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Critical Temperature Range - A temperature range usually between 1450° –1650°F in which carbon steels, low alloy steels and martensitic stainless steels transform to austenite on heating and reverse on cooling. Each composition of steel has its own critical temperature range. Calibration– Comparison of a measurement standard or instrument with another standard or instrument to report or eliminate by adjustment any variation (deviation) in the accuracy of the item being compared. CGA Number– Cylinder/container valve outlet connection number assigned by the Compressed Gas Association. CGA numbers are detailed in CGA Standard V-1. Chemical Abstract Service (CAS)– CAS numbers represent chemical substances recorded in the CAS Chemical Registry System. This numbering system identifies chemical substances by an unambiguous computer Language description of its molecular structure, including all stereo-chemical detail. The CAS number, which has no chemical significance, is simply a number assigned in sequential order to each substance as it enters the Registry System. All specific substances reported in the world’s scientific and technical literature and indexed in Chemical Abstracts (CA) since 1965 (when the Registry System began) are included in this master file. Coefficient of Flow (Cv)– Defined as the actual flow performance in gallons of water per minute at 60°F when inlet pressure (P1) is 1 psig and outlet pressure (P2) is atmospheric (14.7 psia). Compressed Gas Association, Inc. (CGA)– This is a nonprofit technical association whose membership includes many corporations active in all phases of the compressed gas industries. Founded in 1913, the CGA uses experience and knowledge of its members to promote industry wide standards and procedures for safety in the manufacture, storage, transport and use of compressed gases. Corrosive– The ability of a chemical compound to attack and produce irreversible damage to human tissues, such as eyes, skin or mucus membranes. Also, the ability of a chemical compound to attack and eat away rubber, metal and other substances. Cracking Pressure– A term used in back pressure control only (e.g. back pressure regulators, relief valves), for determining the inlet pressure at which flow starts. Creep– Any increase in outlet pressure of a pressure regulator subsequent to lockup. Usually seen as a long term slow pressure increase. This generally indicates a seat leak which is an abnormal condition. Cryogenic– Refers to the field of low temperatures, usually -130°F or below as defined by 173.300(f) of Title 49 of the Code of Federal Regulations. Cryogenic Liquid Container– An insulated container designed to store, handle and transport liquids having boiling points below -130°. Cylinder– A container designed to hold compressed gases or liquefied compressed gases. Cylinders are manufactured and tested according to DOT specifications . Carbide Precipitation - Occurs when austenitic stainless steel is heated within a temperature range of 800°–1600° F, 427°– 870° C for a critical period of time. Carbon moves from a solid solution to grain boundaries and combines with chromium. The metal adjacent to the grain boundaries is left with less chromium and is said to be sensitized. Corrosion resistance is therefore reduced in the grain boundary region. Carbon Arc Gouging - A cutting process by which metals are melted by the heat of an arc using a carbon electrode. Molten metal is forced away from the cut by a blast of forced air. Cerium Tungsten - GTAW tungsten electrode with small amount of the rare earth and nonradioactive ceria added. Improves arc starting and provides for use of wider current range. Characteristics - Special qualities or properties. For instance, some welding machines have certain internal characteristics which allow a welder to perform more welding applications than with other welding machines. Circuit - The complete path or route traveled by the electrical current. A circuit for GTAW can include the welding machine, weld cables, torch assembly, arc, base metal and work clamp with cable. Cold Lap - See preferred term Incomplete Fusion. Conductor - An electrical path where current will flow with the least amount of resistance. Most metals are good electrical conductors. Constant Current (CC) Welding Machine - These welding machines have limited maximum short circuit current. They have a negative volt-amp curve and are often referred to as “droopers”. The voltage will change with different arc lengths while only slightly varying the amperage, thus the name constant current or variable voltage. Constant Voltage (CV), Constant Potential (CP) Welding Machine - “Potential” and “voltage” are basically the same in meaning. This type of welding machine output maintains a relatively stable, consistent voltage regardless of the amperage output. It results in a relatively flat volt-amp curve as opposed to the drooping volt-amp curve of a typical GTAW (TIG) welding machine. Consumable Insert - Preplaced filler metal that is completely fused into the joint root and becomes part of the weld. Contactor - An electrical switch that is used to energize or de-energize output terminals of a welding machine. In some types of welding machines they can be of solid state design, with no moving parts and thus no arcing of contact points. Corner Joint - Produced when the weld members meet at approximately 90° to each other in the shape of an “L”. Crater - A depression at the end of a weld