Skip to main content

Outage Handling in Thermal and Nuclear Power Plants

An outage is when a power plant takes apart its heaviest machinery on a fixed schedule: turbine and generator rotors, turbine shells, stators, and, in a nuclear plant, reactor and spent-fuel heavy loads that must never be dropped where they could reach fuel or safe-shutdown equipment. UTEC Industrial designs, engineers, machines, fabricates, and installs custom material handling systems for aerospace and heavy industry from its Spokane Valley, WA facility, integrating Allen-Bradley PLC and motion control with in-house CNC machining, heat treating, and stress relief. Public guidance written specifically for fossil-fired plants is thin, so this article draws on the Bureau of Reclamation's overhaul and crane manuals, EPRI's turbine-generator shipping and storage guide, the NRC's heavy-load review plan, and OSHA's rules for generating plants and rigging, and it keeps each point tied to the source that supports it. Outage handling equipment sits on the same build chain as any heavy system, design → engineering → parts machining → fabrication → assembly → weld fatigue → stress relief → drives → controls → tuning → monitoring, with the added constraint that it has to be ready, tested, and working on the day the outage starts.

What makes outage handling different from routine plant handling?​

Routine handling moves known loads along known paths. An outage moves the plant's largest components, often with crews and equipment that do not do the job every day, against a schedule measured in lost generation. Reclamation's overhaul manual, written for hydroelectric and large pump units, frames the preparation in terms that apply to any large rotating unit:

  • Weights first. A list of weights of all machine components should be made from the manufacturer's as-built drawings, with approximate weights calculated where the drawings give none. The list is essential for deciding what rigging the overhaul needs.
  • Laydown. Plant drawings are studied to decide where major components will be stored, taking the allowable floor loading into account, with provision to protect any parts stored outside.
  • Schedule. A critical path flowchart shows task order, durations, and which tasks can run concurrently. The schedule should be realistic, possibly a little pessimistic, with extra time allowed for unexpected problems on the first unit.
  • Checklist. A running checklist records completed tasks and includes the testing and adjustments required before the unit is released for operation.

EPRI's guide adds that the largest components of a steam turbine-generator, such as the generator stator, generator rotor, or turbine rotors, may need a specialized contractor in heavy equipment handling and shipping. The handling plan therefore has to start well before the unit comes off line (Reclamation FIST Volume 2-7, 2024, §2.3 and §2.5; EPRI Report 1022193, 2010, §5.3).

How should the crane and rigging be readied before an outage?​

The crane that makes the heavy lifts may have seen little use since the last outage. Reclamation calls for a careful inspection and operational tests of the power plant crane before the overhaul, with any deficiency corrected before it begins; the inspection, idle-crane, and load-test rules are set out in Powerhouse Crane and Gate-Hoist Duty Cycle Requirements.

Rigging gets the same treatment:

  • All rigging the overhaul will need, such as slings, eyebolts, and shackles, should be on hand well before the overhaul starts, selected from the list of weights.
  • Rigging already on site is inspected to make sure it is safe to use, and special lifting devices supplied by the manufacturer, such as those for the generator rotor or turbine shaft, are located and inspected.
  • An onsite dynamometer is calibrated before the overhaul begins, so crews can see the load on a single-point lift or on one leg of a multi-leg sling.
  • Rigging personnel can be sent to a rigging class, and voice-activated headset radios keep the signaler's and operator's hands free (Reclamation FIST Volume 2-7, 2024, §2.4; Reclamation FIST Volume 4-1A, Rev. 3.0, 2026, Appendix §6.5 and §6.7).

