Mixers and agitators offer a unique problem for mechanical seals. Because most mixers or agitators are mounted on top or on the side of a vessel the long shaft being used to mix or agitate usually has an issue with run out. The longer the shaft the bigger the run-out. Agitator Mixer Seals are similar to pump seals with one major exception, they are more prone to shaft runout. The reason is the generally long shaft extension that gives the shaft leverage against bearings and seals. One solution is to mount the seal faces in a fashion that allows run out.