GLOSSARY DEFINITIONS
A B C D E F G H I J K L M N O P Q R S T U V W
A bubble column, or packed tower in which certain components of a gas stream are absorbed into a substantially non-volatile liquid.
Accumulator Drum
A vessel or tank serving as surge capacity for fluids, from which streams are drawn for charging to other points—for example, "reflux accumulator".
Additives
A compound added to a semi-finished product in very small quantities to improve some characteristic of the product, or to prevent certain undesirable reactions from occurring In its use. Examples are viscosity and pour point improvers, anti-oxidants and corrosion inhibitors.
Algae
Seaweeds, pond-scums, and a variety of microscopic plants inhabiting fresh and salt waters in countless numbers.
Aniline Point
A laboratory test for measure of the tendency of an oil to crack.
Anti-Oxidants
See - "Inhibitors".
API Gravity
The API gravity scale is an arbitrary one which is related to the specific gravity of a petroleum product in accordance with the formula:
Degrees API= 141.5 - 131.5
Sp. grav. 60/60
Aromatics
A generic term applied to hydrocarbons having as part of their basic structure the benzene ring.
Asphalt
Brown to black solid or semi-solid bituminous substances occurring in nature or obtained as a residue from the distillation of certain crude petroleums. They consist chiefly of a mixture of comparatively non-volatile hydrocarbons and their derivatives.
ASTM Distillation
ASTM D86-46 An atmospheric batch-type of distillation performed under definite conditions with specific equipment.
ASTM Gum
ASTM gum test D381-46 It is a measure of the existent gum in gasoline as indicated by the amount of non-volatile residue.
A partition placed in a container to cause a fluid to change its direction of flow.
Barometric Condenser
Condensation by direct contact with water set sufficiently high so that the water drains from it through a barometric hot leg into a hot well.
Barrel
The petroleum industry in general uses the 42 U.S. gallon barrel as the standard barrel. Crude oil, for example, is also measured in 42-gallon barrels and crude is bought on that basis.
B/CD
An abbreviation for the term "barrels per calendar day". The figure is usually obtained by computing the total barrels flowing per year and dividing by 365. This value includes all shutdown and standby time.
Bitumen
A generic term applied to naturally occurring hydrocarbons such as native asphalts.
Blending
The process of mixing two or 'more oils having different properties to obtain an oil of Intermediate properties.
Blind
A solid plate or cover designed to prevent the flow of fluids through a nozzle of an equipment or through a pipe.
Blocked-out Operation
Operation of a unit or part of a unit for alternately different processing operations.
Blow-down
A term applied to a system used for the disposal of accumulated wastes, spent process streams, or process fluids during the interruption of the process. It may also be applied as a term to describe these wastes, spent streams, or process fluids.
Blow-down Drum
A tank Into which the contents of a unit may be emptied
when an emergency arises. Usually provided with connections for steam or water injection to prevent ignition of contents. Outlet is connected to blow-down stack.
Bob Gouge
A term applied to the gauge, consisting of a chain or wire rope attached to a float at one end and a pointer at the other, used to indicate the height of fluid in a tank.
Bomb
A laboratory vessel designed for the storage or reaction of materials under high pressures.
Booster Pump
A pump used to raise the pressure level of any fluid stream which has been previously subjected to a pumping operation.
Bottoms
In a distilling operation, that portion of the charge remaining in the still or flask at the end of the run.
Bottom Steam
A term applied to the steam injected into the bottom of a tower or still to effect stripping or light materials.
Break
Separation into two layers such as oil and water.
Breathing
The movement of gas (oil vapours or air) in and out of the . vent lines of storage tanks due to alternate heating and cooling.
Bridge-Wall
A vertical wall serving as one the confining walls of a furnace and used for separating the combustion or radiant zone from the convection zone.
Bromine Number
A measure of the degree of unsaturation of the material to which the test is applied (ASTM D875-46T).
BSD
An abbreviation for the term "barrels per stream day". The total number of barrels of materials flowing through a unit in a given process period divided by the number of actual "on stream" days will yield the average B/SD.
