01 March 2004
Reduce costs of retrofitting a control room to comply with governmental regulations.
By Karen Smith and Brad Walker
Imagine yourself as the engineering team leader of PetroTech, Inc., a petrochemical company with several processing plants throughout the country.
The company decides to upgrade one of its processing facilities to increase production efficiency, and you plan to consolidate three control rooms into one centralized control suite.
To facilitate the redesign of the new control suite, you organize a design team consisting of plant personnel who must develop the basic layout of the building and determine the number of screens required, the console configuration, and the arrangement of the consoles in the room.
You base your decisions for the new control room heavily on budgetary constraints. Even though you want your control room to use the latest in control technology, you have your design team configure it in a similar layout to the original because it worked well and you see little reason for change. Your plant supervisors have briefly referred to communication issues, traffic patterns, the sharing of resources and equipment, and the operators' resistance to change, yet these issues do not drive the decision-making process. The console, utilizing standard features, comes out of a single catalog without discussing other options from other vendors.
After spending $40 million on your control room and plant upgrade, the control room goes online. Control personnel complain about excessive glare on the screens, inadequate console work space, their inability to communicate with other operators, and various distractions caused by traffic and noise in the room. These problems negatively affect the productivity of the work environment, and worker morale starts to degrade. The plant manager notices that there is an increase in employee absenteeism, worker injuries, and accidents in the plant. Your company experiences production losses of more than $50 million in the next three years, and several lawsuits resulting from an explosion are still in litigation.
Although this is a fictional scenario, situations such as this occur in many control rooms in today's manufacturing sector. Management, plant personnel, and control room designers often overlook the console's impact on plant safety, productivity, and operator performance, and they fail to consider ergonomic principles when upgrading or building control suites. Instead of concentrating solely on process control aspects of a control room, designers must consider the working environment of the operators. An optimal working environment becomes even more important as the demands on performance and production increase.
Up to industry to regulate
Ergonomics, which take into account an operator's interaction with his or her working environment, will play an important role in the design of control rooms in the near future. Currently, the government has left the implementation of ergonomic principles up to industry to regulate. However, the Occupational Safety and Health Administration (OSHA) and other standards-based organizations are beginning to address ergonomic concerns in the workplace as evidenced by recent draft regulations and standards.
OSHA believes that the proposed regulations are needed to protect employees from incurring work-related injuries resulting from improper work environments. Under the proposed OSHA regulations, companies are required to invest resources in new equipment design and in redesign of current equipment to bring their workplaces into compliance. Some sources estimate that companies will spend more than $21 billion to alter workplace environments to comply with the regulations.
The International Organization for Standardization (ISO) also has proposed standards concerning the implementation of ergonomics in the workplace. Specifically, ISO Standard 11064, parts 1 through 6, sets forth practical guidelines for the implementation of ergonomics within the control room environment. Current design solutions must take into account these regulations and standards, because when formalized they will become standard practice (currently, only ISO Standard 11064, part 3, has been formally adopted as a standard). Thus, the pending ergonomic standards will serious affect the design of future control rooms.
Between humans and machines
The concept of ergonomics is nothing new. First coined in 1857 by Wojciech Jastrzebowski in a Polish newspaper, the term ergonomics comes from the Greek ergo (work) and nomos (law or rules): work rules. Although the concept of ergonomics has been around for many years, it did not come into accepted usage until 1949 when post-war construction resurrected the term to describe the increasing importance of interactions between humans and machines. It was not until the late 1980s that ergonomic design began to enter the petrochemical processing industry.
Ergonomics involves the interaction of human factors (the physical and mental capacities and limitations of the worker) with the machines and equipment in the work environment. It requires an understanding of all aspects of how employees function and how they interact with various tools and systems when performing tasks. With this understanding, those tasks can be performed in a safe and efficient manner. For example, new knowledge about repetitive stress injuries has modified how we now design keyboards. Adding wrist supports and eventually changing the layout and arrangement of the keys will reduce incidents of carpal tunnel syndrome. As another example, the design of operator seating now takes into account human postural variations and height differences. By supporting the back, legs, and arms, chairs now enhance alertness and productivity.