bead. Current - Another name for amperage. The amount of electricity flowing past a point in a conductor every second. Current Density - The amount of current per square inch of cross-sectional area in an electrode. For any electrode diameter, find the current density by dividing the current value by the electrode cross-sectional area in square inches. Cycle - One cycle equals 360 electrical degrees. For alternating current, current flow is in one direction through a circuit for 180° and in the opposite direction for the other 180°. For 60 cycle power, a cycle is repeated 60 times per second. Some welding machines, especially outside the , require 50 cycle (hertz) power. Hertz stands for cycles per second. Calibration – Comparison of a measurement standard or instrument with another standard or instrument to report or eliminate by adjust-ment any variation (deviation) in the accuracy of the item being compared. Calibration Gas – A gas or gas mixture of accurately known composition used as a comparative standard in analytical instrumentation. Calorie – The amount of heat required to raise the temperature of one gram of water one degree Celsius. Carrier Gas – Gas used with a gas chromatography to carry the sample through the system. Catalyst – A substance that initiates a chemical reaction and allows it to proceed under different conditions than otherwise possible. CGA Number – Cylinder/container valve outlet connection number assigned by the Compressed Gas Association. CGA numbers are detailed in CGA Standard V-1. Chemical Abstract Services (CAS) – CAS numbers represent chemical substances recorded in the CAS Chemical Registry System. This numbering system identifies chemical substances by an unambiguous computer language description of its molecular structure, including all stereo-chemical detail. The CAS number, which has no chemical significance, is simply a number assigned in sequential order to each substance as it enters the Registry System. All specific substances reported in the worldís scientific and technical literature and indexed in Chemical Abstracts, (CA) since 1965 (when the Registry System began) are included in this master file. Chemiluminescence – A species which chemically absorbs and emits light (usually at low temperatures). Chromatogram – The record produced by the gas liquid chromatograph. It is also a measure of instrument performance. Coefficient of Flow (Cv) – Defined as the actual flow performance in gallons of water per minute at 60F when inlet pressure (P1) is 1 psig and outlet pressure (P2) is atmospheric (14.7 psia). Column – Part of the gas chromatography system where the separation of the sample takes place (can be packed or capillary). Combustion – An exothermic oxidation reaction which may occur with any organic compound, as well as with certain elements. Compressed Gas – (1) A gas or mixture of gases having, in a container, an absolute pressure exceeding 40 psi at 70 ?F; or (2) a gas or mixture of gases having, in a container, an absolute pressure exceeding 104 psi at 130 ?F regardless of the pressure at 70 ?F or (3) a liquid flammable material having a vapor pressure exceeding 40 psi at 100 degrees F as determined by ASTM D-323-72. Compressed Gas Association (CGA) – This is a nonprofit technical association whose membership includes many corporations active in all phases of the compressed gas industries. Founded in 1913, the CGA uses experience and knowledge of its members to promote industry wide standards and procedures for safety in the manufacture, storage, transport and use of compressed gases. Corrosive – The ability of a chemical compound to attack and produce irreversible damage to human tissues, such as eyes, skin or mucous membranes. Also, the ability of a chemical compound to attack and eat away rubber, metal and other substances. Cracking Pressure – A term used in back pressure control only (e.g., back pressure regulators, relief valves), for determining the inlet pressure at which flow starts. Creep – Any increase in outlet pressure of a pressure regulator subsequent to lockup. Usually seen as a long term slow pressure increase. This generally indicates a seat leak which is an abnormal condition. Critical Density – The density of a pure material at its critical temperature and critical pressure. Critical Point – The transition point at which the liquid and gaseous states of a substance merge into each other. It is the temperature above which a substance cannot exist in two phases, no matter how great the pressure. See also “Critical Temperature” and “Critical Pressure.” Critical Pressure – At the critical temperature, the highest pressure at which a pure material can exist as a gas in equilibrium with its liquid. Critical Temperature – The temperature above which a gas cannot be liquefied by pressure alone. At this temperature, there is no distinction between liquid and vapor, both having the same density and constituting one homogenous system. Cryogenic Liquid – A liquid having a normal boiling point below -240 F (-151.11 C). Cryoogenic Liquid Container – An insulated container designed to store, handle and transport liquids having boiling points below -130 F. Cylinder – A container designed to hold compressed gases or liquefied compressed gases. Cylinders are manufactured and tested according to DOT/TC/MEX specifications. Complete Joint Penetration: Occurs when the “filler” metal completely fills the groove, and good fusion to the base metal is present.
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