B.S & W
An abbreviation for the term "bottom sediment and water". A volumetric measure of the sediment and water in petroleum products as determined by ASTM D96-46.
Bubble - Cap
A cup-like element of the "bubble-cap tray" placed over the chimney-like "risers" of the tray. It directs the ascending vapours
in a fractionating column into contact with the liquid maintained on the trays.
Bubble - plate
A term applied to the element of a fractionating column consisting of a casting perforated with a multiude of chimney-like "risers" which, in practice, are capped with the bubble-caps.
Bubble Tower Or Column
A fractionating tower so constructed that the vapours generated in a tower pass upward through layers of condensate contained on a series of trays. The vapour passes from a given tray to the next above by bubbling under a cap and out through the liquid layer. An approach to equilibrium between the vapour and the liquid on the tray is thus obtained ; the less volatile components of the vapour condense and the excess liquid overflows to the tray next below and so back to tower bottom.
Bunker Fuel
A class of residual fuel oil possessing high viscosity, requiring burners equipped with preheaters.
See bubble cap.
Carbon Residue
The amount of carbon residue left on evaporating an oil under specified conditions, reported in wt. % of the original sample. See ASTM D 189-46.
Catalyst
Any substance which, by virture of its presence, affects the rate of a chemical reaction and which, in general, remains unchanged at the end of the reaction.
Catalyst Extruded
Catalyst formed by forcing a paste-like mixture through small holes, cutting into short lengths, and drying.
Catalyst Fluidised
A term usually applied to a solid catalyst which has been reduced to particles small enough that the catalyst will flow in the manner of a liquid.
Catalyst lmpregnated
A catalystic medium consisting of a solid porous particle serving as a carrier for the activating salt with which it has been impregnated.
Caustic
A solution of sodium hydroxide (lye) used for the neutralization of oils following acid treatment.
Caustic Neutralization
The chemical reaction in which acidic materials are rendered neutral by the addition of caustic soda.
Caustic Treating
Any process involving the use of a caustic solution for removal of H2 S, mercaptans, and other acidic constituents.
Cetane Number
A measure of the tendency of diesel fuels to knock in an engine.
Clear Gasoline
Unleaded water white gasoline motor fuel.
Coalescer
Generally a device which employs a fixed porous bed of material insoluble in the fluids passed through it and which promotes by mechanical means the coalescence of finely dispersed materials to render them readily separable.
Coke
Carbonaceous material deposited on the catalyst at the catalystic cracking unit during the cracking reaction. Also forms in Platforming and Unifining catalyst more slowly. Sometimes found in hot exchangers as a fouling material.
Colour Stability -
A measure of the tendency of a material to resist change in colour, usually expressed as loss in colour units after storage or exposure to light.
Compressors
A device for raising the pressure level of a gas or vapour to a higher pressure.
Condenser
Equipment used for liquifying oil vapours coming from distil" lation equipment. Generally uses water as cooling medium.
Condensate
The liquid product coming from a condenser.
Conradson Carbon
The carbon residue obtained by combined combustion and evaporation of a petroleum oil in accordance with ASTM testing procedures. (ASTM D 189-46).
Continuous Treater
A piece of equipment, designed to operate continuously, in which a process stream is brought into desired contact with a treating stream and then afforded adequate means of separation. The treating stream brings about desired changes in the chemical composition of the material being processed.
Convection Section
The section of a furnace shielded from direct flame radiation in which heat transfer takes place by conduction and convection from hot exit flue gases.
Conversion
A measure of the degree of catalytic cracking defined as the percent of the gas oil charge which disappears.
% Conversion = 100 X Bbls charged — Bbis cycle oil produced Bbis charged
Cooling Tower
Equipment for recirculating hot water, once used, cooling it by evaporation with air pulled up through the tower by fans, and pumped back to the process units for reuse as cool water.
Copper Number
A measure of the mercaptan sulphur content of a stock expressed as milligrams of mercaptan sulphur per 100 millilitre of sample.
Cracked Stock
Oil which has been subjected to a breaking-down action by heating to high temperatures. Such oil contains a higher percentage of " unsaturated" compounds than does straight run stock from crude. Such unsaturated compounds are desirable in oils used as motor fuels and solvents, but require treating or the addition of inhibitors to make stable finished products.