What makes an outage lift a critical lift, and what goes in the lift plan?​

Reclamation defines a critical lift as a nonroutine lift requiring detailed planning and additional or unusual safety precautions, and it designates as critical:

  • a lift where the load is 75 percent or more of the rated capacity of the crane or hoisting device
  • a lift made with more than one crane
  • hoisting personnel with a crane
  • any lift the crane or hoist operator believes to be critical

Further factors also make a lift critical: an item that is unique and would be irreplaceable if damaged, an item whose damage would have a significant negative impact on the facility or its program commitments, a load that needs exceptional care because of size, weight, close-tolerance installation, or susceptibility to damage, and a lift over or near a critical component. A generator rotor, a turbine rotor, or a stator can meet several of these at once.

The manager who designates a critical lift assigns a designated person, other than the crane operator, to supervise its planning and execution and to confirm that cranes, slings, rigging hardware, and below-the-hook devices are current on inspections and load tests. The written plan, approved by a technically qualified person, contains:

  • the identity of the item and its exact weight and size, plus the total load including all crane and rigging components
  • the sequence of events, equipment positions, lift height, and load radius
  • rigging sketches with lift points, attachment methods, load angle factors, and sling angles
  • the conditions under which the lift is to be stopped, and the coordination and communication procedures
  • the names of the lift supervisor, operator, riggers, and others with key roles
  • for tandem lifts, information showing the hoisting equipment is compatible

Depending on the lift, the plan may also include the load's center of gravity, check or hold points, and a load-path sketch showing the path and height at key points (Reclamation FIST Volume 4-1A, Rev. 3.0, 2026, Appendix §6.9).

How are steam turbine and generator rotors, shells, and stators rigged and supported?​

EPRI's best-practice guide on turbine-generator shipping and storage, prepared for EPRI by a consultancy with utility contributors, sets out what the handling crew needs before a major component moves. Its general considerations include the component's configuration, weight, susceptibility to damage and to tilt and roll, and lifting drawings of the component, especially for rotors, shells, and stator, giving rigging points and center of gravity. It stresses that a drawing showing lifting instructions, dimensions, weights, and center of gravity is important to supply to the transportation vendor, and especially for barge or rail shipment, where correct positioning keeps the load from becoming top-heavy and tending to flip over.

For rotors, the guide's practices are specific:

  • Cradles. Rotors should sit in suitable cradles or frames, and an engineered cradle or frame is recommended to ensure its strength. A metal cradle is preferred over a wooden one, and the rotor should not be in contact with a wooden cradle at any time.
  • Support points. Cradle support points should be the support areas designated on the OEM drawings, not the journal areas, and the rigging points from the lifting drawings must stay accessible for lifting the rotor into and out of the cradle.
  • Restraint. The rotor must be positioned and supported so that it cannot thrust in any direction.
  • Generator rotors. A generator rotor should be oriented in its frame so that the rotor poles are in a vertical plane, to minimize potential damage to the windings.

Preparing these components for shipping, receiving, and storage typically involves rigging with chokers, cranes, and chain falls under site-specific procedures for maintaining, inspecting, and training on rigging equipment, and familiarity with the OEM lifting drawings and their center-of-gravity points is required to handle rotors and shells safely (EPRI Report 1022193, 2010, Table 2-1, §2.2.1, §2.3.1, and §5.3).

What handling does a rotor need while it waits in storage?​

A rotor pulled for a long outage, or held as a spare, becomes a storage and handling problem of its own. EPRI notes that a turbine rotor stored for a long period can develop a slight temporary sag or bow under its own weight if it is not fully supported per the OEM's recommendations, and that the longer the rotor, the more likely bowing becomes an issue. Temporary bow is generally removed by rotating the rotor on the turning gear once it is back in the unit, and the allowable bow is typically specified by the OEM.

Each option for controlling bow has a handling cost:

  • Periodic rotation. The rotor must be removed from storage, rotated, re-preserved, and reinstalled, which needs a crane with enough capacity and rigging to lift and rotate it safely. Damage to the rotor or its preservatives is more likely each time it is handled.
  • Center-span support. Ample center-span and cradle supports that keep the rotor straight are described as a cost-effective and less risky solution.
  • Vertical storage. A rotor can be stored on end, heavier end down, if the building structure and crane support allow it, but the OEM should be consulted first.

