Operator interface systems for controlled environments are becoming more user-friendly.
In the past, ergonomics have not been a prime consideration for industrial designs. But, when industrial engineers and designers omit ergonomics from their plans, they compromise the safe and efficient operation of equipment in controlled environments, which leads to injuries, equipment damage, and costly retrofits.
Although ergonomics play an increasingly important role in the design of operator interfaces and computer systems, the U.S. government has left the implementation of ergonomic principles up to individual industries to regulate. To address workplace concerns, standards-based organizations have released practice guidelines and standards for ergonomics.
For example, the ISO 11064 (Ergonomic Design of Control Centers) international standard recommends a top-down approach to ergonomic controlled environment design that emphasizes functional demands. This approach recognizes that even if a controlled environment is well-designed, the overall system will fail if workers are overloaded, poorly trained, or straining to read illegible operator interface monitors.
With these guidelines available to industry, and with the U.S. Census Bureau reporting that half of all adults use computers in the workplace, more and more companies are discovering that ergonomically sound workstations and operator interface systems are more productive. That’s why the new modus operandi of industrial designers is to account for how operators and systems interface in the working environment.
Perhaps the most important questions in the design of controlled areas and their operator interface systems are, “What does the user want?” and “What is the user trying to achieve?” Each question and its answer will affect the design of a controlled environment and its systems, as well as impact the comfort and productivity of the operators slated to work in those areas.
DESIGN PRINCIPLES
Operator productivity and safety depend on the layout and design of the tools provided to the operators. As such, there are clear advantages to systems created with ergonomics in mind.
Operator interface systems must be able to accommodate a variety of users and their postures. Proper ergonomic design of a workstation takes into account an operator’s posture, movement, and visual comfort.
Posturing
In controlled environments, operators may be seated for long periods of time or be required to stand at a workstation. Operators who are sedentary may suffer from shift work fatigue and decreased alertness because sitting for long shifts reduces blood flow and promotes sleep. Some of the best operator interfaces relieve this fatigue by allowing a wide range of comfortable postures.
Variability in posturing can be achieved by using vertically adjustable workstations that allow users to sit or stand; integrating track balls and joy sticks for input devices; installing keyboards at optimal reach distances to eliminate extreme ranges of motion; and using ergonomically correct chairs that adjust to different heights. Additionally, workstations should be designed to consider eye height, elbow height, and eye-elbow height difference so as to not install components (such as keyboards) too high or too low.
Eye height ranges from 41 to 51 inches for seated workers and from 56 to 69 inches for standing workers, and elbow height varies between 22 and 28 inches for seated workers and 36 to 45 inches for standing workers. Whether seated or standing, the eye-elbow difference is the same. For the U.S. population, that difference ranges from just less than 19 inches (women) to slightly more than 23 inches (men).
Visual comfort
As industries see more and more process automation, operators are spending more time interacting with computer workstations. When these workstations are installed at incorrect levels, an operator’s visual comfort can be compromised by eye strain, neck strain, or a combination of both.
Designers can help prevent operator neck strain by situating workstation monitors at the proper gaze angle. The general recommendation is to place the monitor so that the top of the viewing area is at or slightly below the user’s horizontal eye level. This places the center of the screen at the ideal 15 to 20 degrees below eye level for most monitors.
In controlled areas where operators use several monitors at a time, screens are generally installed in a horizontal arc in front of the workstation. These monitors should be in a user’s direct field of vision. After a period of lateral eye movement, a person’s head will turn automatically when responding to eye movement, and this excessive head and neck rotation can result in strain and fatigue. A common way to prevent this problem is to situate keyboards and other controls in front of the monitors. Writing surfaces and storage spaces should be installed on the sides of these workspaces.
Monitor tilt also impacts visual and postural comfort. Screens that tilt forward increase neck, upper back, and visual discomfort compared to those tilting backward. An optimal tilt angle for monitors ranges from 5 to 20 degrees back from the vertical plane. Despite the chosen angle, care should be taken that ambient lighting does not cause screen reflection and glare.
