Flowserve GTS Series - Manual (Page 4)

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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: mechanical, thermostatic,
and thermodynamic. A mechanical free float trap evacuates water
immediately, whereas other types of mechanical traps and the thermostatic
and thermodynamic traps operate intermittently. 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 start-up 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 condensate 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.
In continuous operation or slow roll, hot inlet steam will enter the turbine
and flow out through the exhaust. This will usually keep the exhaust line
much warmer than in hot standby, reducing the flow of condensate into
the turbine. Of course, the steam trap must be sized for the worst case
condition. If a turbine experiences both hot standby and continuous
operation, the steam trap should be sized for hot standby.
3.11 Located as near the turbine as possible. Long piping distances between
a steam trap and a turbine can cause the trap to steam lock. This occurs
when the line to the trap is filled with superheated steam. Superheated