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Type 28ST

Type 28ST
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Non-Contacting, Steam Turbine Gas Seal A – Seat/Mating Ring B – Face/Primary Ring C – Split Carbon Ring Assemblies Spiral Groove Face Product Description 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. s 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 0.0025mm to 0.0051mm/ 0.0001" to 0.0002", 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.” Primarily for use on steam turbines. Bearing Oil Steam Contamination Dramatically Reduced Increased Safety (reduced noise levels and hazards associated with leaking steam) Standard Designs to Fit Most Single-Stage Turbines Turbine Operational Efficiency Maintained for Years Support Equipment Eliminated Bi-Directional Face Patterns Available End Play/Axial Float Allowance: ±3.20mm/0.125" For Optimum Seal Performance: Steam should have 28˚C to 56˚C/83˚F to 133˚F of superheat at inlet conditions. For Optimum Seal Life: Following a combination of NEMA Standard SM 24-1991 and EPRI guidelines for steam purity is strongly recommended. Consult John Crane for recommended steam purity limits.

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TYPE 28ST Non-Contacting, Steam Turbine Gas Seal Type 28ST Typical Arrangement Bearing Side Steam Chest Side Type 28ST Applications Data The standard Type 28ST is designed to withstand speeds of 122 m/s /400 fps max. and 1000 rpm min. (continuous). It is also slow roll tolerable. The Type 28ST is designed to fit most single-stage turbines without modifications. Standard designs exist for shaft sizes ranging from 25.4mm/1.000" through 108mm/4.250" for most steam turbines, including: Coppus, Dean Hill, Dresser Rand (Terry, Worthington), Elliott, Hayward Tyler, KKK, Murray, Rateau, Spencer...

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TYPE 28ST Non-Contacting, Steam Turbine Gas Seal Type 28ST Typical Leakage Chart* Steam Leakage (lbs./hr.) 7 Steam contamination of bearing oil virtually eliminated. Rust and corrosion of other equipment dramatically reduced. Conventional Segmented Carbon Rings Typical Leakage Chart* Steam Leakage (lbs./hr.) 250 200 150 100 50 0 0 Type 28ST Cost Savings vs. Traditional Seals* Steam Leakage (lbs./hr.) 250 Traditional Seal 200 150 100 COST SAVINGS *Based on an 88.9mm/3.500" shaft diameter.

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TYPE 28ST Non-Contacting, Steam Turbine Gas Seal Materials of Construction SEAL COMPONENTS Face/Primary Ring Seat/Mating Ring Tungsten Carbide Coatings on Ductile Substrates Secondary Seals Carbon/Inconel® Flexible Graphite Zinc-Coated Hardened Steel Inconel is a registered trademark of Inco Alloys International, Inc. John Crane North and Latin Americas Morton Grove, Illinois USA Europe, Middle East, Africa Slough, UK Asia Pacific Singapore For your nearest John Crane facility, please contact one of the locations above. If the products featured will be used in a potentially dangerous and/or...

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