Human fatigue mitigation measures in the specification and design of ships and their environmental condititions.
Module 5 - Fatigue and ship design
- Module 5 highlights human fatigue mitigation measures which may be utilized in the specification and design of ships, their living and working spaces and their machinery installations. Module 1 (Fatigue) should be read prior to going through this module.
- The design principles for fatigue mitigation and management should be considered early in the design process.
- Fatigue is a hazard that affects safety, health and well-being. It presents a considerable risk to safety of life, property, health, security and protection of the marine environment. Because seafarers live and work aboard ships, sometimes for an extended period of time, they may be exposed to conditions that cause fatigue. Therefore, the design, layout and arrangement of working and living areas should be considered as part of mitigating and managing the risk of fatigue on board ships.
- Shipboard ergonomics and the environmental conditions on board are important considerations in ensuring seafarers are provided with the best opportunity to:
.1 maintain safe levels of alertness and performance during work periods;
.2 maintain good health and resilience to fatigue through the provision of adequate rest, recreational and exercise facilities; and
.3 obtain adequate restorative sleep; as highlighted in module 1, inadequate restorative sleep (both quantity and quality) is among the main causes of fatigue and can be affected by the living and working environment on board.
What aspects of ship design can influence fatigue?
- There are various aspects of fatigue that can potentially be influenced by the design of the living, sleeping and working environment. Fatigue can be caused by excessive noise, heat or cold, light, too much or too little humidity and poor air quality, among others, where people live and work.
- Sleeping, living and working areas should be located within the ship to minimize undesired motions, vibrations and noise.
- Appropriate noise levels (SOLAS regulation II-1/3-12) support effective communication and reduce mental workload while on duty, and enhance quality of sleep and rest when off duty. Noise and vibration prediction modelling efforts should be done early in the vessel design process to ensure the most effective design and layout for noise and vibration control and mitigation. See also paragraph 31.3 below, which refers to the Code on noise levels on board ships (resolution MSC.337(91), which is mandatory for some types and sizes of ships.
Accommodation spaces and layout design (design to promote rest and well-being)
- Crew accommodation is often located in positions likely to be affected by machinery-induced noise and vibration (including cargo transfer systems) and propeller-induced noise and vibration. Steps should be taken early in the design stage to alleviate this. Noise sources internal to the accommodation also need to be considered and noise levels generated by the heating, ventilating and air conditioning (HVAC) systems should be controlled.
- Sources of intermittent machinery-induced noise and vibration caused by machinery stopping and starting on a cyclical or irregular basis should also be considered.
- Measures to reduce disturbance from impact noise from human activity in corridors and service spaces above and/or adjacent to accommodation should be incorporated in the ship design.
- Consideration should be given to:
.1 ensuring cabins are cool, quiet, dark and well ventilated;
.2 bunk design, layout and orientation;
.3 mattress, bedding, padding for ship movement, headroom clearance especially upper bunk/deckhead;
.4 insulating and/or isolating sleeping areas;
.5 use of colour and artwork in the cabins; and
.6 use of acoustic insulation and/or other noise-abatement measures.
- Notwithstanding the above, consideration should be given to sounds that need to be heard, e.g. fire alarms.
- Consideration should also be given to providing an accommodation area that is conducive to rest and that aids recovery. As far as reasonably practicable, the following should be considered:
.1 design for minimal crew flow in sleeping quarters;
.2 laundry, changing, hygiene, privacy;
.3 insulation or isolation from cargo, engine, other disturbances (noise and vibration);
.4 design lighting to support day and night sleep (lighting/dimmers and block-out);
.5 ventilation/air quality;
.6 temperature locally adjustable and humidity (design for sleep); and
.7 location and layout of galley and mess room(s).
- It is also important to consider design for recreation and recovery. Aspects to consider include:
.1 range of needs (personality and culture);
.2 privacy and social life;
.3 minimal housekeeping;
.4 gym/training facilities; and
.5 library, media rooms, ease of study.
Workplace design (design for alertness and performance)
- Workplace design, particularly for tasks that require sustained physical or mental exertion, should consider the following aspects:
.1 design of the workplace and workflow for optimum layout (placement, storage, adjustable, visibility, ease of communication, ease of movement, noise, vibration, temperature, humidity);
.2 working position (seated/standing, height, flooring material (shock and balance);
.3 usability (displays and controls incorporate ergonomic and task requirements);
.4 protection from hazards (e.g. provide suitable hand holds, barriers, signs, stairs and surfaces to allow easy movement in bad weather);
.5 design lighting for work spaces to support alertness (colour, natural light access, bright light); and
.6 maintenance – design for maintainability (access envelopes accounting for required tools and motions, etc.).
