By Lieutenant Alana Davis, U.S. Navy

Introduction: When Maintenance Goes Wrong, or Doesn’t Go at All

In May of 2024 I was working as a Submarine Squadron Staff Officer when news of a submarine sailor’s death spread to our office. Sonar Technician 3^rd Class Timothe Sanders was found dead onboard the in-port USS Helena after inadvertently touching an energized 440 Volt electrical panel improperly returned to service following a tagout for maintenance. Having spent the first year of my tour as a Submarine Division Officer assigned to a boat in shipyard drydock, and the following two years at sea, but in and out of continuous maintenance availabilities (CMAVs), I shudder to think STS3 Sanders could have easily been one of my sailors, or me.

When I reported to that submarine in shipyard I was assured we’d deploy again in a few months as the 1.5 year scheduled availability neared completion. One year later, we were finally “underway on nuclear power” with an overworked, mentally drained crew dangerously devoid of at-sea experience. Unfortunately, neither of these scenarios are unique to most U.S. Navy sailors. Standard onboard safety trainings involve cautionary stories of past injuries and deaths from electrocution or exposure to high pressures and temperatures from improper system line-ups. The Government Accountability Office published a study assessing from 2015-2020 75% of planned maintenance periods for submarines and aircraft carriers were delayed, with average delays at 225 days for subs and 113 for carriers. Two main causes identified include unplanned work and limited shipyard workforce capacity. Not assessed was the mental toll such delays take on sailors, with some studies estimating >50% increase of suicides for shipyard aircraft carrier crews versus crews at sea.

The U.S. Naval surface and submarine fleets continue to be plagued by two critical maintenance problems: danger and delays. From my perspective as a junior officer who coordinated, authorized, and supervised countless preventative and corrective maintenance procedures at sea and in shipyard, tackling these problems starts with tackling one essential aspect of nearly every maintenance item: the tagout process. Utilizing smart technologies including 3D Computer Aided Design (CAD) modeling and artificial intelligence/machine learning (AI/ML) advancements to modernize the tagout process will make shipboard maintenance safer and faster, and will serve as a technological foundation for further advancements in maintenance optimization and prioritization.

The Shipboard Tagout Process Today

What does performing a tagout entail? You can start by reading the 100+ page NAVSEA published Tag-Out Users Manual or “TUM”. The stated purposes of utilizing the tagout method are to:

• “Provide for personnel and ship safety and prevent damage to equipment.
• Prevent improper operation when a component, equipment, system or portion of a system is isolated or in an abnormal condition.
• Prevent improper operation when a freeze seal is applied to a system or when other safety devices such as blank flanges are installed for testing, maintenance, or casualty isolation.
• Provide a procedure for use when an instrument is unreliable or not in its normal operating condition.
• Provide standard tag-out procedures.
• Provide a procedure for control of hazardous energy.”

In practice, a tagout starts with a procedure that requires making safe a fluid, air, or electrical system with components experiencing faults, or entering that system to conduct maintenance. To do so safely, typically multiple components within need to be re-positioned or de-energized. Some processes, like rigging a submarine for divers to enter the water around it in port, are routine enough that a written list of every component that must be repositioned and tagged exists in the procedure. By contrast, performing corrective maintenance on a broken component requires an individualized system line-up and tag-out plan. Enlisted sailors must identify and “prove” the validity and system isolations of the proposed tag-out to the Authorizing Officer, usually a junior officer. Sailors should develop this line-up by tracing through the system drawings, then get validation from a second, independent sailor that the isolations are adequate. The Authorizing Officer will review their work, verify the adequacy of the tag-out, and using her own system knowledge, hand trace the sailor’s work and either authorize or non-concur with the tagout. Especially high-risk repair evolutions may require additional approvals from either the relevant Department Head or the Commanding Officer.

From there, the process moves only slightly to the electronic. The sailor will list the components to be tagged for that maintenance item in eTagOut, the tag-out tracking software. The officer again reviews the list in comparison to the system drawing, signs off electronically and prints the component labels with their agreed upon positions to be placed to. She sticks those labels on physical tags, signs for their validity, then orders the sailor conducting the tagout to “reposition components and hang tags as briefed”. One sailor will hang a tag on every component he repositions and signs for the new positions. A second, independent sailor will then second check and sign for the accuracy of the new lineup. The new system lineup will be filed on paper in a binder and maintained until the tags are cleared to restore the system to a its regular line-up or a new tagout replaces the existing one. Some of these documents go back months, even years, and can be forgotten or go un-updated. Worse, with frequent turnover and high volumes of work, paper tracking and electronic tracking can develop differences, leaving the true status of the system in question.

It can take from hours to days for sailors to identify components, prove tagout adequacy, and safely align systems prior to starting even relatively routine maintenance items. The safety and effectiveness of the line-up also largely depends on the system understanding and attention to detail of the writer and approvers of the tagout. But no matter how bright, thorough, and well-trained sailors and repairmen are, we are fallible, particularly when confronted with a dizzying array of tagouts and maintenance items to be performed every day to meet operational deadlines.

