Курсовая работа по дисциплине: Инжиниринг кип
Activation hardware features
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- 1.7 Emergency Shutdown Valves
1.6 Activation hardware featuresHardwired ESD activation means have traditionally been push-in knobs or buttons. These devices have been subject to false activation as individuals can inadvertently lean on them and cause activation. Such buttons are usually protected with a cover that an individual has to physically lift in order to allow the button to be pushed in. Alternatively, buttons are available that have to be “pulled out” in order to activate the signal. Both of these selections require a confirmed action for the ESD activation to prevent false activation by an operator. All devices should only be manually resettable. Each activation point should be labeled with the area of coverage and provided with an identification as to which valves it operates or equipment it shuts down. A specific number should be assigned to each device. The location itself should be highly visible, preferably highlighted in contrasting colors to normal equipment housings. In some instances, it may be beneficial to maintain process inventories of certain process vessels until the incident actually threatens the container since the inventory of the vessel may be crucial to the restart of the facility or the contents may be highly valuable. Loss of inventory may be criticized if frequent false trips of the ESD blowdown system occur. In these cases, an automatic fusible plug blowdown valve could be installed that would activate from the heat of a real fire incident. In this way the false disposal of the inventory would be avoided. ESD system components that are located in areas that would be considered vulnerable to fire exposures (e.g., within tank dike areas, close to pumps, compressors, etc.) should be provided with appropriate fire protection measures to ensure integrity during ESD operation and during major efforts to control an incident. Actuating mechanisms may include control panels, valve actuators, air receivers instrumentation, cabling, tubing, etc. 1.7 Emergency Shutdown ValvesFigure 1.2 illustrates the Emergency Shutdown Valve (ESDV) that acts as a safeguard against exceeding setpoint pressure. During normal operation, the valve remains open for an extended period of time, months or sometimes even years. The ESDV must function as called upon during an emergency and manage the situation. In the event that the setpoint is exceeded or power or signal are lost, the valve will close within one second to isolate the flow. The failure mode of Emergency Shutdown Valves (ESDVs) for gas processing should always fail in the closed position, since this is the only mechanism to resolve gas-fed fires or prevent explosive vapor releases and buildups. The valves should be provided with an automatic fail-close device such as an actuator with a spring return specification. The ESD valves should lock in the fail-safe mode once activated and be manually reset once it has been confirmed the emergency has been resolved. жүктеу/скачать 2,11 Mb. Достарыңызбен бөлісу:
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