The below is a description of a system that aim at preventing potential ignition of gas at a given work place. Develop a Fault-Tree Diagram for this system In system hazard prevention practice where hazard gas may-result into explosion, one preventive measure is the ignition prevention barrier that should shield the gas from being ignited. The failure of this barrier may result from cither the failure of failed hot work prevention, the hot surface shield, the inadvertent flame prevention protection, or the hot particles/gas controller. The hot work prevention is human-based. The hot work requires the worker to obtain a work permit and must be supervised by a foreman while the worker himself is required to conduct self-control at work. These practices must be fulfilled at the work place in order to avoid ignition due to failed hot work prevention measure. It is noted that the work permit needs to be properly issued by the system administrator who should investigate the potential improper work instructions, and must assess the risks before issuing the work permit. When all of these human precautions fail, then the work permit precaution measure fails. Foreman supervision is imminent. The self-control at work requires the worker to have received adequate training. Also, the worker should not operate without a work permit and this is part of the self-control measures. The worker self-control imposes on the worker to verify1 the work permit conditions and to follow the work permit instruction very accurately. The hot surface shield is required and if not applied, will lead to possible ignition. Flame protection may fail due to the inadvertent or unintentional failure of its control which could be the result from both failure to inspect the flame source property and improper flame detection and control. This detection control can result failed flare detection, the unavailability of a flame detector, inadequate detector coverage of the flame source, or unintentional flare direction. The hot particles/gas controller requires proper insulation of the gas transport line and the proper insulation of the work area from the gas transport line.
solution :
1)here our aim is to prevent ignition of gas and failure of any subsystem may lead to failure of whole system
2)fault tree diagram is as follows
ignition of gas
failure of ignition prevention barrier
OR gate
1)failure of hot work prevention
2)failure of hot surface shield
3)failure of inadvertent flame protection
4)failure of hot particle controller
1)failure of hot work prevention
OR gate
i)failure of administrator
ii)failure of worker and foreman
AND gate
a)failure of foreman
b)failure of worker
OR gate
aa)inadquete training
bb)work without permit
2)failure of hot surface shield
i)fail to provide hot surface shield
3)failure of inadvertant flare prevention
OR gate
i)intentional failure of control
ii)unintentional failure of control
OR gate
a)fail to inspect flame source
b)improper flame detection
OR gate
aa)failure of flare detector
bb)unavailabilty of flaredetector
cc)inadquete coverage of detector
dd)unintentional flare direction
4)failure of hot particle controller
OR gate
i)fail to provide insulation of gas line
ii)fail to provide insulation between gas line and work area
4)in this way failure of any component will cause failure of system as per combination in gate system and by knowing reliability or probability of any of this failure we can calculate reliability of this system
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