When to use Sealed and Non-Sealed Homogenizer Shafts

Laboratory homogenizer shaft assemblies have a number of components, all designed to work together to accomplish homogenizing, emulsifying, mixing, cell disruption, and similar processing.   The work performed governs the selection of the homogenizer generator, specifically choosing the correct rotor-stator configuration.  This includes the size (diameter) and the length of the shaft assembly.

For certain homogenizing applications a vital component of a homogenizer shaft assembly is the presence of shaft seals. Homogenizer shaft seals are required in order to protect O-rings, ball bearings, springs, retaining rings, discs, and other delicate components from harsh or abrasive media and from contact with formulations such as vaccines in order to minimize the chance of cross contamination.  Another application is for samples with a high percentage of inorganic substances such as alcohol that could damage these components inside non-sealed shafts.

Shaft seals are not to be confused with shaft bearings located at the top and bottom of rotating shaft in order to keep the rotor shaft centered in the shaft tube.  Bearings are common to all homogenizer shafts.

Lab Homogenizer Shaft Tube Configuration

Homogenizer shaft tubes are fabricated with or without ports.  Those used for standard emulsifying operations may have one or two ports that allow media being processed to circulate within the tube and perform a cooling function.  These shafts are equipped with Teflon (PTFE) bearings and discs located at the top and bottom of the rotating shaft for the centering function described above.

Note that sample entering and exiting these ports is not to be confused with the actual emulsifying action.  That function is provided by the homogenizer generator.  Shaft seals are not generally required for this application.

When processing samples under pressure, in a vacuum or for use with abrasive or adhesive type media a sealed shaft tube without ports is used. As an example, the CAT Scientific 20 mm diameter sealed homogenizer shaft 6423 for processing 500 to 1000 mL samples has a special two-part ceramic slip ring seal.  It is also used to operate with the DK-30 flow-through chamber.  Shafts used in these applications have many more components than those that do not require seals, and for that reason seals are highly critical for protection.

In either case, with or without seals, superior quality shafts are made from Type 304 stainless steel and easily disassemble for cleaning or replacement.  They feature a quick-connect coupling that make them interchangeable. Instruction manuals guide researchers through the process of disassembly and reassembly using rotor and socket wrenches.

Two Lab Homogenizer Maintenance Tips

Never operate your homogenizer dry, as the quick heat build-up will damage or destroy shaft components such as bearings, discs and seals. This means that you also insert the generator into the sample before turning the unit on.

Establish a standard operating procedure to thoroughly clean homogenizer rotor-stator assemblies.

What experience do you have with sealed and non-sealed homogenizer shafts?


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Bob Wilcox

Bob Wilcox has represented CAT Scientific’s family of homogenizers, magnetic stirrers, liquid handling and related laboratory equipment since 2002 when Staufen, Germany-based CAT Ingenieurbüro M. Zipperer GMbH established operations in North America. Bob oversees CAT Scientific laboratory apparatus sales and service organization from the company’s headquarters in Paso Robles, CA. He also is in charge of the parent company’s line of JetCat jet turbines, turboprop, and helicopter power plants for hobbyists’ radio controlled fixed wing and helicopter model aircraft. -- Earlier in Bob’s career he was involved in visual and special effects as well as camera and electronics supervisory responsibilities for the motion picture and television industry.

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