It is essential to know the operating conditions in order to be able to select a suitable mechanical seal. The amount of descriptive data needed depends on the type of sealing function to be performed, but the following specifications must be considered the minimum for all cases: Type of machine, diameter of shaft or shaft sleeve, speed, medium with details of concentration and temperature, and sealing pressure. Further data concerning e.g. the pH-value, solids content or viscosity of the medium can be just as vital in certain cases as the need to take QA measures or not. It is easier to note the operating conditions if a data sheet is used.