The shafts of high-output, high-temperature steam turbines are typically sealed using which method?

• A. Garter springs
• B. Carbon rings
• C. Packing rings
• D. Labyrinth glands

Answer: (D)

A non-contact sealing method that creates a tortuous path for the steam is ideal for high-speed, high-temperature turbine shafts. Labyrinth gland seals use a series of interlocking teeth or grooves between the rotating shaft and the stationary seal housing. Because the seal elements don’t touch the shaft, there’s no sliding wear, so the seal can tolerate high speeds and elevated temperatures without degrading. The narrow, maze-like path dramatically reduces leakage by increasing the effective impedance to flow from the high-pressure side to the low-pressure side, even under demanding conditions.

Other methods rely on packing or carbon rings that press against the shaft with the help of garter springs. Those methods involve sliding contact and packing material, which tend to wear more quickly under the heat and speed of a high-output turbine and can lead to higher leakage and more maintenance. That’s why labyrinth glands are the typical choice for sealing these turbine shafts.