damage. Restoration to original profile is the most straightforward
approach; however, in the long term, profile modifications will likely
have increased benefits.
approach; however, in the long term, profile modifications will likely
have increased benefits.
"Once an approach to repair is established, implementation of the work using
proper procedures and high quality workmanship will maximize the effectiveness
of the repair program.
proper procedures and high quality workmanship will maximize the effectiveness
of the repair program.
"Cavitation pitting repairs are discussed in the subsections below and guidelines
and recommendations for repair work are given. While many plant owners
undoubtedly have implemented effective repair programs which differ from that
presented herein, the discussion is intended to provide a reference for
undertaking work of this nature.
and recommendations for repair work are given. While many plant owners
undoubtedly have implemented effective repair programs which differ from that
presented herein, the discussion is intended to provide a reference for
undertaking work of this nature.
4.2
FREQUENCY OF INSPECTION AND REPAIR
"Cavitation Damage Inspections
"Periodic inspection of a turbine for cavitation damage is an important part of
turbine maintenance. Frequent inspections are particularly important during the
initial period for operation of a new turbine or new runner, as they will enable
cavitation damage to be detected at an early stage and remedial measures to
be effected before pitting becomes extensive. When a new turbine is placed into
operation, the unit should be inspected after about 1500, 4000, and 8000 hours
of operation. For pump-turbines, this frequency should be 750, 1500, and 3000
hours because of the potential for more severe cavitation pitting during pump
operation. For these inspections, a hydraulic engineer from the turbine
manufacturer should be present to inspect any areas of cavitation pitting and to
report on the cause of the damage and possible remedial work to mitigate the
damage.
turbine maintenance. Frequent inspections are particularly important during the
initial period for operation of a new turbine or new runner, as they will enable
cavitation damage to be detected at an early stage and remedial measures to
be effected before pitting becomes extensive. When a new turbine is placed into
operation, the unit should be inspected after about 1500, 4000, and 8000 hours
of operation. For pump-turbines, this frequency should be 750, 1500, and 3000
hours because of the potential for more severe cavitation pitting during pump
operation. For these inspections, a hydraulic engineer from the turbine
manufacturer should be present to inspect any areas of cavitation pitting and to
report on the cause of the damage and possible remedial work to mitigate the
damage.
"Subsequent to the initial inspection program, the frequency of future inspection
should be dictated by the extent of damage which is occurring. For units which
are experiencing minimum damage, the period between inspection can be
increased. However, the frequency of inspection should not be less frequent
than:
should be dictated by the extent of damage which is occurring. For units which
are experiencing minimum damage, the period between inspection can be
increased. However, the frequency of inspection should not be less frequent
than:
Turbines . . . . . . . . . . . . . . . . . . every 24,000 operating hours
or every 4 years
or every 4 years
Pump-turbines . . . . . . . . . . . . . every 12,000 operating hours
or every 2 years
or every 2 years
6