Labyrinth seals are characterised as controlled clearance seals without rubbing contact with the moving parts and with some tolerable leakage. The fluid throttling is achieved in steps, using a series of small chambers, where a sudden irreversible acceleration with subsequent deceleration of the leaking fluid takes place. Every step down in this process of pressure dissipation is accompanied by a loss in pressure. Due to the lack of direct rubbing contact with the moving shaft, the labyrinth seal is well suited for sealing shafts operating at high rotational speeds, as in centrifugal compressors and steam turbines. It requires neither lubrication nor maintenance. The simplest design of a labyrinth packing is with a straight shaft and a straight housing is shown in Fig. 7.18(a). The modified labyrinth designs are of the staggered, stepped, and interference configurations (Figs. 7.18(b)–(e)).
Figure 7.18 Labyrinth seal designs: (a) Straight shaft and straight housing, (b) Staggered, (c) Staggered and stepped, (d) Stepped, (e) Interference
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