In the maintenance of construction machinery, housing components and bearing parts are fundamental elements that directly affect the strength, rigidity, transmission accuracy, and service life of the equipment. Correct selection and application of these parts are essential for ensuring machine reliability and extending operating life.

I. Principles for Selecting Housing Components

1. OEM Priority

   • Housings (such as gearbox housings, transfer cases, hydraulic pump housings, reduction gear housings, etc.) bear loads and provide positioning functions.

   • OEM castings undergo strict material, heat treatment, and machining processes. Original parts should be prioritized to avoid assembly errors or early cracking caused by poor-quality substitutes.

2. Repair vs. Replacement

   • When cracks, deformation, thread damage, or worn positioning holes occur, the repair value must be assessed.

   • Small cracks can be repaired by welding, cold welding, or metal adhesive; if deformation is severe or cracks extend into load-bearing areas, replacement is required.

3. Material and Process

   • Common materials: gray cast iron, ductile iron, alloy steel castings.

   • Check heat treatment condition and hardness to prevent collapse under load due to insufficient hardness, or brittle fracture due to excessive hardness.

4. Fit Accuracy

   • Housing bores, bearing seats, and oil seal holes must maintain standard fit tolerances.

   • After repair machining, ensure alignment of center distance, coaxiality, and perpendicularity; otherwise gear meshing and shaft life will be compromised.

II. Principles for Selecting Bearings

1. Reputable Brands First

   • Common brands: SKF, FAG, NSK, NTN, KOYO, TIMKEN.

   • Reliable domestic brands: Wafangdian (ZWZ), Luoyang (LYC), Harbin (HRB).

   • Counterfeit or inferior bearings should be avoided to prevent early spalling or raceway failure.

2. Matching Specifications and Models

   • Confirm bearing type from drawings or OEM manuals (deep groove ball, tapered roller, spherical roller, etc.).

   • Pay attention to bore size, tolerance grade, clearance (C0, C3, etc.), and cage design.

3. Working Conditions

   • High-speed parts (hydraulic pumps, motors): low-friction, high-speed bearings.

   • Heavy-load parts (reducers, travel devices): spherical or tapered roller bearings with high load capacity.

   • Impact conditions (scrapers, breakers): reinforced bearings with thicker raceways.

4. Lubrication and Sealing

   • Check whether bearings are pre-sealed; otherwise select appropriate grease or oil.

   • For high-temperature or dusty environments, use sealed or shielded bearings.

III. Common Problems and Experience

1. Housings

   • Worn bearing seats → repaired by sleeves or thermal spray.

   • Damaged bolt threads → repaired with thread inserts.

   • Severe deformation → scrapped and replaced.

2. Bearings

   • Common failures: pitting, spalling, burning, cage breakage.

   • Installation: avoid hammering; use proper tools or heating methods.

   • Replacement: inspect regularly; preventive replacement is recommended for travel reducers and hydraulic pumps.

IV. Recommendations for Selection and Management

• Record keeping: maintain logs of replaced housings and bearings, including model, batch, service condition, and lifespan.

• Anti-counterfeit verification: purchase through authorized channels to avoid counterfeit or refurbished parts.

• Spare parts strategy: keep stock of frequently damaged bearings; for large and costly housings, prioritize repair over replacement.