Page 68 - Steam Turbines Design, Applications, and Rerating

Turbine Casing and Major Stationary Components 49

Figure 2.28 Improved brush seals.

Brush seals can be used instead of, or in addition to, the existing
labyrinth seals. One or more labyrinth teeth are removed, and the
brush seals are installed in their place. The typical clearance between
the brush seal ID and the rotating shaft is 0.000 in to 0.005 in. This
reduces the steam leakage by about 30 percent with a reduction in the
size of the gland condenser and associated systems. See Fig. 2.28 for a
typical brush seal installed with labyrinth seals.
Similar designs are being tried by utilizing brush seals in conjunc-
tion with carbon rings to make use of the reduced leakage of carbon
rings and the wearability of brush seals.
But post-1980 and even newer developments supersede the old seal
design and are well worth considering in both new as well as retrofit
situations. One such design is Wavy Face Dry Running Seals. A
detailed description of this type of seal and its use is given in Section
16.1.2.