Electrode: a rod, plate or wire that is used to conduct electric current out of or into any device.
Epsilon X: designation of a new norm that will impact explosimeter design and certification throughout the EC. Also called ATEX or 94/9/EC, this standard becomes EC law on July 1, 2003. While the ATEX is complex, it basically ties together the now separate requirements of explosion-proof certification, ISO qualification for the vendor, and metrology (repeatability of results testing).
Explosimeter: fuel gas detector that measures the % L.E.L. in a given atmosphere sample; hence, they are primarily concerned with the potential of an explosive event. The units are always certified to some norm as being explosion proof.
Explosion: an uncontrolled chemical reaction which generates a large amount of heat and gas in a short period of time.
Explosion-Proof: a unit can be certified as explosion-proof by a variety of methods. A unit can be designed so that no energy or source of ignition (flame or heat) can escape to the surrounding atmosphere. A TDW PIG-SIG® is designed in this manner. The design focus is on the container. A unit can be designed to be intrinsically safe. In this approach, the energy potential within the unit is so low as to be incapable of being a source of ignition. The CATEX+ uses both approaches. The sensor chamber is designed to contain any possible ignition source from escaping the chamber and the overall system's internal energy potential is beneath the limit set as a possible ignition source.
Fermentation Gas: methane gas occurring in nature as the result of biological wastes or landfills.
Field Bend: A field bend has a bend radius equal to or larger than 7 times the nominal pipe diameter. These bends are made in the field during pipeline construction.
Fixed Installation: the terminology commonly used to indicate that a gas monitor is permanently installed, such as in the control panel of a control room, or on an offshore platform or refinery.
Flame Ionization (FID): see also discussion on gas leak detection technologies. Flame ionization is probably one of the oldest technologies in use today for leak detection, though it remains as the standard in terms of sensitivity (1 PPM) and stability. The concept works on the principle that a hydrogen (H2) flame will not conduct electricity, but if a hydrocarbon gas such as methane is present in an atmosphere sample, the hydrocarbon molecules will act as conductors, allowing measurement of the current between 2 electrodes. Extremely sensitive electronics allow measurement down to 1 micro Ampere (0.000001 mA), with 1 mA being equated to 1 PPM. This technology works best in low concentrations, below 100 PPM. Above that amount, fuel gas concentrations are determined using logarithmic scales rather than actual measurement of PPM concentrations.
Flammable (Explosive) Limits: For gases or vapors which form flammable mixtures with air or oxygen, there is a minimum concentration of vapor in air or oxygen below which propagation of flame does not occur on contact with a source of ignition. There is also a maximum proportion of vapor or gas in air above which propagation of flame does not occur. These boundary-line mixtures of vapor or gas with air, which if ignited will just propagate flame, are known as the lower and upper flammable limits (LFL and UFL) or the lower and upper explosive limits (LEL and UEL), and are expressed in terms of percentage by volume of gas or vapor in air. LEL and LFL are different terms for the same concept. In popular terms, a mixture below the LFL/LEL is too "lean" to burn or explode and a mixture above the UFL/UEL is too "rich" to burn or explode.
Flammable (Explosive) Range: The range of flammable or explosive vapor or gas-air mixture between the LFL/LEL and the UFL/UEL is know as the flammable or explosive range. As an example, for methane gas at ambient temperature, the LEL is 5% gas in air by volume, while the UEL is about 15%. All concentrations by volume of methane gas in air falling between 5% and 15% are in the explosive range.
Flashpoint: is the minimum temperature at which a liquid gives off a sufficient vapor to reach 100% LEL.
Flat-Bottom 3-WAY™ Tee: 3-WAY™ Tee where the nipple (or fitting body) is not scarfed. It is normally field scarfed for a particular larger than size-on-size pipe; i.e., 2-inch fitting on a 12-inch pipe.
Fuel Gas: any combustible gaseous mixture used as fuel to provide energy for domestic or industrial use. Fuel gases have the advantage of being transportable through pipes or other means from their source directly to the area where they are used. Fuel gases consist principally of hydrocarbons; that is, of molecular compounds for carbon and hydrogen. All these gases are odorless in the pure state; therefore, sulfur compounds (Mercapan) are commonly added with the unpleasant characteristic smell of sulfur serving to give warning of a leak in the supply lines or gas lines.
