SAFETY LIFE CYCLE MANAGEMENT
When a plant or
any processing facility is designed, various criteria focus on the inherent safety of the plant. Our study shall be specific
to the Process industry only, therefore, I would consider it important to know
the relevant standards that are relevant to the safety system for this industry.
Since this concept has evolved for quite a long so there are certain international
standards governing these areas of the industry. Following are the three international
safety standards covering this area:
1.
IEC-61511
2.
IEC-61508
3.
ISA 84
Firstly, let’s
see what the IEC & ISA stand for!
IEC: International Electro technical Commission
ISA: International Society of Automation.
IEC 61508 is
related to the OEM/manufacturers for product design, development, and
certification. It is for electronic and programmable electronic devices for use
in functional safety applications.
IEC61511/ISA84
is related to the life cycle management of this safety instrumented system in the process industry. It provides guidelines regarding identification, requirement,
safety integrity level determination, installation, commissioning, operation
and maintenance, decommissioning, validation, verification, and change
management related to safety system in a process industry. Please note that ISA84 has adopted the procedures/guidelines
provided in IEC61511.
What are the
basic components of the Safety Instrument system?
It comprises of
sensor, logic solver, and final control element.
A chain is as strong as the weakest link.
When the safety system is required?
It is required
to manage the operational risks during the startup, operation, and shutdown of any
process industry.
Why it is required?
This system
manages the operational risks and avoids production loss, personal injury
or loss of life, asset damage, and environmental damage that might surface in the absence of it.
Why lifecycle management is necessary?
If the SIS is
not designed or maintained then either it will fail to serve its intended
purpose of safety or it shall cause nuisance tripping affecting the business.
SIS is a safety instrumented system
used to implement one or more safety instrumented functions (SIF). SIF is the protection layer used to
protect the process from certain hazardous conditions.
SIL is the risk reduction factor that a
SIF provides to the SIS. Based on individual SIF integrity levels the SIL of
SIS as a whole can also be determined.
According to
IEC61511, the steps involved in a Process safety lifecycle management are:
Safety requirement specification development for the SIS
Design and engineering of SIS
Installation, commissioning, and validation
Operation and maintenance
Modification
Decommissioning
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