According to the different working conditions and medium properties, mechanical seals have high temperature and low temperature resistance, high pressure and corrosion resistance, granular medium resistance and light hydrocarbon medium adaptable to vaporization. Different structural types and materials should be selected according to different uses.

The main parameters of type selection are: pressure of sealing chamber (MPa), temperature of fluid (C), working speed (m/s), characteristics of fluid and effective space for installation of sealing, etc.

The basic principles of type selection are as follows:

1. According to the pressure of the sealing chamber, the seal structure is determined to be balanced or non-balanced, single-end or double-end.

2. According to the working speed, the rotary or static, hydrodynamic or non-contact type are adopted.

3. According to the temperature and fluid properties, determine the friction pair and auxiliary sealing materials, and correctly select lubrication, flushing, heat preservation, cooling and other mechanical seal cycle protection system.

4. According to the effective space of the installation seal, the multi-spring or single-spring or waveform spring, internal or external type are adopted.