NOISE AND LIGHT LEVELS
Operator interfaces are only as good as the environment in which they are installed. Due to their job specifications, operators can be subjected to high levels of stress, which also contributes to shift work fatigue.
Ambient noise, alarms, printers, and traffic through a controlled environment can distract operators and can interfere with communication during emergencies. By routing traffic away from operator interfaces and isolating other equipment from a controlled environment, plant designers can reduce ambient noise. In areas where noise can not be avoided, operator interfaces can be surrounded by acoustical treatments to pad sound levels.
The placement of ambient and task lighting in controlled areas must be considered when selecting an operator interface in order to prevent glare on monitors. Light levels impact alertness, and appropriate light levels are necessary to prevent eye strain. So designers must achieve a careful balance of ambient lighting and task lighting by which operators can successfully use controls. For controlled environments, ambient lighting in a range of 300 to 650 lux is adequate. Task lighting set at about 600 lux should shine on work surfaces.
All elements of operator interfaces should be integrated systematically and as early as possible in a controlled environment’s design phase. The design of the operator interface influences the layout of an operator’s workspace, the location of visual displays, and the size, shape and placement of workstations relative to those interfaces.
INTERFACE SELECTION
Reducing operator stress and enhancing alertness and productivity are the goals of properly selecting an ergonomic operator interface.
Selecting an ergonomic operator interface begins with a task analysis. This is a detailed study of how operators carry out parts of their jobs and how they interact with the equipment used to perform those jobs. Task analysis can include the following considerations: workload, corporate culture, situational awareness, and communication.
Designers also should consider environmental factors such as ambient noise and light levels, as well as the need to share space in the workplace. Interfaces may need to fold up, swing back and forth, or move up and down to allow other work to be performed with in the same footprint. Luckily, today’s manufacturers offer lines of ergonomically friendly designs that maximize controlled area design.
DON’T OVERLOOK COMPONENTS
Tools such as the touch screens, keyboards, and pointer devices are of great importance when designing operator interfaces, too.
Touch screens: Although touch screens are not used in all industrial applications, studies have shown that they are beneficial to operators. When under high levels of stress, some operators have difficulty using a mouse to find and click an icon on the desktop. Those same operators may have less trouble using their finger on a touch screen. The result is more touch screens appearing in high-security and high-stress controlled environment applications.
Touch screens also are the best choices for operator interfaces in hazardous areas. The most popular touch screen technologies include resistive, infrared, and SAW (surface acoustic wave).
Keyboards: A variety of different keyboards are available for operator interfaces. The best devices are built rugged to withstand harsh environments. For example, desktop keyboards may come in corrosion-resistant stainless steel or a durable ABS polycarbonate casing. Membrane mechanical keyswitch keyboards are completely sealed and easily cleaned, making them the preferred choice for harsh chemical environments.
Pointer Devices: A vast number of pointer options are also available for controlled areas. These include trackballs, glide pads, and stainless steel mice. The stainless steel mouse is a recent industrial innovation, and is NEMA 4X rated. The use of an industrial mouse provides operators with a familiar pointing device, which can improve comfort and efficiency.
Finding an operator interface system that considers all of these factors for multiple operators can be a tall order. Changes in controlled environment technology and a better understanding of ergonomics are changing operator interface systems. With more ergonomic systems and components available to industrial consumers, control room designers and engineers will be able to more realistically assess how operators work at their workstations and outfit them with the best systems to increase their comfort and productivity.
Bill Fleming has served STRONGARM, Inc. since 2001. His expertise is built on a 20-year career serving the manufacturing needs of pharmaceutical and other process companies. Fleming is a member of the International Society for Pharmaceutical Engineering. www.strongarm.com
In the past, ergonomics have not been a prime consideration for industrial designs. But, when industrial engineers and designers omit ergonomics from their plans, they compromise the safe and efficient operation of equipment in controlled environments, which leads to injuries, equipment damage, and costly retrofits.
