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Table 1.1 Typical ESD levels
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Table 1.1 Typical ESD levels
Total plant shutdown: A total plant ESD effectively shuts down the total plant or facility under emergency conditions. Isolation valves are closed to stop the flow of combustible, flammable, or potentially toxic fluids and to stop heat input to process heaters or reboilers, and rotating equipment. Activation of a total plant ESD should not stop or impede the operation of fire protection or suppression systems, deluge systems, sump pumps, or critical utilities such as instrument or process air. Unit shutdown and depressurization: This shutdown layer isolates an entire process unit, process train, or process area involved in a fire or other emergency, thus limiting the supply of fuel. This includes pumps, vessels, compressors, etc., which comprise an entire process unit up to and including plot limit boundaries. Associated emergency depressurization systems for process vessels and equipment should be applied when it is necessary to reduce the potential of a boiling liquid expanding vapor explosion (BLEVE), or to reduce inventories of hazardous materials. Equipment shutdown: A system of equipment stoppage and emergency isolation valves that are used to isolate individual equipment within a process unit and prevent the release of potentially toxic material in the event of a fire, rupture, or loss of containment. Equipment protective system shutdown: Systems that are usually provided for the protection of centrifugal pumps, rotating and reciprocating gas compressors, gas expansion and combustion gas turbines, electric motors, generators, and forced or induced draft air fans. Although it would be easy to institute a total plant shutdown for every incident, it would not be cost-effective, as many small incidents occur relative to large incidents, which do not warrant the shutdown of the entire facility and would reduce the economic return on the investment. жүктеу/скачать 2,11 Mb. Достарыңызбен бөлісу:
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