7500 Series CEMA Screw Conveyor
Rotary Shaft Seals

The 7500 Series Shaft Seals are offered in two different versions: the 7550 for use in most powder applications, and the 7520 for slurries or very abrasive applications. The key component of the 7500 rotary shaft seal design is the solid elastomer, which is made from FDA approved silicone and can handle temperatures up to 400F degrees. The elastomer is molded slightly smaller than the shaft size so that an interference fit is achieved. It is this tight fit that seals the shaft, which stops material from migrating past, and drives the two rotating faces called “rotor cups”. The rotating rotor cups compressed against the two stationary stator plates is what creates the primary seal that stops product leakage. These dynamic seals are also air purged at 5 to 7 PSI above any pressure in the vessel to assist in maintaining a positive seal.

The air purged 7500 series seal turns with the shaft, providing a major benefit to customers. Alternative sealing options like rope packing remain stationary while the shaft is turning, which can score and damages the shaft. This can lead to expensive maintenance when you have to replace the shaft. With CinchSeal, the internal seal elements turn with the shaft, thereby eliminating the risk of shaft damage.

The 7550 shaft seal series features rotor cups made from a special mineral filled PTFE blend, and are the wearable part of the seal. On the 7520 model the rotor cups are made out of aluminum that we hard coat with a special process that gives them a hardness of 62 on the Rockwell scale (the same hardness as Tungsten Carbide). The hard coated aluminum rotor cups run against inner and outer PTFE stators, which are now the wearable part of the seal and will be replaced when worn.

When buying a repair kit for the 7550 model, it would consist of a new solid elastomer and new PTFE rotor cups. If you have a 7520 model a repair kit consists of a new elastomer and two new PTFE stator plates (see exploded views below). All these pieces compress into the mechanical seal as you tighten down the cover plate with the 4 screws and the optimum seal face load is established.

The newly rebuilt seal is bolted up to the machine where it will run for thousands of hours of leak-free service before a repair kit is needed. Contact us for more information!