CH440 Main shaft step Cone Crusher Bushing 442.7120-01

Technical Specifications: Main Shaft Step Washer 442.7120-01

The Main Shaft Step Washer (also known as the Step Bearing Plate) is a critical hydraulic support component for Sandvik CH440 cone crushers. Located between the main shaft and the hydroset piston, this bronze wear part supports the entire weight of the moving assembly while enduring massive vertical crushing loads.

Core Advantages: Metallurgy and Precision

Unlike general machinery bushings, the crusher step washer operates in a boundary lubrication regime. Our crusher spares are engineered to exceed standard aftermarket limits through advanced manufacturing:

• Centrifugal Casting Technology: We utilize high-speed centrifugal casting to produce a dense, non-porous bronze structure. This ensures the part can withstand compressive stresses exceeding 300 MPa without deformation or cracking.
• Optimized Lead Distribution: Our C93700 alloy contains 20-22% lead, evenly distributed within the copper-tin matrix. This acts as a solid lubricant, preventing galling (scuffing) during startup or low-pressure idle periods.
• Precision CNC Grinding: The mating surfaces are ground to a mirror finish (Ra 0.4). This ensures an immediate, perfect seal with the steel step plate, facilitating the formation of the hydrostatic oil film.

Performance Comparison

Field data derived from hard-rock mining applications demonstrates the efficiency of our 442.7120-01 replacement parts compared to conventional sand-cast alternatives:

• Service Life: Extended by 20-30% due to superior material density and lack of casting defects.
• Friction Coefficient: Reduced by approximately 15%, leading to lower hydraulic oil temperatures in the hydroset tank.
• Reliability: Strict quality control eliminates the risk of “impregnated sand” often found in cheaper castings, which can score the expensive main shaft.

Field Diagnosis: When to Replace

As experienced crusher part suppliers, we advise checking the step washer during every liner change. Look for these signs:

1. Uneven Wear Pattern: If the washer is worn thinner on one side (tapered wear), it indicates a tilted main shaft or a damaged piston wearing plate. Replace immediately to prevent shaft failure.
2. Embedded Debris: If the bronze surface has embedded metal chips or grit, the oil filtration system may be compromised.
3. Thickness Limit: Measure the thickness. If wear exceeds 2-3mm from nominal dimension, the oil grooves may become too shallow to support the hydrodynamic wedge, leading to rapid overheating.

Workshops And Warehouses

Cross-Brand Compatible

Our aftermarket spare parts are engineered to be fully interchangeable with OEM components across major brands, ensuring identical fit and function.

Frequently Asked Questions (FAQ)

Q1: Why do you recommend changing the steel plate along with this bronze washer?
The steel piston wearing plate and this bronze step washer work as a matched friction pair. If you install a new bronze washer against an old, scored steel plate, the new part will wear out in less than 50 hours. Always replace them as a set.

Q2: Is part number 442.7120-01 compatible with the older H4800?
Yes. The Sandvik CH440 is the successor to the Hydrocone H4800. The internal hydroset components, including the step washer, are generally interchangeable. Please provide your serial number for double confirmation.

Q3: How do I store this part if I keep it in stock?
Bronze is soft and susceptible to corrosion. Keep the step washer flat (to prevent warping) in its original wooden crate, away from moisture. Do not stack heavy steel parts on top of the finished bronze surface.

Expert Tip regarding Installation: When installing the 442.7120-01 Step Washer, cleanliness is paramount. Even a single grain of sand between the washer and the piston can cause high spots, leading to immediate failure. Apply a liberal coating of clean hydraulic oil to both sides before assembly. Ensure the anti-rotation dowel pin is aligned but not bottoming out.