The Study Of Layer Of Protection Analysis In Safety Instrumented System Of C4 Tank Farm In Olifin Plant

The manufacturing in the petrochemicals is a high safety risk process.In order to protect the continue process,it is running with Basic Process Control System,Safety Instrument System SIS and the others protection method.The prevention of leakage and its consequence is the main objective in the manufacturing.The model of protection method-Onion Model,is the protection template in the petrochemicals industry.It is the difficult question that how to identify the safety risk in application scenario,allocate to SIS and the others protection layer,build the effective barriers.Hazard and Operability Study HAZOP is not detailed,cannot get the Risk Reduction Factor RRF of SIS.Layer of Protection Analysis LOPA,is the methodology that base on the Onion Model.It aims to reduce the risk,checks the specialty,effectiveness,reliability,auditability of the protection layer,and gets Risk Reduction Factor RRF in SIS and Safety Integrity Level SIL.After assessment,SIS loop is made for robustness of subsystem,the selection of instrument,the determination of maintenance method and test interval.Safety Requirement Specification SRS includes the functional safety description,architecture of subsystem,maintenance requirement and etc.LOPA identifies the effective protection layers,and organizes the protection layers of Basic Process Control System BPCS,SIS,other safety equipment,Fire and Gas System,prevents from the safety incident and the massive consequence.The objective is to comply with Onion model and build SIS,build the automatic system for process,to reduce safety risk to the tolerable level,to protect the daily process.The thesis studied LOPA and the relative standards,selected and used a suit of formal.It covers the different maintenance method and test interval,calculates reliabilities data of instrument and probability of failure on demand PFD,determinates the architecture of subsystem,maintenance method and test interval.The thesis works for the method of SIL classification,robustness of subsystem and maintenance for reliability.The abusage of LOPA can get the wrong SIL class and incorrect subsystem with the incorrect maintenance,and incorrect reliability of SIS.Finally,the methodology of Layer of Protection Analysis in Safety Instrumented System was used in C4 Tank Farm in an Olifin Plant.It was used to classify the SIL,built the SIS loop,determinated the maintenance method and test interval,calculated the loop PFD,and compare with SIL requirement.After PFD is on target,the SIS loop is correctly designed.It can protect the process effectively.