Table 1. Effects of Whole Body Vibration Frequency (Hz)
Heat strain occurs
whenever the body gener- ates more heat than can be dissipated. Injuries due to cold exposure can be either freezing related (i.e. frost- bite) or nonfreezing (i.e. frost nip), which can result from more than 10 hours of exposure to cold. Protective clothing is
4-10 5-7
10-18 13-20 13-20 20-23
critical for combatting injuries due to heat or cold. Personal protective equipment (PPE) can also act as a barrier against a variety of haz- ards (flying debris, cuts, etc.). However, if PPE is improperly fit or in poor condition, it may create more hazards. Maintain your PPE in good work- ing condition, replace items in poor condition and make sure the PPE fits workers properly. Noise. Sound is the result of pres-
sure fluctuation generated by vibra- tions from some source; hearing is the phenomenon of sensing sound vibra- tions. Noise is unwanted sound. Noise in metalcasting facilities has been observed when working near a furnace, using air-powered tools to compact sand in a mold, using saws or sanders to finish parts, and operating construc- tion equipment/tractors or fork trucks. Noise can be annoying and
distracting, cause hearing loss, affect performance and productivity, interfere with spoken communication, cause physiological stress, raise blood pres-
Symptoms
Discomfort Abdominal pain
Influence on breathing Muscle contraction Chest pain
Urge to urinate Head symptoms
Influence on the speech Increased muscle tone
Source: Rasmussen, G. (1982). Human Body Vibration Exposure and Its Measurement Technical Review. Bruel & Kjaer Instruments Inc., Denmark.
Individual differences
among the characteristics of a person, including gender, weight, anthropometry and strength, also should be con- sidered. Examples of indi- vidual differences observed at metalcasting facilities include having to reach because items are stacked too tall, or straining because facilities and workstations
sure, accelerate heart rate, slow diges- tion and increase muscular tension. A normal noise level range is defined as 40-50 dB. For offices and factories, it is recommended that background noise not exceed 55 dB. According to OSHA, any noise at or above 85 dB requires mitigation. Ear plugs can reduce noise levels by 30 dB for noises between 85 and 100 dB, and ear muffs can reduce noise by 40-50 dB for noises greater than 100 dB. Cognitive Stresses, Individual Dif-
ferences, Visual Demands. Cognitive stressors are conditions exceeding a person’s mental workload. Examples observed at metalcasting facilities include timed actions and rushing to finish work, alarms going off in a noisy environment and scenarios requiring workers to select from different pro- cedures. To reduce the effects of these stressors, choose symbols and signals carefully and minimize and simplify the information provided.
are designed for the opposite gender. Visual demands can become exces-
sive in low light conditions. For exam- ple, a dim area might make it difficult to complete an inspection task. To determine if visual demands are unac- ceptable, use a light meter to measure the foot candles or lux in an area, and compare the results to recommended tables for various types of tasks.
Follow-Up Evaluations Follow-up visits to each of the 11
metalcasting facilities involved in the training were made from one to three months after the training to determine what, if any, changes were imple- mented, and to further evaluate the effectiveness of the training program. Worker observation and interviews with employees and managers were conducted to review the effectiveness of the training sessions and company progress with their ergonomic pro- grams. Typical questions for managers addressed what type of feedback was
Fig. 2. Adding pallets to raise the part storage height in this facility eliminated unnecessary bending. 26 | MODERN CASTING October 2011
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