Rotary Shaft Seal Glossary

Aramid/PTFE Packing – packing made of filament yarn, impregnated with PTFE, and processed with lubricant. It is used with reciprocating and centrifugal mixers and valves, acids, solvents, food and chemicals industries, and abrasive substances in paper mills. Aramid packings are strong, low weight, and resistant to abrasion and impact. They can be made waterproof if epoxy is added, and can be installed as is or as end rings into packing ring seals.

Auxiliary Equipment / Systems – peripheral equipment used in conveyors, chillers, compressors, and other types of process equipment that may be an integral part of the extrusion process to optimize efficiency and ease of operation.

Auxiliary Stuffing Box – a packed box shaft seal that is used to seal equipment casing where the shaft passes through it. It has a tightening mechanism with continuous adjustment of the compression of the packing using springs or screws. Its purpose is to prevent leakage of product between sliding or turning equipment parts.

Abrasive Powder Sealing  seals used in low to highly abrasive powder processes like sugar, cement, gypsum, starch, salt, porcelain, talc, and silica. Sealing abrasive products is difficult because the abrasive product can damage the seal material as well as the shaft.

Air-purged Seals – use air purging to flush the seals with clean air. This helps prevent external debris and contaminants from entering the sealing area and protects process mixers, blenders, screw conveyors, and other bulk-handling equipment from damage and corrosion. With air-purged seals it’s important to remember the following:

When the air is piped from existing plant air directly into the seal, it creates pressure to push the rotor against the stator and closes the sliding interface to stop any material from going into or out of the screw conveyor.

Air-purged shaft seals perform best when purged with continuous air pressure set at 5 to 8 PSI higher than internal vessel pressure. The air purge improves the seal life of the internal parts by creating a higher pressure inside of the seal, producing a natural air barrier that keeps product out of the seal and inside of the equipment.

The air keeps the rotating seal faces cooler by reducing temperature caused by friction. This helps prolong the life of the seal by adding closing force to the seal faces as they wear from use so product can’t leak by.

All-metal Seals – seals with the outer surface made from metal materials like aluminum and stainless steel.

Battery Powder Sealing – sealing powders and coating slurries for making anodes and cathodes in lithium battery production. These contain a large percentage of solid particles and binders of different chemicals, sizes, and shapes. Rotary shaft seals prevent battery slurry mix or powder from leaking out in upstream and downstream mixers. Unattended leaks can result in downtime, wasted product, lower product quality, environmental pollution, and respiratory injury. Reliable sealing means containment of the battery mix within the mixing system while excluding contaminants.

Bulkhead Seals – are generally used to prevent flooding of the bulkhead seal’s adjacent compartments. They use hydrogel-filled foam to engage and seal against the spinning shaft when water is present. These seals do not touch the shaft during normal operation and can withstand any shaft speed and substantial shaft motion without causing wear.

Cartridge Seals – are designed for fast installation and removal from rotary shaft equipment. The cartridge seal is a set of seal components on a shaft sleeve and in a seal gland, built as a single unit. They are typically assembled and pre-set at the factory. They are designed to replace lip seals and packing, and can be easily press-fit into conveyor adapter plate without altering the adapters.

CEMA – Conveyor Equipment Manufacturers Association that was started in 1933 and is focused on creating and ensuring compliance with conveyor equipment industry standards for design, technology, application, and safety.

Cement Sealing – a shaft seal installed on screw conveying and mixing/blending equipment in cement processing applications. The sealing is done in 3 stages of cement manufacturing, during:

  • conveying the raw mix to a raw mill bin for grinding to a fine powder (raw meal)
  • conveying cooled clinker to cement ball mill hoppers
  • grinding and mixing clinker with gypsum to create cement

Cheese Seal – a shaft seal installed on mixing and blending equipment in cheese processing applications such as processed, restricted-melt, standard-melt, and quick-melt cheeses.

Chemical Resistance – the ability of material to protect against chemical attack or solvent reaction without being degraded by it. A chemically resistant material acts as a barrier to prevent the corrosive substance from permeating into it.

Chocolate Tank Seal – an industrial shaft seal used in chocolate processing applications. Prevents chocolate leakage that results in wasted time and resources.

CIP Capable Sealing – Clean-in-Place seal, or CIP seal, designed to stay in place while cleaning off debris. It is especially important in food applications, where the same chemicals used to flush the system would be used to clean the seal gland.

CinchPack Seals  CEMA screw conveyor seals designed for price conscious OEMs.  The CinchPack is available in all 5 CEMA sizes and has the same dimensions and is a direct replacement for the waste pack seal.

CinchSeal® – a self-adjusting and maintenance-free rotary shaft seal designed for CEMA screw conveyors and bulk solid mixing and blending equipment. FDA-approved silicon and PTFE-wearable seal components make the seal sanitary and safe for food, pharmaceutical, and chemical bulk-processing applications. Seal housings are offered in a variety of materials, including 316L stainless steel.

