Workplace Design I Gaurav Singh Rajput

Workplace design | Gaurav Singh Rajput | gauravkrsrajput I Gaurav Singh Rajput I gauravsinghrajput I gauravkrsrajput

1. Workplace D e s i g n B y : G a u r a v S i n g h R a j p u t @ g a u r a v k r s r a j p u t

2. WORKPLACE DESIGN ANTHROPOMETRY Anthropometry deals with the measurement of the dimensions and certain other physical characteristics of the body such as volumes, centers of gravity, inertial properties, and masses of body segments. There are two primary types of body measurement: static and dynamic (functional). What is sometimes called engineering anthropometry is concerned with the application of both types of data to the design of the things people use

3. Static Dimensions Static dimensions are measurements taken when the body is in a fixed (static) position. They consist of skeletal dimensions (between the centers of joints, such as between the elbow and the wrist) or of contour dimensions (skin surface dimensions such as head circumference).

4. Dynamic (Functional) Dimensions These dimensions are taken under conditions in which the body is engaged in some physical activity. In most physical activities (whether one is operating a steering wheel, assembling a mousetrap, or reaching across the table for the salt) the individual body members function decide the dynamic dimensions.

5. Conversion…. Although there is no systematic procedure for translating static anthropometric data into dynamic measurements, Kroemer (1983) offers the following rules of thumb that may be helpful: Heights (stature, eye, shoulder, hip): reduce by 3 percent. Elbow height: no change, or increase by up to 5 percent if elevated at work. Knee height, sitting: no change, except with high-heel shoes. Forward and lateral reaches: decrease by 30 percent for convenience, increase by 20 percent for extensive shoulder and trunk motions.

6. Principles in the Application of Anthropometric Data Design for Extreme Individuals : In designing certain features of our built physical world, one should try to accommodate all (or virtually all) the population in question. In some circumstances a specific design dimension or feature is a limiting factor that might restrict the use of the facility for some people; that limiting factor can dictate either a maximum or minimum value of the population variable or characteristic in question.

7. Principles in the Application of Anthropometric Data Designing for Adjustable Range : Certain features of equipment or facilities can be designed so they can be adjusted to the individuals who use them. Some examples are automobile seats, office chairs, desk heights, and footrests. In the Design of such equipment, it frequently is the practice to provide for adjustments to cover the range from the 5th percentile female to the 95th percentile male of the relevant population characteristic (sitting height, arm reach, etc.).

8. Principles in the Application of Anthropometric Data Designing for the Average : First of all, there is no "average" individual. A person may be average on one or two body dimensions, but because there are no perfect correlations it is virtually impossible to find anyone who is average on more than a few dimensions. Often designers design for the average as a cop-out so that they do not have to deal with the complexity of anthropometric data. Designing for the average should only be done after careful consideration of the situation and never as an easy way out.

9. Using anthropometric data in design 1. Determine the body dimensions important in the design ( e.g . Sitting height as a basic factor in seat-to-roof dimensions in automobiles]. 2. Define the population to use the equipment or facilities. This establishes the dimensional range that needs to be considered (e.g., Children, women, U.S. civilians, different age groups, world populations, different races). 3. Determine what principle should be applied (e.g., design for extreme individuals, for an adjustable range, or for the average). 4. When relevant, select the percentage of the population to be accommodated (for example, 90 percent, 95 percent) or whatever is relevant to the problem. 5. Locate anthropometric tables appropriate for the population, and extract relevant values. 6. If special clothing is to be worn, add appropriate allowances (some of which are available in the anthropometric literature). 7. Build a full-scale mock-up of the equipment or facility being designed and using the mock-up, have people representative of large and small users walk through representative tasks. All the anthropometric data in the world cannot substitute for a full-scale mock-up .

