Because of their hermetically sealed design, magnetically coupled pumps are ideal when used for crystallising, toxic, ammable and en- vironmentally hazardous liquids. The contain- ment shell between the two parts of the mag- netic coupling seals off the pumped medium to the outside. A mechanical seal is thus not re- quired. The magnetic coupling pumps are thus far more resistant to wear and consequently are generally entirely maintenance-free. A seal- ing-pressure system is therefore not necessary.