Industry and Government Efforts

The tagout process is not unique to the Navy. Lockout/Tagout or “LOTO” is a standardized Occupational Health and Safety (OSHA) practice across industries. Much like the Navy, though, mishaps from procedural non-compliance also occur – to the order of 50,000 injuries U.S.-wide annually.

Software companies like Quentic are beginning to tackle LOTO deficiencies via advanced digital systems. Their technology focuses on implementing tracking monitors on shopfloors, providing LOTO-related training like workflows and checklists, and tracking equipment performance metrics like downtimes and protocol adherence. What these capabilities lack is the ability to address the validity of the planned tagout itself. Though the technology integrates with components, it does not provide a holistic system understanding and user-interface to check for safety compliance prior to conducting a LOTO procedure, vice after the equipment manipulations have taken place.

As of July 2026, the Department of Navy is directly partnering with software firms to modernize different aspects of maintenance practices. Two companies, Air and Fathom5, have been tasked to modernize how the Navy manages repair processes with the goal of achieving 90% fleet readiness. This collaboration focuses on implementing AI to existing enterprise logistics software to connect disparate maintenance systems help units get ahead of equipment failures by predictive algorithms, faster part identification, and automated work order processing. This integration should speed up maintenance efforts broadly, particularly regarding repair part location and procurement, but again does not tackle technologizing the time-intensive and error-fraught tagout process.

Naval Adoption of Model-based Systems Engineering (MBSE)

In February 2026, Congress amended the FY25 National Defense Authorization Act portion on Navy vessel design to require that functional design certification for crewed and undersea vessels be based on 3D modeling of the vessel to include all major distributive systems. Years prior, in 2020, the Navy and Marine Corps took a broader step towards digital modernization, releasing the Digital Systems Engineering Transformation Strategy, laying out the framework to transition traditional “document-centric” systems engineering practices to “digital-centric” ones. The strategy aims to apply data analysis and modeling via a modern Model-based Systems Engineering (MBSE) approach thereby formalizing the use of integrated digital modeling, incorporating AI/ML into software development, and merging design and development tools with simulation and testing ones.

Since the early 2000s the Navy has been putting 3D CAD modeling technology to good use. The Virginia Class SSN was the first U.S. warship completely designed using CAD and visualization technology. The USS America and proceeding America Class LHAs utilized CAD software including ShipConstructor and Autodesk throughout the design and construction process capturing essential engineering components to include structural, C4I, electrical, propulsion, and auxiliary systems. It’s safe to say all future Naval vessel design efforts will continue to rely heavily on 3D CAD technologies. However, it is up to the government to appropriately negotiate Government Purpose Rights to ensure these models and accompanying technical data are appropriately accessible to the Department of War and the Department of the Navy.

MBSE Provides the Backbone for Tagout Process Revolution

How does this recent DoN embrace of digital MBSE practices in design enable modernization of the tagout process? It starts by providing confidence that high-fidelity digital systems models exist along with the software backbones to manipulate and test within them. Some of the broad functions of MBSE include to: “offer a scalable and traceable digital model of the system and it’s requirements… ensure that all requirements are validated in the operational environment of the system… (and) enable stakeholders to interact within the collaborative modeling environment…” These models and manipulation functions are exactly what ship’s force and shipyard repair activity will require to digitally address system line-ups for tagouts.

Since interactive digital systems models already exist, if a digital tagout platform was built out of this, here’s what the tagout process could look like:

• A shipboard maintenance item requires tags to be hung. The sailor preparing to conduct the maintenance opens the AI-enabled digital tagout generating software. She selects the appropriate digitized system diagram, the compent she intends to conduct maintenance on, and inputs additional information on other conditions for the maintenance like ship conditions, limitations, or specific safety requirements established by the Commanding Officer.
• The software absorbs that information and outputs a recommended valve line-up and list of components to manipulate and hang tags on. This output can be visually verified with a testing function where flow paths could be demo-ed and relay a written risk assessment for conducting the repair based on its real-time record keeping of all the other maintenance and tagouts taking place onboard.
• Once the sailor is content with the software’s recommendation, the results for the pending tagout are transmitted to enlisted divisional leadership and an officer for review and approval. Once the tagout is authorized and properly hung, the digital system is updated with the touch of a button to visually reflect every component’s new status.

Time to conceptualize and generate a tagout would now take minutes rather than hours. The additional manpower hours required to hand-route paper diagrams for review prior to starting a maintenance item are eliminated, drastically reducing lead-up time to commence work within any system. Besides reducing time and increasing confidence in safety, a digital process also relieves the headache and confusion of tracking every shipboard component position on paper. Currently, submarine officers on watch track the thousands of tags hanging across the boat via a massive binder full of paper logs and a few mounted, plastic covered diagrams of critical system components that get marked with grease pen whenever they’ve been manipulated from their “normal” status.

