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PRO Shaft Seal 2-3/4″ Shaft & 4″ Tube

The PSS PRO Shaft Seal is a mechanical face seal utilizing PSS Shaft Seal’s proven stainless steel and carbon sealing components but adding reinforced silicone bellows, a secondary shaft retention collar, 316 stainless steel hose clamps (rolled edges and non-perforated), and an optional Nitronic 50 rotor upgrade (for highly corrosive environments). Designed specifically for applications that will require increased durability and resistance to harsh, corrosive, high-pressure, and otherwise demanding environments, the PSS PRO Shaft Seal is a specialized mechanical seal suitable for various applications with unmatched performance.

As with PSS Type A & B Seals, the PRO 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 stationary carbon flange is attached to a heavy-duty silicone bellows attached to the vessel’s stern tube (shaft log) with 316SS hose clamps. The stainless-steel rotor is fitted on the shaft in front of the carbon flange and is used to compress the bellows. The rotor is then secured to the shaft with set screws, and the shaft retention collar is installed. This compression (pre-load) maintains constant contact between the two mating faces of the stainless-steel rotor and carbon flange, allowing the PSS to compensate for the variable axial movement due to propeller thrust. In addition, the carbon flange is over-bored to the shaft diameter, allowing it to “float” around the shaft and thus compensate for most misalignment and vibration from the drive line. The stainless-steel rotor is sealed to the shaft by two O-rings recessed into the rotor’s bore. These O-rings rotate with the shaft and the stainless-steel rotor and therefore do not experience wear during operation.

Components:

Shaft Retention Collar

The PYI Shaft Retention Collar is designed to help retain the propeller or rudder shaft in a vessel in the event of catastrophic failure of the coupling or if the shaft comes free from the coupling. The double-split design provides maximum axial holding power with quick and efficient assembly with the shaft installed. The design fully engages the shaft without marring. Easily installed where major disassembly would otherwise be required. Greater axial holding power than set screws or one-piece clamping collars. Effective on hard and soft shafts.

Rotor

The rotor on the PRO seal is manufactured 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; in addition, a locking collar is placed in front of the rotor and further retains the propeller or rudder shaft in case of catastrophic failure of the coupling or if the shaft comes free from the coupling. As on the Type A seal, the stainless steel rotor further polishes the carbon stator during the initial hours of operation.

Carbon Stator

The high-density resin-impregnated carbon stator is manufactured from an advanced composite that is first mixed, 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, unlike a lip seal or a plastic face seal. In addition, the high density of the carbon greatly increases longevity and wear resistance. Several commercial vessels have recorded over 40,000 (over 4-1/2 years of continuous operation) engine hours on the same original components.

Bellows

The bellows on both the PRO and Type B PSS seals are constructed out of high-temperature silicone laminated with either 4 or 5 plies of polyester fabric (aramid in larger sizes) and covered with a layer of fluorosilicone. In addition, both ends of the bellows are sealed so no water can get into the polyester/Aramid fabric. The 4 or 5 fabric inlay provides excellent strength to abrasion and resistance to pressure without loading the silicone. On the larger models, the strength is greatly increased by using stainless steel hoops laid into the convolutions of the bellows.

Hose Barb

For high-speed vessels (planning hulls or vessels powering over 12 knots), it is required that a positive water supply be plumbed to the PSS Shaft Seal for lubricating and cooling the seal faces. There are many water supply sources; review the PSS Shaft Seal Installation Instructions for more information and note that all plumbing must follow the standards and practices of proper boat plumbing. In most cases, a slow-speed boat with no bearing in the shaft log does not require positive water feed and can 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 to ensure the vent hose is never below the water line, even if the boat heels. Again, review the PSS Shaft Seal Installation Instructions for more details on venting the seal.

Specifications:

• Temperature Limits: -13°F to 425°F (-25°C to 220°C)
• Pressure Limits: 40 PSI (2.75 BAR)
• Shaft RPM Limits: 10,000 RPM
• Carbon Graphite: Lapped to 4 HLB (0.000044″ tolerance)
• 316SS / Nitronic 50: Faced to 9 Ra
• Bellow Material: Molded formed silicone/fabric

Product Dimensions:

• Shaft Diameter: 2-3/4″
• Stern Tube Diameter: 4″ to 4-1/8″
• Uncompressed Length: 9.988″
• Approx. Compressed Length: 8.988″
• Rotor Diameter: 5″
• Stern Cuff Length: 1.3″