sil review

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Emergency shutdown (ESD)

SIL study Have you heard about SIL studies? What does it mean?

What does SIL, SIF and SIS mean?

Terms defined in ANSI/ISA-84.00.01-2004 (IEC 61511-1) Functional Safety: Safety Instrumented Systems for the Process Industry Sector

SIF: Safety Instrumented Function

SIS: Safety Instrumented System: Sensor + logic solver + final element

SIL: Safety Integrity Level: Level used for specifying the safety integrity requirement of SIFs. There are 4 levels:

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SIL study Have you heard about SIL studies? What does it mean?

What does SIL, SIF and SIS mean?

ANSI/ISA-84.00.01-2004 (IEC 61511-1)

Functional Safety: Safety Instrumented Systems for the Process Industry Sector

SIF: Safety Instrumented Function

SIS: Safety Instrumented System: Sensor + logic solver + final element

SIL: Safety Integrity Level: Level used for specifying the safety integrity requirement of SIFs. There are 4 levels:

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SIL study

Step 1: SIL Determination, “assignment workshop”

Identification of Instrumented Interlocks on the P&IDs = inventory of Safety Instrumented Function (SIF)

For each SIF: • Qualitative evaluation of consequences if the event the SIF is

designed to safeguard from

• Qualitative evaluation of the likelihood of the event

• Determination of risk level (likelihood * consequence) and resulting SIF required performance (SIL level)

Deliverable: SIL assignment logsheet / worksheets

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SIL study LIKELIHOOD CATEGORY

DEFINITION POTENTIAL FREQUENCY

A Possibility of repeated incidents 20 or more times per Facility life

B Possibility of isolated incidents 5 times per Facility life

C Possibility of occurring sometime Once in Facility life

D Not likely to occur Once every 10 Facility lives

E Practically impossible Once every 100 Facility lives

CONSIDERATIONS CONSEQUENCE CATEGORY Health/Safety Public Disruption Environmental Impact Financial Impact

Abbreviation S – Safety P – Public E – Environmental F – Financial

I Fatalities/ Serious Impact on Public

Large Community (10,000+)

Major/Extended Duration/ Full Scale

Response

Major Impact to Company

(>$50 million)

II Serious Injury to

Personnel/ Limited Impact on Public

Small Community (1,000 to 10,000)

Serious/Significant Resource

Commitment

Significant Impact To Company ($2 - $50 million)

III Medical Treatment for Personnel/ No Impact

on Public

Minor (10 to 100)

Moderate/Limited Response of Short

Duration

Moderate Impact To Company

($500M - $2 million)

IV Minor Impact on

Personnel

Minimal to None

(1 or 2)

Minor/Little or No Response Needed

Minor Impact To Company

($50M-$500M)

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SIL Study

Step 1 – Assignment workshop

? ?

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SIL Study


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SIL Study


? ? ?

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SIL Study


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SIL Study

Step 1: SIL Determination, “assignment workshop”

Deliverable: SIL assignment logsheet / worksheets

Summary:

What is the second step of the SIL?

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SIL Study

Step 2: calculations and recommendation

SIS Performance Verification

Evaluate the performance of each SIF, based on device selection, architecture, voting, testing etc.

Compare to required SIL level and specify modifications to the SIF design (device selection, component redundancy) or testing intervals

Deliverable: SIS Performance Verification Results and recommendations

sil review

Engineering