To select a seal it is not enough simply to specify the medium in general. For an optimum choice of seal it is absolutely essential to quote media-specific data, too, such as:

• composition of a mixed product
• concentration of the medium
• any solid content in % and grain size
• pH value
• viscosity
• density
• explosive, toxic or radioactive
• corrosive constituents.

It is also necessary – especially for acids and bases – to specify not only the concentration but also the temperature, as this has a great bearing on the choice of materials.