gle shift. The power for the machine is expected to cost $0.25/h and maintenance is priced at $1000/year. Demand for this product is expected at the current rate for the next 10 years. Currently, three operators are needed for this process, but only one is expected to be required with the new machine. Assume that the company uses $25/h for an employee. The company uses a minimum attractive rate of inter- est at 10% annually or at an equivalent amount. Should you as the manager of the ergonomics department recommend this purchase and what is the net present worth?
135
Assessment and design of the physical environment
About the chapter
The physical work environment can have a significant effect on productivity, safety and health, worker satisfaction, and employee turnover. Ergonomists and other specialists are often asked to determine whether the environmental conditions in particular settings are satisfactory. Dirty, cluttered, and poorly organized work, traffic, and storage areas are one common problem. Other potential concerns include exposure to hazardous materials, tem- perature extremes, inadequate lighting, or noise levels. Addressing these issues requires knowledge of how environmental conditions impact people, assessment methods, and a toolbox of solutions. Engineering solutions that involve altering the environment are the most fundamental approach but are often expensive. Less expensive solutions include administrative controls, such as job rotation, rest breaks, and employee selection, as well as implementing better methods of housekeeping. Providing protective equipment and clothing is another potential solution in some situations.
Introduction
The natural and man-made environments we live and work within vary greatly. In daily life we accommodate ourselves to these environments in a variety of ways. We employ heating systems and wear warm clothing when the atmosphere is cold and use cooling systems and wear light clothing when it is hot. We turn up the light when it is dark and shut our doors against loud and undesirable noise. Ergonomic designers must go beyond these commonplace procedures and either deal with environmental controls directly or through specialists in heating, ventilation, air-conditioning, illumination, and acoustics.
In interacting with specialists, the ergonomic designer must coordinate the activities of various specialists and provide informed guidance to help develop cost-effective solutions.
At the most basic level, the goal of the ergonomic designer is to ensure that the work environment is safe, comfortable, and conducive to the tasks people need to perform.
Man-made environments, such as those found within buildings or other structures, can often be modified to keep them safe and comfortable. However, many environments pose challenges that cannot be solved by implementing environmental controls, for techni- cal or economic reasons. In the latter situation, ergonomic designers must focus on other means of protecting workers from dangerous or unpleasant environmental conditions. In some cases that means limiting exposure of people to environmental conditions, such as temperature extremes or noise. In other situations, special equipment or devices must be developed that allow workers to safely perform in unfriendly environments. Linemen and road crews, cleaning up after an ice storm, for instance, would naturally prefer to work in a more pleasant environment, but emergency operations must be maintained.
Other challenges to ergonomic engineers include developing and maintaining bet- ter means of housekeeping, specifying lighting that appropriately accommodates task requirements, and designing clothing and equipment to help workers more safely and comfortably endure the necessarily hostile work environment. Protecting people from excessive noise in the workplace is another important concern.
Cleanliness, clutter, and disorder
Dirty, cluttered, or poorly organized work environments can lead to health problems and accidents, reduce employee morale and productivity, and reduce the quality of the prod- ucts and services produced by a manufacturer or service provider. Some of the many ways this can happen include the following:
• People can slip on spilled liquids or powders or trip over small objects or clutter on the floor, resulting in serious injuries. Scraps and small sharp objects may also cause cuts when people wipe them off surfaces or clothing.
• People’s ability to move about their environment might be impeded by stacks of work in process (WIP) or other objects unnecessarily cluttering work or storage areas, aisles, and passageways. Such clutter also might block access to equipment and tools, obstruct visibility, or even create a fire hazard.
• Tools, parts, or other objects stacked on shelves or cluttering a work surface may use up much of the available space and significantly interfere with people’s abil- ity to do their tasks as intended, not to mention find something they happen to be looking for, leading to delays and problems such as using the wrong tool. Objects on crowded surfaces may also fall off onto people or be damaged when they hit the floor.
• Dirt and grime accumulated on light fixtures, windows, walls, ceilings, and else- where in the facility can greatly reduce the brightness of the work environment, interfering with people’s ability to perform essential visual tasks, in general, creating an unpleasant effect.
• Toxic, irritating, allergenic, carcinogenic, tetragenic (potentially causing birth defects), or otherwise harmful substances may cause health problems when they contact the skin or are ingested when workers smoke or eat without first washing their hands.
These substances may also be brought home by workers on their clothing, exposing family members, such as children or pregnant women, who may be particularly sen- sitive to their effects.
• Dusts, vapors, and gases may enter the air and be inhaled, resulting in serious health problems. They also might accumulate in significant quantities to create fire and explosion hazards or contaminate products that are being produced.
• Poor sanitation might lead to the spread of disease within facilities and is a special concern in health-care settings and food industries.
Other examples along these lines can be easily imagined. One traditional solution is better housekeeping and maintenance, as expanded upon in the following section.
