Using new material combinations for VCS main propulsion shafts is expected to save $4M per shaft. U.S Navy photo
The main objective of this project is to identify appropriate solution(s) to the bearing journal wear observed on the VCS main propulsion shafts that is capable of increasing the current shaft replacement cycle from 72 to no less than 96 months. The project will also develop and provide potential solutions for the mitigation of the grooving wear.
The inspections of in-service VIRGINIA Class submarines (VCS) main pro¬pulsion shafts have revealed noticeable grooving of the electro-slag strip (ESS) cladding on the propulsor bearing journal. Naval Sea System Command (NAVSEA) is overseeing a series of coordinated efforts to investigate three individual tasks: (1) identifying the root cause and solution to the bearing journal wear; (2) increasing the VCS main propulsion shaft change-out periodicity to 96 months or more; and (3) developing technologies to provide the necessary background knowledge to achieve the goal of a 144-month shaft change-out periodicity for the Ohio Replacement Program (ORP).
In developing these potential solutions, Navy Metalworking Center (NMC) and the Institute for Manufacturing and Sustainment Technologies (iMAST) will combine the knowledge and the data obtained from the on-board instrumentation suite and use it to provide the Navy with realistic alternatives for improving the lifetimes of VCS main propulsion shafts.
Cost savings originating from longer shaft operational lifetimes can be realized through two primary mechanisms: the increase in shaft change-out periodicity and the need for fewer spare shafts. The cost of each shaft change-out is calculated at $4M, including the labor and material for the replacement of the shaft itself ($3M) and the refurbishment at the vendor ($1M). Indirect cost savings can be attributable to the avoidance of costs involved in the procurement of additional shafts as the current 72 month change out schedule is increased to 96 months or beyond. Considering the cost of a spare shaft ($3.7M), additional savings can also be obtained by decreasing the number of spares.
An Integrated Project Team (IPT) has been formed, consisting of Naval Surface Warfare Center, Carderock Division- Ships Systems Engineering Station (NSWCCD-SSES), Naval Sea Systems Command (NAVSEA), and General Dynamics Electric Boat (GDEB) to oversee shafting programs including this project. Jorgensen Forge and Erie Forge and Steel, Inc., as manufacturers of the main propulsion shaft for VCS will participate to facilitate transition and implementation of project results.
NMC will be primarily responsible for the materials testing and evaluation tasks and iMAST will be responsible for the fluid dynamics modeling and on-board instrumentation suite development tasks. Success begins when NMC and iMAST provide the Navy IPT with the required information regarding the properties of the journal bearing material and the fluid flow conditions in the bearing and also when the Navy implements a solution to the current bearing wear issue.
Note: This project is a joint COE effort between the Institute for Manufacturing and Sustainment Technologies (iMAST) and the Navy Metalworking Center (NMC).
General Dynamics Electric Boat Corporation
Institute for Manufacturing and Sustainment Technologies
Naval Sea Systems Command (NAVSEA)
PMS 450 Virginia Class Program Office
Naval Surface Warfare Center, Philadelphia Detachment