Safety management is critical for process industries like Oil, Gas, Chemicals, and Petrochemicals to implement and follow the safety standards of IEC Standards. It demands stringent verification of the Safety Integrated System (SIS) that provides the required risk reduction and meets the Safety Integrity Level (SIL) for each Safety Instrumented Function (SIF) during its operation. #IEC61508 #sil #sif #sis #pfd #rrf #wordoftheweek #erp #erpsoftware #softwareservices

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Stricter Requirements
Lower Failure Rate
Not used in the
Process Industries
Used in the
Process Industries
SIL
Lower Integrity
Looser Requirements
Higher Failure Rate
4
3
2
1
SIL is the Safety Integrity Level (SIL) that must be met by a particular Safety
Instrumented Function (SIF) implemented by a Safety Instrumented System
(SIS) in any process-type manufacturing industry.
Safety Integrity Level

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SIL is a measure of risk reduction factor provided by a specific SIF. SIL is
normally expressed as a level from 1-4, which is a measure of risk reduction
provided by a specific SIF.
SIL 4 provides the greatest risk reduction factor and has the highest level of
security integrity
SIL 1 provides the lowest risk reduction and has the lowest level security integrity.
Take the example of a SIF with SIL 4 in the table chart above. The Risk Reduction Factor (1/PFD) would be interpreted as
that one in 10,000 to 100,000 would fail within a year. Safety availability is the interpretation of the behavior of the SIF from
the point of view of its success.
>0.00001 to <0.0001 >10,000 to <100,000
>1000 to <10,000
>100 to <1,000
>10 to <100
>99.99 to <99.999
>99.0 to <99.99
>99 to <99.9
>90 to <99
>0.0001 to <0.001
>0.001 to <0.01
>0.01 to <0.1
Probability Of Failure On
Demand (PFD)
Risk Reduction
Factor (1/PFD)
Safety Availability (1-PFD)
SIL
4
3
2
1

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IEC 61508 is the basic, first, and foremost functional safety standard
applicable to all industries. In case, if there is no industry-specific
functional safety standards for products, IEC 61508 can be applied.
IEC 61508 series provides functional safety for the lifecycle of Electrical/
Electronic/Programmable Electronic Safety-related Systems (E/E/PE, or
E/E/PES) relating to the part of overall functional safety of EUC (Equipment
Under Control). It addresses functional safety of a device or system that
perform automated safety functions such as sensors, control logic, or
other related electronic or software activities.
Functional safety
Overall Safety
Part of the overall safety relating to the process and
the "Equipment Under Control" which depends on
the correct functioning of the "E/E/PE safety related
systems" and other risk reduction measures
Freedom from unacceptable
Risk

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Few other standards have been published under the umbrella of
IEC 61508 serving as guidelines for the application of functional safety to
specific sectors.
IEC
61508
Trasportation
Energy
Household
Medical
Buildings
Industrial
.EN 5012x - Railway applications
IEC 61496-1 - Electro sensitive
protective equipment light barrier
IEC 61131-6 - Programmable
controllers
ISO 13849 - Safety control systems
IEC 61800-5-2 - Electrical power
drive systems
ISO 13850 - Emergency stop
IEC 62061 - Machinery
ISO 10218 - Robots
.ISO 26262 - Road Vehicles
.ISO 15998 – Earth-moving
machinery
.ISO 25119 - Tractors and
machinery for agriculture and
forestry
.EN 31 / EN 115-Lifts