hydrocarbons : organic compounds of hydrogen and carbon whose densities, boiling points,and freezing points increase as their molecular weights increase. All though composed of only two elements, hydrocarbons exist in a variety of compounds, because of the strong affinityof the carbon atom for other atoms and for itself.The smallest molecules of hydrocarbonsare gaseous, the largest are solids. Petroleum is a mixture of many different hydrocarbons. hydrometer : an instrument with a graduated stem, used to determine the density of liquids.The liquid to be measured is placed in a cylinder, and the hydrometer placedin the liquid.The hydrometer floats at a certain level in the liquid, depending on the density of the liquid. in-line system : a type of automatic sampling system where the probe and extractor are located directlyon the pipeline and the sample is withdrawn from the liquid stream. innagebob : a pointed,cylindrical weight attached to the end of agauge tape.The tapeand bob are usedto measure liquidheightinatank.Thebob keeps the tape verticalso that an accurate reading can be obtained form the tape. innage measurement : a measure of the liquid heightina tank fromthe bottom of the tankor datum plate to the top of the liquid.
innage tap-and-bob procedure : a methodof measuring the heightof the liquidin a tankusinga pointed gauger’s bob and a graduated tape. In this method, the liquidheightis measured from the bottom of the liquid to the top. Compare outage tape- and-bob procedure. kerosene : a light, flammable hydrocarbon fuel or solvent. light ends : the lighter hydrocarbon molecules that comprise gasoline, light kerosene, heptane, natural gas, and so forth. light fuels : fuels, such as gasoline, that have relatively high volatility. light products : petroleum fractions, such as ethylene,that are relativelylight in molecular weight. liquid calibration procedure : a method of determining a tanks capacity by filling and withdrawingfrom the tank accuratelydetermined volumes of liquid. liquid cut : the mark on the gaugetape indicatingthe height of the liquid. master tape : a measuring tape that has been certified accurateat a specified temperature and tension by the National Institute of Standards and Technology. liquid head stress : the hydrostatic pressure of the liquid intanks of 500 barrels or more, which causes the shell to expand and contract.
gauge tape : a graduated, metal, non- sparking, noncorrosive measuring tape used with a gauge bob to measure the height of the liquid in a storage tank. gauging height : the distance from the gauge, or reference, point from the bottom of a tank to a gauge, or reference, point at the top of the tank, usually on the hatch. gear pump : a rotarypump that moves fluid by means of two contra-rotating, meshing gear wheels. The teeth of one wheel mesh with the spaces between the teeth of the other wheel. The fluid enters one side of the pump and is forced through by the moving gears, and is dischargedon the other side.
gravity : see density .
gross volume : the total amount of liquidin a storage tankexcludingany adjustments for S&W, temperature, or density. Compare net volume. hatch : 1.An openingin the roof of tank through which agauginglinemay belowered to measure its contents. 2. Theopeningfrom the deck intothe cargo space of ships.
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