Plants that convert chemical energy, the binding energy of atomic nuclei, water energy, wind energy, tidal energy, solar energy and geothermal energy into electrical energy and/or thermal energy. As a rule, thermal energy (from the combustion of coal, oil or gas, from nuclear fission, from solar energy or from the thermal energy of the interior of the earth) is converted in turbines into mechanical energy. Generators coupled with the turbines then produce the electrical energy. The exhaust steam is condensed by cooling in condensers and is returned to the boiler (water-steam circuit). In the case of water, wind and tidal power stations, the turbines or generators are driven directly by the respective form of energy. An exception are heating power stations, which supply their thermal energy in the form of hot water for industrial heating requirements or for residential district heating.

Mechanical seals can find application in all the pumps used by a power station. In conventional plants they include effluent pumps, dosing pumps, generator/stator cooling pumps, main condensate pumps (condensate pumps), hot water pumps, heating condensate pumps, heating water recirculation pumps, heating water booster pumps and cooling water pumps.

In flue gas desulphurization systems there are feed water pumps, circulation pumps, booster pumps and feed pumps.

The operational availability of a power station is closely bound up with the reliability of its mechanical seals. In all the different areas of a power station mechanical seals are able to satisfy to a high degree the requirements on general operational safety, maintenance-free running, low leakage and economic efficiency (price/performance ratio).

To do so, the seal must be of a rugged, tested and reliable design, the seal's surroundings on the pump side must be optimized, and the specified handling instructions stipulated in the installation and operating manuals must be observed. With requirements differing in the various types of power station – and in various areas of the same power station – there is a diversity of seal types and seal arrangements. For a mechanical seal to live up to expectations, the following points should be heeded: 

• Use high-grade mechanical seals in key areas; changing a seal is trequently several times more expensive than the seal itself.
• The better and more uniform the water quality, the higher the operational safety.
• With critical media (abrasive, corrosive, radioactive) or with recurring special operating conditions (e.g. vacuum applied to the mechanical seal at standstill), it is recommended to use double or tandem mechanical seals (e. g. for main condensate pump, nuclear auxiliary pump).
• Provide for speedy replacement of the mechanical seal, e.g. by using cartridge units, in order to reduce the length of time the power station or plant section is out of operation and to safeguard staff against unnecessary nuclear radiation.

To achieve an optimum result, the operator, planner, pump builder and mechanical seal manufacturer must cooperate (e.g. information about changes to the method of operation is essential for proper matching of the face materials).