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A: George Lavoie, Meco Seal div. Woodex Bearing, says:

No application is routine, even for screw conveyors and bucket elevators, which are the workhorses of solids processing. As you specify the build details of your mechanical conveyors, remember to verify the compatibility of the auxiliary components, especially the seals and bearings.

These components, like the conveyors themselves, must be designed and built to suit the material and process. What type of seal should you use? What materials are inside the seal? What bearing material is best? By doing a little research upfront, you can learn which materials and configurations will work best in your application. This will not only extend the service life of your conveyors and components but will also give you better process performance.

Seals for explosion prevention
Shaft seals and other components give off heat and/or discharge static electricity as the equipment operates, and few processes warrant more attention to detail than those involving potentially explosive materials. While using a liquid barrier to cool the shaft seals is effective, this approach is usually unacceptable in dry processes. But alternatives exist. Figure 1 shows an ATEX-compliant soft-face seal that uses high-lubricity materials instead of a liquid cooling barrier.

The prescribed temperature and pressure limits of the machinery and process will guide your seal choice. These parameters vary considerably so each seal must be engineered individually. This will prolong sourcing and manufacturing, so plan accordingly. 

Seals for sanitary applications
Seals for sanitary applications also require special attention. Seals in sanitary applications usually require stainless steel and FDA-approved plastics and other elastomeric materials. Which combination of materials is best will depend, as always, on a variety of factors. These include how hot the process becomes, how abrasive the material is, and how fast the shaft turns. Talk with vendors about your materials, final product, and process or complete the application data sheets they offer. Only then can suppliers recommend the proper seal design for your machine and process. 

Questions to consider include: Will the conveyor process a single material or a variety of them? What are the properties of the different materials? What about washdown procedures: How often will the conveyor be cleaned and what chemicals will be used? The answers to these and other questions will determine whether a stainless steel, aluminum, or nylon seal is most compatible and guide the choice of other components, including valves, gauges, and regulators.

Meco Seal div. Woodex Bearing, Georgetown, ME, manufactures custom-engineered shaft seals.