National Oilwell Varco Drawworks Clutch & Drive Spares

1. Product Introduction

This curated spare parts package includes high-load transmission components, precision bearing hardware, industrial-grade sealing elements, and heat-treated fasteners for NOV drawworks clutch systems. Key part numbers include the 641171 21-tooth low clutch drive sprocket, 641166 bearing spacer, 629684 48-tooth shifting clutch gear, neoprene sponge gaskets, nitrile rubber O-rings, precision shims, and graded hex head cap screws. Manufactured under strict quality control protocols, these parts meet API 7K and ISO 9001 certifications for oilfield drilling equipment, delivering consistent performance under high-torque, high-vibration operating conditions.

2. Functional Description

Each part performs a mission-critical role in drawworks power transmission and equipment protection: the 21T/52T/83T sprockets deliver precise torque transfer for high/low speed clutch operation; bearing spacers and retainer rings maintain proper shaft alignment and prevent radial movement; neoprene/rubber seals and gaskets block lubricant loss and external contamination; heat-treated fasteners provide consistent clamping force to resist vibration-induced loosening; and precision shims enable fine-tuning of bearing preload to eliminate premature wear. Together, these components ensure smooth clutch shifting, stable power delivery, and extended overhaul intervals for drilling drawworks.

3. Structural

• Sprockets & Clutch Gears: Forged alloy steel construction with precision-machined teeth (HRC 45-50 hardness) for wear resistance and zero backlash meshing; 21T low clutch, 52T high input, and 83T low drive sprocket configurations for optimized gear ratio matching.
• Bearing Components: Precision-ground inner/outer bearing races (641155/641154), heavy-duty retainer rings, and custom spacers for strict radial/axial load management; designed for tapered roller bearing compatibility in high-torque drawworks shafts.
• Sealing Elements: Neoprene sponge gaskets (2.5-inch wide, 3/16-inch thickness) and 90-durometer nitrile O-rings for temperature resistance (-40°F to 275°F) and effective fluid/lubricant containment.
• Fasteners & Hardware: Grade 8 hex head cap screws, locking nuts, and spring lock washers with cadmium plating for corrosion resistance; torque-rated to 120-180 ft-lbs to withstand rig vibration.
• Shim Kits: Precision-ground steel shims (0.005”, 0.007”, 0.020”, 1/16” thickness) for accurate bearing preload adjustment and shaft alignment calibration.

4. Applicable Operating Conditions

These NOV spare parts are validated for extreme oilfield drilling environments, including:

• Land and offshore drilling rig drawworks (high/low clutch drive systems, catshaft assemblies)
• High-torque power transmission (up to 15,000 ft-lbs rated load) under continuous duty cycling
• Exposure to drilling mud, crude oil, brine, and extreme temperature fluctuations (-20°F to 300°F)
• Preventive maintenance and emergency overhaul of NOV drawworks clutch and bearing modules
• Routine replacement of worn fasteners, seals, and spacers in rig power transmission systems

5. Maintenance & Troubleshooting Best Practices

Maximize component lifespan and prevent costly failures with these field-proven guidelines:

• Inspect clutch sprockets and gear teeth every 1,000 drilling hours for wear, chipping, or pitting; replace parts at the first sign of tooth degradation to avoid slippage.
• Check bearing spacers and retainer rings for misalignment every 500 hours; verify proper preload using precision shims to reduce friction and heat buildup.
• Replace neoprene gaskets and rubber O-rings every 1,500 hours to prevent lubricant leakage and contamination ingress.
• Torque all fasteners to OEM specifications during installation; re-torque after 24 hours of initial operation to counteract vibration-induced loosening.
• Store spare seals and gaskets in a cool, dry environment to preserve material elasticity and prevent premature degradation.

We supply the following spare parts:

