Gas Turbine Handbook : Principles and Practices

266 Gas Turbine Handbook: Principles and Practices
backup field equipment.
Special design consideration was required to minimize the
stresses of thermal cycling in major equipment items such as the
gas and steam turbines, heat recovery steam generator and vacuum
deaeration condensing system consistent with a life expectancy of 30
years.
The plant’s operation reflects these considerations. During the
last six years the plant has generated 4,647,000 megawatt hours of
power for the utility. GEC has accumulated 1,150 successful starts on
41,750 hours of operation.
These performance indicators show that the design has met the
challenge. Since inception they are:
Operating Availability 89.7%
Peak Periods Availability 98.0%
Forced Outage Factor 1.25%
The availability factor of GEC is impacted by the way maintenance
is scheduled and executed. The annual inspections are scheduled
to coincide with the utility’s low usage period, typically March
and April. Because the plant is scheduled off anyway, we will usually
extend our maintenance schedule to minimize overtime expenses.
For example, a combustion inspection at a base load plant can be
performed in 36-40 hours working around the clock. We will perform
the same inspection in a week using a single shift.
MAINTENANCE POLICY
The maintenance associated with the plant is accomplished
through use of the operator/technicians and contract maintenance
support. All maintenance is tracked and equipment histories recorded
through use of a computerized maintenance management system that
also tracks inventory of spare parts. This same system is used for
purchase of all materials.
The technicians are highly trained in the detailed operation of
the plant. They are also highly skilled mechanics capable of disassembly,
inspection and repair of mechanical and electrical equipment.
The technicians are assigned specific systems for which they are responsible
and accountable. Each is required to be the system’s expert;