10. Work spaces Work-space envelopes consist of the three-dimensional spaces that are reasonably optimum for seated or standing persons who perform some type of manual activity. Thus (for example) control devices and other objects to be used usually should be located within such space. The reasonable limits of such space are determined by functional arm reach, which is influenced by such variables as direction of arm reach, the nature of the manual activity, the use of restraints, apparel worn, the angle of the backrest, and personal variables such as age, sex, ethnic group, and handicaps.

11. Work spaces Whenever feasible, such spaces should be designed with consideration for the personal characteristics of the population to use the facility. It is fairly standard practice to design such space for the 5th percentile of the using population, thus making it suitable for 95 percent of the population. Thus, with such special populations the design of the work space requires particular (and sometimes individual) attention.

12. Work-Space Envelopes for Seated Personnel The limits of the work-space envelope for seated personnel are determined by functional arm reach, which in turn is influenced especially by the direction of arm reach and the nature of the manual activity (i.e., the task or function) to be performed. Functional arm reach is also influenced by such factors as the presence of any restraints and by the apparel worn. Some examples of the effects of these variables are given for illustration.

13. Work-Space Envelopes for Seated Personnel

14. Work-Space Envelopes for Standing Personnel

15. DESIGN OF WORK SURFACES Horizontal Work Surface Area: The horizontal work surface area to be used by seated and "sit-stand" workers generally should provide for manual activities to be within convenient arm's reach. Certain normal and maximum areas were proposed by Barnes (1963) and Farley (1955) and have been used rather widely. 1. Normal area - This is the area that can be conveniently reached with a sweep of the forearm while the upper arm hangs in a natural position at the side. 2. Maximum area - This is the area that could be reached by extending the arm from the shoulder.

16. Normal and maximum working area

17. Horizontal and slanting work surface Although most office activities such as reading and writing are carried out on horizontal surfaces such as desks and tables, Eastman and Kamon (1976) propose that (where feasible) a slanted surface be used. In their study they found that subjects using slanted surfaces (12° and 24°) had better posture, showed less trunk movement, and reported less fatigue and less discomfort than when using horizontal surfaces. Bridger (1988) found similar results, as depicted in Figure 13-12. When using a slanted surface (ISO) subjects sat with less bending of the neck, a more upright trunk, and less trunk flexion than when using a horizontal work surface. The evidence seems clear that using slanted work surfaces for visual tasks, such as reading, offers considerable advantages in terms of posture over traditional horizontal work surfaces.

18. Horizontal and slanting work surface

19. Work-Surface Height: Seated If a work surface is too low, the back may be bent over too far; and if it is too high, the shoulders must be raised above their relaxed posture, thus triggering shoulder and neck discomfort. When discussing work-surface height some confusion may be introduced if a distinction is not made between work-surface height and working height. Work surface height is simply the height of the upper surface of a table, bench, desk, counter, etc. measured from the floor. Even this simple notion becomes a little complex when slanted work surfaces are referred to; usually the height of the front edge and the angle of the surface are specified. Working height; however, depends on what one is working on. When writing on paper, the working height is the same as the work-surface height. When using a-keyboard (typewriter or computer) the working height is taken as the height of the home row of keys (the " asdfghjkl " row on a standard keyboard). When washing vegetables in a sink, the working height is actually below the work-surface height.

20. General Principles for Seated Work Surfaces There are a few general principles related to work-surface heights If at all possible the work-surface height should be adjustable to fit individual physical dimensions and preferences. 2. The work surface should be at a level that places the working height at elbow height. 3. The work surface should provide adequate clearance for a person's thighs under the work surface.

21. Seated Work-Surface Height and Arm Posture In recent years some investigators have recommended reducing work-surface heights, generally to permit relaxed postures of the upper arms with respect to working height. Working with relaxed upper arms and elbows at about 90° provides comfort and helps maintain straight wrists, which can be beneficial when performing repetitive tasks such as typing or electronic assembly. On the basis of a European survey, Bex (1971) reports that the most common heights of desks have, in fact, been reduced from about 30 in (76 cm) in 1958 to about 28.5 in (72 cm) in 1970. Based on his own and other anthropometric data, he argues for a further reduction of fixed desk heights to about 27 in (68.6 cm).

