The sealing face of the rotating seat is machined with three-dimensional V-grooves. With no sharp edges at the groove exit where dirt particles can accumulate, all particles are drawn through the sealing gap. Dirt deposits are prevented and a self-cleaning effect thus achieved. Temperatures of up to 450°C can arise in steam turbines, preventing the use of conventional sealing elements such as O-rings in the spring-loaded part of the gas seal. The company's answer to the problem is to use a metal bellows as secondary seal for the stationary seal face; this ensures interruption-free operation and guarantees the high level of reliability reached by the seal in field tests. An operating pressure limit of 25 bar and the attainable sliding velocity of 120 m/s open up an extensive range of uses in steam turbines with shaft diameters of up to 180 mm. The seal prevents the formation of dense fogging around the turbine at low external temperatures.
Burgmann, Feodor, Dichtungswerke Gmbh & Co, Postfach 1240, Wolfratshausen, Germany 82502. Tel: 49-8171-230; Fax: 49-8171-231214.