be_ixf;ym_202104 d_10; ct_50

In-Situ machining avoids costly propeller shaft removals

USNS Watson class propeller shaft seal liner machining in drydock

Goltens was contracted by Bayonne Drydock & Repair Corp. to perform an inspection and conduct in-situ machining of two propeller shafts on the USNS Watson, a large, medium speed roll on-roll off vessel belonging to Military Sealift Command, while the 33,644 DWT vessel was in drydock.

Initial inspection revealed that the shaft seal had worn channels in the port and starboard shaft seal liner surfaces during operation and the journal surface needed to be restored in-place or the shafts would need to be removed for the repair (at a cost of roughly $850,000 per shaft removal).

Having done this repair on the USNS Sisler (T-AKR 311) in November 2010, and many other times on vessels around the world, Goltens immediately mobilized its tools and specialists to the shipyard to begin the repair. Complicating the repair was the very narrow width of the exposed journal surface giving Goltens roughly 90mm width to mount its tools and complete the precision work.

After making slight modifications to the tooling to fit it to purpose, Goltens began the machining to renew the surfaces with the least amount of material removal possible.

  • USNS Watson in drydock in New Jersey

  • Machining of 848mm tail shaft

  • Machining of 848mm tail shaft

  • Machining nearing completion

IN-SITU MACHINING PROJECT FACTS

USNS Watson (T-AKR-310)
Ship Type: Large, Medium-Speed
Port Dia. Post-Machining: Ro-Ro 847.99mm
Starboard Dia. Post-Machining: 847.47mm

PROPELLER SHAFT REPAIRS

  • Removed roughly .60mm from the diameter of the port propeller shaft seal liner and roughly 1.0mm from the starboard and machined both to a clean surface
  • Finish polished port and starboard propeller shaft seal liners to between 0.20 and 0.25 Ra.

IN-SITU RESULTS

Goltens’ ability to perform the repair in-situ and restore the shaft to its original diameter saved the customer the time and expense of replacing the generator shaft or attempting the repair offsite.

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