22. Seated Work-Surface Height and Thigh Clearance Work-surface height is also influenced by seat height, the thickness of the work surface, and the thickness of the thighs. The clearance between the seat and the underside of the work surface should accommodate the thighs of the largest user. ANSI (Human Factors Society, 1988) recommends 26.2 in (66.5 cm) as the minimum height for the underside of a non adjustable seated work surface. With adjustable-height work surfaces, small users can adjust the height so that the working height is at elbow height with their feet on the floor.

23. Seated Work-Surface Height and Thigh Clearance ANSI (Human Factors Society, 1988) recommends a range of height adjustments for the underside of the work surface of 20.2 to 26.2 in (51.3 to 66.5 cm). This works fine unless the work surface is unusually thick or the object being worked on is large in the vertical dimension. When the work surface cannot be lowered sufficiently for proper arm posture and thigh clearance, a thinner work surface should be considered.

24. Seated Work Surface Height and Nature of the Task

25. Work-Surface Height: Standing The critical features for determining work-surface heights for standing workers are in part the same as for seated workers, i.e., elbow height and the type of work being performed. Figure 13-13 shows recommended heights for precision work, light work, and heavy work as related to elbow height ( Grandjean , 1988). For light and heavy work the recommended work-surface heights are below elbow height, whereas that for precision work is slightly above (generally to provide elbow support for precise manual control). We recommend, however, that precision tasks be performed sitting down.

26. Work-Surface Height: Standing

27. General Principles of Seat Design Promote Lumbar Lordosis - When standing erect, the lumbar portion of the spine (the small of the back just above the buttocks) is naturally curved inward (concave), that is, it is lordotic . Natural lumbar lordosis aligns the vertebrae of the spine in a near vertical axis through the thigh and pelvis, as shown in Figure 13-15. However, when one is sitting with the thighs at 90°, the lumbar region of the back flattens out-and may even assume an outward bend (convex), that is, it becomes kyphotic . as shown in Figure 13-15. This occurs because the hip joint rotates only about 60°, forcing the pelvis to rotate backward about 30° to achieve the 90° thigh angle. Lumbar kyphosis results in increased pressure on the discs located 'between the vertebrae of the spine.

28. General Principles of Seat Design

29. Minimize Disc Pressure The discs between the vertebrae can be damaged by excessive pressure. Unsupported sitting, i.e., not using a backrest, increases disc pressure considerably over that experienced while standing. Nachemson and Elfstrom (1970), for example. found that unsupported sitting in an upright, erect posture (forced lordosis ) resulted in a 40 percent increase in pressure compared to standing. Unsupported sitting in a forward slumped posture increased pressure 90 percent compared to standing.

30. Minimize Static Loading of the Back Muscles Andersson (1987) reports that muscular activity as measured by electromyography (EMG) is similar when standing or sitting. In fact;-EMG -activity-decreases when sitting in a forward slumped posture, even though, as discussed above, this posture produces maximum pressure on the discs. There are ways, however, to relax the muscles without sacrificing the discs. Andersson and Ortengren (1974) found a reduction in muscular activity in the back when the backrest was reclinedup to 110⁰ beyond which little additional relaxation was found. The effects of a lumbar support on EMG activity have been mixed ( Andersson ; 1987).

31. Reduce Postural Fixity Grieco (1986) discusses the problem of postural fixity, that is, sitting in one position for long periods without significant postural movement. This is especially common when using a computer where the hands remain on the keyboard and the eyes are fixed on the screen. The human body is simply not made to sit in one position for long periods of time. The discs between the vertebrae depend on changes in pressure to receive nutrients and remove waste products. Discs have no blood supply; fluids are exchanged by osmotic pressure. Sitting in one posture-no matter how good it is-will result in reduced nutritional exchanges and in the long term may promote degenerative processes in the discs.

