Sanitary Mag Mixers. When Should You Use One?

March 4, 2014
Sanitary Mag Mixers Eliminate the Need for a Mechanical Seal, Ensuring Sterility

Sanitary Mag Mixers Eliminate the Need for a Mechanical Seal, Ensuring Sterility

Whether it is top entry, bottom entry or side entry, all traditional sanitary mixers/agitators have one thing in common- they all have some type of mechanical seal, separating the vessel interior from the outside environment where the impeller shaft enters the vessel. These can range from a very simple single mechanical seal to very sophisticated (and expensive) seal arrangements designed to maintain a sterile barrier.  But they all have one and without proper maintenance they will all fail sooner or later, potentially exposing the contents of the vessel to the surrounding environment.  If you want to eliminate this possibility there is now a readily commercially available alternative; the sanitary magnetic mixer, or mag mixer.

Sanitary mag mixers have no mechanical seals.  Most consist of three main components:

  1. A 316L stainless steel mounting plate that is welded into the vessel.
  2. An impeller that mounts onto a spindle on the weld plate.  The impeller has magnets mounted to it.
  3. A drive unit.  The drive unit connects to the bottom of the tank.  The drive has a powerful magnet mounted to the output shaft.

The sanitary mag mixer is a relatively simple device.  The impeller mounts onto the weld plate on a spindle that has a bearing on it.  Different manufacturers have different bearing designs, the most common is to use a hardened material as a thrust bearing.  The drive unit locks to the bottom of the weld plate.  When the drive rotates, its magnet locks onto the magnet in the impeller causing it to turn.  Like we said, simple.

What are the advantages of the mag mixer over tradition type mixers?  The biggest advantage is sterility.  There is no seal.  In critical applications such as bioreactors this is really important.  Seal failure can be catastrophic.  This is equally true in many other pharmaceutical sterile mixing applications.
There are other advantages as well.  Because they are bottom mounted, sanitary mag mixers don’t require the head space that traditional mixers do.  Also, sanitary mag mixers will mix until the vessel is almost completely empty, often not the case with traditional agitators.

How well do sanitary mag mixers agitate?  Very well.  We have tested them in our facility and on low viscosity liquids we have had no problem creating a vortex in vessel.  The units come in multiple sizes that will cover vessels ranging from as small as 10 liters up to 10,000.  They can be used on higher viscosity liquids as well.  You should consult a representative of the mixer company to get a unit properly sized for your application.

Here is a Picture in our Shop of a Sanitary Mag Mixer Mounted to a Jacketed Tank

Here is a Picture in our Shop of a Sanitary Mag Mixer Mounted to a Jacketed Tank

Can you CIP a sanitary mag mixer?  Yes you can.  We normally sell the Steridose Sterimixer.   Steridose brought the first commercial sanitary mag mixer on the market and in our opinion, offer the most compelling product.  They offer two impeller designs.  Both are CIP/SIP capable.  One has a more open design that is suited better for hard to clean products.

So if you need a vessel with a mixer and you want to ensure sterility, or have head space problems or simple don’t want to deal with mechanical seals consider the sanity mag mixer as an alternative.  If you have a specific need and would like to discuss it, contact us and go over your application with one of our sales engineers.  We are here to help.