Dough Flow Seal – custom-made seal designed for dough flow mixers. It is used for slurries, mixes, semi-solids, and dry powders in food applications. It is an upgrade from lip seals on screw conveyor drive adapter plates such as Dodge, Link Belt, and Falk Gear.

Dough Pump Seal – seal used in bakery applications on dough pumps to feed a stream of dough to downstream dividers and forming equipment.

Dynamic Seals – seals used in rotating, reciprocating, or oscillating motion between surfaces.

Gaskets – static sheets that fill the space between two or more mating surfaces to prevent product leakage.

Gland Packing / Gland Seals – use square rope packing that is compressed around the diameter of the shaft to create the seal between the shaft and the seal housing. The rope packing is designed to wear with normal equipment operation. Gland packings are known to scorch or wear the shaft over a period of time, requiring the shaft to be replaced or repaired.

Lip Seal – seals a rotary, reciprocating, or oscillating shafts. The specific design of a lip will vary depending on the application. Many seal types have so-called lips as part of their design. The main goal of a lip seal (also known as a radial or rotary seal) is to lubricate, prevent contaminants, confine pressure, and separate fluids. Common examples include strut seals, hydraulic pump seals, axle seals, power steering seals, and valve stem seals.

Mechanical Packing – mechanical packing and other old sealing techniques rely on ropes. There are several types of ropes, such as gland packing made from natural fibers and old ropes, and more modern packing using braided materials. These ropes are wedged into the gap that is found between the shaft and the wall of the process equipment. Companies turned to this method for the initial installation savings because it was simple to install and maintain. There are also different materials that can be used to create mechanical packing ropes, which is essential for certain industries, such as food and chemical processing, to prevent contamination.

O-rings  are most common sealing devices used in a wide range of static and dynamic applications. Their simple, symmetrical diameter design, vulcanized in molds, enables both single and double sealing. The O-ring material and hardness selection depends on the size of the sealing joint, chemical composition, temperature, and pressure.

Packing  Packing is an inexpensive stationary method of sealing processing equipment. Even though it “grips” the shaft to limit leakage, its stationary design can cause wear to the shaft within time.

Pneumatic Seals – are seals that are engineered for pneumatic applications, with cylinders and valves triggered by air. Pneumatic seals operate in dynamic applications, normally with rotary or reciprocating motions.

Radial Seal – seals where compression is applied to the outside and inside diameter. They can be dynamic or static. Dynamic radial seals are used in applications that have a reciprocating, rotating or oscillating motion between the mating components being sealed. Static radial seals operate with a relative motion between the mating surfaces.

Rotary Air Lock Seal – a valve that separates a pressure variance, sealing off airflow from a hopper, bin, or conveying line, allowing product to pass through it.

Rotary Shaft Seals – shaft seals that are used in rotary applications such as a shaft or rotating bore. Rotary shaft seals provide sealing between rotating and stationary machine components or between two components in relative motion. They keep the bearing or system lubrication in and prevent contamination of the system by external objects. A typically design consists of two main parts:

A cylindrical metal case or an elastomer piece that provides an interference fit to seal statically against the housing bore.

A sealing lip made of an elastomeric or thermoplastic material that seals dynamically and statically against the shaft. The sealing edge is formed by molding, cutting or grinding. It is usually pressed against the counter face of the shaft surface, with a certain radial load, by a garter spring. The edge of the sealing lip and the shaft counter face surface form the most important functional area of a rotary shaft seal.

Screw Conveyor Seals – rotary shaft seals designed for CEMA screw conveyor equipment.

Shaft Seals – provide a non-leaking seal between the shaft and the wall of the process equipment. They contain the bulk materials inside of the equipment, preventing any contamination or leakage. The shaft seals are proven effective in sealing ribbon blenders, paddles mixers, airlocks, and screw conveyors.

Static Seals  seals, operating against mating surfaces that have no relative motion between each other. O-rings are common axial or radial static seals, depending on the direction of compression.

USDA Dairy Seals  seals that are approved by the United States Department of Agriculture. They are USDA certified for meeting safety standards in dairy processing industries. Their design can utilize acorn nuts to isolate fastening threads during production runs, manufactured 1/8” radii in the internal 90-degree corners to eliminate bacteria build-up and provided through holes when necessary to allow for cleaning of the threaded holes.

USDA Meat and Poultry Seals  seals that have received a certificate from the United States Department of Agriculture for meeting hygiene requirements for the design of meat and poultry processing equipment.

Vacuum Seals – seals used to prevent ambient air from flowing into the vacuum when vacuum technology components are detachably joined. There are different types of seals, depending on the application and pressure range.  O-rings are the most frequently used of all seals.

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Rotary Shaft Seals