Cracking
A decomposition process of making oils of low boiling range (100°F to 550°F) to be used for motor fuels and burning oils from oils of high boiling range (550°F to 800°F) such as gas oil and fuel oil.
Cresylate
Product of reaction of caustic with olifinic hydrocarbons.
Crude Petroleum
A naturally occurring mixture, consisting predominantly .of hydrocarbons, and/or of sulphur, nitrogen and/or oxygen derivatives of hydrocarbons, which is removed from the earth in liquid state or is capable of being so removed. Crude petroleum is commonly accompanied by varying quantities of extraneous substances such as water, inorganic matter and gas.
Cut
A portion of the distillate from a distillation tower which is kept separate from the remainder of distillate. In running crude at the Crude Unit for example, the product may include a light naphtha cut, heavy naphtha cut, kerosene cut, etc. each of which is collected separately.
Cut Back
To reduce the viscosity of an oil by mixing with It another oil of lower viscosity.
Cycle Stock
Gas oil which has been subjected at least once to the cracking process, and which is ordinarily lower in API gravity for a given boiling point, lower in aniline number,' higher in unsaturation
and aromaticity, and more refractory toward further cracking than the virgin charging stock from which it was made.
Cyclic Compound
A compound containing a ring molecular structure.
Cyclones
A device to separate solids from vapour by centrifugal action.
A device, usually some form of a fractional distilling column, used for removing butane from a hydrocarbon stream.
Decanted oil
Any oil which is separated from heavier material by pouring off from the top of the container. In general usage applied to our refinery refers to slurry oil removed from the bottom of the main
fractionator at the catalytic cracking unit after settling out the catalyst.
Dehydrogenation
Removal of hydrogen usually by a catalytic process. Powerforming is an example.
Demulsifier
Equipment or a chemical for separating emulsions into separate layers.
Desalter
Equipment for removing salt from crude oil.
Diesel Index
Measures diesel fuel ignition quality.
Diesel Index Number = (API Gravity) X (Aniline Pt.) X (0-01)
Diplegs
Pipe extensions on cyclones that dip underneath the catalyst bed level to return separated catalyst back to the bed.
Distillation
Distillation generally refers to vapourization processes in which the vapour evolved is recovered, usually by condensation and a separation is effected between those fractions which vapourize and those which remain as liquid.
Doctor Test
A laboratory test to determine when a stock is sweet.
Downcomer
A pipe which carries the overflow liquid from one tray to the next lower in a fractionating or stripping bubble tower.
Dry Gas
Gas which contains little or no recoverable naphtha (condensables). Refinery fuel gas from the VRU is an example of " dry gas".
The highest temperature reading observed on the distillation thermometer during the laboratory distillation procedure. (ASTM D86-46)
Etnyl Fluid
A commercial form of tetraethyl lead. This mixture contains certain additional ingredients which are added chiefly for the purpose of preventing deposits of lead oxide from building up in the engine.
Excess Air
Air above that required to provide the exact amount of oxygen required for complete combustion in a firebox.
Exchanger
Closed coil heat exchangers (tube and shell type) are used throughout the plant wherever there is a possibility of conserving heat. Hot oil is run counter current to cold oil.
Explosive Limits
The range of percentages of a combustible material in the presence of air which will explode; often expressed as a percent of the lower explosive limit as determined on an M. S. A. combustible gas
testing. "
In ASTM distillation (d86-46) the maximum temperature observed on the distillation thermometer. Final Boiling Point.
Filter
A porous article or mass as of cloth, paper, sand, or charcoal, through which a liquid is passed to separate from it matter held in suspension, or in some cases, dissolved impurities or colouring matter.
Fire
Refers to "fire point" which is the temperature to which a material must be raised to support continuous combustion when tested under standard conditions (ASTM D92-46).
Flash Point
Flash point is the temperature at which an oil will vapourize sufficiently to support combustion momentarily. Used extensively to determine oil storage conditions. (ASTM D93-46, D56-36, D92-46).
