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Figure 5: The danger of eva-
porating condensate

Figure 4 shows an example of turbine system
drainage in a conventional power plant. The live
steam line is also heated specifically via a sepa-
rate warm-up valve. The drainage lines marked
with the steam trap symbol consist of two valves.
Installing only one drainage valve would cause a
flow stoppage in the drainage lines once closed.
This would cause the pipeline to cool down and
fill with condensate, creating condensate heads
beneath the turbine measuring several metres.
Certain operating circumstances can lead to a
sudden fall in pressure that causes the conden-
sate to evaporate. As a result, the built-up con-
densate shoots upwards into the turbine or other
hot plant components, see Figure 5. This can
cause severe damage, such as thermal shock
cracks and damage to the turbine blades.
Preventing this requires constant drainage with a
steam trap. The dirt collector should not exceed is usually set to a mechanically adjustable minimum Figure 6: Arrangement of
0.5 m in length when draining the turbine. Figu- lift. This lift position removes the constantly arising turbine drainage valves
re 6 shows such a combination, consisting of condensate. A level sensor monitors operation and
a multi-stage drainage valve with parallel steam triggers a full opening of the valve if the level of
trap and bimetallic regulator. condensate rises. Figure 7a shows a schematic
This type of steam trap is robust, easy to main- illustration of this kind of controlled drainage with
tain and has the right regulator type for the small optional steam trap. Figure 7b shows a drainage
quantities of condensate in this application. This process triggered by the level sensor detecting the
trap must not be insulated, however. The quan-
tities of condensate removed via the steam trap
are small because the condensate arises only as
a result of the heat loss in the respective draina-
ge line. Angular drainage valves have the advan-
tage of avoiding a pipe bend, allowing the con-
densates to flow into the downstream pipeline
without deflection.

Steam turbine drainage
in nuclear power plants

Turbines in nuclear power plants are operated with
saturated steam or only very slightly superheated
steam. This leads to condensate in the turbine hou-
sing and pipelines during operation that must con-
stantly be removed. Although small quantities can
be dealt with using steam traps, the drainage valve

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