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US guided missile sub Michigan back in water after 18 months in dry dock

USS Michigan
USS Michigan (SSBN 727) undocked at Puget Sound Naval Shipyard & Intermediate Maintenance Facility March 16, 2021. Photo: US Navy

US Navy guided missile submarine USS Michigan (SSBN 727) returned to water on March 16 after spending over a year and a half in dry dock as part of her extended refit period.

The 39-year-old submarine undocked at Puget Sound Naval Shipyard & Intermediate Maintenance Facility where it is receiving repairs that will allow it to put in a few more years of service before retiring.

Michigan is the second-oldest boat in the class, and is expected to retire roughly a year after the lead boat, USS Ohio, bows out in 2027.

According to Melissa Kittrell, assistant project superintendent, Code 327, Operations Department Submarine Program, PSNS & IMF mechanics got to work on Michigan as soon as it was nested on Pier 6, May 22, 2019. They were able to begin relief valve testing and begin preparations to transition from ship’s systems to shore power, before it was moved into dry dock July 9.

Despite the challenges brought on by the COVID-19 pandemic, the project team was also able to complete some additional work that was originally scheduled for the next major maintenance period, along with the work planned for the current ERP, said Kittrell. This work included preservation and repairs to the ship’s superstructure and the main ballast tanks.

The team also completed work on various hatches; work on the sail; the replacement of the ship battery; a shaft change out; work on the steering and diving systems; and work on the external hydraulic plant; among a variety of jobs on other systems and components, Kittrell said.

Since some of the work that was accomplished during this availability isn’t done often, there were lessons learned and documented that could help speed up the same jobs in the future.

“New work was added to completely disassemble and restore the Emergency Diesel Generator, which required extensive interference removals and clearing of rigging paths,” said Kittrell. “We learned a lot about the restoration of the Emergency Diesel Generator and will be passing these lessons on to the project teams who will be tasked with this intrusive repair on future availabilities. We also learned more about the sequencing of work in shaft alley that will help plan work strings and progress work in a more efficient manner.”

Michigan is one of four Ohio-class boats that have been converted from ballistic to guided-missile submarines. The submarines were originally designed to serve for 30 years but were later certified for 42-year service lives, consisting of two approximately 19-year periods of operation separated by an approximately 4-year midlife nuclear refueling overhaul.

Eight submarines in the class are homeported at Bangor, WA, in Puget Sound, while the other six are homeported at Kings Bay, GA, close to the Florida border.

The first of the Columbia-class SSBNs that will replace the Ohios has started construction and is scheduled to start its first deterrent patrol in 2031.