This document discusses mechanical seals and tandem seals used in equipment. It describes the components of mechanical seals including rotary elements like carbon rings and stationary elements like tungsten carbide rings. It discusses types of mechanical seals such as single seals, double bellow seals, and unbalanced seals. It explains that hydraulic balance percentage below 65% can cause leaks. The document also covers barrier fluids used with tandem seals, circulating barrier fluids and quench fluids to control heat and removal, and suitable barrier fluids for different temperature ranges.