32. Provide for Easy Adjustability Adjustable furniture is fundamental to good human factors design. Studies have shown that providing adjustable seats increases productivity (Springer, 1982) and reduces complaints of shoulder and back pain (Shute and Starr, 1984). The problem is that workers are usually not aware of the adjustability features available on their chairs and rarely use the ones they know about. In a survey of 2000 air traffic controllers it was found that only about 10 percent adjusted their seats during the day and more than half were not even aware of some of the adjustments that were available. The personal experience of one of your authors confirms this among newspaper employees. One feels like a hero when showing someone how to adjust their backrest angle or backrest height to achieve a more comfortable posture.

33. ARRANGING COMPONENTS IN WORKSPACE Ideally, we would like to place each component in an optimum location for serving its purpose. This optimum would be predicated on human capabilities and characteristics, including sensory capabilities and anthropometric and biomechanical characteristics. The optimum location would facilitate performance of the activities carried out in the space. Unfortunately, it is usually not possible to place each component in its optimum location. Placing a control in the optimum location for fast response may separate it from the display to which it is related. To bring order to such potential chaos requires setting priorities and making trade-offs.

34. PRINCIPLES OF ARRANGING COMPONENTS IN WORKSPACE Importance Principle: This principle states that important components be placed in convenient locations. Importance refers to the degree to which the component is vital to the achievement of the objectives of the system. The determination of importance usually is a matter of judgment made by people who are experts in the operation of the system.

35. PRINCIPLES OF ARRANGING COMPONENTS IN WORKSPACE Frequency-of-Use Principle: This principle states that frequently used components be placed in convenient locations. For example, the activation control of a punch press should be conveniently located because it is used very frequently. A copying machine should be near a typist.

36. PRINCIPLES OF ARRANGING COMPONENTS IN WORKSPACE Functional Principle: The functional principle of arrangement provides for the grouping of components according to their function, such as the grouping of displays, controls, or machines that are functionally related in the operation of the system. Thus, temperature indicators and temperature controls might well be grouped Electric power distribution instruments and controls usually should be in the same general location.

37. PRINCIPLES OF ARRANGING COMPONENTS IN WORKSPACE Sequence-of-Use Principle: In the use of certain items, sequences or patterns of relationship frequently occur in the operation of equipment or in performing some service or task. The items would be so arranged as to take advantage of such patterns.

38. PRINCIPLES OF ARRANGING COMPONENTS IN WORKSPACE In putting together the various components of a system, no single guideline can, or should, be applied consistently across all situations. But in a very general way, and in addition to the optimum premise, the notions of importance and frequency probably are particularly applicable to the more basic phase of locating components in a general area in the work space The sequence of use and functional principles tend to apply more to the arrangement of components within a general area.

39. Time vs Principles of control

40. Types of Data for Use in Arranging Components 1. Basic data about human beings - Anthropometric and biomechanical data are especially relevant, but other types of data may also be useful, such as data on sensory, cognitive, and psychomotor skills. Such data generally come from research undertakings and are published in various source books. 2. Task analysis data - These are data about the work activities of people who are (or would be) involved in the specific system or work situation in question. 3. Environmental data - This category covers any relevant environmental features of the situation, such as illumination, noise, vibration, motion, heat, traffic and congestion, etc.

41. Links Relationships between components, be they people or things, are called links. Types of Links - communication links , control links, and movement links. Communication and control links can be considered as functional. Movement links generally reflect sequential movements from one component to another. Some versions of the three types of links are 1. Communication links a. Visual (person to person or equipment to person ) b. Auditory, voice (person to person. person to equipment. or equipment to person ) c . Auditory . Non voice (equipment to person) d. Touch (person to person or person to equipment)

42. Links 2. Control links a. Control (person to equipment) 3. Movement links (movements from one location to another) a. Eye movements b. Manual movements, foot movements or both c. Body movements

43. GENERAL LOCATION OF CONTROLS AND DISPLAYS WITHIN WORK SPACE It is reasonable to assume that any given component in a system or facility would have some reasonably optimum location, predicated on whatever sensory, anthropometric, biomechanical , or other considerations are relevant. Although the optimum locations of some specific components probably would depend on situational factors, some generalizations can be made about certain classes of components.

