Failure emergency trip

NO or NOT No electricity supply Grid failure, transformer failure and such like No cooling, reaction temperature rises Emergency trip... 

Probability of failure of the independent protection barriers (total probability of failure on demand) emergency trip system (0.01) not yet installed additional safety function (0.01) = 0.0001... 

Scenario number 1 Equipment number Scenario title Cooling control failure and failure of the emergency trip system ... 

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... 

For both failure modes, terminations caused by conditions other than the DG and its immediate support systems were not counted. Conditions that invalidated tests or demands for this study Include any operating errors that would not have prevented the DG from being restarted and brought to load in a few minutes without corrective maintenance incorrect trip signals that would not have been operative in the emergency mode and minor water or oil lea)cs that would not have precluded operation of the DG in an emergency. 

Class 1 safety instrumentation loops include alarms and trips on storage tanks containing flammable or toxic liquids, devices to control high temperature and high pressure on exothermic-reaction vessels, and control mechanisms for low-flow, high-temperature fluids on fired heaters. Other Class 1 instruments include alarms that warn of flame failure on fired heaters, and vapor detectors for emergency valve isolation and sprinkler-system activation. All of these alarms, shutdown valves, and other critical instruments are regularly proof-tested to a well-defined schedule. 

Within 20 to 35 minutes after the heater was fired, a fire-water sprinkler system tripped. A heater flame failure alarm occurred a short time later. Witnesses stated flames were over 50-ft. (15 m) high in approximately five seconds after the tube ruptured. The fire damages were the greatest on the third and fourth levels of the process unit as 10- to 12-mph winds carried flames and destructive heat into the unit. There was an excellent response by the emergency squad with eight hose lines reinforcing the fixed fire-water deluge systems. 

Vendors should provide free trairrirrg to prrrchaser s techtriciarrs for operation and maintenance as well as handling emergency situations for all items purchased. At many locations, steady power supply may not be always available. There should be no detrimental effect on the product s quality due to power tripping/ short-duration power failures. 

Selection of initiation criteria does not always guarantee fulfilment of acceptance criteria when the single failure criterion is assumed. The response time became adequate after an adjustment was made to the system. Emergency operating procedures and operator training are satisfactory regarding consideration of failures in the safety systems. Diverse initiation criteria wiU be implemented in the new reactor trip system. 

An independent poison ball safety system is provided to assure that the reactor is driven and maintained subcritical in the event of failure of part or all of the Horisontal Hod System due, for example, to an earthquake, or in the event of actuation of the emergency raw-water cooling system which would result from primary loop depressurisation. Upon receipt of a trip signal, the balls are released to fall by gravity into vertical channels in the active sone of the reactor Excess hopper capacity is provided to assure that the balls fill the channels to a level above the top of the active zone. 

Parameters which are monitored for Ball <3X) circuit trip actuation are earthquake (magnitude 5 or greater on the modified llercalli scale) emergency cooling water flow to reactor failure of neutron flux to decay following a IX safety circuit crip, and reactor-supercritical-a ter a safety rod scram. ... 

Trip Devices. A trip device ensures that an approach beyond a safe limit (or, in some cases, the initiation of an entanglement) stops or reverses the machine movement, within a maximum prescribed time, usually 0.2 seconds. Trip devices include mechanical screens or barriers, which activate a switch upon trip, photo-electric (p-e) curtains, or pressure-sensitive mats. Trip devices differ from emergency stops in that they are activated by the involuntary action of the person at risk. The main problems associated with the use of trip devices are maladjustment of the device, or the machine s brake, or failure of these elements. The unproven reliability of some types of trip devices limit their use as secondary forms of guarding, or where limited access is required, e.g. for loading and unloading. 

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