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Why Use A PSS Shaft Seal ?

Flexible Design

In addition to carrying standard sizing, a major advantage of the PSS Shaft Seal is its ability to be customized to adapt to an existing installation or design. Because of the ability to design the seal to fit most existing systems, engineers are unconstrained by seal size requirements. The time frame for custom seals is usually very low, 3 to 4 weeks.

Reliable & Durable

Due to its simple design the PSS Shaft Seal is durable and reliable, with a typical life span of 25,000 running hours. Under clean water conditions the seal can exceed 100,000+ running hours. The unique "float design" & flexibility of the PSS Shaft Seal allows for substantial axial movement of the shaft while still operating correctly.

Low Maintenance & Ease of Installation

Minimal maintenance is required under normal working conditions with replacement parts readily available. Unlike other sealing systems, the seal does not wear the shaft or surrounding materials during operation which results in longer maintenance intervals.


The PSS Shaft Seal consists of three basic components, the stainless steel rotor, carbon stator and the bellow.
shown below is a detailed image and description of each component. Please note that the size and aesthetics of each component may vary depending on the application.
The PSS stainless steel rotor is slid down the shaft and is secured to the shaft with set screws at 90° for maximum holding power. Precision tolerances are maintained by computer controlled lathes. The faces have a number 9 micro finish and are perpendicular to the bore to prevent run-out as the collar rotates. The carbon graphite stator will polish the face of the rotor during the first few minutes of operation. The stainless steel rotor should not need to be replaced under normal operating conditions.
The PSS stainless steel rotors are available in two different materials depending on application, 316L stainless steel or Nitronic 50.
PSS Shaft Seal rotor close up

316L Rotor

Chemical Composition (wt%)

C Si Mn P S Ni Cr Mo Cu N
0.028 0.40 1.50 0.036 0.023 10.2 17.2 2.07 0.34 0.06

Mechanical Properties Spec.

Hardness: BHN 215
Tensile Strength: 116,820 psi
Yield Strength (0.2%): 69,070 psi
Elongation: 43.9%
Reduction of Area: 68.6%
Grain Size #: 5.0
PSS Shaft Seal type B rotor close up

Nitronic 50 Rotor

Chemical Composition (wt%)

C Mn P S Si Ni Cr V Mo Co N Cb
0.038 4.85 0.029 0.004 0.36 11.89 21.79 0.15 2.28 0.14 0.320 0.154

Mechanical Properties Spec.

Hardness: 134HBW
Tensile Strength: 84.5 ksi
Yield Strength (0.2%): 38.5 ksi
Elongation: 65%
Reduction of Area: 80%
Grain Size #: 6.0


Carbon-graphite is a versatile seal face material used with mating rings of harder material. The PSS carbon has superior wear characteristics and broad chemical resistance.

The face of the carbon is finished to a flatness of 4 helium light bands (measured .000044" of variation over entire lapped surface). The grade of carbon used in the PSS has an operating temperature over 500°F (+260°C), and cannot melt if the seal runs dry, unlike a rubber lip seal or plastic face seal.

The high density of the carbon greatly increases the longevity and wear resistance. Over 40,000 hours (over 4.5 years of continuous operation) has been recorded on the same original component. The carbon graphite stator should not need to be replaced under normal operating conditions.

PSS Shaft Seal carbon graphite stator

Mechanical Properties Spec.

Density: 1.68 g/cm3
Hardness: 65 - 80 HS
Compressive Strength: 147 Mpa
Bend Strength: 54 Mpa
Friction Coefficient: 015mm
Porosity: 0.3%
Finished Flatness: 4 helium light bands (measured .000044" of variation over entire lapped surface)
Operating Temperature: 500°F (+260°C)
Materials: carbon graphite
Size: Varies depending on application
Operating Temperature: 500°F (+250°C)
PSS shaft seal carbon graphite stator

Carbon graphite is a self lubricating material, and is a versatile seal face material used with mating rings of harder materials such as silicon carbide, alumina, or tungsten carbide. Carbon has superior wear characteristics and broad chemical resistance.


The PSS Bellows offer the best combination of durability, strength & elasticity, and in addition to carrying standard sizing, can be engineered in a number of configurations to meet various application requirements. The most common configuration is composed of two ends (connectors) and a convolution region where the ends provide the assembly interface and the convolution (bellows) region provides for the design application travel / required flexibility. The application dictates the material requirement with standard options available in Nitrile or Silicone.

Nitrile rubber PSS Shaft Seal bellow

Nitrile Bellow

Nitrile rubber's single most important property is its exceptional resistance to oils and non-polar solvents. It also offers good gas impermeability, abrasion resistance and better thermal stability than most general purpose elastomers.

Chemical Composition (wt%)

Hardness Shore A Tensile (MPa) Tensile (psi) Elongation
60 - 90 13.8 - 14.5 1,455 - 2,100 150% - 400%

Mechanical Properties Spec.

Typical applications: Oil resistant seals that may be exposed to daylight or other forms of radiation.
Advatanges: Good resistance to oils. Improved ozone resistance.
Upper continous service temp: 100°C
Min. temp. for sealing applications: -20°C
Min. non-brittle temp.: -30°C
Silicone PSS Shaft Seal bellow

Silicone Bellow

The silicone bellow material meets and exceeds the properties listed in SAE J20 Class A and provides superior low and high temperature resistance. The bellow is reinforced with multiple plies of aramid fabric and the Fluorosilicone Cover creates an oil and fuel resistant barrier protecting the exterior surface from the possibility of damage from splash or spill.

PSS silicone bellow closeup

Original Properties

Temp. Range: -55°C - 175°C
Durometer, points Shore A: 55 - 75
Tensile, min, MPa: 5.5
Elongation, min, %: 200

Oven Aging Conditions

Change Limits: 70 hours / 175°C
Durometer, points Shore A: +10
Tensile, max %: -15
Elongation, max, %: -40

Coolant Immersion Change Limits

Hours at Boiling Point: 70 hours
Volume, %: 0 - +40
Durometer, points Shore A: -10 - +10
Tensile, max, %: -30
Elongation, max, %: -25

Oil Immersion Change Limits

Change Limits: 70 hours / 100°C
Volume, max %: 0 - +45
Tensile, max %: -40

Compression Set °C

70 hours, max, %: 40
Cold Flexibility (°C): -40
PSS silicone bellow closeup

Polyestor / Aramid Fiber

Width: 91.4 cm
Thickness: 0.48 mm
Tensile Warp Wise: 648 N
Tensile Weft Wise: 610 N
Elongation Warp Wise: 15.7%
Elongation Weft Wise: 17.4%


Have any questions regarding a custom PSS seal ? Call or email us !

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