Packless Shaft Seal 7/8

A maintenance-free dripless stuffing box and packing gland replacement for both sail and power boat drivetrains.

For a 7/8 " diameter Shaft with a Stern Tube measuring between 1 1/2" and 1 3/4".

Dimensions

• Shaft Diameter: 7/8"
• Stern Tube Diameter (D): 1 1/2" to 1 3/4"
• Total Length (A): 6.975"
• Total Length (Compressed A): 6.225 "
• Rotor Diameter (B): 2.375 "
• Carbon Cuff Diameter (C): 2 "
• Stern Cuff Length (E): 1.5 "

The PSS Shaft Seal from PYI, is the number one selling marine mechanical shaft seal worldwide and is installed as standard equipment by many of the worlds most reputable boat builders and yards. The PSS Shaft Seal is also recognized as the premiere retrofit (aftermarket) seal on the world market. Certified by Bureau Veritas, ABS & Rina Classification Societies. Never repack a stuffing box or replace a lip seal again with the PSS Shaft Seal.

Owners, boat builders and yards recognize the advantages and value of installing the PSS (Packless Sealing System) as it eliminates the maintenance, constant adjustment & cost associated with traditional packing type glands. Aside from these benefits, the PSS Shaft Seal helps to eliminate water in the bilge (100% water tight) & wear to the propeller shaft.

The PSS Shaft Seal is a mechanical face seal that is created between the flat surfaces of the rotating stainless steel rotor and the stationary carbon flange. The stationary carbon flange is attached to the vessels stern tube with hose clamps and the carbon flange is attached to the front side of the bellows with hose clamps. The stainless steel rotor is fit on the shaft in front of the carbon flange. The stainless steel rotor is used to compress the bellows before the collar is secured to the shaft with set-screws.

This compression (pre-load) maintains contact between the faces and allows the PSS to compensate for the thrust from the propeller. The carbon stator is bored larger than the shaft diameter, allowing it to “float” around the shaft and compensate for most misalignment and vibration problems. The stainless steel rotor is sealed to the shaft with o-rings. These o-rings rotate with the shaft and stainless steel rotor and do not experience any wear during operation. This static o-ring seal enables the PSS Shaft Seal to be fit on shafts that have have some wear or pitting, unlike lip seal designs which require a clean area for the lip seal to ride on. This type of carbon face seal is not as sensative to interuption of water flow or operation in silty water, when compared to other sealing options.

The three PSS components consist of;

Carbon / Graphite Stator

The high density, resin impregnated carbon/graphite stator is a space age composite that is first mixed, molded and then formed under pressure. The blanks are then baked, machined and lapped. The face of the carbon is finished to a flatness of 4 helium light bands (measured .000044" of variation over entire lapped surface). the grade of carbon used in the PSS has an operating teperature over 500 degrees Fahrenhite (+260 Celsius), and can not melt if the seal runs dry, unlike a rubber lip seal or plastic face seal. The high density of the carbon greatly increases the longevity and wear resistance. Several commercial vessels have recorded over 40,000 engine hours on the same original components. The carbon should not need to be replaced under normal operating conditions.

Stainless Steel Rotor

The Type A stainless steel rotor (316L) is slid down the shaft and is secured to the shaft with set screws at 90 degrees for maximum holding power. the carbon will polish the face of the rotor during the first few minutes of operation. The rotor should not need to be replaced under normal operating conditions.

Bellows

The Type A bellows seal is made from rubber (EPDM - Ethylene Propylene), and has a temperature rating of -65 degrees to 300 degrees Fahrenheit (-50 to +145 Celsius). EPDM is known for its good resistance to weathering. The bellows must be inspected on a regular basis for any sign of wear, aging or chemical deterioration. It is recommended that the bellows be replaced every 6 years. Bellows may need to be inspected more frequently in an environment where non-sealed batteries emit sulfuric acid. Sulfuric acid vapor will accelerate rubber deteriation, as will an ozonater. PSS Maintenance Kits containing bellows and other replacement parts are available.