Eccentric: In contrast to concentric parts that share the same center, eccentric parts deviate from having a common center.

Eccentricity (shaft): The extent to which a circular shaft deviates from its outer diameter as it rotates in relation to its true centre.

Eddy current: Electrical currents generated within conductive materials in response to changes in the magnetic field. These currents induced magnetic fields within the material.

Effective diameter: In the context of metal bellows construction, it refers to the diameter at which pressure penetrates between the metal plates. It is used to determine the hydraulic diameter of the seal face.

Efficiency: A measurement of the output power of a piece of equipment divided by the power it consumes. It is always expressed as a value between 0 and 1.

Elasticity: A physical property of materials that enables them to return to their original shape after being deformed.

Elastic range: In materials science, the elastic range refers to the range of stress in which a material can be deformed and still return to its original shape upon the removal of stress.

Elastomer: A substance with viscoelastic properties, often used interchangeably with rubber. Elastomers have the ability to return to their original shape after being subjected to stress.

Electrical run-out: Non-uniform electrical properties of a shaft material resulting in deviations from a perfect circular shape. Unlike mechanical run-out, which refers to eccentricity of the shaft, electrical run-out pertains to non-uniformities within the shaft.

Electrolysis: A chemical reaction occurring when ions in a liquid carry an electric current.

End-suction pump: The most common type of centrifugal pump featuring a horizontal shaft with an impeller located at the end. Fluid enters the pump casing through the end and is discharged from the top.

Endurance limit: The maximum level of stress that a metal can withstand indefinitely without experiencing fatigue failure.

End-user: The ultimate user of a particular equipment or product. There may be various intermediaries involved between the manufacturer and the end-user, such as distributors or third-party integrators.

Entrance suction loss: The loss of suction pressure that occurs between the pump inlet and the impeller.

EPA: Environmental Protection Agency. A governmental agency tasked with protecting human health and the environment.

EPR: Ethylene Propylene Rubber. An elastomer made from a copolymer of ethylene and propylene. Commonly used for sealing water-based and petroleum-based products.

Equivalent length: A measure used to calculate the frictional losses caused by fittings (e.g., bends, tees, valves) in a piping system. It represents the length of a straight pipe that would cause an equivalent pressure drop.

Erosion: The gradual degradation of system materials due to the abrasive action of the fluid. If the process fluid contains solid particles, erosion can be more pronounced.

External gear pump: A type of pump that uses gears to displace the fluid being processed. The gears are housed in a casing with minimal clearance. As the gears rotate, the liquid is trapped between the gear teeth and transported from the inlet to the outlet.

Expeller: A gland seal mechanism employed to reduce the bypass pressure from the pump into the sealing area. Typically used in slurry pumping applications, it utilizes centrifugal force and component tolerances to achieve its sealing effect.

Extrusion: The displacement of an O-ring into a gap due to fluid pressure.

Eye of the Impeller: The central portion of the impeller where the process fluid initially enters and then moves outward towards the outlet or discharge.

Related Links

• Pump Glossary
• Pump info