Barrier Seals

Stein Circumferential Barrier Seals

The circumferential barrier seal is a bore contacting device, highly effective as a gas seal and adaptable to many types of service. In most cases. Stein Seal Company provides circumferential bather seals as a standard device with our dry gas seal packages as shown in the figure below.

Stein’s custom-engineered bather seals can be mounted behind any type of dry gas seal. When mounted on the bearing side of a dry gas seal and buffered with an inert gas or air

  • These seals will act as a barrier to prevent the leakage of hazardous gases from entering the bearing cavities
  • Exclude oil from getting into the dry gas seal area if the compressor bearing is lubricated with oil
  • In the event of a dry gas seal malfunction, the circumferential bather seal will contain the excessive loss of compressor gases until the compressor is safely shut down

Circumferential seals are field proven, with over 30 years of experience in aircraft gas turbine engine and industrial turbomachinery applications. These seals are readily available to meet the stringent and demanding requirements of today’s turbomachinery industry.
Stein’s commitment to continuous product improvement and on-going R&D programs has produced cost effective, high performance circumferential seals.

Bore Contact Circumferential Seals

Inherent Safety Features

The overlapping joints of the seal segments are designed with a specified circumferential end gap. When the seal bore wears out after several years of normal operation or under abnormal operating conditions, the seal ring segments become archbound: the gap in the joints closes and the bore contacting circumferential seal becomes a minimal clearance bushing. Once the circumferential seal has worn into a bushing mode seal leakage increases, however, no further wear or increase in leakage is noticeable. This feature provides the capability of continued safe operation until a shutdown can be performed and prevents a possible catastrophic failure.

A new seal ring: gaps al the overlapping joints and sealing bore geometry is clearly visible.

A seal ring with simulated bore wear: sealing bore geometry is worn away and the joint gaps are closed.

The Benefits of Stein’s Barrier Seals

  • Very low buffer gas consumption – in most cases a few tenths of an SCFM.
  • Prevention of hazardous dry gas leakage from entering bearing cavities
  • Exclusion of bearing oil from dry gas seal area
  • Provision for safe shutdown upon wear-out
  • Virtually unlimited shaft axial travel
  • Minimal seal cavity space required
  • Available in cartridge assemblies for easy installation and removal
  • Horizontally-split assemblies available for applications where access to the end of the shaft is not possible
  • Bi-directional – no sensitivity to direction of rotation
  • Demonstrated performance over a wide range of operating conditions
  • Field-proven longevity – over five years of seal life at normal operating conditions

Barrier seal with a stepped housing outer diameter

Horizontally split barrier seal

Split-type circumferential barrier seals are one of Stein’s specialty products. Split seals originally developed for steam and gas turbines can be readily adapted to centrifugal compressors. The split seals can be easily and quickly installed in seal cavities without major tear down of turbomachinery components.
If you have questions regarding the Stein cost-effective split-type circumferential seal assemblies, please contact our Engineering Department.
“NACE” approved materials readily available upon request.

Barrier seal with a flanged seal housing

Engineered Performance Capabilities

Size
Diameters: Proven seal designs exist from 1.0 inch to 40.5 inches sealing diameter.
Axial Length: Typical values are from 1.0 to 1.5 inches.

Operating Conditions

Buffer Gas Pressure Differential (toward the dry gas face seal vent).
Normal operation: 2 to 12 psid (dp controller recommended)
Emergency conditions: In excess of 50 psid
Temperature From subzero to 450 degrees F and higher (depending on static seal materials such as 0-rings)
Shaft speed: Maximum shaft speed capability is equal to or greater than dry gas face seals
Stein Seal performs static and dynamic testing to verify design predictions. Test conditions include transient and steady state scenarios to simulate actual operating conditions and to ensure good performance in field.
Stein has over two dozen dynamic test rigs capable of speeds up to 50,000 rpm and able to handle a broad range of sizes and media. Typical test gases used are air, N2, or CO2, and are available at pressures up to 3500 psig.