Emergency shutdown protection requirements

Fire water pumps should be dedicated solely to fire protection. They may be used to feed into a backup system for emergency process cooling, but not as the primary supply. Valving for this connection should be accessible for prompt shutdown when required under fire emergency conditions. 

For the purposes of this assessment, the emergency is determined to be complete when energy input has been removed from the process unit, major equipment has been secured from damage, and the environment is protected from an uncontrolled hazardous release. The process unit may not be totally secure at this point however, it is considered safe. In some cases, this definition may reduce the primary emergency shutdown requirements. 

For non-change type trigger events, PSSR is verifying that the process is safe for startup, all maintenance has be completed, and other facility requirements have been met (for example, a PSSR following a maintenance turnaround or after an emergency shutdown). Again, the PSSR provides a second layer of protection that all other policies and procedures are complete. 

Risk avoidance involves eliminating the cause of the hazard. This is accomplished by changes in the inherent risk features of a process or facility, e.g., using noncombustible fluid as a heat transfer medium (i.e., hot oil system) instead of a combustible fluid (e.g., diesel oil). Risk reduction concerns the provision of prevention measures or protection features that will lessen the consequences of a particular incident. Some examples include firewalls, firewater sprays, emergency shutdown systems, etc. Most facilities include some aspect of risk reduction measures simply due to prescriptive or even performance based regulatory requirements. 

Emergency shutdown and power set-back. The requirements of the automatic protective system are two-fold. First, and more important, it is designed to protect against the release of radioactive fission products to the atmosphere. The barriers... 

Eor self-contained drilling rigs or tender rig derrick sets, any associated, independent offshore fire protection system alarm and emergency shutdown systems and relief, flare, vent, and drain systems should meet the minimum requirements established for the platform. These systems should be integrated with the overall platform fire protection system alarm and emergency shutdown systems and relief, flare, vent, and drain systems. 

The Ground Test Reactor would have to be designed with normal shutdown, emergency shutdown, and restart capabilities. These would be required for normal test and maintenance evolutions, as well as for reactor protection from potential casualties and engineered safeguards for a potential reactor accident condition. 

Safety features on the loop included burst disks for over-pressure protection on the gas side and pressure relief valves on the water side. An emergency shutdown could be commanded by the user, or triggered automatically in the event a safety device was activated. The emergency shutdown would command the turbines to shut down and turn off alt heater power. A safety barrier to provide noise reduction and to protect against debris (in the event of a catastrophic failure) was considered. The requirements for the barrier had not been finalized at the time the project was canceled. 

Critical safety systems are usually considered to be those that are necessary for safe plant operation during processing and also those required for the safe shutdown of the plant in the event of an unanticipated malfunction. Within an incineration plant, examples of critical safety systems inclnde agent monitoring systems, testing or inspection of pressure rehef valves, ventilation flow and control systems, fire protection systems, emergency alarm and shutdown systems, process interlocks, and furnace temperature control systems. 

Why is a manual shutdown needed at all The process requirements specification defines how manual shutdown should be executed from the process perspective. Operators are often provided with manual pushbuttons to initiate equipment shutdown. Operators are expected to initiate trained responses to a variety of shutdown indicators, such as process indications, process alarms, observed events, protective alarms, emergency alarms, or procedures. 

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. 

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