A–B–C–D–E–F–G–H–I–J–K–L–M–N–O–P–Q–R–S–T–U–V–W–X–Y
Elastomer
A natural or synthetic elastic material composed of long, chainlike molecules that are capable of recovering their original shape after being stretched to great extents. Under normal conditions the long molecules making up an elastomeric material are irregularly coiled. With the application of force, the molecules reconfigure themselves to distribute the applied stress returning to its original configuration when the stress is removed. Used in synthetic rubber parts such as O-rings.
Elbow
A female threaded or socket fitting used for changing direction in a run of pipe or tubing.
Electric Actuator
An electromechanical device that uses an electric motor to drive through a gearbox to an output shaft which is connected to a valve stem.
Electro-Hydraulic Actuator
A hydraulic actuator powered from an integrally mounted hydraulic power unit requiring only an electrical supply and control signal.
Electroless Nickel Plating
An auto-catalytic reaction used to deposit a coating of nickel phosphorous alloy on a substrate without passing an electric current through the solution to form the deposit. This plating technique is mostly used to prevent corrosion and wear on metallic materials. Refer to ASTM B 656 (a standard guide which provides information about ENP) and ASTM B 733 (a specification which defines requirements for ENP).
Elongation
Percentage increase in original length (strain) of a specimen produced by a tensile force (stress) applied to the specimen. Ultimate elongation is the elongation at the moment the specimen breaks.
Embrittlement
Loss of ductility of a material due to chemical or physical change.
EMC (Electro-Magnetic Compatibility)
Electro Magnetic Compatibility is the ability of an equipment or system to function satisfactorily in an electromagnetic environment without introducing intolerable electromagnetic disturbances to anything in that environment (IEC definition).
Emergency Sealant Injection (Fitting)
To obtain tight shut off in an emergency situation, a sealant can be injected into a specially designed groove in the seat rings and/or in the stem seal pockets. Available for most ball valves and gate valves.
EMO (Electric Motor Operated)
The actuation of a valve by electric motor.
EN Standard
It refers to European Standard.
Enclosure
Housing for control equipment to provide protection appropriate to the environment in which the equipment is to be used. They are normally designed to meet the requirements of I.E.C. and/or N.E.M.A. who designates the degree of protection according to published definitions.
End Bevel
Weld end preparations for butt-welding. Governed by ASME B16.25.
End Connection
The type of connection supplied at the ends of a valve which allows its installation on a pipeline. Weld end (WE), raised face flange (RF), ring-type joint (RTJ) are the most common end types.
End Stops
Mechanical device to limit the open and closed position of the actuator.
ENP (Electroless Nickel Plating)
Surface treatment of metal to protect against corrosion.
EPDM
The abbreviation stands for Ethylene Propylene Diene Monomer. It is a popular seal material that is compatible with fireproof hydraulic fluids, ketones, hot and cold water and alkalis. But, it is not compatible with most oils, gasoline, kerosene, aromatic, aliphatic hydrocarbons, halogenated solvents and concentrated acids.
Equal Percentage Flow Characteristic
An inherent flow characteristic which for equal increments of rated travel will ideally give equal percentage changes of the existing flow.
Erosion
Progressive loss of original material from a solid surface due to mechanical interaction between that surface and a fluid, a multicomponent fluid or impinging liquid or solid particles. Because of the broad scope of this term, it is recommended that it normally be qualified to indicate the relevant mechanism or context, for example cavitation erosion, liquid impingement erosion, solid impingement erosion, beach erosion, etc.
ESDV (Emergency Shutdown Valve)
The Pipeline Safety Regulation (A guide to the Pipelines Safety Regulations 1996 – Guidance on Regulations: ISBN 0-7176-1182-5 82) states that an “emergency shut-down valve” is a valve which is capable of adequately blocking the flow of fluid within the pipeline at the point at which it is incorporated. In the absence of a definition, “adequate” is taken to mean sufficient for a particular purpose. Minor internal leakage past the ESDV may be accepted providing it does not represent a threat to safety. The rate of leakage should be based on the installation’s ability to control safely the hazards produced by such a leak.
ESW (Electroslag Welding)
A highly productive welding process for thick materials. It involves the melting of the surfaces of the metal workpieces and the filler metal with a molten slag to cause coalescence. An electric arc is passed through the slag to heat it, but the arc itself is extinguished by the slag.
Expanding Gate Valve (also Double Expanding Gate Valve)
A gate valve that is comprised of a separate gate and segment that, as the valve operates, the gate and segment move without touching the seats, permitting the valve to be opened and closed without wear. In the closed position the gate and segment are forced against the seat. Continued downward movement of the gate causes the gate and segment to expand against the seats (see Mechanical Seal). When the valve reaches its full open position the gate and segment seal off against the seats while the flow is isolated from the valve body.
Explosion Proof
The prevention of explosion triggered by electrical components through containment in special housings. A requirement for electrical devices such as solenoids and switches when exposed to a potentially explosive environment.
Explosive Decompression (also referred to as AED)
Phenomenon occurring in rubber seals after exposure to high pressure gas. This gas permeates into the elastomer through flaw sites present in all molded rubber products. During an equilibrium shift (rapidly lowered pressure), the gas expands within the seal causing internal ruptures in high shear modulus (hard) materials and surface blisters in low shear modulus (soft) materials.
Extended BDV (Blow Down Valve)
Used on buried valves where the drain plug is inaccessible. Instead, a line is piped above ground, terminating in a small valve. Line pressure is used to blow-out condensates and other material which settles in the bottom of the body cavity.
Extension Bonnet
A bonnet with an extension between the stem seals and bonnet flange for hot or cold service.
Extensions
The equipment applied to buried valves to provide above ground accessibility to operating gear, blow down and seat lubrication systems.
External Coating
Coating applied to protect valves against various environments i.e. sea air, salt water, earth buried and normal air exposure.
Extrusion
Pressure-induced distortion or extension of part of a seal into the clearance gap between mating seal surfaces.