Glossary E

Effective diameter

  • In metal bellows terminology it is the calculated diameter where the pressure penetrates between the metal plates. This number is used to determine the hydraulic balance diameter of the seal face.


  • Power out of the equipment divided by power in.

Elastic range

  • The stressed part retains its memory and returns to its original shape.


  • A rubber like material that, when compressed and then released will return to 90% of its original shape in less than five seconds.


  • A process involving chemical change caused by the passage of an electric current through a liquid.

Endurance limit.

  • Beyond this point the metal will fatigue without increasing the stress.


  • Environmental protection agency. A government agency with a mandate to protect the environment.


  • Ethylene propylene rubber. The most common elastomer used in the sealing of water based and higher pH materials. Cannot be used in petroleum products.


  • Permanent displacement of a portion of the O-ring into a gap, under the action of fluid pressure.

Eye of the impeller

  • The center of the impeller, where the fluid enters.