Solutions & Case Studies
Tapered Roller Bearing Alternative
Customer: A natural gas drilling rig manufacturer
The Application: When drilling for natural gas the drilling mud often returns to the surface under pressure from a gas pocket below. A Rotating Drilling Head or Flow Diverter is used to seal the drive connection at the surface and provide a rotating connection for the return mud piping. The Flow Diverter must have a large enough bore for the drill string to pass through so the bearings are often larger than their required capacity. Two large tapered roller bearings provide for both the radial and thrust loads, but a thin section pilot bearing is often needed to maintain a constant seal gap in the upper and lower positions.
The Problem: The Company had been using Timken tapered roller bearings in the two Grant Rotating Drilling Head they sold and serviced. Whenever a seal failure occurred drilling mud would get into the bearings. The bearings would silt up with fine stone particles and begin to rust. In the past, Timken cones could be disassembled, cleaned, and polished. However, Timken’s new cage design does not permit the rollers to be removed for this maintenance, so new bearings must now be used whenever a seal failure has occurred. This is not only expensive, but has become very difficult, due to the long lead times these large bore bearings are experiencing. Timken is the only traditional bearing company who manufactures these sizes.
The Product developed: With so many of these large bore bearings that only needed cleaning available in the Company’s shop, our initial idea was to create a retrofit cage design that enabled these bearings to be reconditioned and used again in service. We designed and proto-typed a machined steel cage with slots in the cage bars that were to be bent with a screwdriver to retain or remove the rollers. The initial tests went well, but the cost of the cage and the lead time required for any new bearings were still a problem.
Using this feedback we proposed that the bearing be changed to a unitized full complement angular contact ball bearing that would have the same boundary dimensions as the original tapered roller bearings, but have the ability to be easily disassembled, cleaned, and reassembled. New balls could be used if necessary. We presented the benefits of our new design to the Company and convinced them to place a production order for both sizes.
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