When do you want to choose a sealless pump tube vs pump tube with a seal? Basically the only time you would consider a mechanical seal tube is if you were pumping something that is going to crystalize and clog up the leak path that guides the liquid back into the vessel on a sealless model (the slit that is on the side of the lower bearing housing) and even then if you keep a sealless pump tube flushed and clean that would prevent that from happening. Almost all of the pump tubes that get shipped by Lutz Pumps these days are sealless.
How do we choose between a Lutz Pump Tube with a Rotor vs the Impeller Tube? The rule of thumb on the rotor/impeller is rotor is high flow at low head and the impeller is the other way around or if the specific gravity/viscosity of the liquid starts to get heavier it is best to consider the impeller. Our Chemworld Team prefers the impeller because it covers the bases more.