Excluder Seals

Buna excluder seal kits are available in many sizes.

Excluder seals are a type of lip seal that actually rotates with the shaft. The skirt extends out and slightly downward to seal small tank openings.

Sharpe Mixers' excluder seal kits have really gained in popularity over the last couple of years, especially in the food industry. Seals are are available in almost any size from 1.0" to 6.63" as a standard. They are available in both Buna N and Viton material.

Sharpe excluder seal kit

Buna excluder seal kits are our most popular, and suitable for most applications. They are stocked and available for quick shipment (excluding large quantity orders).

Viton excluder seal kits are designed for higher temperature applications, and can ship in 1-2 weeks.

For more information, visit our web site at http://www.sharpemixers.com/!

Next generation dry-running mechanical seals

Sharpe Mixers has partnered with Roplan AB of Sweden, a leading supplier of sanitary and industrial mechanical seals, to develop our RD line of dry-running mechanical seals. The Sharpe Mixers Dry Running RD Mixer Seal has been designed specifically for use in mixers, agitators and reactors where possible product contamination from barrier fluids is not allowed. The design is capable of handling 0.15” total run-out. A proprietary Carbon blend virtually eliminates the face squeal that is common with other seal brands. The seal is available with a plain mounting flange or with a debris well.

The first generation of the seal was similar to existing products in the market such as Flowserve’s VRA or John Crane’s Type 32 mechanical seals. We are now releasing the next generation of this product which surpasses anything currently in the market in its adherence to ASME’s Bioprocessing Equipment (BPE) standard. Both Sharpe Mixers and Roplan are working with the BPE committees on seal design. The design has been updated to enhance cleanability. Internal surfaces have been sloped to facilitate drainage, including the debris well flush ports. All non-metal wetted components are either FDA approved or USP Class VI rated, standard. Internal metal surfaces have been polished to a minimum 20 Ra finish, standard. For the same cost as another supplier’s basic, non-pharmaceutical seal you could have a fully BPE compliant seal!

The seal comes as a cartridge assembly (see image below) for easy installation and the proper running height is pre-set with the cartridge clips. No more measuring! Just bolt the seal plate down, slide the shaft through, and tighten the setscrews. Wetted metal parts are etched with a heat number which is traceable to a mill test report to verify proper alloy to help simplify your system validation.

Seals can be made with special materials as well to accommodate your needs. If you want the most BPE compliant dry-running mixer seal on the market, come to Sharpe Mixers.

Materials of Construction

Rotary Seal: FDA approved Carbon

Stationary Seal: FDA approved Silicone Carbide
Metal Components: 316L Stainless Steel

Elastomers: USP Class VI FPM or EPDM Standard

Performance Capability

Temperature: Up to 300F (149C)

Pressure: Full vacuum to 200PSI (13.8 bar)

Speed: Up to 350 RPM

Sizes: 5/8” – 3”

Mechanical Seals

The majority of mixers operate in an "open" tank, or a vessel which is vented to the atmosphere. However, many mixers must operate in a "closed" tank, which requires a seal to contain the contents of the vessel. This may be required for various reason such as a pressure differential within the tank, product toxicity, flammability, environmental reasons, or in the case of side-entering or bottom-entering mixers, simply to stop the product from leaking out of the tank. Mechanical seals are used where very little or no tank emissions are allowed.

The family of shaft seals known as mechanical seals is the most advanced type of seal used in the mixing industry. They can handle the highest pressures, maintain nearly leak free operation, and require minimum maintenance if installed and operated properly.

Mechanical seals are increasing in popularity due to the growing environmental restrictions regarding leakage from process tanks.

There are hundreds of mechanical seal designs, but they all are variations of a basic layout consisting of a collar mounted on the shaft which usus springs to push a ring (which also rotates with the shaft) against another ring which is held stationary. The rings rotate against each other riding on a thin layer of lubricant, and the springs hold them so tightly together that leakage through the seal is reduced to an immeasurable amount.

The mating surfaces of the rings must be perfectly flat to seal properly, and are manufactured to tolerances measured in "light-bands". The rings must also be extremely hard to endure the pressure and wear, so they are usually mede up of ceramic, carbon, silicon carbide, tungsten carbide or similar material.

The stationary "seat" is held in place and maintains a static seal with the mounting housing using gaskets or o-rings. The rotating elements of the seal must attain a static seal with the shaft using o-rings, wedges or packing.

There is a type of mechanical seal that requires no lubricant. These "dry running" seals use a carbon ring rotating against a harder ring so the carbon ring is that sacrificial part. Any debris shed by the seal can be captured by an optional "debris well", which is flushed during a cleaning cycle. These seals are common in the pharmaceutical industry.

- Jeremy Higginson