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Figure 2-8. Design Requirments Element: Assignment of Component-Level Grades
Chapter 2 Implementation Guidance for Operational Configuration Management
Fully Developed Element - s1073ch20029

In establishing boundaries between facility systems and essential supporting systems, arbitrary but
reasonable boundaries may be defined. Essential support services include electric and control power,
instrument air, lubricating oil, and ventilation.
There are two primary approaches, one recommended and one alternate, for establishing system
boundaries for essential support systems. The recommended approach is to extend the safety system
boundaries to include essential support items out to an appropriate interface, such as an isolation valve.
The alternate approach Is to deem the essential support systems to have safety portions. According to
the recommended approach for air-operated equipment, the air controller, solenoid switches, and air
isolation valves would be considered part of the basic safety system, while equipment upstream of the
valve would be considered part of the instrument air system. According to the same approach for
electrically operated equipment, the electrical components, including limit switches, out to and including
the first breaker, would be considered part of the basic safety system, and the components upstream of
the breaker would be considered part of the electric power system.
Assignment of Component Grades. Component grades should be assigned in a manner analogous to
system grading. Best Available Design Information should be used to identify the design requirements
associated with each component and determine the design requirement types associated with each
component. In some cases, the design requirements might indicate that a component is not essential to
the system's top-level function. For example, a safety cooling-water system might have a chemical
release monitor with an environmental design function, but no safety design function. Component
grades should be assigned on the basis of the applicable types of design requirements. The component
grade should be based on the most important type of applicable design requirements.
As previously stated, the default component grade is the same as the system grade. In many cases, the
component is graded consistently with its system. The net result of component grading may be the
downgrading of certain components that are not essential to the top-level category of design
requirements for the system. For example, local instrumentation to support maintenance might not be
needed to fulfill either safety, environmental or mission requirements. If there is any doubt with regard to
downgrading a component, the component should retain the system grade until associated design
requirements are fully reconstituted. If a component appears to have design requirements of a higher
grade than its system, the system might be incorrectly graded or the component might be in the wrong
With the exception of components whose design requirements have been established and found to be
adequate and outside the equipment scope criteria, all components within a CM system should be
included in the CM program, even those without a safety, environmental, or mission function. Once the
design requirements are fully established and adequate, the CM equipment scope criteria may be used
to consider component exclusions. However, the inclusion of components other than safety,
environment, and mission ones is generally advisable for CM systems to enhance overall configuration
As with system grading activities, other ongoing activities will periodically identify new information
relevant to component grading. New design activity, for example, might add new systems as well as
new components to existing systems. The DR adjunct program might uncover facility design
requirements that affect component grading. Moreover, system walkdowns or operational activities
might identify previously overlooked components. The impact of new information on component grading
should be taken into consideration. While component grading is generally a one-time activity, its results
are subject to review and revision as necessary when new information becomes available.

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