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Figure 1.1 Layers of Protection Analysis
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- 1.3 Levels of shutdown
| Figure 1.1 Layers of Protection Analysis
Source: Nolan, D. P. (2019). Process Controls. Handbook of Fire and Explosion Protection Engineering Principles for Oil, Gas, Chemical, and Related Facilities 1.2 Activation mechanismsMost ESD systems are designed so that several mechanisms can initiate a facility shutdown. These mechanisms are provided by both manual and automatic means. Typically, these include the following: Manual activation from a main facility control panel; Manual activation from a strategically located initiation stations within the facility; Automatic activation from confirmed fire and gas detection system alarms; Automatic activation from process instrumentation set points (e.g., “high-high” vibration). An automatic ESD could be activated where a gas monitor detects gas. All sources of ignition would be shut off, the station isolated. In addition, ventilation fans might be turned on to clear gas from the building. Manual shutdown stations are common in manned facilities and allow an individual to shut down a section of a facility quickly. These stations are usually located outside of buildings on the normal route of travel, so that they can be activated while on the way out of the emergency situation. 1.3 Levels of shutdownThe activation logic for an ESD system should be kept as simple as possible. Typically, most facilities specify plateaus or levels of ESD activation. These levels activate emergency measures for increasing amounts or areas of the facility as the incident or the degree of hazard from the initial event increases. Low hazards or small area involvement would only require a shutdown of individual equipment, while major incidents would require a facility shutdown. The isolation of one portion of a facility should not present a hazard to another portion of the facility; otherwise, both should be shut down. Typical ESD levels utilized in process industries are described below and highlighted in Table 1.1. жүктеу/скачать 2,11 Mb. Достарыңызбен бөлісу:
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