2-1Body Dimension Illustrations
2-3Reaching — Grasping — Moving Illustrations
2-4Guard Openings vs. Distances from Point of Danger
Today, successful machines or products must not only perform their intended functions, and perform to customers’ expectations, but they must do so without creating unnecessary hazards that could cause personal injury or property damage. Although no machine is perfectly safe (nothing is perfectly safe), machines are expected to be reasonably safe. They are expected to meet not only safety standards required by governmental codes and regulations, but also standards and criteria found in voluntary industry standards, as well as applicable international standards. In addition, they are expected to consider information and guidance found in textbooks, handbooks, and design manuals, and guidance found in various industry publications (technical journals, published seminar papers, magazine articles, etc.). Even industry customs and practices should be considered when addressing machine safety.
Machines (products in general) need to be designed to minimize, within reason, the possibility of personal injury or property damage. Machine designers must anticipate situations and events that are reasonably foreseeable relative to individuals operating the machine, individuals working on or around the machine, and individuals simply in the vicinity of the machine. They must consider the various ways the machine could cause or become involved in a mishap and the various ways a person could get hurt. Designers must consider the possibility / likelihood of a person getting caught, nipped, pinched, drawn-in, trapped, entangled, crushed, struck, run over, cut, sheared, abraded, punctured, injected, jolted, vibrated, dragged, flung, wrenched, radiated, burned, scalded, blinded, deafened, poisoned, sickened, asphyxiated, shocked, electrocuted, overexerted and overextended, as well as losing a grasp, losing footing, losing balance, slipping, tripping, misstepping, falling on, falling into and falling off. In addition, machine designers must consider the machine’s potential to cause harm to animals (unintentionally becoming caught, injured or killed), property (being struck, contaminated, chemically altered, weakened, flooded, overloaded or burned), or the environment (unacceptably polluting or unacceptably altering environmental or biological systems). The best and most effective time to assure a machine is reasonably safe is during the design process, not after.
Ergonomics is closely tied with machine safety. Ergonomics, sometimes referred to as ‘human factors,’ is a technical discipline concerned with (relative to design of machinery) interrelationships between humans and equipment. Ergonomics is applied for the purpose of integrating human capabilities and limitations with equipment characteristics, not only to reduce operational and safety issues and problems, but also to improve human-work effectiveness. The types of problems that can be mitigated by the application of human factors include: the failure to perform a required task, performing a task that should not have been performed, the failure to recognize a hazardous condition, a wrong decision in response to a problem, inadequate or inappropriate response to a contingency, or poor timing to a response, to name a few. For a machine to be reasonably safe for its operators or bystanders, ergonomics (human factors) must be part of the design process.
The subjects of machine safety and ergonomics have been written about in a number of well-researched books. In addition, industry safety standards have been created through collaborations of experts in their fields. It should be noted that the books and standards cited at the end of this chapter are not the only literature to which one should refer. They represent, however, a useful cross-section to which a machine designer can refer to understand today’s expectations. The reader must understand that the material in this chapter is necessarily brief and general in nature. Hopefully, this introduction will encourage every designer to read further and seek a better understanding of the subjects. Section 2.5 of this chapter provides a list of recommended resources.
Ergonomics is a discipline that studies humans, their characteristics, capabilities, and limitations, in relationship with their surroundings. Relative to machine design, it is the science of designing a workspace environment and machine interface to fit the user. Like safety, ergonomics is a broad topic that is the subject of many excellent texts. Poor ergonomics can result in either acute injury or long-term repetitive use injury. It is essential to consider not only the physical geometry and arrangement of workspaces, but also the forces involved and the frequency in which they are encountered during a given workday. Actions like bending, reaching, grasping, lifting, turning, positioning, applying force, and releasing all must be conducted with proper ergonomics to achieve efficiency and assure a safe workplace.
Ergonomics issues one must consider when designing equipment and work space are:
•Operator body and workspace dimensions
•Operator performance capabilities and limitations
This section is meant to be an introductory reference only. The reference books and industry standards cited at the end of this chapter provide detailed information for the reader on these subjects.
•A list of books and industry standards are provided in Section 2.5 of this chapter.
BODY AND WORKSPACES DIMENSIONS
The figures and tables in this section represent only one set of data; many sets are available that generally represent information that has been accumulated by various groups and individuals over the years. Care must be taken to choose and refer to the appropriate information source for any given design task at hand.
BODY DIMENSIONS
Anthropometry is the study of body dimensions for the purpose of understanding human variations. Figures 2-1, 2-2, and related information are examples of anthropometric information available from various sources. The information in Tables 2-1 and 2-2 provide basic body dimensions representative of the adult civilian population in the United States. This type of information is particularly useful when designing workstations and controls and when determining various task assignments.
WORKSPACE, CLEARANCES, ENCLOSURES AND ACCESS OPENINGS
Machine workspaces for routine operation as well as maintenance and repair must be designed to accommodate operators as well as maintenance personnel. Interior access openings must be sized appropriately for the various purposes for accessing the area, whether for normal machine operation or for maintenance or repair. Openings must not only accommodate those parts of the individual needing access, but must also be large enough to accept whatever equipment the individual must
