PSS Type A Dripless Mechanical Propeller Shaft Seal for 3 1/4" to 3 3/4" Shafts

PSS Type A Dripless Mechanical Propeller Shaft Seal for 3 1/4" to 3 3/4" Shafts

The PSS Type A Dripless Mechanical Propeller Shaft Seal is a mechanical face sealing system designed for marine propulsion shaft installations. The seal creates a sealing interface between a rotating stainless steel rotor and a stationary carbon graphite flange, eliminating the need for conventional stuffing box packing.

This range is available for 3 1/4", 3 1/2", 3 5/8" and 3 3/4" propeller shafts, with multiple stern tube connections ranging from 4 1/2" to 7" nominal diameter.

The stainless steel rotor is mounted directly on the propeller shaft and secured with set screws. The stationary carbon flange is attached to a flexible rubber bellows, which is secured to the stern tube with hose clamps. Compression of the bellows maintains contact between the two sealing faces.

The mechanical arrangement accommodates fore-and-aft shaft movement caused by propeller thrust, while the carbon flange can float around the shaft to compensate for minor misalignment and vibration.

Key Features

• Dripless mechanical face seal: Sealing interface between rotating stainless steel and stationary carbon graphite.
• Packing-free design: No conventional stuffing box packing required.
• Stainless steel rotor: Precision-machined rotating sealing component.
• Carbon graphite flange: Stationary sealing face connected to the bellows.
• Flexible nitrile bellows: Provides compression to maintain contact between sealing faces.
• Dual O-rings: Seal the stainless steel rotor against the propeller shaft.
• Set screw mounting: Secures the rotor to the shaft.
• Axial movement compensation: Accommodates fore-and-aft movement associated with propeller thrust.
• Misalignment accommodation: Floating carbon flange allows limited movement around the shaft.
• Water connection: Hose barb for cooling and lubrication water.
• Available shaft diameters: 3 1/4", 3 1/2", 3 5/8" and 3 3/4".

Technical Specifications

Available Models and Dimensions

All dimensions are in inches. The stern tube dimension (B) represents the compatible outside diameter range. Dimension (C) is the uncompressed length, (D) is the rotor diameter and (E) is the stern cuff length.

Mechanical Face Sealing System

The PSS Type A shaft seal creates a sealing interface between the rotating stainless steel rotor and the stationary carbon graphite flange.

The rotor is installed on the propeller shaft and compresses the bellows before being secured with set screws. The compressed bellows maintains contact between the sealing faces and accommodates axial shaft movement associated with propeller thrust.

The carbon flange has an enlarged bore, allowing it to float around the propeller shaft and accommodate minor alignment variations and vibration.

Rotor and O-Rings

The stainless steel rotor has a diameter of 6" across all 44 configurations. Two recessed O-rings seal the rotor against the propeller shaft.

The O-rings rotate with the shaft and rotor rather than sliding along the shaft during normal operation.

Flexible Bellows and Stern Tube Connection

The molded nitrile bellows connects the stationary carbon flange to the stern tube and is secured with hose clamps.

All models require approximately 1" of bellows compression. The stern cuff length is either 2" or 2.5", depending on the selected stern tube connection.

Water Supply and Lubrication

The PSS Type A seal includes a hose connection for cooling and lubricating water. High-speed vessel installations require a positive water supply to the sealing faces.

Water supply and venting arrangements must be selected according to the vessel's operating conditions and installation requirements.

Dimensions and Selection

Select the appropriate PSS Type A seal using the following parameters:

• A - Propeller Shaft Diameter: 3 1/4", 3 1/2", 3 5/8" or 3 3/4".
• B - Stern Tube Outside Diameter: Select the appropriate connection size and compatible diameter range.
• C - Uncompressed Length: Verify the axial length before bellows compression.
• Approximate Compression: 1" for all listed models.
• D - Rotor Diameter: 6" for all listed models.
• E - Stern Cuff Length: 2" or 2.5", depending on the configuration.

Different stern tube sizes may have different uncompressed lengths and cuff dimensions, even when the propeller shaft diameter is identical. Verify the dimensions of the selected article before installation.