Although ergonomics play an increasingly important role in the design of operator interfaces and computer systems, the U.S. government has left the implementation of ergonomic principles up to individual industries to regulate. To address workplace concerns, standards-based organizations have released practice guidelines and standards for ergonomics.
For example, the ISO 11064 (Ergonomic Design of Control Centers) international standard recommends a top-down approach to ergonomic controlled environment design that emphasizes functional demands. This approach recognizes that even if a controlled environment is well-designed, the overall system will fail if workers are overloaded, poorly trained, or straining to read illegible operator interface monitors.
With these guidelines available to industry, and with the U.S. Census Bureau reporting that half of all adults use computers in the workplace, more and more companies are discovering that ergonomically sound workstations and operator interface systems are more productive. That’s why the new modus operandi of industrial designers is to account for how operators and systems interface in the working environment.
Perhaps the most important questions in the design of controlled areas and their operator interface systems are, “What does the user want?” and “What is the user trying to achieve?” Each question and its answer will affect the design of a controlled environment and its systems, as well as impact the comfort and productivity of the operators slated to work in those areas.
DESIGN PRINCIPLES
Operator productivity and safety depend on the layout and design of the tools provided to the operators. As such, there are clear advantages to systems created with ergonomics in mind.
Operator interface systems must be able to accommodate a variety of users and their postures. Proper ergonomic design of a workstation takes into account an operator’s posture, movement, and visual comfort.
Posturing
In controlled environments, operators may be seated for long periods of time or be required to stand at a workstation. Operators who are sedentary may suffer from shift work fatigue and decreased alertness because sitting for long shifts reduces blood flow and promotes sleep. Some of the best operator interfaces relieve this fatigue by allowing a wide range of comfortable postures.
Variability in posturing can be achieved by using vertically adjustable workstations that allow users to sit or stand; integrating track balls and joy sticks for input devices; installing keyboards at optimal reach distances to eliminate extreme ranges of motion; and using ergonomically correct chairs that adjust to different heights. Additionally, workstations should be designed to consider eye height, elbow height, and eye-elbow height difference so as to not install components (such as keyboards) too high or too low.
Eye height ranges from 41 to 51 inches for seated workers and from 56 to 69 inches for standing workers, and elbow height varies between 22 and 28 inches for seated workers and 36 to 45 inches for standing workers. Whether seated or standing, the eye-elbow difference is the same. For the U.S. population, that difference ranges from just less than 19 inches (women) to slightly more than 23 inches (men).
Visual comfort
As industries see more and more process automation, operators are spending more time interacting with computer workstations. When these workstations are installed at incorrect levels, an operator’s visual comfort can be compromised by eye strain, neck strain, or a combination of both.
Designers can help prevent operator neck strain by situating workstation monitors at the proper gaze angle. The general recommendation is to place the monitor so that the top of the viewing area is at or slightly below the user’s horizontal eye level. This places the center of the screen at the ideal 15 to 20 degrees below eye level for most monitors.
In controlled areas where operators use several monitors at a time, screens are generally installed in a horizontal arc in front of the workstation. These monitors should be in a user’s direct field of vision. After a period of lateral eye movement, a person’s head will turn automatically when responding to eye movement, and this excessive head and neck rotation can result in strain and fatigue. A common way to prevent this problem is to situate keyboards and other controls in front of the monitors. Writing surfaces and storage spaces should be installed on the sides of these workspaces.
Monitor tilt also impacts visual and postural comfort. Screens that tilt forward increase neck, upper back, and visual discomfort compared to those tilting backward. An optimal tilt angle for monitors ranges from 5 to 20 degrees back from the vertical plane. Despite the chosen angle, care should be taken that ambient lighting does not cause screen reflection and glare.
NOISE AND LIGHT LEVELS
Operator interfaces are only as good as the environment in which they are installed. Due to their job specifications, operators can be subjected to high levels of stress, which also contributes to shift work fatigue.
Ambient noise, alarms, printers, and traffic through a controlled environment can distract operators and can interfere with communication during emergencies. By routing traffic away from operator interfaces and isolating other equipment from a controlled environment, plant designers can reduce ambient noise. In areas where noise can not be avoided, operator interfaces can be surrounded by acoustical treatments to pad sound levels.
