Emergency shutdown systems components

Backup power supplies are often essential. It is important to also consider the implications of hardware or software failure. Redundancy should be built into any system. It is also prudent to consider a specific emergency shutdown device (BSD). No single failure of a component within the human-computer interaction (HCI) should cause the failure of the HCI. 

The extensive use of passive systems to assure plant safety eliminate some traditional safety-related auxiliary systems (e g. injection systems) or strongly simplify others, reducing the number of redundant components (e.g. boron emergency shutdown). 

Should an emergency occur requiring immediate shutdown and over-ride of normal sequenhal shutdown, an EMERGENCY STOP pushbutton is provided for this purpose. This device interrupts power to all components in the oxidation unit control circuit, shuts down all motors, and closes the vacuum line valve and the chlorine pressure-reducing valve (PRV). The EMERGENCY STOP pushbutton is also used as a reset device to restore the system to normal operating status after an alarm situation has occurred. 

Emergency Infrequent incidents requiring shutdown for correction of the condition or repair of damage in the system. There is no loss of structural integrity. These include unlikely off-normal conditions which individually are not expected to occur during the plant lifetime. However, when integrated over all plant components, events in this category may be expected to occur a number of times. These may result in minor incidents, that is an occurrence which results in ... 

The economic impact of a spurious or nuisance trip of an ESD system can be disastrous. An ESD system is an important layer of protection to prevent and prevent hazardous situations from occurring. So, it is needless to mention that the ESD system must be extremely reliable and function on demand. During an emergency, it must put the process in a safe state in orderly fashion. Also ESD systems design shall be based on a fail safe independent system, that is, ESD systems are such that during a failure of a component the process reverts to a condition considered safe and not a vulnerable serious hazardous event. Reliability and availability are major parameters for ESD system performance. Reliability is a function of system failure rate (its reciprocal) and mean time between failures. Spurious trip conditions may initiate a so-called fail safe incident that may result in accidental shutdown of equipment or processes. However, undetected process design errors or operations may initiate dangerous incidents that may disable the safety interlock and may even cause accidental process... 

Requirements for the availability of the electrical power sources should be stated for all operational states. These include off-site sources on-site generators (diesels and gas turbines, including associated fuel reserves) batteries and associated control protective, distribution and switching devices. The operability requirements should be such that sufficient power will be available to supply all safety related equipment necessary for safe shutdown of the plant, and for the mitigation and control of accident conditions. The operabihty requirements should determine the necessary power, redundancy of supply lines, maximum permissible time delays and necessary duration of the emergency power supply. Equivalent requirements should be stated for other power sources (for example, the pneumatic power system). Particular care should be taken to ensure that electrical supplies remain adequate in shutdown operations, when many systems and components will be out of service for maintenance. 

The action functional component represent all the possible predetermined response actions which should occur upon reaching apredetermined alarm/action setpoint. Response actions could include activation of audible and/or visual alarms, annunciation of specific alarm conditions and locations, hardcopy of past and present gas concentrations or environmental conditions, notification of local and remote emergency response personnel, activation of emergency safety control systemsl l through relays such as gas supply source and equipment shutoffs, HVAC system shutdown with 100% exhaust, or one-pass cleanroom air flow operations. The predetermined response actions should follow established emergency response procedures and policies of your organization and all applicable environmental, health, and safety regulations to protect both personnel and the environment and minimize the extent and effect of any hazardous situations. 

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