POWER April 2016 - 23

5. Highly susceptible areas. It is very
important to conduct inspections to identify
attemperator cracking downstream of spray
injection, such as in this high-pressure steam
bypass to cold reheat piping. Courtesy: Tetra
Engineering Group
poration process should pay attention to
earlier records of failures and past recommendations.
Currently, there is no rigid
mold that a program has to emulate. A
level of flexibility remains available to
upgrade the programs as plant managers
see fit.
Existing programs are allowed to
combine an old set of procedures with
new ones. For example, an active FAC
program can work with a new CPS piping
plan and risk assessment, Grade 91
inspection plan, and hanger inspection
plan. Similarly, an active CPS piping
plan and risk assessment and a thermal
shock/impingement assessment can
work with a new Grade 91 inspection
plan and hanger inspection plan. There
are no restrictions on how to implement
an O&M program. What matters is that
every aspect of Chapter VII is taken into
consideration.
The sole mission of the ASME B31.1
is to promote safety. The B31.1 Code
plants, components at risk continue to
be piping immediately downstream of the
sprays, including the HP steam bypass to
the CRH (Figure 5) and the HRH bypass
to the condenser. Ultrasonic shear wave
is one of the preferred nondestructive
testing methods to detect early failures.
These inspections are to be conducted
every three years.
The B31.1 code also deals with water
and steam hammer. Although these
events are not frequent, they are equally
important to monitor for. By definition,
water hammer involves large loads
that act aggressively on pipes. Any sudden
change in velocity in a liquid-filled
line can produce large pressure pulses,
which can damage the integrity of the
system. Rapid valve closing or opening
is a major factor. Steam hammer
occurs for similar reasons. Rapid closure
of turbine stop valves can result
in large loads. Accumulated condensate
can be driven through steam and drain
lines at high speed, producing highimpact
loads when it hits pipe bends
and valves. " Chapter VII Operation and
Maintenance " procedures emphasize the
need for recordkeeping and detailed descriptions
of such events.
Implementation at CCGT Plants
If a CPS program is absent, immediate action
is required. A program that monitors
corrosion, creep, fatigue, and inadequate
piping support systems is appropriate for
all power generating facilities.
If a maintenance program is already
present, only an update is needed. A comprehensive
review will establish the portions
that agree with the latest guidelines
and the ones that lack conformance. In
addition to code compliance, the incorApril
2016 | POWER
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POWER April 2016

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