PSS PRO Dripless Mechanical Propeller Shaft Seal for 3/4"–3 3/4" and Ø20–95 mm Shafts

PSS PRO Dripless Mechanical Propeller Shaft Seal for 3/4"–3 3/4" and Ø20–95 mm Shafts

The PSS PRO Dripless Mechanical Propeller Shaft Seal is a mechanical face sealing system for marine propeller shaft installations. It is designed for applications requiring a reinforced sealing assembly with a secondary shaft retention collar, stainless steel components and a flexible silicone bellows.

The PSS PRO range accommodates imperial propeller shaft diameters from 3/4" to 3 3/4" and metric shaft diameters from 20 to 95 mm. Different stern tube connection sizes are available to match the vessel's shaft installation.

The seal operates through contact between a rotating stainless steel rotor and a stationary carbon graphite stator. The rotor is secured to the shaft, while the carbon stator is attached to a reinforced bellows connected to the stern tube. Compression of the bellows maintains contact between the sealing faces and allows for axial movement caused by propeller thrust.

Key Features

• Dripless mechanical face sealing: Contact between a rotating stainless steel rotor and stationary carbon graphite stator.
• Imperial and metric shaft sizes: Available for 3/4"–3 3/4" and Ø20–95 mm propeller shafts.
• 316L stainless steel rotor: Precision-machined rotating sealing component.
• Carbon graphite stator: Stationary sealing surface that accommodates minor shaft misalignment and vibration.
• Secondary shaft retention collar: Provides additional shaft retention in the event of a coupling failure or disconnection.
• Dual nitrile O-rings: Seal the rotor against the propeller shaft without sliding against the shaft during normal operation.
• Primary and backup set screws: Secure the stainless steel rotor to the shaft.
• Reinforced silicone/fabric bellows: Provides axial compression to maintain sealing face contact.
• Stainless steel reinforcement rings: Standard on the larger PRO shaft seal sizes, with smaller configurations available with reinforcement options.
• 316 stainless steel hose clamps: Rolled edges and non-perforated clamp bands with hose clamp protection.
• Cooling water connection: Hose barb for supplying water to the mechanical sealing faces.
• Optional Nitronic 50 rotor: Alternative rotor material for installations exposed to highly corrosive environments.

Technical Specifications

Available Shaft Diameters

Dimensional Reference

Each PSS PRO configuration is identified by the propeller shaft diameter and stern tube outside diameter. Installation dimensions vary according to the selected article number.

All dimensional values except metric shaft diameters are expressed in inches. The nominal stern tube size must be selected according to the actual outside diameter of the stern tube.

How the Mechanical Seal Works

The PSS PRO mechanical seal creates a sealing interface between the rotating stainless steel rotor and the stationary carbon graphite stator.

The carbon stator is attached to the reinforced silicone bellows, which is connected to the vessel's stern tube using 316 stainless steel hose clamps. The rotor is mounted on the propeller shaft and positioned to compress the bellows before being secured with set screws.

This compression maintains contact between the sealing faces and compensates for axial movement caused by propeller thrust. The carbon stator is designed with clearance around the shaft to accommodate minor misalignment and drivetrain vibration.

Shaft Retention Collar

The PSS PRO includes a secondary shaft retention collar. It is mounted on the propeller shaft to help retain the shaft if the coupling fails or the shaft becomes disconnected from the coupling.

The collar uses a double-split design and provides additional axial holding capability without requiring removal of the shaft during installation.

316L Stainless Steel Rotor

The stainless steel rotor forms the rotating sealing face and is secured to the propeller shaft using primary and backup set screws. Two recessed nitrile O-rings provide a seal between the rotor and the shaft.

The standard rotor is manufactured from 316L stainless steel. A Nitronic 50 rotor option is available for applications requiring increased corrosion resistance.

Carbon Graphite Stator

The stationary carbon graphite stator contacts the stainless steel rotor to create the mechanical face seal. Its surface is precision-lapped, and the stator is supported by the flexible bellows.

The stator accommodates limited shaft misalignment and vibration while maintaining contact with the rotating sealing face.

Reinforced Silicone Bellows

The PSS PRO bellows is manufactured from high-temperature silicone reinforced with layers of fabric. Its flexible construction allows controlled axial compression while maintaining the stationary sealing face against the rotor.

Stainless steel reinforcement rings are used on applicable sizes to increase structural support. The bellows is connected to the stern tube using non-perforated 316 stainless steel hose clamps with rolled edges.

Cooling Water Connection

A hose barb connection allows raw water to enter the shaft seal assembly to cool and lubricate the mechanical sealing faces.

For high-speed vessels operating at or above 12 knots, a positive water supply is required. The cooling water connection and installation arrangement must follow the vessel's operating conditions and the applicable PSS installation instructions.

Selection and Installation

Before ordering, verify the following dimensions:

• Propeller Shaft Diameter: Select the exact imperial or metric shaft diameter.
• Stern Tube Diameter: Measure the outside diameter of the stern tube and select the corresponding connection size.
• Uncompressed Length: Check the overall axial space required for the selected configuration.
• Compressed Length: Confirm the final installation length after bellows compression.
• Rotor Diameter: Verify the available clearance around the shaft.
• Stern Cuff Length: Confirm sufficient stern tube engagement for the bellows connection.

Individual configurations have different installation lengths, rotor diameters and stern cuff dimensions. Select the correct PSS PRO article number for the shaft and stern tube combination before installation.