Machinist’s Mates — MMs — on conventional (non-nuclear) surface ships operated the main propulsion turbines, reduction gears, ship’s service turbine generators, and auxiliary machinery in the engine room and auxiliary machinery spaces of steam-powered surface ships. Surface ship MMs stood watch in the ship’s engine rooms — maintaining propulsion plant operation during underway periods — and performed machinery maintenance throughout their engineering department tours. The engine room environment in WWII and Cold War era surface ships, with asbestos-insulated turbine casings, steam piping, and auxiliary equipment, placed MMs in sustained contact with asbestos throughout their engineering watch-standing and maintenance work.

Engine Room Watch and Asbestos

MMs standing engine room watch in surface ships built with asbestos construction were in the most asbestos-intensive spaces aboard the vessel:

  • Main propulsion turbine casings — the main propulsion turbines in destroyer, cruiser, and carrier engine rooms had asbestos insulation on turbine casing external surfaces. MMs assigned to propulsion turbine watch stations monitored turbine operation while in immediate proximity to the asbestos-insulated turbine casings throughout each engineering watch
  • Reduction gear and associated equipment — the reduction gear transmitting turbine power to the propeller shaft had asbestos insulation on gear casing surfaces and associated lube oil system components in some engine room configurations
  • Main steam throttle valves — MMs operating the main propulsion throttle valves during maneuvering and watch operations worked directly with the high-temperature throttle valve body, with asbestos packing in the throttle valve stuffing box

Auxiliary Machinery Spaces and Maintenance

MMs performed maintenance on engine room and auxiliary machinery space equipment throughout their engineering tours:

  • Distillation plant operation and maintenance — freshwater distillers (evaporators) producing potable water from seawater used asbestos-insulated steam supply piping and distiller casing insulation in WWII and Cold War era designs, maintained by MMs in auxiliary machinery spaces
  • Lube oil purifier maintenance — routine fuel oil and lube oil purifier bowl cleaning — a frequent task performed by MMs — disturbed asbestos-containing purifier bowl gaskets at each cleaning interval
  • Heat exchanger maintenance — MM waterbox cover removal and tube cleaning on lube oil coolers and feedwater heaters disturbed asbestos waterbox gaskets at each maintenance interval
  • Pump and motor maintenance — MM maintenance on bilge pumps, freshwater pumps, and engine room auxiliary pumps involved disturbing asbestos-containing pump casing gaskets and motor insulation

Surface vs. Nuclear MM Distinction

This page covers conventional surface ship MMs — non-nuclear designated Machinist’s Mates aboard steam-powered surface combatants and auxiliary vessels. Nuclear-qualified MMs (nuclear ratings) operated in nuclear-powered submarine and carrier engineering spaces with a distinct asbestos exposure profile addressed in the Nuclear Machinist’s Mate rating page.

VA Claims for Surface MM Veterans

VA presumptive service connection under 38 CFR § 3.309(d) covers asbestos exposure from steam plant operation and maintenance in Navy engineering spaces. Machinist’s Mates who served in engine room and auxiliary machinery billets aboard steam-powered surface ships built before the mid-1970s asbestos phase-down and have since been diagnosed with mesothelioma, asbestosis, or asbestos-related lung cancer may qualify for VA disability benefits. The MM rating carries one of the highest direct-contact asbestos exposure profiles in the Navy due to sustained watch-standing in asbestos-insulated engine rooms and hands-on machinery maintenance.