PSS Type A Dripless Mechanical Propeller Shaft Seal for Ø65–95 mm Shafts

PSS Type A Dripless Mechanical Propeller Shaft Seal for Ø65–95 mm Shafts

The PSS Type A Dripless Mechanical Propeller Shaft Seal is a packing-free mechanical face seal for marine propeller shaft installations. It forms a sealing interface between a rotating stainless steel rotor and a stationary carbon graphite flange, providing a dripless alternative to traditional stuffing box packing.

This range covers metric propeller shafts with diameters of 65, 70, 75, 80, 85, 90 and 95 mm. Multiple imperial stern tube connection sizes are available, allowing the seal to be selected according to the propeller shaft diameter, stern tube outside diameter and available installation space.

The carbon flange is attached to a flexible nitrile bellows using hose clamps, while the opposite end of the bellows fits over the stern tube. The stainless steel rotor is mounted on the shaft, compresses the bellows and is secured with set screws. This compression maintains contact between the sealing faces and accommodates fore-and-aft shaft movement caused by propeller thrust.

Key Features

• Dripless mechanical face seal: Contact between a rotating stainless steel rotor and stationary carbon graphite flange.
• Packing-free construction: Does not require traditional stuffing box packing.
• Metric shaft compatibility: Available for 65, 70, 75, 80, 85, 90 and 95 mm propeller shafts.
• Imperial stern tube connections: Nominal diameters from 3 1/4" to 6".
• Stainless steel rotor: Secured directly to the propeller shaft with set screws.
• Carbon graphite flange: Stationary sealing surface that can accommodate minor misalignment and vibration.
• Dual O-rings: Recessed into the rotor bore to seal against the shaft.
• Molded nitrile bellows: Provides the compression required to maintain sealing face contact.
• Axial movement compensation: Accommodates fore-and-aft shaft movement associated with propeller thrust.
• Water connection: Hose barb for cooling and lubrication water.
• Model-specific dimensions: Three rotor diameters and two stern cuff lengths.

Technical Specifications

Available Shaft Sizes and Rotor Dimensions

The rotor diameter and stern cuff length depend on the shaft diameter and selected stern tube connection. All dimensions except the shaft diameter are expressed in inches.

Available Models and Dimensions

Dimension A is the metric propeller shaft diameter. Dimension B indicates the compatible outside diameter range of the stern tube. Dimension C is the approximate overall length, D is the rotor diameter and E is the stern cuff length. All dimensions except A are in inches. The approximate bellows compression is 1" for every listed model.

*The source data for articles 02-75M-600 and 02-95M-500 contains dimensions requiring confirmation before selection.

Mechanical Face Sealing System

The PSS Type A shaft seal operates through contact between two flat sealing surfaces: the rotating stainless steel rotor and the stationary carbon graphite flange.

The carbon flange is attached to the front of the bellows, while the opposite end of the bellows is fitted over the stern tube. The rotor is installed on the propeller shaft and compresses the bellows before being locked in position with set screws.

This preload maintains sealing face contact while allowing for axial movement of the shaft resulting from propeller thrust.

Stainless Steel Rotor and O-Rings

The rotor is manufactured from stainless steel and provides the rotating sealing face. Two recessed nitrile O-rings seal the rotor against the propeller shaft and rotate together with the shaft.

The available rotor diameters are:

• 65 mm shaft: 4.2" rotor.
• 70–80 mm shafts: 5" rotor.
• 85–95 mm shafts: 6" rotor.

The rotor is secured to the shaft using set screws.

Carbon Graphite Flange

The stationary carbon graphite flange provides the non-rotating sealing face. Its surface contacts the stainless steel rotor, creating the mechanical seal.

The carbon flange is over-bored relative to the shaft, allowing it to float around the shaft and accommodate minor misalignment and vibration.

Molded Nitrile Bellows

The flexible nitrile bellows connects the stationary carbon flange to the stern tube using hose clamps. It provides the axial compression required for the mechanical seal to function.

All listed versions have an approximate bellows compression of 1". Depending on the selected article, the stern cuff length is 2" or 2.5".

Cooling and Water Supply

The PSS Type A seal incorporates a hose connection for supplying cooling and lubricating water to the sealing faces.

High-speed vessels operating at 12 knots or above require a positive water supply. Lower-speed installations require an appropriate water supply or venting arrangement.

Dimensions and Selection

Choose the correct shaft seal using the following dimensions:

• A - Propeller Shaft Diameter: 65, 70, 75, 80, 85, 90 or 95 mm.
• B - Stern Tube Diameter: Compatible outside diameter range, expressed in inches.
• C - Approximate Length: Overall axial length before bellows compression.
• Approximate Compression: 1" for all listed versions.
• D - Rotor Diameter: 4.2", 5" or 6".
• E - Stern Cuff Length: 2" or 2.5", depending on configuration.

Before ordering, check the propeller shaft diameter, stern tube outside diameter, available installation space and water supply arrangement. Select the article number that matches both shaft and stern tube dimensions.