The underlying principle of ergonomic design is to promote worker health and safety. This makes economic sense because improving working conditions in the control room correspondingly can affect operator performance, productivity, and overall job satisfaction. These factors translate into reduced absenteeism and higher plant productivity. Additionally, more emphasis on workplace safety results in fewer incidents of injury and accident, thus reducing worker's compensation and insurance costs for the company.
This statement is supported by a recent National Institute for Occupational Safety and Health (NIOSH) study of five companies that incorporated in their facilities ergonomic designs that addressed work-related musculoskeletal disorders. The NIOSH study found that these companies reduced their worker's compensation costs by as much as 91%.
The design and selection of the control console demonstrates the advantages of ergonomic design. Console operator productivity and safe operation of the plant depend on careful consideration of the selection, layout, and design of the tools provided to the operator. The operator's tools for controlling the plant—the keyboards, work space, and monitors, e.g., the console itself—should be of utmost importance in the design of the overall control room.
You should not implement console selection in a haphazard manner or without input from the end user. Ideally, it should be incorporated as early as possible in the project's design phase. The ergonomic principles used in console design influence the layout of the operator's work space, the location of visual displays, and the size, shape, and placement of the individual console relative to those displays. Good ergonomic design principles also consider how the console relates to other aspects of the control suite, such as lighting, room layout, access, egress, and ventilation of the room. Failure to implement ergonomic principles in a timely manner affects all of these things and can affect the overall cost and efficiency of the control room.
Ergonomics is a broad concept that covers all aspects of the human-machine interface in a work environment. Its application to the specific topic of console design is no less broad, because there are many factors to consider in something as simple as how a human physically and mentally interacts with console components. To apply ergonomics to console selection, you first must understand what tasks a human performs and what principles of ergonomic design come into play in the performance of those tasks.
Ergonomic console selection begins with a thorough task analysis. A task analysis is a detailed study of how operators perform the various components of their jobs and how they interact with others and with the machines and equipment that are used to perform the job.
Task analysis includes but is not limited to the following considerations: workload, task load, corporate culture, situational awareness, and communication.
Ergonomic design principles
Once you have thoroughly analyzed the tasks that each operator undertakes, use general principles of ergonomic design to determine the safest and most efficient methods to maximize human performance. Proper ergonomic design of a control console takes into account the operator's body postures, movement, and visual comfort. Environmental factors, such as ambient noise and illumination levels, are also considered. The goal of a properly selected, ergonomic console is to reduce operator stress and to enhance alertness at all times so operators can remain focused on their tasks. The following principles are of use in the selection of ergonomically designed control consoles.
Postural variability: Control personnel usually remain seated for long periods of time. This sedentary behavior can add to shift-work fatigue and reduced operator alertness, because it decreases blood flow and causes sleepiness. The best consoles can relieve shift-work fatigue by permitting the widest range of comfortable postures. This is done by:
- using adjustable-height consoles that allow the operator to either stand or sit at the controls
- using trackballs or joysticks
- placing keyboards at optimized reach distances to help eliminate extreme motion ranges and twisting of the body
- using ergonomically correct chairs that easily adjust to a variety of users in a multiuser environment
Visual comfort: Increased process automation means that operators spend a greater proportion of their time interacting with computers. Therefore, optimal placement of monitors or visual display units (VDUs) is critical to ensure that operators can successfully carry out their duties without eyestrain. The following parameters all contribute to an operator's visual comfort.
