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SIL Review

What is SIL Study?

SIL Study means performing SIL assessment, preparing a SRS (Safety Requirements Specification) report and performing SIL verification activities in order to check SIL (Safety Integrity Level) status of the target device or product. SIL Study method uses LOPA (Layer of Protection Analysis) method and QRA (Quantitative Risk Analysis) method.

LORA method

QRA method

SRS Report Cases

SIS ID :

SIS-x-L0XXX

Service :

xxxx  Compressor Suction Scrubber LL level  with Gas blow-by to drain seal drum and potential damage to drum

TAG # :

0x-LLT-XXX

Required SIL :

SIL 1

Demand rate on SIS :

Low demand

Test interval :

1 year (to be confirmed by SIL verification)

Response Time :

Refer to general Requirements

Method :

De-energize to trip

Safe state :

Emergency Shutdown Valve (ESDV xxxx) between compressor suction scrubber and drain seal drum closed

Reset Type :

Refer to general Requirements

Nuisance Trip Req’s :

Refer to general Requirements

Special Diagnostics

Transmitter usual diagnostic by PLC

Manual Shutdown

Existing (manual control of ESDV xxxx)

Regulatory Req :

Refer to general Requirements

MTTR :

4 hours expected

Cause & Effect Diagram

 

EFFECT

DESCRIPTION

Close shutdown valve to drain drum

    
 

cause

  

TAG

07-ESDV-100

    

Tag

Description

Alarm Tag

Trip Point

    

Notes

15-L010

Suction scrubber Low Low level

15-AT-020

To be defined

X

    

 

Hazard Control Principle

  • Hazard elimination or inherent safety.
  • Add-on safety devices(including M out of N structure)
  • Provide Warning Devices”
  • Develop Procedures and Training
    SIL Low demand mode of operation(Average probability of failure to perform its design function on demand PFD) High demand or continuous mode of operation(Probability of a dangerous failure per hour PFH)
    1 10-2 < PFD < 10-1 10-6 < PFH < 10-5
    2 10-3 < PFD < 10-2 10-7 < PFH < 10-6
    3 10-4 < PFD < 10-3 10-8 < PFH < 10-7
    4 10-5 < PFD < 10-4 10-9 < PFH < 10-8
    • PFD(Probability of Failure per Demand)
    • PFH(Probability of Failure per Hour)