Generator rotors typically do not need rotating during long-term storage if they are adequately supported, although a bowed generator rotor can make alignment more difficult during installation. In practice, then, the storage cradle is part of the lifting plan: its supports, its access to rigging points, and the crane capacity at the storage location all have to match the rotor (EPRI Report 1022193, 2010, §3.2.1.2 and §3.3.1.2).

How are slings and rigging hardware controlled during outage work?​

Outage rigging is used hard for a few weeks and then stored, which puts weight on inspection. OSHA's sling standard sets the baseline:

  • Daily. Each day before use, the sling and all fastenings and attachments are inspected by a competent person.
  • Alloy chain periodic inspection. Alloy steel chain slings receive a thorough periodic inspection at intervals based on frequency of use, severity of service, nature of lifts, and experience, never more than 12 months apart, with a record kept.
  • Proof tests. New, repaired, or reconditioned alloy chain slings are proof-tested before use and the certificate retained. Welded end attachments on wire rope slings are proof-tested at twice rated capacity before initial use.
  • Removal criteria. Wire rope slings are removed at 10 randomly distributed broken wires in one lay or 5 in one strand, or wear of one-third of the original outside wire diameter. A chain sling is removed from service if a hook's throat opens more than 15 percent or the hook twists more than 10°.
  • Heat. Alloy chain working load limits must be reduced above 600 °F per the manufacturer, and chain heated above 1,000 °F is permanently removed from service, which matters wherever rigging can contact hot plant components.

Reclamation's overhaul manual adds that the weight of any part should never be guessed and that rigging should never be assumed to be strong enough, because sling angles and other factors can load it far above what is expected (OSHA 29 CFR 1910.184-2019; Reclamation FIST Volume 2-7, 2024, §3.3).

How do nuclear plants control heavy loads during outages?​

In a nuclear plant, the handling question is not only whether the load stays on the hook but where it would land if it fell. The NRC's heavy-load guidance grew out of NUREG-0612, Control of Heavy Loads at Nuclear Power Plants, published in 1980. Its review plan for overhead heavy load handling systems, NUREG-0800 Section 9.1.5, defines a heavy load as any load weighing more than one fuel assembly and its handling device, and puts its main emphasis on critical load handling, where an inadvertent operation or equipment malfunction could cause a release of radioactivity, a criticality accident, inability to cool fuel in the reactor vessel or spent fuel pool, or loss of safe shutdown. It treats a dropped heavy load as an internally generated missile against which safety equipment must be protected.

The review plan restates the NUREG-0612 §5.1.1 programmatic guidelines, which apply to heavy load handling in all areas housing safety-related equipment:

  • A. Safe load paths defined to minimize the potential for a load drop on irradiated fuel or safe-shutdown equipment, clearly shown in procedures and equipment layout drawings.
  • B. Procedures for heavy loads near irradiated fuel or safe-shutdown equipment, identifying the required equipment, inspection and acceptance criteria, handling steps, the safe load path, and other precautions.
  • C. Operators trained, qualified, and conducting themselves per chapter 2-3.1 of ASME B30.2-2005.
  • D. Crane inspection, testing, and maintenance per chapter 2-2 of ASME B30.2-2005 before use.
  • E. Lifting devices: special lifting devices meeting ANSI N14.6, or slings selected to ASME B30.9.
  • F. Crane design to CMAA-70 (2000) and chapter 2-1 of ASME B30.2-2005.

In Generic Letter 85-11, the NRC concluded that implementing these Phase I guidelines made a load drop extremely unlikely, and it did not make the Phase II measures, such as interlocks, mechanical stops, single-failure-proof cranes, or load-drop analyses, a generic requirement for operating reactors (NRC NUREG-0800, Section 9.1.5, Rev. 1, 2007, §I and §III.3; NRC NUREG-0612, 1980; NRC Generic Letter 85-11, 1985).

