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Sổ tay kỹ sư cơ khí P19

process approach becomes one of continuous operation. The substitution of processes can be applied on a fundamental basis, for example, substitution of airless spray for conventional spray equipment can reduce the exposure of a painter to solvent vapors. Substitution of a paint dipping operation for the paint spray operation can reduce the potential hazard even further. In any of these cases, the automation of the process can further reduce the potential hazard (Table 74.5). 74.7.2 Isolation Application of the principle of isolation is frequently envisioned as consisting of the installation of a physical barrier (such as a machine guard or. | 74.8 DESIGN AND REDESIGN 2213 process approach becomes one of continuous operation. The substitution of processes can be applied on a fundamental basis for example substitution of airless spray for conventional spray equipment can reduce the exposure of a painter to solvent vapors. Substitution of a paint dipping operation for the paint spray operation can reduce the potential hazard even further. In any of these cases the automation of the process can further reduce the potential hazard Table 74.5 . 74.7.2 Isolation Application of the principle of isolation is frequently envisioned as consisting of the installation of a physical barrier such as a machine guard or device-refer to Tables 74.3 and 74.4 between a hazardous operation and the workers. Fundamentally however this isolation can be provided without a physical barrier through the appropriate use of distance and in some situations time. Perhaps the most common example of isolation as a control strategy is associated with storage and use of flammable solvents. The large tank farms with dikes around the tanks underground storage of some solvents the detached solvent sheds and fireproof solvent storage rooms within buildings are all commonplace in American industry. Frequently the application of the principle of isolation maximizes the benefits of additional engineering concepts such as excessive noise control remote control materials handling as with radioactive substances and local exhaust ventilation. 74.7.3 Ventilation Workplace air quality is affected directly by the design and performance of the exhaust system. An improperly designed hood or a hood evacuated with an insufficient volumetric rate of air will contaminate the occupational environment and affect workers in the vicinity of the hazard source. This is a simple but powerful symbolic representation of one form of the close relationship between atmospheric emissions as regulated by the Environmental Protection Agency and occupational exposure as .