What is LOPA and SIS?

Field Instrumentation
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LOPA - Layer of protection analysis

A semi quantitative tool for analyzing and accessing process safety risks on a process unit Uses numerical technique to evaluate the adequacy of existing or proposed layers of protection against known hazards All LOPA starts with a determined consequences to defend against LOPAs are more Subjective than Objective

LOPA Ratio

-A mathematical factor that defines the amount of a safety gap -Feeds to the SIS side -Equal to SIS or SIS amounts -Higher the TMFL or consequence the larger the ratio and associated SIL to fill.

LOPA process calculation
LOPA process calculation574×373 26.8 KB

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SIS Process

Safety Instrumented System -Consist of an engineered set of hardware and software controls that are defined as a critical system and this system will mitigate or stop a determined hazard in a process or unit. -A SIS is engineered to be independent and to perform specific control function -SIS is composed of sensors,logic solvers and end devices with connection system between each item.

SIS Process Calculation

SIS process calculation