Beyond Tags: Further Opportunities for Smart System Integration into Maintenance Practices

The U.S. surface and submarine navies have already been using logistics-focused software for years to assist in shipboard maintenance tracking and preparation. This technology group includes:

• Planned Maintenance System Management Information System (PMSMIS): Web application to track new and revised PMS documents.
• Ships’ 3-M: Database for maintenance-related execution data.
• Open Architecture Retrieval System (OARS): Enables 3-M reporting, analysis, and user metrics.
• System Scheduler (SKED): Provides the capability to schedule and manage maintenance events and allows reporting of completed maintenance while providing sailors the ability to submit first-person technical feedback what was conducted.

Onboard a submarine is the crew’s “3MC” (Maintenance and Material Management Chief) who oversees the 3-M related systems data and upkeep. Department Heads, Division Officers, and enlisted divisional leadership monitor and update their required preventative and corrective maintenance plans within SKED. Divisions accomplish periodic (weekly, monthly, quarterly, etc) required maintenance items on schedule as well as document new material deficiencies as they arise.

But even with the help of logistics software, two critical problems remain:

• The burden of maintenance, both at sea during shipyard availabilities, is immense and overwhelming. Perfectly planning maintenance sequences are nearly impossible, resulting in re-opening freshly closed systems and re-work due to poor sequencing and late-discovered equipment.
• Surface and submarine crews are more accustomed to operating in a peacetime environment when “fighting hurt” is not required and returning to port for repairs is possible. Making quick decisions on how system damage should be triaged and how to best rig and repair a ship to keep fighting at sea vice when it would endanger the life of the vessel and crew is not a skillset submarine crews at sea regularly, or voluntarily, practice.

The existence of digital PMS-updated documentation and sailor-updated 3-M tracking in SKED means there is a rich digital data source of historic and current system and component level maintenance that is unique to every surface and submarine vessel. This detailed data is ideal for training AI/ML algorithms on ship-specific system and component intricacies and vulnerabilities. Combine this data-driven learning with smart 3D CAD system models and you have a ship-specific comprehensive maintenance planning tool in peacetime and a maintenance triage assistant in war.

• AI/ML can advance maintenance planning by optimizing maintenance by need precedence and can eliminate system-entry redundancy by analyzing for optimal sequences of required maintenance and required testing. For example, assessing component age and likelihood of faulting means an AI-based planning tool could recommend conducting a testing procedure earlier which would likely ID the predicted component fault. Without this modeling, maintenance might have otherwise gone on within that system prior to the test, only to have to be re-conducted post a test failure.
• AI/ML planning tools integrated into a user-friendly CAD system software that generates system line-ups and tagouts means Commanders can rapidly assess best and worst-case scenarios and rank system faults based on highest assessed risk to ship and crew. This software is a Commander’s decision aid when equipment fails or is damaged at sea and can provide rapid damage assessment. This tool can predict how much time the vessel might have to keep fighting or recommend the conservative system line-ups that might be required to make it back to port.

Conclusion: Not a Sailor Replacement, But a Lifesaving Tool

The nuclear submarine force instills a list of concepts in every sailor known as the “Watchstanding Principles”, which include: Integrity, Ownership, Level of Knowledge, Questioning Attitude, Forceful Back-Up, Formality, and Procedural Compliance. Modern advancements in 3D modeling, interactive software, and AI/ML will never negate the need for these principles, but they can support these principles as operator aids.

The Navy is taking steps toward a technical revolution in advanced 3D modeling for vessel design and construction and in logistics software integration enabling smarter maintenance planning. But the revolution is missing a critical objective: improve the day-to-day lives of the sailors maintaining these vessels by tackling what takes up too much of their time and incurs them too much unmitigated risk. This can be done by leveraging existing CAD models, user-interfaces, and AI/ML algorithms, to digitize the existing labor intensive and risk-fraught paper tagout process. Tackling the tagout process with smart software can lead to further time saving and risk reducing advancements in maintenance planning in port and better repair triage at sea.

The benefits don’t just stop with the Navy. There are nearly 2,800 reported incidents readable on OSHA’s database described by the key word “lockout/tagout”, too many of which also include the words injury or death. Sailors and industry workers alike do their best to keep systems running and keep people safe. But methods for doing so when conducting the ever-present maintenance and repairs that require tagouts rely on manual primitive processes. The digital era for maintenance is here. It’s time for the Navy to make a change. Tag, you’re it.

Lieutenant Alana Davis is a U.S. Navy submarine officer and a force manpower planner under the Chief of Naval Personnel. She was previously assistant operations officer aboard the USS Michigan (SSGN-727) and a staff officer at Task Force 54 in Bahrain. She holds a bachelor’s degree in engineering sciences from Harvard University and  an MBA from the University of Florida.

The views presented here are those of the author and do not represent the views of the U.S. Navy, the Department of Defense, or any other organization with which the author is affiliated.

Featured image: Damage Controlman 3rd Class Dylan Hasley, a Sailor assigned to the Wasp-class amphibious assault ship USS Bataan (LHD 5), uses a portable exothermic cutting unit (PECU) to cut apart a detachable anchor chain link which needed to be replaced after its taper pin had become stuck, in the ship’s forecastle, Sept. 23, 2026. (U.S. Navy photo by Mass Communication Specialist Seaman Apprentice Jackson C. Rott)