Hydrocarbon Processing - November 2022 - 39

Maintenance
and Reliability
J. RISKO, TLV Corp., Charlotte, North Carolina
Trip your turbine troubles: Optimize the reliability
of steam-driven turbines
Steam turbines are essential for successful
operations in refining and petrochemical
plants, such as at the wet gas
compressor and regenerator air blower
of a fluidized catalytic cracking unit
(FCCU). However, other smaller turbines
can also perform critical functions
that are important to the overall operation
of production units. Much focus is
commonly given to the main production
process itself; as a result, turbine reliability
improvement considerations may be
secondary-that is, until severe damage
occurs, sometimes causing manufacturing
shutdowns for weeks on end.
As one example, severe turbine issues
in a medium-size refinery shut down
both the FCC and hydrogenation and
catalytic cracking (HCC) units for more
than 5 wk, resulting in production losses
exceeding $65 MM. Such incidents can
be mitigated by optimizing the steam
quality that drives turbines. This requires
designing effective condensate
drainage from both the supply lines and
respective turbine installations, as well
as disentraining wetness from the steam
flow to mitigate against erosion, precipitate
and slug damage.
Following the delivery of high-quality
steam, turbines must also be adequately
drained of condensate to help prevent
trips during startup, corrosion during
idle periods, condensate accumulation
during operation, and hydraulic shock to
downstream steam lines or equipment.
Condensate removal also helps reduce
precipitate buildup.
Optimizing the steam system quality
begins with proper design of the main
utility headers. This requires effective
collecting leg design, proper selection,
placement and maintenance of condenFIG.
1. Even simple, single-stage turbines are sophisticated equipment requiring appropriate care.
sate discharge locations (CDLs)-including
the steam traps and valves-
and installing high-efficiency moisture
separators upstream of steam turbines.
Although most of the steam trapping
requirements are relatively simple, load
calculations should be done to properly
size the traps used to drain condensate
from any inlet separator used and from
the exhaust side of back pressure or
vacuum turbines relative to the potential
higher load from steam wetness and condensation.
Although not a common consideration,
the condensate loads at both
the separator and the turbine exhaust
side can be substantial.
When properly designed and installed,
a high-quality steam supply helps
optimize turbine efficiency and reduce
reliability issues associated with blade
erosion, plating, turbine trips and severe
damage from hydraulic shock.
Vacuum/condensing turbine installaFIG.
2. Lowering risk requires reducing the
probability of failure (PoF) for an equipment
asset. In the case of turbines, this can correlate
to lowering the probability of failure caused
by condensate.
tions require additional design considerations
relative to the steam quality supplied
to the ejectors. Improvements to
steam quality can be achieved by incorpoHydrocarbon
Processing | NOVEMBER 2022 39

Hydrocarbon Processing - November 2022

Table of Contents for the Digital Edition of Hydrocarbon Processing - November 2022