General housekeeping and maintenance
As implied by the previous discussion, good housekeeping is important in almost any imaginable work facility, and is especially important when toxic or hazardous materials
are present or used in the production process. Some general requirements and elements of an adequate housekeeping program are as follows:
1. Cleaning and maintenance should be scheduled on a frequent periodic basis to ensure that dirt and clutter do not build up over time to unacceptable levels; to mini- mize leaks from machinery, storage drums, and other sources; and to ensure that air filters and ventilation systems work properly.
2. Spilled liquids, dusts, and other objects should be immediately cleaned up using appropriate methods that do not add to the problem. In particular, toxic materials, acids, and otherwise reactive or hazardous materials should normally be neutralized or diluted before attempting to remove them. Also, centralized vacuum systems that exhaust their contents outside the facility are preferable to portable vacuum cleaners that recirculate air. Use of the latter systems, as well as sweeping, can cause dust to become airborne and increase the chance that potentially toxic materials will be inhaled.
3. Washrooms and showers should be provided to workers in dirty jobs. A common criteria is one water tap and shower for every three workers to ensure they do not have to wait too long to clean up.
4. Work and traffic areas should be clearly marked to separate them from temporary storage areas for work in progress (WIP). Otherwise, there is a tendency for WIP to accumulate and block work areas and aisles.
5. Convenient, easily accessible locations should be designated for storing tools, parts, and other essential items used in the workplace. These locations should be periodically monitored to ensure that items are placed in the designated locations and, if they are not, to determine necessary changes to ensure work areas will not be cluttered.
6. Waste containers or other disposal devices should similarly be provided in conve- nient locations. Waste containers should be emptied on a frequent periodic basis to ensure they are not filled beyond capacity.
Despite the obvious benefits of following good housekeeping practices, any ergonomist with significant industrial experience will agree that many, if not most, organizations have difficulty maintaining a clean, uncluttered work environment for their employees. This tendency is especially true for small manufacturing faculties, but even larger organizations devoting significant efforts to housekeeping often have significant room for improvement.
Part of the issue is that housekeeping is often viewed as a janitorial task, separate from the day-to-day responsibilities of most employees. Another issue is that clutter has a tendency to build up over long periods. In our experience, it is not unusual to find tools, equipment, and parts that have been sitting around unused for years, sometimes even taking up valuable space on the shop floor!
5S programs
As part of the so-called lean revolution in manufacturing, many companies in recent years have been looking for ways to produce more with less. Implementation of a 5S-plus safety program is often the starting point for such efforts. 5S (Hirano, 1996) can be viewed as a systematic approach for continuously improving housekeeping that goes well beyond the traditional janitorial perspective of this topic, and in so doing addresses many of the root causes of a dirty, cluttered, disorderly work environment.
At the most basic level, 5S is a five-step process followed to continuously improve a selected work area, usually involving workers drawn from the particular work area selected for improvement and a 5S expert who facilitates each step of the process. An important part of 5S is to take photographs showing what the work area looked like before and after going through the process (Box 4.1).
These photographs are often posted at the work site to publicize what was done and maintain awareness of the need for continuous improvement.
The five steps in the 5S process are S1—Sort
S2—Set in Order S3—Shine S4—Standardize S5—Sustain
Note that the names given to the steps are rough translations of Japanese terms, reflecting the fact that 5S originated in Japan. Each of these steps will now be briefly reviewed.
Step 1 Sort. The first step of 5S is to take an inventory of all items currently in the work area. A red tag is placed on all items that do not need to be present in the analyzed area.
The latter items are then moved to a temporary holding area. Unless someone claims that a red-tagged item needs to be returned to the work area within a preset time (often 2 weeks), it is discarded, sold, given away, or otherwise disposed.
It is easy to see that the first step of the 5S procedure can free up space and eliminate clutter. In practice, participants are sometimes reluctant to throw away familiar, but unused, items. A common comment is along the lines of, “you never know when (blank) might be handy.” Placing the items in a holding facility for some time can often help modify such reactions. As time passes, most people become more accustomed to the fact
BOX 4.1 BENEFITS OF 5S
5S is particularly interesting to many organizations because a successful 5S program can do much more than improve housekeeping. For example, consider the case of Wabash International, the largest manufacturer of truck trailers in the United States.
At the end of its fiscal year in 2001, Wabash reported a loss of $232.1 million, and debt approaching half a billion dollars. A change in management took place in May, 2002, and a 5S program was implemented shortly afterward. The company turned a profit for the first time in several years of $25 million in the first half of 2004. In October, 2004, Wabash received the U.S. Senate Productivity Award. Shortly before receiving the award, Wabash invited a group of about 100 members of the Wabash Valley Lean Network to visit their main production facilities in Lafayette, IN, to see what they had accomplished. Some of the benefits of 5S reported to the group by Wabash International included (1) reduced space requirements, allowing them to roughly double production without investing in larger facilities; (2) an 80% decrease in accidents; (3) large improvements in productivity and product quality; and (4) greatly improved employee morale. During the plant tour, employees at the site enthusiastically discussed the before-and-after photographs prominently displayed throughout the site at individual work areas. More importantly, they all seemed to have plans for future improvements.
that familiar, but useless, objects are no longer there, and begin to perceive the advantages of a less cluttered environment.
