacture this critical component using ASTM B505 C93700 High-Leaded Tin Bronze via a Centrifugal Casting process. This method spins the molten alloy at high speeds, forcing impurities to the inner diameter (which are machined away) and creating a dense, non-porous grain structure. This ensures the bushing can withstand the “hammering” effect of crushing hard granite or iron ore without fatigue cracking.

Metallurgy: The Science of Anti-Seize

Standard bronze alloys (like Aluminum Bronze) are too hard for this application and will score the expensive main shaft. Our C93700 alloy is specifically engineered for Symons crushers:

• 10% Lead Content: The high lead content exists as microscopic pools within the copper matrix. Under extreme load or oil starvation, this lead smears onto the shaft, creating a solid lubricant barrier that prevents metal-to-metal welding.
• Embeddability: The material hardness (60-80 HBW) allows abrasive silica fines—which inevitably bypass seals—to embed into the soft bronze rather than grinding the steel shaft.

Field Diagnosis: When to Replace

Proactive maintenance is cheaper than a shaft replacement. Monitor these signs to determine the health of your crusher spares:

1. The “Hot Spot” Check
During a liner change, inspect the bushing bore. If you see localized dark blue or black patches (Heat Checking), the bushing has lost its concentricity and is rubbing unevenly. This is often caused by a bent countershaft or improper backing.

2. Vertical Scoring
Run your fingernail down the bore. If you can feel vertical scratches, it means contaminants are circulating in your oil. If the scratches are deeper than 0.5mm, the oil film cannot be maintained, and the bushing must be replaced.

3. Backing Material Failure
Symons bushings are often installed with a backing compound. If you see chunks of epoxy in the oil filter, the bushing has likely come loose in the eccentric bore and is “working” (moving), which will destroy the eccentric casting.

Installation Best Practices: Locking and Freezing

Installing the 2214-3930 requires more than just a press fit. Follow this expert procedure:

1. Cryogenic Shrink: Cool the bushing to -50°C using Dry Ice or Liquid Nitrogen. This shrinks the OD by approximately 0.08mm, allowing it to drop into the eccentric.
2. Locking Compound: Unlike HP series bushings, Symons bushings often require a Locking Compound (Epoxy) to be applied to the top flange or OD to prevent rotation. Ensure the eccentric bore is degreased thoroughly before application.
3. Alignment: You have a limited window (approx. 2 minutes) to align the oil feed holes before the bushing expands and locks. Use guide pins.

Compatibility

This part is a direct dimensional replacement for:

• Symons / Nordberg 4¼ Ft (4.25ft) Standard Cone Crusher
• Symons / Nordberg 4¼ Ft (4.25ft) Short Head Cone Crusher
• OEM Part Reference: 2214-3930

Performance Upgrade Data

[Expert Note] Never use “Aluminum Bronze” or “Manganese Bronze” for this specific inner bushing application. While they are stronger, they lack the necessary lead content and will destroy your main shaft within 500 hours. Stick to the OEM-specified High-Leaded Tin Bronze (C93700) for safe, long-term operation.