1. Product Introduction
This BOMCO TC450-21(6X7) crown block parts inventory covers all critical subassemblies: main crown block structural components, fastline sheave assemblies, and deadline deflector sheave parts. All parts are direct-fit replacements engineered to match the original crown block design specifications, requiring no on-site machining or modification for installation.
2. Key Functional Specifications
- Sheave Assemblies: φ1524mm main sheaves and 42” OD deadline deflector sheaves with precision-machined wire rope grooves, designed to reduce rope abrasion and support 450-tonne hoisting loads.
- Bearing Systems: Large-format precision bearings (304.8X393.7X107.95mm) engineered for high radial and axial loads, enabling smooth sheave rotation and minimizing friction during hoisting operations.
- Fastening & Retention Parts: High-tensile bolts, spring washers, and snap rings rated for vibration-resistant locking, preventing loosening in rigorous rig operating conditions.
- Sealing & Retention Components: Custom seals and elastic collars that retain lubrication, block dust and debris, and extend bearing service life in harsh field environments.
3. Structural & Quality Advantages
- API 8C Compliance: All load-bearing components meet API 8C standards for drilling lifting equipment, with full material certification and load-testing validation for safe rig operation.
- Precision Machining: Sheave grooves and bearing seats undergo CNC machining and laser calibration, ensuring perfect alignment with wire rope diameters and OEM assembly specs.
- Wear & Corrosion Resistance: Sheave surfaces feature hardened alloy layers (hardness ≥55 HRC) to reduce rope wear; fasteners and structural parts have zinc coating to resist rust and corrosion.
- Plug-and-Play Compatibility: Full dimensional matching with original BOMCO TC450-21(6X7) parts, allowing seamless replacement without custom modifications.
4. Applicable Operating Conditions
These TC450-21(6X7) crown block parts are validated for use in the most demanding drilling environments, performing reliably under these conditions:
- Load Rating: Maximum 450-tonne static load, compatible with standard 6X7 wire rope configurations
- Drilling Scenarios: Onshore land drilling rigs, offshore jack-up rigs, and semi-submersible drilling platforms
- Environmental Limits: Ambient temperatures -40℃ to 65℃, high-salt offshore air, dusty onshore sites, and high-humidity tropical environments
- Service Modes: Continuous hoisting duty, intermittent lifting operations, and periodic crown block overhauls
5. Preventive Maintenance & Service Recommendations
Follow these field-proven maintenance steps to extend part life and avoid unsafe crown block operation:
- Daily Pre-Use Checks: Inspect sheave grooves for wear, check for lubricant leaks at bearing seals, and verify bolt tightness to prevent loosening.
- Monthly Inspections: Clean sheave surfaces, re-torque all high-tensile bolts, and inspect snap rings and elastic collars for damage.
- 1000-Hour Service: Relubricate bearings, replace worn seals, and check sheave alignment for wire rope centering.
- 5000-Hour Overhaul Prep: Inspect bearing wear patterns, replace press plates, and check for cracks in sheave hubs.
- 10,000-Hour Major Overhaul: Replace all bearings, seals, and worn sheaves; inspect all structural pins and fasteners for fatigue, and re-certify load capacity.
We supply the following spare parts:
| EQUIPMENT NAME | Crown Block Assembly | ||
| MAKE | BOMCO | ||
| MODEL | TC450-21(6X7) | ||
| SERIAL NUMBER | 11000028590 | ||
| SL. NO. | DESCRIPTION | PART NUMBER | UOM |
| 1 | Sheave φ1524 | Ea. | |
| 2 | Press plate | Ea. | |
| 3 | Bolt with hole in head M24X80 | Ea. | |
| 4 | Iron wire with zinc coat φ2 | Ea. | |
| 5 | Elastic collar for hole using 90 | Ea. | |
| 6 | Bearing 304.8X393.7X107.95 | Ea. | |
| 7 | Sunk screw with groove M10X20 | Ea. | |
| 8 | Name plate | Ea. | |
| 9 | Guide sheave assembly | Ea. | |
| 10 | Main sheave assembly?? | Ea. | |
| 11 | Auxiliary sheave assembly | Ea. | |
| 12 | Bolt M18X35 | Ea. | |
| 13 | Spring washer 18 | Ea. | |
| 14 | Self-threading screw ST3.5×13-C-H | Ea. | |
| 15 | Pin | Ea. | |
| 16 | Sheaves, 42″ OD, 1-5/8” WR | Ea. | |
| 17 | Bearing Set | Ea. | |
| 18 | Seals | Ea. | |
| 19 | Snap Ring | Ea. | |
6. Field Failure Repair Cases (Real Drilling Site Scenarios)
Case 1: Sheave Bearing Seizure & Hoisting Delay
Issue: A TC450 crown block main sheave seized during hoisting, causing rough wire rope movement and halting drilling operations.
Root Cause: Failed bearing seals allowed dust and debris to contaminate the precision bearing, leading to friction and seizure.
Resolution: Installed OEM-matched precision bearings and new seals, thoroughly lubricated the assembly, and realigned the sheave. Smooth rotation was restored, and hoisting operations resumed safely.
Case 2: Loose Sheave Bolts & Vibration Damage
Issue: Excessive vibration from the crown block caused press plate bolts to loosen, risking sheave displacement and safety hazards.
Root Cause: Worn spring washers and insufficient bolt torque led to fastener backing out under continuous rig vibration.
Resolution: Replaced all M24 bolts, spring washers, and press plates, torqued fasteners to API specifications, and secured with zinc-coated retaining wire. Vibration-related loosening was fully resolved.
Case 3: Deadline Deflector Sheave Wear & Rope Abrasion
Issue: Severe wire rope abrasion and uneven wear on the deadline deflector sheave, risking rope failure and downtime.
Root Cause: Worn sheave groove surfaces and misaligned deflector sheave assembly causing uneven rope contact.
Resolution: Installed new 42” OD deflector sheaves and bearing sets, realigned the assembly, and adjusted rope tension. Rope abrasion was eliminated, extending wire rope service life.
7. Frequently Asked Questions (FAQ)
| Question | Answer |
| Are these parts direct fits for BOMCO TC450-21(6X7) crown block (SN 11000028590)? | Yes, every part is engineered to match OEM dimensions, load ratings, and API 8C standards, ensuring 100% bolt-on fit without modification. |
| Do these bearings support the 450-tonne crown block load rating? | Absolutely. The precision bearings are rated for the full 450-tonne static load capacity, designed for smooth, low-friction sheave rotation under heavy hoisting loads. |
| Can these parts be used for full crown block overhauls? | Yes. This list includes all critical overhaul spares: sheaves, bearings, seals, fasteners, and retention parts to complete a full TC450-21(6X7) crown block rebuild. |
8. Procurement Guidance & Call to Action
For drilling rigs relying on the BOMCO TC450-21(6X7) crown block, sourcing high-quality, API-compliant spare parts is essential to minimizing unplanned downtime, ensuring lifting safety, and extending the service life of this critical hoisting component. This parts list serves as a definitive procurement standard and technical reference, simplifying your sourcing process for emergency repairs, scheduled maintenance, and full crown block overhauls.
