PSS Type B Dripless Mechanical Propeller Shaft Seal for Ø100–150 mm Shafts

PSS Type B Dripless Mechanical Propeller Shaft Seal for Ø100–150 mm Shafts

The PSS Type B Dripless Mechanical Propeller Shaft Seal is a mechanical face sealing system for marine propulsion installations with metric propeller shaft diameters from 100 to 150 mm. The sealing interface is formed between a rotating stainless steel rotor and a stationary carbon graphite stator, providing a packing-free alternative to conventional stuffing box arrangements.

The Type B assembly uses a Super Duplex 2507 stainless steel rotor, carbon graphite stator and reinforced silicone/fabric bellows with stainless steel support rings. The rotor is secured to the propeller shaft, while the bellows connects the stationary stator to the stern tube. Pre-compression of the bellows maintains contact between the sealing faces and accommodates axial shaft movement associated with propeller thrust.

Different configurations are available for metric propeller shafts and imperial stern tube connections. The correct seal is selected according to shaft diameter, stern tube outside diameter and installation dimensions.

Key Features

• Dripless mechanical face seal: Flat sealing interface between rotating stainless steel and stationary carbon graphite components.
• Metric shaft compatibility: Designed for propeller shafts from 100 to 150 mm.
• Super Duplex 2507 rotor: Precision-machined stainless steel rotating sealing component.
• Carbon graphite stator: Stationary sealing face with an oversized bore to accommodate minor shaft misalignment and vibration.
• Dual recessed O-rings: Seal the rotor against the propeller shaft and rotate together with the shaft.
• Reinforced silicone bellows: Silicone and fabric construction with stainless steel support rings.
• Axial movement compensation: Bellows pre-compression maintains sealing face contact during fore-and-aft shaft movement.
• Water injection connections: Provide cooling and lubrication water to the sealing system.
• Imperial stern tube connections: Available in multiple nominal diameters depending on the selected shaft size.
• Packing-free design: Does not require conventional stuffing box packing.

Technical Specifications

Available Models and Dimensions

The table below shows the specified installation dimensions for each listed configuration. Dimension A is the metric propeller shaft diameter, B is the compatible stern tube outside diameter, C is the uncompressed length, D is the rotor outside diameter and E is the stern cuff length. All dimensional values except shaft diameter are in inches.

All listed configurations have an approximate bellows compression of 1" to 1 1/4" and stern cuff length (E) of 2.5".

Mechanical Face Sealing System

The PSS Type B seal operates through contact between two precision-machined sealing surfaces: the rotating stainless steel rotor and the stationary carbon graphite stator.

The rotor is mounted on the propeller shaft ahead of the carbon stator and compresses the bellows before being secured in position. This compression maintains contact between the sealing faces and allows for fore-and-aft shaft movement caused by propeller thrust.

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

Super Duplex 2507 Stainless Steel Rotor

The Type B rotor is manufactured from Super Duplex 2507 stainless steel. It provides the rotating sealing face and is secured to the propeller shaft.

Two recessed O-rings seal the rotor against the shaft. The O-rings rotate together with the rotor and shaft, rather than sliding along the shaft surface during normal operation.

The specified rotor outside diameters are:

• 100 and 110 mm shafts: 7" rotor diameter.
• 115, 120, 130 and 140 mm shafts: 7.875" rotor diameter.
• 150 mm shafts: 8.875" rotor diameter.

Carbon Graphite Stator

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

The Type B stator incorporates dual water injection connections for supplying cooling and lubricating water.

Reinforced Silicone Bellows

The PSS Type B bellows is manufactured from silicone reinforced with multiple layers of fabric. Stainless steel support rings reinforce the bellows against operating pressure.

The bellows is secured to the stern tube using hose clamps. Its compression maintains contact between the carbon graphite stator and stainless steel rotor.

The specified configurations have an approximate compression of 1" to 1 1/4" and a stern cuff length of 2.5".

Water Supply and Cooling

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

For high-speed vessels operating at 12 knots or above, a positive water supply is required. Lower-speed installations must follow the applicable water supply or venting arrangements.

Dimensions and Selection

Select the correct Type B shaft seal using the following dimensions:

• A - Propeller Shaft Diameter: Metric shaft diameter.
• B - Stern Tube Diameter: Compatible outside diameter range, expressed in inches.
• C - Uncompressed Length: Overall axial dimension before bellows compression.
• Approximate Compression: 1" to 1 1/4".
• D - Rotor Diameter: Outside diameter of the rotating stainless steel rotor.
• E - Stern Cuff Length: 2.5".

Before ordering, verify the propeller shaft diameter, stern tube outside diameter, required installation space and cooling water arrangement. The complete article number identifies the shaft diameter and stern tube connection.