Flash Distillation
Vapourization in which all the vapour formed remains in contact with the residual liquid during the vaporization process.
Flash Tower
A tower in which the entering feed consisting of a vapour-liquid mixture is flashed. The tower may or may not have reflux and plates but no reboiler and effects a rough separation of the feed into
vapour and liquid.
Floating Head
The head over the end of a tube bundle within a heat exchanger which is not anchored to the shell but is free to move longitudinally to allow for thermal expansion.
Flooding
A condition which occurs in a fractionating column when the vapour velocity in the tower exceeds a critical value. This increased velocity is accompanied by increased pressure drop through the liquid; this results in excessive liquid build up on the trays.
Fractionation
Separation of a material into several parts by repeated operations, such as distillation, crystallization, precipitation, etc. As ordinarily used in the plant, fractional distillation is meant.
Fresh Feed
Feed stock that enters the unit for the first time as differentiated from recycle feed.
Fuel Oil
Any liquid petroleum product used for the generation of heat in a furnace or firebox, the controlling factors being cost and adaptability.
Furnace
An enclosed vessel in which heat for transmission is produced by fuel combustion.
Furnace Oil
A heavy oil suitable for combustion in a furnace.
A term originally used by gas companies, meaning oil suitable for making gas.
Gasoline
A petroleum product suitable for use as fuel in the present-day automobile or aircraft engines. A petroleum proJuct of low initial boiling point (about 100°F) and a more or less uniform distillation range up to the maximum boiling point, the latter point varying with different gasolines from about 250°F to 400°F. end point.
Gland Oil
Oil injected into the shaft packing at pumps to prevent the escape of material being pumped.
Gum (Gasoline)
A mixture of compounds of high molecular weight believed to be formed by the polymerization and oxidation of unsaturated materials in gasoline. Gum formation is accelerated by long storage, heat, presence of air and certain metal catalyst. It is very undesirable in gasoline.
A metal plate located at the end of a heat exchanger for the purpose of directing the flow from one bank (series) of tubes into another bank. Also, a pipe or vessel, with one or more inlet connections and a multiplicity of take-off connections used as a common supply to
various other vessels.
Heavy Ends
A term used in speaking of oils where the distillation range is of importance, meaning the highest boiling portion present. The maximum or end point as obtained in the 100 cc distillation of a sample of gasoline is determined largely by the amount and character of the "heavy ends" present in the gasoline.
Hot Spot
A localized area of excessive temperature on a furnace tube or reactor shell.
Any substance, the presence of which, even in very small amounts, greatly diminishes the rate of a chemical reaction. The unqualified term most often refers to an anti-oxidant which is added to gasoline to reduce the formation of gum.
Initial Boiling Point
Temperature at which the first drop is recovered in an Engler distillation.
Innage
A measure of the depth of liquid in a tank or other container. Normally, tank gauges are innage gauges unless otherwise specified.
Intercooler
A cooler located at an intermediate stage of an absorber for lowering the temperature of the absorbing liquid as it descends in the column; or a cooler placed between stages in a multi-stage compressor to remove the heat of compression.
Isomerization
The process whereby a straight-chain hydrocarbon is changed to an isomeric form without change of molecular weight.
A term used to describe a bypass line i.e., a pipe leading around equipment, or from one line to another.
A general term covering the class of refined oils boiling between 350°F and 572°F used in domestic oil lamps and cooking stoves. Also used as fuel in some internal combustion engines.
The lead contents of gasoline components do not usually blend volumetrically. Accordingly, the TEL content is converted to a lead index scale which does blend volumetrically. The resultant lead index is then converted back to a TEL content. It is specially useful in blending gasolines to a certain octane level by calculating the TEL required.
Leading
The addition of Tetraethyl Lead to hydrocarbon naphtha.
Lead Susceptibility
The improvement in octane number realized from the addition of incremental quantities of tetraethyl lead to a gasoline fraction.
Lean Oil
In an absorbing process, the oil which is leanest In the components being absorbed.
Light Ends
In any given batch of oil. that portion of lowest boiling point. In gasoline the portion distilling off up to about 158°F. In making lubricating oils, the "light ends" or light distillates must be removed in order to produce finished oils of high flash point.
