1. IEC 61511 / ISA 84 Safety Lifecycle
The safety lifecycle is defined as an
engineering process that includes all of
the steps necessary to achieve required
functional safety. The lifecycle addresses
all necessary activities involved in the
implementation of safety-related systems,
occurring during a period of time that
starts at the concept phase of a project
and finishes when all of the safety-related
systems are no longer available for use.
IEC 61511 identifies 12 key activities
related to safety lifecycle management. To
simplify things, the sequential phases are
often grouped into three main phases:
Analysis, Implementation, and Operation.
For more information, go to:
www.DeltaVSIS.com

2. IEC 61511 / ISA 84 Safety Lifecycle
Management of Functional Safety and Analysis
Functional Safety Assessment and Auditing The main focus of the Analysis phase is to identify the required
Management of Functional Safety involves the identification of safety instrumented functions and to define the related safety
management activities that are necessary to ensure functional functional and safety integrity requirements.
safety objectives are met. A hazard and risk assessment is performed to identify and assess
Functional Safety Assessments should be carried out at various risk related to the hazardous events of the process and associated
stages during the implementation and operation phases of the equipment. Based on risk reduction requirements that result from
safety lifecycle. This activity assesses the functional safety that is the HAZOP, safety functions are allocated to protection layers.
achieved by the SIS. The choice of the assessment team These can be safety instrumented functions, or non-SIS safety
membership is important. The team should include technical, functions such as relief valves, rupture disks, diking, etc. Finally,
application, and operations expertise as well as at least one senior the specification of the functional and integrity requirements for
competent person not involved in the project design team. each safety instrumented function are documented in the safety
requirement specifications (SRS).
Safety Lifecycle Structure and Planning Implementation
Safety planning defines the activities that are required to be The Implementation phase is the phase in which the SIS is
carried out along with the persons, department, organization or designed, engineered, installed, commissioned and validated.
other units responsible to carry out these activities. This planning Designing and developing other means of risk reduction is the
is updated as necessary through-out the entire safety life cycle. development of non-SIS safeguards such as relief valves, rupture
Adequate planning should exist to ensure that the SIS meets the disks, diking, etc.
safety requirements. This includes the definition of the safety Validation is the final step to validate that the installed and
lifecycle, including the inputs, outputs, and verification activities. commissioned SIS and its associated safety functions achieve the
A Safety Management System (SMS), or Safety Plan, must be in requirements as stated in the safety requirement specification.
place to ensure that functional safety objectives are met and
appropriate auditing processes are defined. This includes
procedures for assessment, auditing, management of change,
configuration management, and timely implementation of
recommendations. The SMS defines who does what, and
includes policies and procedures for competency management.
Verification Operation
Verification demonstrates by review, analysis and/or testing The objective of the Operation phase of the lifecycle is to ensure
that the required outputs satisfy the defined requirements that the required SIL of each safety function is maintained and to
for the appropriate phases of the safety life cycle identified by ensure that the hazard demand rate on the safety system and the
the verification planning. availability of the safety system are consistent with the original
design assumptions.
If there are any significant increases in hazard demand rate or
decreases in the safety system availability between the design
assumptions and those found in the operation of the plant which
would compromise the plant safety targets then changes to the
safety system will have to be made in order to maintain the plant
safety.
www.DeltaVSIS.com