John Crane, Inc. Non-contacting Gas Seal for Steam Turbines Type 28ST

Type 28ST combines proven rotating groove technology and high-temperature secondary seals to reduce steam leakage by nearly two orders of magnitude, as compared to traditional sealing devices, such as segmented carbon rings and labyrinths. This steam-lubricated, end-face cartridge seal reacts instantaneously and automatically to maintain a safe face gap despite sudden changes in operating conditions. A stable seal face gap, typically 0.0001" to 0.0002"/0.0025mm to 0.0051mm, is the result of specially designed rotating grooves, which pump steam radially inward into a nongrooved portion of the seal known as the "sealing dam." Applications Steam Turbines Driven Machinery