Step 2 Set in Order. The second step of 5S is to arrange the remaining items in an orderly fashion and clearly designate a correct location for each item. From the perspective of Hirano in his discussion of the visual workplace, it should be obvious when something is out of place or missing. This objective can be attained in many different ways. Typical examples include the following:
1. Hanging tools on boards on which the shape of each tool is prominently traced out in the appropriate location. This makes tools more visible and eliminates the tendency to pile up tools in jumbled heaps on work surfaces.
2. Placing parts in transparent legibly labeled trays.
3. Color coding and numbering schemes to designate logical groupings and ordering of manuals placed on shelves.
4. Marking the appropriate location where incoming parts and WIP should be placed.
5. Hanging signs that prominently identify particular areas and the location of equipment in the work facility.
6. Rearranging equipment to open up the work area, and otherwise improve the layout.
It is easy to see that performing the first two steps of 5S on a periodic basis can go a long way toward reducing clutter and preventing it from building up in the first place. This can lead to some obvious productivity improvements by making it easier for people to quickly find things when they need them and reducing the time needed for people and materials to move around the facility.
Step 3 Shine. This third step of 5S, often also called sanitize, is to carefully clean even traditionally ignored parts of work areas and equipment and then paint them white so that dirt or grime will stand out. An important element of this process is to assign clean- ing responsibilities to specific workers to create accountability. Proper cleaning supplies must also be made readily available following 5S guidelines analogous to those for tools.
Painting everything white reflects the original focus in Japan on creating the so-called visual workplace, where even minor problems stand out and become obvious. One of the advantages of this approach is that maintenance issues such as minor leaks in hoses and fittings become obvious long before serious problems occur. A second advantage is that the environment becomes much brighter. Many 5S participants find the often dramatic transformation from a dark, dirty environment to be a great improvement and are quite enthusiastic about what they have accomplished.
Step 4 Standardize. The fourth step of 5S often overlaps greatly with steps 1 and 2. This follows because the number of tools, dies, fixtures, parts, and types of equipment needed for a particular process can often be reduced by standardizing processes, tools, and the products they provide to customers. This, in turn, helps reduce clutter and can greatly increase productivity. Some examples of how the need for particular items might be elimi- nated through standardization are as follows:
• A company might switch from producing 10 colors of a product to the four most popular, thereby reducing both the type and amount of paint that must kept in inventory.
• A company might switch from using both screws and rivets to using rivets alone, thereby reducing the types of tools and parts needed in the work area.
Another issue is that completing step 2 of 5S can in some cases lead to new arrangements of production equipment, which might change the way particular tasks will be done. If
so, Step 4 of 5S will also involve developing standard operating procedures for the new arrangements.
Step 5 Sustain. The last step of 5S is to develop ways of sustaining the improvements that have been made. Ideally, the first four steps of 5S are made part of each worker’s job so that the improvement process is continued on a permanent basis. Companies also might publicize the 5S program with a newsletter and conduct periodic 5S inspections to dem- onstrate commitment. Inspections should use a standard evaluation method, so workers know exactly what is expected of them and how well they are doing. Some companies publicize the results of these inspections by presenting 5S awards to encourage friendly competition between different areas of the facility.
Lighting and illumination
Like other environmental conditions such as cleanliness and order, lighting can have a negative effect on human performance and safety. Part of the issue is that poor lighting can interfere directly with the tasks people perform because vision is one of the major senses guiding human activities. Hence, inadequate lighting can cause workers to misread signs or instruments, or make other mistakes, resulting in lower productivity and reduced safety.
The solution to inadequate lighting is not always more light but better light instead.
As expanded upon in the following sections, there are many ways of improving lighting conditions that can be cheaper and more effective than simply investing in more light fixtures. Placement and maintenance of light sources is at least as important as the number of light fixtures. Well-chosen paints and finishes on ceilings, walls, floors, and work surfaces can also play an important role, as can modification of the task to reduce visual demands.
Luminous environment and its measurement
Much of the available light in a given environment might come directly from the sun or from a light fixture. Light also arrives after reflecting off of floors, walls, ceilings, and other surfaces. The amount of luminous energy falling on a surface is called the illumination.
The latter quantity is measured in units of footcandles (fc) or lux (lx), where 1 fc is equal to 10.76 lx (Box 4.2). The illumination level of a particular surface depends upon both the intensity and location of the available light sources (Figure 4.1). The amount of light energy from a source that arrives at a particular surface decreases with distance and is also related to the orientation of the surface with respect to the light source.
Getting a bit more precise, the illumination (E) at the surface where the visual task takes place, assuming the light comes from a single point source, depends on the intensity (I) of the light source, the distance (d) between the light source and the visual task location, and the cosine of the angle (β) between a line perpendicular to the surface and the light source. This relationship is described by the equation
E I
= d2cosβ (4.1)
Note that if the light source is directly overhead, the angle β is 0, resulting in the simplified equation
E I
= d2 (4.2)