What are the three ways to protect fuel and safe-shutdown equipment from a dropped load?​

Beyond the programmatic guidelines, the review plan asks the licensee to satisfy one of three criteria for loads near irradiated fuel or safe-shutdown equipment:

  • A. Keep the load away. Mechanical stops or electrical interlocks prevent movement of heavy loads over irradiated fuel or near equipment essential for safe shutdown, so that a single load drop cannot disable redundant trains of a system needed for safe shutdown.
  • B. Show the drop is survivable. Analysis demonstrates that releases from damaged spent fuel would be no more than 1/4 of the 10 CFR Part 100 limits of 300 rem thyroid and 25 rem whole body; that damaged fuel or racks would not reach a configuration with k-eff above 0.95; that damage to the reactor vessel or spent fuel pool would not cause leakage that uncovers the fuel; and that damage to equipment would not cause loss of safe-shutdown functions.
  • C. Make the drop extremely unlikely. A single-failure-proof handling system combines a crane built to the single-failure-proof crane criteria the review plan references, with cranes designed to ASME NOG-1-2004 for a Type 1 crane accepted as meeting them, and suitable lifting devices.

Under the third option, the crane's quality assurance program covers procurement, design, fabrication, installation, inspection, testing, and operation, with at least eight elements: design and procurement document control; instructions, procedures, and drawings; control of purchased material, equipment, and services; inspection; testing and test control; nonconforming items; corrective action; and records. A special lifting device for recurrent lifts in critical areas, such as the reactor head, vessel internals, or spent fuel casks, should have dual independent load paths or a single path with twice the ANSI N14.6 design safety factor. Slings should be metallic, chain or wire rope, and should either give dual load paths or be rated for twice the handled load.

The ASME crane standard itself has moved on: ASME NOG-1-2025 is the 2025 edition of ASME's rules for construction of top-running multiple-girder overhead and gantry cranes at nuclear facilities, while the NRC review plan's acceptance refers to the 2004 edition (NRC NUREG-0800, Section 9.1.5, Rev. 1, 2007, §III.4; ASME NOG-1-2025).

How is hazardous energy controlled on handling equipment in a generating plant?​

At a power generation installation, lockout and tagout for the plant's energy sources falls under OSHA's generating-plant standard rather than the general-industry rule. Paragraph 1910.269(d)(1) applies its lockout/tagout provisions to the control of energy sources in installations for electric power generation, while installations in a generating facility that are not an integral part of, or inextricably commingled with, the generation process remain under 1910.147. The generating-plant rule then sets requirements that bear directly on outage handling:

  • Program. Under 1910.269(d)(2)(i), the employer maintains energy control procedures, training, and periodic inspections so that equipment where unexpected energizing, start-up, or release of stored energy could occur is isolated and rendered inoperative before servicing.
  • Stored energy. Under 1910.269(d)(6)(v), after lockout or tagout devices are applied, all potentially hazardous stored or residual energy is relieved, disconnected, restrained, or otherwise rendered safe. A rotor hanging on a crane brake, a gate or cover blocked in a raised position, or a charged hydraulic accumulator on a lifting fixture is stored energy of this kind.
  • Group lockout. Under 1910.269(d)(8)(ii)(C) and (D), when several crews or crafts are involved, one authorized employee coordinates the group lockout, and each authorized employee attaches a personal device to the group lockout device or lockbox.
  • Shift changes. Under 1910.269(d)(8)(iii), procedures ensure continuity of lockout or tagout protection during shift or personnel changes, which matters in an outage running around the clock.

A PLC stop is not an isolation point: the general-industry rule defines push buttons, selector switches, and other control-circuit-type devices as not being energy-isolating devices (OSHA 29 CFR 1910.269-2014; OSHA 29 CFR 1910.147-1989).