Vertical height: There are two schools of thought regarding the optimal vertical height for monitors. The first argument places the monitors where the top of the screen is at eye level. This reduces strain on the neck muscles by keeping the head in an upright position. However, this posture, when held for long periods, can lead to discomfort and fatigue. The second argument is to place the monitors at midlevel where the bottom of the screen is level with the work surface. Lower monitor positions reduce neck strain by allowing a greater variety of appropriate neck postures. In addition, lower positions allow the monitors to be closer to the subject without increasing eyestrain.
Eye-screen distance: The optimal distance between an operator's eyes and a monitor is dependent on the operator's average points of visual accommodation and convergence. Accommodation is the distance at which eyes focus on an object. When the eyes are relaxed, the point of accommodation averages about 80 centimeters and shifts farther as a person ages. As the visual target moves closer, eyestrain and blurred images result. Convergence is the inward adjustment made by eyes when viewing close objects. The average point of convergence when the eyes are relaxed and looking straight ahead is 115 centimeters, and it is 89 centimeters when looking downward at a 30° angle. Eyestrain increases when the visual target moves closer than this point, because the eye muscles must work harder to focus.
Lateral location: Control personnel rely upon multiple VDUs arrayed horizontally in an arc in front of them. Monitors should sit in the operator's direct field of vision, because after an amount of lateral eye movement, the head automatically rotates in response to the eye movement. Any excessive head and neck rotation is likely to result in discomfort and fatigue. To reduce fatigue, keyboards and other controls should sit in front of the monitors, and writing surfaces and storage spaces should be on either side of the work space.
Screen tilt: Monitor tilt also influences an operator's postural and visual comfort. Forward-tilted monitors increase neck, upper back, and visual discomfort compared to monitors tilted backwards. The optimal tilt angles for monitors range from 5° to 20° from the vertical plane. However, it is important that ambient lighting does not cause screen reflection and glare.
Environmental factors: There are factors that intrude into control operators' personal work space and distract them from their tasks. This space normally extends 3 to 6 feet from a person. Properly positioned consoles reduce the detrimental effects of environmental factors, protect the operator's personal space, and reduce work-related stress.
Traffic patterns: The arrangement of consoles in a control room significantly affects the level of traffic between them. Console layouts should separate visitors and other nonproduction personnel from operators while limiting any obstacles that might impede communication between operators.
Noise reduction: Process control operators are subject to tremendous stress, and stress is a major cause of shift-work fatigue. Ambient noise, alarms, printers, and traffic through the control room all distract the operator and increase stress. Excessive control room noise also interferes with communications during emergencies. You can reduce ambient noise by routing traffic away from the control workstations, by isolating printers and other equipment from the control room, and by applying acoustical treatments to the space surrounding the console.
Illumination levels: Light levels significantly affect human physiology and human performance. Sufficient light is necessary for operators to see the tasks before them without experiencing eyestrain. Ambient lighting in the range of 300 to 750 lux is adequate for control room environments. The ambient lighting throughout a room also affects an operator's level of alertness. Task lighting in the range of 600 lux—the level found in most brightly lit offices—should shine on each console's work surface to support reading and writing tasks. Placement of both task and ambient lighting is an important consideration in console selection to prevent glare on monitors.
Prevalent console design
As a result of pending ISO standards and OSHA regulations, many console manufacturers are now incorporating ergonomic features in their workstation designs. This gives the control room designer an opportunity to achieve the ideal console configuration, because consoles now have more optional features available. All of these advanced ergonomic features promote operator productivity and alertness. Listed below are some of the features that are becoming increasingly prevalent in new console design.
Integrated task lighting: Some console manufacturers offer lighting integrated into their products. Individualized task lighting casts an even wash of light across the work surface to support the operator without affecting adjacent operators' ability to view console display information. The task light adjusts to illuminate the work surface and not the monitor screen or the operator. The intensity of the light is also adjustable to provide adequate illumination for reading and writing, which reduces eye strain and fatigue caused by low lighting levels.