- Additionally, design of control centres such as machinery control room layout, cargo control room layout and the bridge, should consider the integration of people with equipment and systems to enhance system resilience to crew fatigue, as well as reducing mental overload and boredom.
How can ergonomics support the mitigation and management of fatigue on ships?
- Ergonomics/human factors are defined as the scientific discipline concerned with the understanding of interactions among human and other elements of a system, and the profession that applies theory, principles, data and methods to design in order to optimize human well-being and overall system performance.
- Ergonomically designed work systems enhance safety, effectiveness and efficiency. They support shipboard tasks under all conditions, including situations where people may be fatigued.
- The ergonomics approach to design is human-centred. This means that all designable components (e.g. ship, ship's systems, equipment, service) are fitted to the characteristics of the intended users, operators or workers (e.g. seafarers, maintainers) rather than selecting and/or adapting humans to fit the system and/or product. This should be done by considering:
.1 the intended target population;
.2 the task, goal or intended outcome of the system, product or service; and
.3 the environment in which the design is to function.
- Both the needs and limitations of the end users (e.g. seafarers, maintenance or repair teams) should be considered during the design of ship systems and equipment. Those with experience and knowledge of the requirements of ship systems and equipment should be consulted, as far as possible, during the design and construction phases of new ships. Early and continued participation and involvement is regarded as an efficient design strategy, especially within ergonomics, since, in addition to improving the design, it reduces late-stage re-work and increases user acceptance.
- Ergonomic design is task-oriented: it takes into account differences that can be observed between the designed task and the way the task is actually performed. Activities in performing a task are affected by variations and changes in context, procedures, equipment, products or materials, for example.
- The relations between the conditions and demands placed on the seafarer and their response to being exposed to such conditions and their effects need to be considered in the design of ship systems, services, products and tasks in order to avoid impairing effects on the individual. The response to conditions and demands is dependent on individual characteristics (e.g. body size, age, capacities, abilities, skills).
- Standards are available giving guidance on how to incorporate ergonomics into the design process, e.g. ergonomic principles in the design of work systems. A list of appropriate standards are included in the reference list.
What tools are available for designing/building fatigue resistant ships?
- The application of ergonomic standards and guidance is effective for improving the working environment, particularly those that deal with environmental conditions (such as temperature, noise, vibration, ventilation).
- Computer simulation tools can be used to support ergonomic design. These are increasingly being used to assess both the impact of environmental conditions as well as work and living design ergonomics. Examples include virtual reality and three-dimensional computer aided design. Use of aimulation tools is encouraged as they allow early and more cost-effective evaluation of various aspects of design. There are a variety of design tools that can be applied early in the design process to assist the ship designer in ensuring that specified limits are not exceeded. Wherever possible, and if available, anthropometric data and standards should be utilized to support ergonomic design.
- Environmental conditions also extend across structural design, propulsion, hull forms and several other aspects of design. Often, constructional solutions may be employed to improve environmental conditions. For example, the transmission of noise can be reduced by the insertion of acoustic insulation; similarly, structural resilience techniques can be used to alleviate vibration problems.
- Use of Finite Element Analysis (FEA) and noise and vibration prediction tools to reduce noise and vibration is generally more cost-effective than post- construction noise and vibration mitigation.
- Similarly, seakeeping prediction tools may be used, together with ship and propeller model testing, to predict velocity and acceleration levels that can affect habitability.
What rules and guidance are available for designing/building a fatigue resistant ship?
- There are a number of rules, regulations, standards and guidelines designed to enhance environmental shipboard conditions, which can be used by the ship designer to reduce fatigue. This is a developing field and the designer should check for new material.
- Some aspects of crew accommodation are subject to regulations under th International Labour Organization's Maritime Labour Convention (MLC), 2006, in particular Title 3 (Accommodation, recreational facilities, food and catering). Crew accommodation is also subject to national standards. Classification societies have guidance and optional notations for aspects of environmental conditions (e.g. noise and vibration) for certain ship types (see reference section for examples). Designers are encouraged to refer to the relevant guidelines.
