Joint mécanique PSS de type B


For 100mm to 150mm (4" to 6") shaft diameters

The Type B PSS Shaft Seal is a mechanical face seal. The sealing surface is created between the flat surfaces of the rotating stainless-steel rotor and the stationary carbon flange. The stationary carbon flange is attached to the front side of the bellow with hose clamps, and the back end of the bellow fits over the Stern tube and is secured with hose clamps. The stainless-steel rotor is fit on the shaft in front of the carbon flange. The stainless-steel rotor is used to compress the bellow before the rotor is secured to the shaft with set-screws. This compression (pre-load) maintains constant contact between the two flat faces of the stainless-steel rotor and carbon flange, allowing the PSS to compensate for the variable fore and aft movement due to propeller thrust. The carbon flange is over-bored to the shaft diameter allowing it to “float” around the shaft and thus compensate for most misalignment and vibration problems. The stainless-steel rotor is sealed to the shaft by two O-rings that are recessed into the bore of the collar. These O-rings rotate with the shaft and stainless-steel rotor and do not experience wear during operation.



How a PSS Type B Shaft Seal Works
  • 1
    This clamp assembly maintains the PSS Type B preload / compression without the need for set screws.
  • 2
    A seal is created between the two flat surfaces of the carbon stator and the stainless steel rotor.
  • 3

    Water is fed into the PSS Shaft Seal for cooling/lubricating the seal faces on high speed vessels.

  • 4
      The stationary carbon stator is attached to the nitrile bellow, which is attached to the stern tube (shaft log)
  • 5
    Stainless steel rings are fit to the bellow for increased strength, support and durability.
  • 6
    Hose clamps secure the PSS Type B Shaft Seal to the stern tube and onto the carbon stator.



Rotor of PSS shaft seal type B
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 stainless steel rotor used on the PSS Type B Shaft Seal is made from Nitronic 50 stainless steel.


Carbon of PSS shaft seal type B
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 high 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 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


Bellow rings of PSS shaft seal type B
The PSS Type B Shaft Seal uses metal rings around the bellow for added strength due to the high pressures that the seal may encounter.


Hose Barb of PSS PRO
For high speed vessels (12+ knots), a positive water supply is required to be plumbed to the PSS Shaft Seal for the purpose of lubricating and cooling the seal faces. Please review the PSS Shaft Seal Installation Instructions for more information on pickup points for water supply. In most cases, a slow speed boat (less than 12 knots) that does not have a bearing the shaft log does not require positive water feed and can simply be vented. Ideally, the vent line will be run at least 2-3 feet above the water line and will be as close to the center line as possible. This will ensure the vent hose is never below the water line, even with significant heeling. PSS Shaft Seal Installation Instructions has more more details on venting the seal.


Bellow du joint mécanique PSS de type B
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 silicone bellow material meets and exceeds the properties listed in SAE J20 Class A and provides superior low and high temperature resistance. The Fluorosilicone Cover creates an oil and fuel resistant barrier protecting the exterior surface from the possibility of damage from splash or spill.


Bellow close up of PSS shaft seal type B
The bellow is reinforced with multiple plies of aramid fabric.


The PSS Shaft Seal has been thoroughly tested and approved by these certifications.
RINA certification


Bureau Véritas certification





What is a PSS Shaft Seal ?

Removing the shaft coupling



PSS Shaft Seals are available around the world. Use the map below to find the nearest PSS Shaft Seal dealer to you.