This standard provides functional. performance. and initial design requirements for the fuel oil system for diesel generators that provide safety-related emergency omite power for light water reactor nuclear power plants. This standard addresses the mechanical equipment associated witb the fuel oil system@ with the exception of the engine mounted components. These components@ which are mounted directly to the engine structure itself@ are excluded except to define interface requirements. It also includes the instrumentation and control functional requirements. The standard excludes motors@ motor control centers@ switchgear@ cables@ and other electrical equipment used in the operation of the fuel oil system@ except to define interface requirements. Purpose. The purpose of this standard is to define those features of fuel oil systems required to ensure an adequate fuel supply to safetyrelated emergency diesel generators@ and to pro.vide perfonnance and design criteria to ensure sufficient fuel is available for supply to the emergency diesel generators under all plant conditions.