The placement of ambient and task lighting in controlled areas must be considered when selecting an operator interface in order to prevent glare on monitors. Light levels impact alertness, and appropriate light levels are necessary to prevent eye strain. So designers must achieve a careful balance of ambient lighting and task lighting by which operators can successfully use controls. For controlled environments, ambient lighting in a range of 300 to 650 lux is adequate. Task lighting set at about 600 lux should shine on work surfaces.
All elements of operator interfaces should be integrated systematically and as early as possible in a controlled environment’s design phase. The design of the operator interface influences the layout of an operator’s workspace, the location of visual displays, and the size, shape and placement of workstations relative to those interfaces.
INTERFACE SELECTION
Reducing operator stress and enhancing alertness and productivity are the goals of properly selecting an ergonomic operator interface.
Selecting an ergonomic operator interface begins with a task analysis. This is a detailed study of how operators carry out parts of their jobs and how they interact with the equipment used to perform those jobs. Task analysis can include the following considerations: workload, corporate culture, situational awareness, and communication.
Designers also should consider environmental factors such as ambient noise and light levels, as well as the need to share space in the workplace. Interfaces may need to fold up, swing back and forth, or move up and down to allow other work to be performed with in the same footprint. Luckily, today’s manufacturers offer lines of ergonomically friendly designs that maximize controlled area design.
- Vertically adjustable systems typically provide up to 30 inches of counterbalanced repositioning with rotational articulation. They can be attached to a wall, floor post, ceiling, or machine top.
- Console systems are designed to provide improved process visibility.
- In-wall stations fit into the confines of a shallow wall, minimizing the protrusion in to the controlled environment. Front door access permits interior access to internal components without compromising the wall seal.
- On-wall stations mount directly to the wall via tabs or holes in the rear of the enclosure. They are suited for controlled areas where space is at a premium.
- Mobile systems allow operators to bring the interface to the process, eliminating the need for multiple fixed stations. Mobile systems are suited for bulk product, batch pre-weigh or quality assurance applications, and they usually are outfitted with integrated weight scales, bar code scanners, and label printers.
DON’T OVERLOOK COMPONENTS
Tools such as the touch screens, keyboards, and pointer devices are of great importance when designing operator interfaces, too.
Touch screens: Although touch screens are not used in all industrial applications, studies have shown that they are beneficial to operators. When under high levels of stress, some operators have difficulty using a mouse to find and click an icon on the desktop. Those same operators may have less trouble using their finger on a touch screen. The result is more touch screens appearing in high-security and high-stress controlled environment applications.
Touch screens also are the best choices for operator interfaces in hazardous areas. The most popular touch screen technologies include resistive, infrared, and SAW (surface acoustic wave).
Keyboards: A variety of different keyboards are available for operator interfaces. The best devices are built rugged to withstand harsh environments. For example, desktop keyboards may come in corrosion-resistant stainless steel or a durable ABS polycarbonate casing. Membrane mechanical keyswitch keyboards are completely sealed and easily cleaned, making them the preferred choice for harsh chemical environments.
Pointer Devices: A vast number of pointer options are also available for controlled areas. These include trackballs, glide pads, and stainless steel mice. The stainless steel mouse is a recent industrial innovation, and is NEMA 4X rated. The use of an industrial mouse provides operators with a familiar pointing device, which can improve comfort and efficiency.
Finding an operator interface system that considers all of these factors for multiple operators can be a tall order. Changes in controlled environment technology and a better understanding of ergonomics are changing operator interface systems. With more ergonomic systems and components available to industrial consumers, control room designers and engineers will be able to more realistically assess how operators work at their workstations and outfit them with the best systems to increase their comfort and productivity.
Bill Fleming has served STRONGARM, Inc. since 2001. His expertise is built on a 20-year career serving the manufacturing needs of pharmaceutical and other process companies. Fleming is a member of the International Society for Pharmaceutical Engineering. www.strongarm.com