LPG
Liquefied petroleum gas. Usually propanes, butanes, or a mixture of the two.
A compound containing a radical group "-SH". These compounds have a very offensive odour, which is detectable even when they are present in extremely small concentrations.
Merox
A patented process for the sweetening of naphtha involving the use of a catalyst.
Motor Octane Number
See Octane Number. Motor.
Oils of low boiling range (SOT to 440°F) usually of good colour and odour when finished.
Naphthalene
A saturated ring molecule composed entirely of carbon and hydrogen. There may be two or more attached saturated rings in a naphthalene molecule.
Naphthenic Crude
A crude the characteristics of which are similar to or approach those of naphthenic hydrocarbons. A Watson and Nelson characterization factor of less than 11 -50 is used to denote this type of crude.
Nozzle
A nozzle is a flanged opening in a tower, drum or large pipe used for connecting lines.
A measure of the tendency of a motor fuel to knock in an Itnernal combustion engine as compared with a mixture of normal heptane and iso-octane in the same engine. Thus an octane number of
100 means that the fuel being measured knocks under the same conditions as pure iso-octane and fuel with an octane number of 50 knocks under the same conditions as a 50-50 mixture of normal heptane and iso-octane.
Octane Number Motor
The motor octane number is a measure of the antiknocking characteristic of gasoline. Its numerical value is expressed as that percentage of iso-otane which must be mixed with normal heptane in
order to match the knock intensity of the gasoline when tested in a standard motor fuel testing engine.
Octane Number, Research
The research octane number is a measure of the antiknocking characteristic of a gasoline when tested under less severe conditions than those employed for obtaining the motor octane number.
Octane Number, Road
The road octane number is a measure of the knocking tendencies of a gasoline under normal driving conditions. It is estimated by the formula M+2/3 (R.-M) where M and R are the motor octane and 'research octane values, respectively of the fuel. This quantity may also be determined under specified conditions in test automobiles.
Once-through
A once-through operation is a single pass of the reactants through a reactor.
Operating Factor
The ratio of the total "on-stream" time of a unit to the total time that it could have been on stream if it did not have to be shut down for cleaning, repair and stand-by service.
Orsat
Apparatus for determining concentrations of 02, CO, and Co2 in flue gases.
Overhead
In a distilling operation, that portion of the charge which is vapourised, led off through suitable lines and condensed in cooling coils back to liquid, thus separating it from the portion of the charge remaining in the still.
A crude which has basic properties similar to those of the saturated straight chain paraffins. A characterization factor greater than 11-81 is used to denote this type of crude.
pH
A measure of acidity. Logarithm of the inverse of the hydrogen ion concentration.
Plate
A substantially horizontal structure supported in a vertical cylindrical chamber and adapted for intimately contacting vapours or gases rising from below the structure to bubble through the retained liquid. The plates are usually of the bubble cap type, valve type or perforated plates. Also, a cover to close manway openings in a vessel.
Platforming
It is patented regenerative catalytic reforming process developed
by United Oil Products Company to produce a high yield of a high-
octane gasoline from virgin naphthas.
Platformate
The catalytically reformed product from the Platformer.
Plenum
The collecting chamber for flue gas on a furnace or vapours from cyclone separators.
Polymer
An organic compound formed by combining of unsaturated or cyclic compounds.
Priming
Roughly equivalent to puking.
Puking
A still is said to "puke" when the oil foams and rises in the still so high that part of the charge is driven overhead through the vapour line in the liquid state.
Pump-out Line
A line for removal of the material in a vessel without any loss. Usually used on unit or individual equipment shutdowns.
Purge
The cleaning or removal of existing materials by displacing with another medium.
Sudden cooling of hot products by injection of cold oil.
That portion of the furnace coils which is located in such a manner as to be exposed to direct radiation from the flames.
Range Tube
A part of a flow-indicating instrument that determines the pressure differential range over which it will operate, and which can be changed to suit requirements of the service in which the flow instrument is operating.