Personal environment system: Some consoles give personnel control of the amount of ventilation and heat at their workstations. Taking the lead from aircraft designers, one manufacturer has integrated into its console design individualized user-adjustable ventilation controls similar to those positioned above each passenger in an airplane. Individualized radiant heaters also can be coordinated with console location to enhance operator comfort.
Acoustical considerations: Specialized alarm systems integrated into the workstation configuration reduce the chaos that arises from indistinguishable alarm sources. These alarms direct the signal to a specific point in a console configuration that enables control personnel to differentiate the origin of the signal. To further reduce noise, flashing lights can replace audible alarms of less urgent nature.
Adjustable work surface heights: Any posture maintained for sustained periods can lead to discomfort and fatigue. To reduce fatigue and enhance alertness, control personnel need to be able to vary their body postures. One method is to incorporate user-adjustable work surfaces. Operated pneumatically or by an electric drive system, these work surfaces adjust to promote standing or sitting postures. This is particularly useful in emergency situations when operators frequently stand because they need high mobility and clear lines of site to overview screens.
Console versatility: The ideal console configuration should be versatile enough to accommodate various room layouts and task allocations. Conventional console designs consist of a static framework that houses the displays and control instrumentation. Because of their fixed nature, adjusting them to individual needs can be costly or impractical. In contrast, custom console designs are more flexible, because their core framework can adjust to enable them to be more ergonomically correct.
Incorporate large overview
Before computers came into the control room environment, operators relied upon chart recorders, gauges, switches, and other analog controls that resided in the plant to monitor the various processes. Although the introduction of computers provided more comprehensive information to the operators, computers also limited what the operator was able to see at any point in the plant operation. To compensate, operators tried to increase the number of monitors on the consoles to match the number of points they wanted to see. Because there was a limit to the number of screens that an operator could safely and efficiently monitor, and because the plant often was located far from the control room, the operator lost the ability to see the overall picture (situational awareness) and became disconnected from the workings of the plant.
Control room designers have begun to incorporate large overview displays in control room design, enabling operators to recapture some of the big picture. Overview displays can sit in front of the consoles, and operators can view them from as far as 30 feet, permitting several operators to view the same information simultaneously. Sharing the same amount and type of information helps reduce operator stress during critical periods or emergencies. Overview displays also enhance operator mobility by acting as a common reference point as operators move from one station to another.
Despite the benefits of overview displays, they are not without drawbacks. Cost is one factor that has had a major impact on their adoption in the control suite. Overview displays also can take up valuable space, and they require adequate access areas behind the units for ventilation and maintenance. Careful attention must be given to the placement and vertical height of overview screens in relation to consoles, because improper placement causes excessive eyestrain and line-of-sight issues.
Ergonomic design is safety
From a corporate standpoint, ergonomic design is all about time and money. Companies have been reluctant to embrace the additional costs involved in selecting consoles based on sound ergonomic principles, because they are unaware of the potential savings that can offset those costs and may be unaware that optional and improved console designs are available.
From an employee standpoint, ergonomic design is all about safety. Ergonomic principles rest on fostering a safe working environment that relieves the worker from undue physical and psychological stress and fatigue. Consoles that employ many of the new ergonomic features can actually reduce worker injuries and accidents and boost employee morale. This translates into increased plant production and lower manufacturing costs.
Proper ergonomic design provides a good compromise between corporate financial concerns and worker safety. The benefits of increased production and reduced operating expenses can often offset the additional costs of implementing ergonomic principles when improving the work environment.
In addition, by integrating ergonomic principles early in the design phase, companies can foresee potential conflicts between the overall control room design and the requirements of console operators. This proactive approach can reduce or eliminate not only costs associated with ergonomic design but also costs arising from the necessity to retrofit a control room that failed to consider implementation of ergonomic design.
Behind the byline
Brad Walker and Karen Smith are president and vice president of Brad Adams Walker Architecture, P.C. in Denver. Write Smith at Ksmith@bawatch.com.