Sources of Changes cont'd

DOESTD107393

Acceptable operations changes are only those that have been documented and evaluated to ensure

consistency with the design requirements. Unreviewed operations changes can cause inadvertent

deviations from the design requirements. For example, adjustments in instrument and equipment

setpoints can have adverse secondary effects on such engineering considerations as safety margins and

response times. Similarly, lifted leads, jumpers, and other temporary physical changes need careful

attention.

Maintenance activities can also be a major contributor to changes in the facility. Effective controls are

essential to ensure that unevaluated changes are not introduced into the facility by maintenance

personnel. Therefore, clear guidance on the conduct of maintenance should be provided to ensure that

the differences between a change and routine maintenance are known and understood. Under adequate

change controls, the maintenance organization may not make physical changes except when it is acting

as the constructor for an approved physical change or is making changes within the design envelope.

Maintenance activities that change the facility without an evaluation for consistency with the design

requirements are unacceptable. The work control program, which manages and sequences

maintenance activities in the field, is the vehicle to implement effective change control.

Acceptable maintenance activities involve the routine repair or restoration of facility hardware without

altering the physical or functional characteristics (i.e., the design requirements). Maintenance may

replace a part or SSC with an identical item (i.e., identical make and model number, identical constituent

parts, identical function, etc.). Identical replacements do not involve a change to the physical

configuration, the facility documentation, or the design requirements. An equipment replacement with

anything other than the identical part constitutes a change. In other words, the facility physical

configuration is no longer the same, and the corresponding facility documentation should be updated to

reflect the physical change.

To support maintenance activities, the design engineering organization may predefine acceptable

replacements or changes (other than the identical item) and provide this information to the

maintenance organization in the form of a design envelope. Design envelopes provide the

preapproved set of limits or constraints within which changes may be made without exceeding the

design requirements. Maintenance changes that lend themselves to design envelopes are changes to

torque values, maintenance assembly sequences, machining tolerances, heat exchanger tube plugging

limits, rotating equipment vibration limits, or other routine activities where design envelopes can be

established. If a proposed change is not within the bounds of the defined design envelope or if no

envelope has been provided, the change involves a design change and may not be made without

design engineering evaluation.

Procurement of replacement parts to support maintenance activities can introduce unidentified and

uncontrolled changes. Procurement changes may result from changes in suppliers or changes in

production by current suppliers. For example, the procurement organization might purchase a slightly

different (but manufacturer's equivalent) lubricant for a pump. Procurement of replacement parts that

differ from the original item should be identified for technical review. Any difference, including a so-

called manufacturer's equivalent, needs to be formally evaluated and documented by the design

engineering organization to ensure that safety and reliability have not been degraded and that

conformance to the design requirements is maintained. Timely identification and evaluation of

procurement changes can enhance maintenance productivity.

Each facility will need to thoroughly review existing work practices to identify every change source.

Some change sources are subtle and can be overlooked. For example, facility and document changes

can be introduced through software changes. Software has diverse applications, from supporting

design analysis and documentation to performing safety functions as part of the facility configuration.

As such, software changes can lead to any of the three basic change types. Software that reflects

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