1. NATIONAL OILWELL VARCO {641171} SPROCKET, 21T LOW CLUTCH DRIVE
2. NATIONAL OILWELL VARCO (641166} BEARING, SPACER
3. NATIONAL OILWELL VARCO {7817671} GASKET, NEOPRENE SPONGE, 2.5 INCH WIDE
4. NATIONAL OILWELL VARCO {10090433-001} WASHER
5. NATIONAL OILWELL VARCO {10041450-001} SCREW
6. NATIONAL OILWELL VARCO {7000399-001} SCREW
7. NATIONAL {7000391-11} SCREW, HEX HEAD CAP {5/8” x 3/4” Item # 11}
8. NATIONAL OILWELL VARCO {10090408-001} SCREW
9. NATIONAL OILWELL VARCO {10660086-001} O-RING, RUBBER
10. {NATIONAL OILWELL VARCO {10090372-001} WIRE, TIE
11. NATIONAL OILWELL VARCO {10124938-001} WASHER, SEAL
12. NATIONAL OILWELL VARCO {10090336-001} SCREW
13. NATIONAL OILWELL VARCO {10519744-001} SCREW
14. NATIONAL OILWELL VARCO {11399140-001} GASKET, GUARD ADAPTER
15. NATIONAL OILWELL VARCO {10070323-001} WASHER, SEALING
16. NATIONAL OILWELL VARCO {10059083-001} SPONGE, RUBBER
17. NATIONAL OILWELL VARCO {10059381-001} SPONGE, RUBBER
18. NATIONAL OILWELL VARCO {10059134-00} SPONGE, RUBBER
19. NATIONAL OILWELL VARCO} {10059360-001} SPONGE, RUBBER
20. NATIONAL OILWELL VARCO {10037224-001} NUT
21. NATIONAL OILWELL VARCO {10037232-001} NUT
22. NATIONAL OILWELL VARCO {10050876-001} WASHER
23. NATIONAL OILWELL VARCO {10490361-592} SCREW
24. NATIONAL OILWELL VARCO {10090406-001} SCREW
25. NATIONAL OILWELL VARCO {10036214-001} SCREW
26. NATIONAL OILWELL VARCO {10090405-001} SCREW
27. NATIONAL OILWELL VARCO {641161} SPACER
28. NATIONAL OILWELL VARCO {641160} SPACER
29. NATIONAL OILWELL VARCO {629707} RING, BEARING RETAINER
30. NATIONAL {629690} RING, BEARING RETAINER
31. NATIONAL OILWELL VARCO {641172} SPACER
32. NATIONAL OILWELL VARCO {641167} SPACER
33. NATIONAL OILWELL VARCO {641170} SPACER
34. NATIONAL OILWELL VARCO {641169} SPACER
35. NATIONAL OILWELL VARCO {641162} SPACER
36. NATIONAL OILWELL VARCO {641159} RING, BEARING RETAINER
37. NATIONAL OILWELL VARCO {656287} SPACER, CATSHAFT REMOVAL BLANKING
38. NATIONAL OILWELL VARCO {7805052} FITTING, ALEMITE
39. NATIONAL OILWELL VARCO {6803089} BUSHING
40. NATIONAL OILWELL VARCO {6803030} BUSHING
41. NATIONAL OILWELL VARCO {609866} SCREW
42. NATIONAL OILWELL VARCO {700039511} SCREW
43. NATIONAL} {7619050} WASHER, 1/2″ REGULAR SPRING LOCK (760205)
44. NATIONAL OILWELL VARCO {ZS8664} BEARING, DS
45. NATIONAL {7619058} WASHER, 5/8″
46. NATIONAL OILWELL VARCO {700030411} SCREW
47. NATIONAL OILWELL VARCO {629684} CLUTCH, 48T GEAR TOOTH SHIFTING
48. NATIONAL OILWELL VARCO {629687-A} ROLLER ASSEMBLY, SPROCKETS, HI AND LOW INPUT
49. NATIONAL OILWELL VARCO {641155} RACE, INNER BEARING
50. NATIONAL OILWELL VARCO {641154} RACE, OUTER BEARING
51. NATIONAL OILWELL VARCO {ZS7871} BEARING, ODS
52. NATIONAL {622868-3} SHIM, .005″
53. NATIONAL {622868-2} SHIM, .007″
54. NATIONAL {622868-1} SHIM, .020″
55. NATIONAL {622868} SHIM, 1/16″
56. NATIONAL OILWELL VARCO {641152} SPROCKET, 83T LOW DRIVE INPUT
57. NATIONAL OILWELL VARCO {641156} SPROCKET, 52T HIGH INPUT DRIVE
58. {7817170} GASKET, NEOPRENE RUBBER 3/16 X 2
59. {41840} Screw, 7/8 Inch X 2 Inch

Field Repair Case Studies (Real-World Drilling Scenarios)

Case 1: Clutch Slippage & Power Loss (21T Sprocket Failure)

A land drilling rig experienced sudden low-clutch slippage and reduced hoisting power, traced to worn teeth on the 641171 21T drive sprocket. Replacing the worn sprocket with a new OEM-equivalent unit and realigning the bearing spacer (641166) restored full torque transfer, eliminating downtime and preventing further damage to the clutch assembly.

Case 2: Bearing Misalignment & Seal Leakage

An offshore rig reported gearbox lubricant leakage and abnormal shaft vibration, caused by a damaged bearing retainer ring (629707) and misaligned spacer. Installing a new retainer ring, replacing the sealing washer, and adjusting with precision shims stopped leakage, corrected shaft alignment, and extended bearing life by 40%.

Case 3: Fastener Fatigue & Guard Adapter Failure

A workover rig experienced a loose guard adapter due to fatigued hex head screws and worn lock washers. Replacing the damaged fasteners (7000391-11, 7619050) and installing a new guard adapter gasket (11399140-001) secured the assembly, reducing vibration and preventing safety hazards during operation.

Frequently Asked Questions (FAQ)

Question	Answer
Are these parts fully compatible with standard NOV drawworks clutch systems?	Yes, all parts are engineered to match OEM dimensions, material specs, and performance standards, ensuring direct drop-in fit for NOV drawworks high/low clutch drives and bearing modules.
What is the hardness rating of the sprocket and clutch gear teeth?	Sprockets and clutch gears feature a hardened tooth surface with HRC 45-50 hardness, delivering exceptional wear resistance and extended service life in high-torque drilling operations.
How do I select the correct shim thickness for bearing preload adjustment?	Refer to your NOV drawworks service manual for specified preload tolerances; our shim kit includes 0.005”, 0.007”, 0.020”, and 1/16” thicknesses to meet precise alignment requirements.

Procurement Guidance & Value Proposition

Secure these high-quality NOV drawworks spare parts to build a robust maintenance inventory, minimize rig downtime, and ensure compliance with industry drilling standards. Each component is manufactured to deliver OEM-level performance, durability, and reliability, making this lineup the ideal choice for routine stock replenishment, emergency repairs, and full drawworks overhauls. With precise fit, premium materials, and consistent quality, these parts reduce long-term maintenance costs and keep your drilling equipment operating at peak efficiency. Reach out to finalize your customized parts order and secure reliable supply for your drilling operations.