44. Visual Displays The normal line of sight is usually considered to be about 15° below the horizon. Visual sensitivity accompanied by moderate eye and head movements permits fairly convenient visual scanning of an area around the normal line of sight . The area for most convenient visual regard (and therefore generally preferred for visual displays) has generally been considered to be defined by a circle roughly 10° to 15° in radius around the normal line of sight . There are indications that the area of most effective visual regard is not a circle around the line of sight but rather is more oval.

45. Visual Displays

46. Hand Controls The optimum location of hand control devices is, of course, a function of the type of control, the mode of operation, and the appropriate criterion of performance ( accuracy, speed, force, etc.). Controls That Require Force – Figure shows the serious reduction in effective force as the arm is flexed when it is pulled toward the body. The maximum force that can be exerted by putting is about 57 to 66 cm forward from the seat reference point, and this span, of course , defines the optimum location of a lever control (such as a hand brake) if the pulling force is to be reasonably high.

47. Controls That Require Force

48. Controls on Panels Many controls are positioned on panels or in areas forward of the person who is to use them. Because of the anthropometric and biomechanical characteristics of people, controls in certain locations can be operated more effectively than those in other locations.

49. Controls on Panels

50. Two hand controls Some operations require the simultaneous use of controls by both hands. For example, in the operation of some metal-forming presses , the operators have to press two push buttons-for safety reasons to keep the hands away from the press when it is activated. In some instances these push buttons ("palm" buttons operated by the palm of the hand) are at eye level. This location was suspected of being responsible for a high rate of muscular strain and sprain Injuries.

51. Foot Controls Foot controls generally need to be located in fairly conventional areas; such as those depicted in Figure. These areas, differentiated as optimal and maximal, for toe-operated and heel-operated controls, have been delineated on the basis of dynamic anthropometric data. The maximum areas indicated require a fair amount of thigh or leg movement or both and preferably they should be avoided as locations for frequent or continual pedal use. Incidentally, Figure is predicated on the use of a horizontal seat pan; with an angular seat pan (and an angled backrest) the pedal locations need to be manipulated accordingly. Figure generally apply to foot controls that do not require substantial force.

52. Foot Controls

53. Mirror-Image Arrangements In some process control and nuclear power plants two control panels with identical controls and displays may exist in the same facility. For example , some nuclear power plants have two reactors, each with its own set of control panels . Some machines have controls on two sides so the operator can work from either side . Mean response times with the non mirror-imaged arrangement were faster than with the mirror-imaged panel, especially during the early trial blocks. The difference between mirror- and non mirror-imaged configurations grew smaller as subjects continued to practice and became more accustomed to the mirror imaged panel .

54. SPACING OF CONTROL DEVICES Inadvertent "touching errors" in the use of knobs of various diameters as a function of the distances between their edges were examined. In this instance the errors dropped sharply with increasing distances between knobs up to about I in (2.5 cm ), while beyond that distance performance improved at a much slower rate. When separate comparisons were made between knob centers (rather than edges), however, performance was more nearly error-free for knobs of 1/2-in (1.2 cm) diameter than for the larger knobs.

55. GENERAL GUIDELINES IN DESIGNING INDIVIDUAL WORKPLACES In designing workplaces some compromises are almost inevitable because of competing priorities. In this regard, however, appropriate link values can aid in the trade-off process . • First priority: Primary visual tasks • Second priority: Primary controls that interact with primary visual tasks • Third priority: Control-display relationships - (put controls-near associated displays , compatible movement relationships, etc.) • Fourth priority: Arrangement of elements to be used in sequence • Fifth priority: Convenient location of elements that are used frequently • Sixth priority: Consistency with other layouts within the system or in other systems