openings should provide not only room for reaching and working, but also additional space for an individual to be able to see.
Figure 2-1: Body Dimension Illustrations
Additional anthropometric and workspace information can be found in industry standards ISO 14738, EN 547-1, EN 547-2, ISO 15534-1, ISO 15534-2 and ISO 15534-3 (see details in Section 2.5), ISO 14738 being particularly useful for designers of machinery.
Table 2-1: Body Dimensions, Inch
Adapted from: Pheasant, 20021
OPERATOR PHYSICAL CAPABILITIES AND LIMTATIONS: REACHING / GRASPING / MOVING / LIFTING
Ergonomics relative to individuals’ physical capabilities and limitations also plays an important role in the design of machinery, not only to make the machine functional and productive, but also to assure the workspace is reasonably safe. Issues of physical movement strength and limitations, and exposure to surrounding environmental conditions must be understood during the design process.
Table 2-2: Body Dimensions, Metric
Adapted from: Pheasant, 20022
Equipment, tools, or work areas that require reaching, grasping, or moving things must be designed to accommodate the strength capabilities and limitations of ordinary operators — being mindful of gender differences. Gender differences must be considered and planned for.
The illustrations in Figure 2-3 are examples of ergonomic information that can be found in the available literature (see citations at the end of this chapter). These types of illustrations are often accompanied with specific force (weight) limits, often representing the 5th percentile adult male (the weakest fifth percent) for the cited population group. Industry standard EN 1005-3 recommends that force limits for professional users correspond to the 15th percentile of the whole adult population (males and females) between 20 years and 65 years of age. For machines intended for domestic users, forces should be limited to the 1st percentile (the weakest one percent) of the same total population. This EN 1005-3 standard also provides de-rating factors for movement velocities, movement frequencies, and application durations. For an understanding of capabilities/limits one might expect in a given situation, refer to and compare data from several sources, understanding what the information and chart numbers represent.
Figure 2-2: Clearances for Work Spaces
Source: Sanders and McCormick, 19933
Note: These clearances may qualify as confined spaces and require a safety assessment.
Among the types of movement and force limits to be considered include (but are not limited to):
•Pedal force limits
•Handwheel rotational force limits
•Hand-cranking force limits
•Finger-grip/squeeze and hand-grip/squeeze strength limits
•Hand-grasped item twisting force limits
•Weight carrying limits in various carrying modes
•Arm — up, down, in, out, pull, push — force limits
•Whole body pushing, pulling force limits
•Lifts above shoulder height weight limits
Table 2-3: Access Openings
Source: MIL-HDBK-759
Figure 2-3: Reaching — Grasping — Moving Illustrations
Lifting is often required of machine operators while operating equipment or moving material into or out from a machine. An operator may be required to perform many lifts during a normal shift. There are limits to how much total lifting a person can do in a given workday, and it is dependent on the geometry of the lift, the weight involved, and the frequency of performance. When determining if a lifting task is reasonable, the Applications Manual for the Revised NIOSH Lifting Equation should be consulted (available online at www.cdc.gov under “lifting,” which, at the time of this book’s printing, was http://www.cdc.gov/niosh/docs/94-110/). It is recommended that a qualified professional review any ergonomic lifting scenarios.
Additional human physical performance information can be found in industry standards EN 1005-2, EN 1005-3, EN 1005-4 and EN 1005-5, MIL-STD-1472, and the book Human Factors Design Handbook, EN 1005.3 is particularly helpful for machine designers.
•Obey all applicable codes and standards when designing any machine for human interaction. See the recommended resources in Section 2.5 for more information.
•Safety and ergonomics are broad and specialized topics. Have a qualified professional evaluate all applications.
MACHINE SAFETY: DESIGN PROCESS
A properly designed machine must be reasonably safe for its intended or foreseeable use. This means that it is not just safe for operators and individuals working around the machine while it is operating and performing its primary function, but it is also safe for individuals involved with all aspects of the machine. This includes:
1.Initial assembly and set-up
2.Production job set-up
3.Machine start-up
4.Normal production operation
5.Unusual production circumstances
6.In-production adjustments, clearing and troubleshooting
7.Cleaning and routine maintenance
8.Non-routine maintenance
9.Relocation
10.Decommissioning and scrapping4
In
