Mechanical seals consist of two surfaces which slide against each other The surfaces are pressed together by a spring. Between these two surfaces a f luid film is generated by thepumped product.This f luid f ilm prevents t hat t he mechanical seal t ouches t he stat ionary ring. The absence of this f luid f ilm will result in f rict ional heat and the destruct ion of the mechanical seal (dry run of the pump).The spring is in the product . The product pressure acts addit ional to the spring on the rotat ing seal part .Therefore standard mechanical seals are used only for a pressure up to 10 bar. For higher pressures, balanced mechanical seals are used.