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3.5 Steam traps should be installed at regular intervals (every 30 to
50 m or 100 to 150 ft) in the steam main with correctly sized
condensate pockets.
3.6 Steam traps should be installed upstream of isolation valves that
are regularly closed.
3.7 Insulation of sufficient thickness should be installed on the piping to
prevent excess radiation losses that result in condensate formation.
Insulation should be dry, weatherproofed, and undamaged.
If your steam piping system lacks one or more of these features you
may experience more problems with water slugs entering the turbine
and with condensate collecting in the turbine. These problems will be
further worsened if the steam main temperatures are near or at the
saturation temperature of the steam. Typically, turbines that are distant
from the source of the steam experience more problems because
radiation losses have caused the steam temperatures to drop and
condensate formation to increase. Also, condensate from upstream in
the system will flow downstream if steam traps are not installed and
functioning properly at regular intervals along the steam main.
To reduce problems caused by water in the turbine, the case drain of
the turbine should be piped to a steam trap with the following features:
3.8 Mechanical free float actuation. There are a wide variety of steam
traps on the market that fall into three basic categories: mechani-
cal, thermostatic, and thermodynamic. A mechanical free float trap
evacuates water immediately, whereas other types of mechanical
traps and the thermostatic and thermodynamic traps operate inter-
mittently. Intermittent operation can allow condensate to back up
into the turbine and possibly the seals, which is undesirable.
3.9 Automatic air venting. This feature is necessary to prevent air
present during startup from locking the trap and preventing it from
evacuating water.
3.10 Adequate size for condensate load. For instance, a turbine that is
placed in hot standby will experience a much higher condensate
load than a turbine that operates continuously or in slow roll. In hot
standby, radiation losses from the exhaust pipe will cause conden-
sate to form and run down into the turbine. If the exhaust line enters
the bottom of the exhaust steam main, condensate running along
the bottom of the main will enter the turbine as well. It will take a
large trap to prevent condensate from flooding the turbine and the
seals.
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