Reference Manual

18−5
Typical Specifications:
D easy-e, EW, or HP
D Whisper Trim
D FIELDVUE digital valve controller with low
travel cutoff
Optional:
D Inline diffuser (if extra noise attenuation is
needed)
Turbine Bypass
Steam turbines generate electricity through
pressure reduction and are becoming increasingly
popular. Each turbine can have multiple take-off
points so one unit can simultaneously feed the
medium and low pressure headers. In order to
minimize unplanned downtime, a bypass valve is
installed in parallel with the turbine to ensure
pressure reduction occurs even when the turbine
is offline. Most of the steam produced in paper
mills is not at the required conditions for all
applications. Thus, some degree of steam
conditioning is warranted in either control of
pressure and/or temperature to protect
downstream equipment. Steam conditioning
valves represent state-of-the-art control of steam
pressure and temperature by integrally combining
both functions within one control element unit.
These valves address the need for better control
of steam conditions brought on by increased
energy costs and more rigorous plant operation.
These valves also provide better temperature
control, improved noise abatement, and require
fewer piping and installation restrictions than the
equivalent desuperheater and PRV.
Design Considerations:
D High pressure and temperature
D Noise and vibration
D Large turndown
D Tight shutoff (Class V)
D High cycling operation
D Stroking speed
Typical Specifications:
D TBX
D Whisper Trim
D Bore-Seal
D FIELDVUE digital valve controller with low
travel cutoff
Optional:
D Separate PRV (easy-e, HP or EH) with a
Desuperheater
D WhisperFlo Trim
D 2625 booster(s)
Condensing and Cooling System
Even though it decreases cycle efficiency, a
condenser is essential to provide a “cushion” or
location to dump steam when a portion of the
process is down and still benefit from electrical
power production. The condenser is a shell and
tube heat exchanger which operates at a vacuum.
Cooling water passes through the tubes and
condenses the steam on the outside of the tubes.
The cooling water passes through a closed
system back to a cooling tower where the heat is
discharged to the atmosphere. Due to seasonal
temperature variations, all cells of a cooling tower
are not always in use. Butterfly valves are used to
isolate cells or even bypass the cooling tower.
Condensed steam accumulates at the bottom of
the condenser in the hotwell. The condensate is
then pumped to the condensate collection tank to
begin the cycle again. Since the condensate is
near saturation, a minimum level must be
maintained to prevent pump cavitation and a
minimum flow is required to prevent overheating.
Condensate Recirculation Valve
The condensate recirculation valve is similar to the
feed pump recirculation valve in that it also
protects the pump from cavitation. Inlet pressure
and temperature differ from the feedwater system.
The dissimilarities from the feedwater system
include the inlet pressure and temperature. Inlet
sizing often indicates that flashing is occurring,
however, experience shows this is always a