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2.5 Shaft damage, especially in the area of the carbon rings. Check the
integrity of the overlay. It is possible for steam to leak beneath the
overlay if improperly applied.
2.6 Check the turbine alignment. The shaft runout and the perpendicu-
larity should meet normal pump standards. The concentricity may
be much larger than that typically seen in a pump.
Talk to the operations and maintenance personnel regarding the above
concerns. Find out if there are any other issues regarding turbine reliabil-
ity and performance.
3
Inspection of Steam Turbine Piping and Application
of Steam Traps
Water is a problem for turbines in general, but poses some unique
challenges for mechanical seals. Hot water under pressure at the OD
of the seal faces will flash to form steam as it crosses to the atmospheric
pressure at the ID of the faces. The expansion ratio when water is
converted to steam is over 1600 to 1. This generates a large force that
causes the faces to separate, resulting in high leakage. The GTS seal is
robust and can recover from normal water slugs that occur during start
up. However, operation in water will result in high leakage that is not
generally acceptable for prolonged operation.
As a practical matter, altering the turbine piping to remove water and
improve performance of the turbine and mechanical seals is not an
option for most end users. However, inspecting the piping can yield useful
information about potential problems that may be reduced or eliminated
through the application of mechanical free float actuated steam traps.
Check your piping system for the following:
3.1 Piping should slope downward 10 cm per 10 m (4 inches per 30 ft)
in the direction of steam flow to aid condensate drainage.
3.2 Piping should be straight and free from sags where condensate
could collect and create a slug of water.
3.3 Eccentric reducers should be used instead of concentric reducers,
to prevent condensate from pooling upstream of the reducer and
creating a slug of water.
3.4 Equipment supply lines should be connected to the top of steam
mains, not the bottom, so that dirty condensate running along the
bottom of the mains does not flow into the equipment.
3
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