Shaft Seal 45mm Shaft & 3-1/4" Tube
This Type A PSS Shaft Seal is a mechanical face seal. The sealing surface is created between the flat surfaces of the rotating stainless-steel rotor and the stationary carbon flange.
The PSS Shaft Seal is the #1 selling marine mechanical seal worldwide and is installed as standard equipment by many of the world's most reputable boat builders and boat yards. The PSS Shaft Seal is also recognized as the premiere retrofit (aftermarket) seal on the world market. Boat builders and boat yards recognize the advantages and value of installing the PSS, as it eliminates the maintenance, constant adjustment, and cost associated with traditional packing-type glands. Aside from these benefits, the PSS Shaft Seal helps to eliminate water in the bilge (100% watertight) and wear to the propeller shaft.
How Does it Work?
- Two nitrile o-rings seal the stainless steel rotor to the shaft and will not experience wear.
- A primary set screw and a backup set screw (2 sets) are used to secure the stainless steel rotor to the shaft.
- A seal is created between the two flat surfaces of the carbon stator and the stainless steel rotor.
- Water is fed into the PSS Shaft Seal for cooling/lubricating the seal faces on high-speed vessels.
- The stationary carbon stator is attached to the nitrile bellow, which is attached to the stern tube (shaft log).
The rotor is made out of 316L stainless steel and machined to a 9-12Ra finish on precision CNC lathes. It is secured on the shaft using 2 pairs of set screws positioned at a 90-degree angle for maximum holding power. The stainless steel rotor further polishes the carbon stator during the initial hours of operations.
The high-density, resin-impregnated carbon stator is manufactured from an advanced composite that is first mixed and molded and then formed under pressure. The blank parts are then baked, machined, and lapped to a measured flatness of 4 helium light bands (measured at 0.000044" of variation over its entire lapped surface). The grade of carbon composite used in the PSS Shaft Seal has a maximum operating temperature of 500°F (+260°C) and cannot melt if the seal runs dry for a short period of time, unlike a lip seal or a plastic face seal. In addition, the high density of the carbon greatly increases longevity and wear resistance. As a result, several commercial vessels have recorded over 40,000 engine hours (over 4 1/2 years of continuous operation) on the same original components.
The bellows on the Type A seal are molded out of a Nitrile compound. Nitrile is known for its good resistance to petroleum products. In addition, it provides the best combination of durability, strength, and elasticity necessary for this application.
For high-speed vessels (12+ knots), a positive water supply is required to be plumbed to the PSS Shaft Seal for lubricating and cooling the seal faces. Please review the PSS Shaft Seal Installation Instructions for more information on pickup points for water supply. In most cases, a slow-speed boat (less than 12 knots) that does not have a bearing on the shaft log does not require positive water feed and can simply be vented. Ideally, the vent line will be run at least 2-3 feet above the waterline and as close to the centerline as possible. This will ensure the vent hose is never below the water line, even with significant healing. PSS Shaft Seal Installation Instructions have more details on venting the seal.
- Temperature Limits: 5°F to 225°F (-15°C to 107°C)
- Pressure Limits: 15 PSI (1 BAR)
- Shaft RPM Limits: 10,000 RPM
- Carbon Graphite: Lapped to 4 HLB (0.000044" tolerance)
- 316SS / Nitronic 50: Faced to 9-12 Ra
- Bellows Material: Molded Nitrile - PVC
- Shaft Diameter: 45mm
- Stern Tube Diameter (inch): 3-1/4" to 3-3/8"
- Approximate Length: 9.2175 in.
- Approximate Compression: 1 in.
- Rotor Diameter: 3.75 in.
- Stern Cuff Length: 2 in.