What do contract crews and mobile equipment add to outage risk?​

Outages bring in contractor crews, rented cranes, and aerial equipment that do not know the plant. OSHA's generating-plant standard covers the operation and maintenance of generation installations of electric utilities and equivalent installations of industrial establishments, along with related installations such as fuel and ash handling, including coal conveyors. It addresses the contractor problem directly: under 1910.269(a)(3)(i), before work begins, the host employer must inform contract employers of the characteristics of its installation that relate to the safety of the work and of known conditions related to that safety.

Mobile equipment has its own per-shift requirement. Under 1910.269(p)(1)(i), the critical safety components of mechanical elevating and rotating equipment receive a thorough visual inspection before use on each shift, where critical safety components are those whose failure would result in free fall or free rotation of the boom.

Reclamation's practice adds the human layer:

  • Crane operators should familiarize themselves with the rotor lifting device and with signals from the designated signaler before a rotor lift.
  • Two-way headset radios let the signaler give hand signals while the operator keeps both hands on the controls.

The combined effect is that an outage lift has a defined supervisor, a briefed contractor, an inspected machine, and a signaler, rather than relying on one operator's judgment (OSHA 29 CFR 1910.269-2014; Reclamation FIST Volume 2-7, 2024, §2.4 and §3.3; Reclamation FIST Volume 4-1A, Rev. 3.0, 2026, Appendix §6.9).

What sensing, interlocks, and controls protect outage lifts?​

The intelligence layer on an outage crane and its fixtures enforces the plan when the crew is tired and the schedule is tight:

  • Zone restriction. The NRC's first protection option is mechanical stops or electrical interlocks that keep heavy loads away from irradiated fuel and safe-shutdown equipment. One way to build such interlocks is bridge and trolley position sensing that feeds logic blocking travel into a restricted zone while a heavy load is on the hook, with the mechanical stops as the physical backstop.
  • Load sensing. A calibrated dynamometer or crane scale in the rigging shows the actual load, and Reclamation cites it specifically for stuck parts such as a head cover or a thrust block, where the crane can otherwise overload the rigging before the part breaks free.
  • Limits. OSHA 1910.179(n)(4)(i) requires the upper limit switch of each hoist to be tried out under no load at the beginning of each operator's shift, and 1910.179(n)(4)(ii) states that the upper-limit hoist limit switch shall never be used as an operating control.
  • Safety logic. Safety functions such as emergency stop and zone permissives run in a safety controller. Rockwell Automation rates a GuardLogix 5580 primary controller with a safety partner for applications up to SIL 3 and PL e, and ISO 13849-1:2023 is the standard for designing the safety-related parts of the control system. IEC 60204-1:2016 sets general requirements for the electrical equipment of machines.

UTEC Industrial, a Rockwell Automation Recognized System Integrator, builds Allen-Bradley ControlLogix and CompactLogix control systems for heavy handling equipment in UL 508A panels (NRC NUREG-0800, Section 9.1.5, Rev. 1, 2007, §III.4; Reclamation FIST Volume 2-7, 2024, §2.4 and §3.3; OSHA 29 CFR 1910.179-2016; Rockwell Automation 1756-RM012J-EN-P-2025; ISO 13849-1:2023; IEC 60204-1:2016).

How should custom outage handling equipment be specified and scheduled?​

Custom fixtures, cradles, lifting beams, and carts are often what makes an outage lift possible, and they have to arrive tested. Reclamation notes that it is often helpful to fabricate special lifting devices or install a trolley track to ease disassembly, and it sets the acceptance rule for any shop-fabricated lifting device or fixture: designed and certified by a qualified engineer, tested at 125 percent of its rated safe working load, and built with a safety factor of at least 5:1 on tensile strength. EPRI's guide recommends engineered, preferably metal, cradles that support rotors at the OEM-designated points and keep the rigging points accessible.