Noise and vibration
- IMO has implemented requirements and resolutions aimed to protect the seafarer from unacceptable levels of noise:
.1 SOLAS regulation II-1/3-12 (Protection against noise).
.2 Code on noise levels on board ships (resolution MSC.337(91)) (this Code is mandatory under SOLAS regulation II-1/3-12, which entered into force on 1 July 2014); and
.3 Code on noise levels on board ships (resolution A.468(XII)) fixes permissable maximum limits of noise depending on the type of space.
- In addition, MLC, 2006, Title 4 addresses noise and vibration. Relevant ISO/IEC standards on noise and vibration should also be considered throughout the design process (see references).
Working spaces
- Regulations and standards exist for dealing with improvements to working spaces which may help in reducing fatigue and its effects. These are developed by organizations such as IMO, ISO/IEC and classification societies. Reference to these standards in ship design is encouraged (see reference section).
References
- American Bureau of Shipping (ABS), Guidance Notes on Noise and Vibration control for inhabited spaces. September 2017.
- American Bureau of Shipping (ABS), Guidance Notes on the Application of Ergonomics to Marine Systems. February 2014. ww2.eagle.com
- American Bureau of Shipping (ABS), Guide for Crew Habitability on Ships. February, 2016.
- Calhoun, S. R., (2006). Human Factors in Ship Design: Preventing and Reducing Shipboard Operator Fatigue, in Department of Naval Architecture and Marine Engineering, University of Michigan.
- ClassNK, Noise and Vibration Guideline (2nd Edition), June 2014.
- ClassNK, Guidelines for the mandatory Code on noise levels on board ships (3rd Edition), March 2018.
- DNV GL Comfort Class: Rules for classification, Ships, Part 6 Additional class notations, Chapter 8 Living and working conditions, Section 1 Comfort Class - COMF. 1. January 2017.
- IMO MSC/Circular.834, Guidelines for engine-room layout, design and arrangement.
- IMO MSC/Circular.982, Guidelines on ergonomic criteria for bridge equipment and layout.
- ISO 11064-1:2000 Ergonomic design of control centres – Part 1: Principles for the design of control centres.
- ISO 1999:2013 Acoustics – Determination of occupational noise exposure and estimation of noise-induced hearing impairment loss.
- ISO 20283 Mechanical vibration – Measurement of vibration on ships:
. Part 2 (2008): Measurement of structural vibration
. Part 3 (2006): Pre-installation vibration measurement of shipboard equipment
. Part 4 (2012): Measurement and evaluation of vibration of the ship propulsion machinery
. Part 5 (2016): Guidance for measurement, evaluation and reporting of vibration with regard to habitability on passenger and merchant ships.
- ISO 2631 (Series) Mechanical vibration and shock – Evaluation of human exposure to whole-body vibration.
- ISO 26800:2011 Ergonomics -- General approach, principles and concepts.
- ISO 6385:2016 Ergonomics principles in the design of work systems.
- ISO 6954:2000 Mechanical vibration and shock – Guidelines for the overall measurement, reporting and evaluation of vibration with regard to habitability on passenger and in merchant ships.
- ISO 8468:2007 Ships and marine technology – Ship's bridge layout and associated equipment - Requirements and Guidelines.
- ISO 9241-110:2006 Ergonomics of human-system interaction – Part 110: Dialogue principles.
- ISO 9241-210:2010 Ergonomics of human-system interaction – Part 210: Human-centred design for interactive systems.
- ISO 9241-5:1998 Ergonomic requirements for office work with visual display terminals (VDTs) – Part 5: Workstation layout and postural requirements.
- ISO 9241-6:1999 Ergonomic requirements for office work with visual display terminals (VDTs) - Part 6: Guidance on the work environment.
- ISO/TS 20646:2014 Ergonomics guidelines for the optimization of musculoskeletal workload.
- Lloyd's Register, Rules and Regulations for the Classification of Ships, July 2016 – Part 7 Other Ship Types and Systems – Chapter 12 Passenger and Crew Accommodation comfort.
- Lloyd's Register, Ship Vibration and Noise, Guidance Notes, Rev 2.1, 2006.
- Lloyd's Register, The Human-Centred Approach: A Best Practice Guide for Ship Designers, Lloyd's Register 2014 (available from www.webstore.lr.org Marine/Technical Guides).
