PSS Type B Dripless Mechanical Propeller Shaft Seal for 4" to 6 1/2" Shafts

PSS Type B Dripless Mechanical Propeller Shaft Seal for 4" to 6 1/2" Shafts

The PSS Type B Dripless Mechanical Propeller Shaft Seal is a mechanical face sealing system designed for marine propulsion installations with propeller shaft diameters from 4" to 6 1/2". The seal creates a sealing interface between a rotating stainless steel rotor and a stationary carbon graphite stator, providing a packing-free alternative to conventional stuffing box seals.

The Type B design incorporates a reinforced silicone and fabric bellows with stainless steel support rings, a carbon graphite sealing face and a precision-machined stainless steel rotor. The assembly is designed to accommodate axial shaft movement, vibration and minor misalignment while maintaining contact between the sealing faces.

The range includes 60 configurations with different shaft diameters, stern tube connection sizes and installation dimensions.

Key Features

• Dripless mechanical face seal: Sealing contact between a rotating stainless steel rotor and a stationary carbon graphite stator.
• Packing-free design: No conventional stuffing box packing required.
• Reinforced silicone bellows: Silicone construction reinforced with multiple layers of fabric.
• Stainless steel support rings: Reinforce the bellows for increased strength.
• Stainless steel rotor: Precision-machined rotating sealing component.
• Carbon graphite stator: Stationary sealing face attached to the bellows.
• Dual O-rings: Seal the rotor against the propeller shaft.
• Axial movement compensation: Bellows compression maintains contact between the sealing faces during shaft movement.
• Misalignment accommodation: Floating carbon stator allows limited movement around the shaft.
• Water injection connections: Cooling and lubricating water supply connections.
• Available shaft diameters: 4", 4 1/4", 4 1/2", 4 3/4", 5", 5 1/2", 6" and 6 1/2".
• Pressure rating: Up to 50 PSI (3.5 bar).
• Shaft speed limit: 7,000 RPM.

Technical Specifications

Available Models and Dimensions

All dimensions are in inches. The stern tube diameter (B) indicates the compatible outside diameter range. The uncompressed length (C) is measured before installation compression. All versions have an approximate compression of 1" to 1 1/4" and a stern cuff length (E) of 2.5".

Mechanical Face Sealing System

The PSS Type B operates through contact between two mechanical sealing faces: a rotating stainless steel rotor and a stationary carbon graphite stator.

The rotor is installed directly on the propeller shaft and secured with set screws. The carbon stator is connected to the flexible bellows, which is fastened to the stern tube with hose clamps.

Compression of the bellows creates the pressure required to maintain contact between the two sealing surfaces. This arrangement accommodates fore-and-aft shaft movement caused by propeller thrust.

Stainless Steel Rotor

The Type B rotor is manufactured from Super Duplex 2507 stainless steel. It is machined to a precision surface finish and provides the rotating face of the mechanical seal.

Two recessed O-rings seal the rotor against the propeller shaft. The O-rings rotate with the rotor and shaft rather than sliding against a stationary component during normal operation.

The rotor diameter depends on the selected shaft size:

• 4" and 4 1/4" shafts: 7" rotor diameter.
• 4 1/2" to 5 1/2" shafts: 7.875" rotor diameter.
• 6" and 6 1/2" shafts: 8.875" rotor diameter.

Carbon Graphite Stator

The stationary carbon graphite stator provides the non-rotating sealing surface. Its flat contact face works against the stainless steel rotor to form the mechanical seal.

The carbon stator is designed to accommodate limited shaft movement and alignment variations. It includes dual water injection ports for connection to a positive cooling and lubricating water supply.

Reinforced Silicone Bellows

The PSS Type B shaft seal uses a reinforced silicone bellows incorporating multiple layers of fabric and stainless steel support rings.

The bellows provides the axial compression required to maintain sealing face contact and is designed to withstand pressure within the specified operating limits.

All listed configurations have an approximate compression requirement of 1" to 1 1/4" and a stern cuff length of 2.5".

Water Supply and Cooling

The Type B seal includes water injection connections for cooling and lubrication of the mechanical sealing faces.

For vessels operating at speeds of 12 knots or higher, a positive water supply is required. Installations operating at lower speeds must follow the applicable water supply and venting requirements.

Dimensions and Selection

Select the correct PSS Type B shaft seal according to the following parameters:

• A - Propeller Shaft Diameter: 4", 4 1/4", 4 1/2", 4 3/4", 5", 5 1/2", 6" or 6 1/2".
• B - Stern Tube Outside Diameter: Select the appropriate nominal size and compatible outside diameter range.
• C - Uncompressed Length: Overall axial length before installation compression.
• Approximate Compression: 1" to 1 1/4".
• D - Rotor Diameter: 7", 7.875" or 8.875", depending on shaft size.
• E - Stern Cuff Length: 2.5" for all listed models.

Before ordering, confirm both the propeller shaft diameter and stern tube outside diameter, together with the required axial installation space and water supply arrangement.