A specification for outage handling equipment should therefore state:

  • the component weights and centers of gravity from the OEM lifting drawings, with the rigging points and support points the equipment must respect
  • the rated capacity, the 5:1 design basis, and the 125 percent proof test, with the certifying engineer identified
  • the storage, laydown, and floor-loading limits at the point of use
  • any interlocks, limits, or load indication the fixture must provide, and how it ties into the crane's controls
  • the date by which the equipment must be delivered, tested, and ready, set back from the outage start on the critical path

The Corps of Engineers makes the scheduling point from its own hydro work: providing service-ready cranes on schedule is very important to avoid impacts on plant operations and follow-on contracts, and contractors inexperienced in custom crane and hoist machinery have caused costly delays. UTEC Industrial performs factory acceptance testing and on-site commissioning, so a fixture's load test and control checks can be completed and documented before the outage window opens (Reclamation FIST Volume 2-7, 2024, §2.4 and §2.5; EPRI Report 1022193, 2010, §2.2.1; USACE EM 1110-2-3006, 2024, ¶20-6).

Related Articles

References​

  • Reclamation FIST Volume 2-7: Mechanical Overhaul Procedures for Hydroelectric and Large Pump Units. U.S. Department of the Interior, Bureau of Reclamation, 2024.
  • Reclamation FIST Volume 4-1A, Rev. 3.0: Maintenance Scheduling for Mechanical Equipment. U.S. Department of the Interior, Bureau of Reclamation, 2026.
  • EPRI. Shipping Preparations and Storage of Turbine and Generator Components: Best Practices, Report 1022193. Electric Power Research Institute, 2010.
  • NRC NUREG-0800, Section 9.1.5, Rev. 1: Overhead Heavy Load Handling Systems. U.S. Nuclear Regulatory Commission, 2007.
  • NRC NUREG-0612: Control of Heavy Loads at Nuclear Power Plants: Resolution of Generic Technical Activity A-36. U.S. Nuclear Regulatory Commission, 1980.
  • NRC Generic Letter 85-11: Completion of Phase II of "Control of Heavy Loads at Nuclear Power Plants" NUREG-0612. U.S. Nuclear Regulatory Commission, 1985.
  • ASME NOG-1-2025: Rules for Construction of Overhead and Gantry Cranes (Top Running Bridge, Multiple Girder). ASME, 2025.
  • OSHA 29 CFR 1910.269-2014: Electric Power Generation, Transmission, and Distribution. U.S. Department of Labor, 2014.
  • OSHA 29 CFR 1910.147-1989: The Control of Hazardous Energy (Lockout/Tagout). Occupational Safety and Health Administration, 1989.
  • OSHA 29 CFR 1910.184-2019: Slings. U.S. Department of Labor, 2019.
  • OSHA 29 CFR 1910.179-2016: Overhead and Gantry Cranes. U.S. Department of Labor, 2016.
  • USACE EM 1110-2-3006: Mechanical and Electrical Design of Hydroelectric Power Plants. U.S. Army Corps of Engineers, 2024.
  • Rockwell Automation 1756-RM012J-EN-P-2025: GuardLogix 5580 and Compact GuardLogix 5380 Controllers Safety Reference Manual. Rockwell Automation, 2025.
  • ISO 13849-1:2023: Safety of machinery — Safety-related parts of control systems — Part 1: General principles for design. International Organization for Standardization, 2023.
  • IEC 60204-1:2016 (Ed. 6.0): Safety of Machinery -- Electrical Equipment of Machines -- Part 1: General Requirements. International Electrotechnical Commission, 2016.

Ready to Discuss a Material Handling System?​

UTEC Industrial designs, engineers, machines, fabricates, and installs custom material handling systems for heavy industry, from the stress-relieved structure and drives to the Allen-Bradley PLC controls, tuning, and monitoring that run them, at its Spokane Valley, WA facility. Send UTEC the application, loads, and duty cycle to start a system review.

Request a Quote →

Questions? Call (509) 922-1832 or email sales@utec.co

Last updated on