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Gas-Lubricated Seal

The rotating ductile ring with a high performance coating is the main distinctive
feature to other dry gas seals. It offers outstanding wear resistance in low speed
conditions e.g. coast down or turning where contacting of seal faces is inevitable. The
required radial space of this seal is smaller than existing Dry Gas Seals and the seal fi ts into small seal cavities, as you fi nd them in process gas screw compressors, without making any compromise with regard to seal reliability.
The stationary spring loaded unit is supplied as a sub cartridge in combination with a rotating ductile seat integrating secondary functions such as centring and secondary sealing by means of an O-Ring allow the use of this seal as a component seal.


  • Gas-lubricated
  • Bi-directional
  • Ready-to-fit cartridge unit
  • Single, double, tandem seal and tandem with intermediate labyrinth available

Product specification example

Standards and approvals



Seal face: Carbon graphite antimony impregnated
Seat: Ductile stainless steel with DM-TiN coating
Secondary seals: FKM (V) or other materials
depending on product gas composition
Metal parts: 1.4006 or other stainless steels.

Operating range

Pressure: p = 0 … 50 bar (0 … 725 PSI)
Temperature: t = -30 °C … 200 °C (-22 °F … +392 °F)
Sliding velocity: vg = 0.6 … 200 m/s (2 … 656 ft/s)

Recommended applications

Oil and gas industry
Refining technology
Petrochemical industry
Hydrocarbon gas
Centrifugal compressors
Dry process gas screw compressors

Product variants

MDGS Tandem seal
Application: Where small product leakages of process gas are admissible, e.g. on gas pipeline compressors. Seal on the atmosphere side acting as a safety seal. The tandem arrangement provides a particularly high degree of operational safety. The seal on the product side and the seal on the atmosphere side are able to absorb the complete pressure differential. Under normal operating conditions the full pressure is reduced only by the seal on the product side. The space
between the seal on the product side and the seal on the atmosphere side is cleared by a connection “B” to the flare. The pressure differential to be sealed by the seal on the atmosphere side equals the flare pressure, so the leakage to the atmosphere side or to the vent is very low. If the main seal fails, the second seal acts as a safety seal.

MDGS Tandem seal with intermediate labyrinth
Application: Where product leakages to the atmosphere as well as buffer gas leakages to the
product are inadmissible, e.g. on H2, ethylene or propylene compressors. With this version the
product pressure to be sealed is reduced via the seal on the product side. The entire process gas leakage is discharged via connection “B” to the flare. The seal on the atmosphere side is pressurized with buffer gas (nitrogen) via connection “C”. The pressure of the buffer gas ensures that a current flows via the labyrinth to the primary vent outlet.

MDGS Dual Seal
Application: Where product leakages to the tmosphere are inadmissible and tandem arrangements are not suitable because of too small product gas pressures. Buffer gas leakages into the product must be admissible (buffer pressure p3 > p1). This seal is used when a neutral buffer gas of suitable pressure is available. Typical applications are to be found mainly in the chemical industry, e.g. on HC gas compressors. A buffer gas, e.g. nitrogen, is fed between the
seals via connection “C” at a higher pressure than the product pressure. One part of the buffer
gas leakage escapes to the atmosphere side and the other part to the product.

Applicable ranges shown in the product introduction are limit values for each standard material.
Applicable ranges, performance data and figures can serve only as a guide for selection and therefore in actual use there will be some cases where general specifications cannot be applied due to unknown factors or constraints.
Please check the applicability before use.
The contents are subject to change without notice for improvement.


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