Reactor
A vessel in which a reaction takes place. Most often refers to the catalyst vessel in a catalytic process.
Reactor Effluent
The mixture of products leaving a reactor.
Reboiler
A tubular heat exchanger placed at the bottom of a fractionating tower or stripper to supply the necessary tower heat. The liquid from the bottom tray passes through the reboiler where it is heated by indirect exchange with a hotter liquid or by steam. The heated liquid and vapours formed then return to the bottom of the tower. A direct-fired coil may sometimes be used instead of a tubular exchanger.
Recirculation
The re-passage of one or more of the components of a stream through a given system.
Recycle
That portion of the products of a process which is re-submitted to the process.
Reduced Crude
The bottoms remaining from a distillation of crude oil are referred to as "reduced crude". The terms 20%, 40% and 60% reduced crude represent crude which have been reduced to 20%, 40% and 60% of their original volume by distillation. See also "residuum"
Reduction
A distillation where the oil remaining in the still (the bottom) is an important product of the run, this bottom being concentrated (reduced) to viscosity or other required test by distilling off the lighter portions of the charge.
Reflux
The condensed distillate which is returned to the top of a fractionating tower to serve as a heat and material-transfer medium in the fractionation process. It is frequently called "pump-back" by plant operators.
Reflux Rate
Rate of addition of a cool liquid to a tower in order to remove heat and thereby to induce reflux in the tower.
Reformate
Product of a reforming operation.
Reforming
The submission of virgin naphthas to a cracking operation for the purpose of producing a product of improved knock value by changing the molecular structure.
Refractive Index
Ratio of the velocity of light in a vacuum to its velocity in a substance. Useful in identifying substances.
Refractory
A hard lining used to resist abrasion or heat. Used in reactors, regenerators, furnaces and lines.
Can also mean difficult to crack. Oils that have been cracked
once are refractory.
Regeneration
Process by which coke deposited on a catalyst is burned off and the catalyst thereby reactivated. In general, any process by which a spent material is made available for reuse.
Regenerator
The vessel in which regeneration of used catalyst or other material takes place.
Regular Gasoline
A name used to designate a lower octane motor gasoline as compared to a higher grade called "Super-Premium".
Reid Vapour Pressure (RVP)
The vapour pressure at 100°F. as determined in the laboratory.
Research Octane Number
See Octane Number, Research.
Residual Fuel Oil
Reduced crude or viscous residuums obtained from refinery operations and suitable for burning in a furnace or firebox.
Residuum (Resid.)
The coloured, highly viscous oil remaining in a still from a charge of crude oil, after the more volatile portion of the charge has been distilled off.
Rich Oil
The exit oil stream from an absorber. So called because it is relatively rich in those components which it is designed to absorb.
Riser
One of a number of small vertical pipes extending slightly above the surface of a bubble plate through which vapours from the next lower plate pass upward.
Road Octane Number
See Octane Number, Road.
Run Down Line
Lines of pipe leading to the tanks from process units.
Running Gauge
A tank gauge which is taken at a time when material is being pumped into or out of the tank.
A measure of viscosity of petroleum products as determined in a Saybolt viscosimeter (ASTM D88-44).
Scale
The general term refers to any hard incrustation formed on equipment. When ferrous structures rust, the iron oxide corrosion products usually remain in the form of a scale. When natural waters
are passed through equipment, deposits of calcium and magnesium salts occur.
Scrubber
A piece of equipment designed to remove a particular component from a gas or vapour stream usually by counter current contact with a liquid.
Scrubbing Tower
A vessel designed to act as a scrubber.
Sensitivity (Octane)
A term referring to the difference between the research and motor octane ratings, the .more sensitive fuels exhibiting greater differences. The sensitivity represents the decrease in octane rating of a fuel occasionsd by a change in the severity of test conditions from the research to the motor method.
Separator
A device, usually a drum, employed for the division of a multiphase system (usually two phase) into its constitutent phases. May be used to separate vapours from liquids or liquids of different densities.
Separator Drum
A synonym for "separator" but is more specifically applied to small, cylindrically-shaped containers.
Severity Factor
A factor usually associated with cracking processes to indicate the severity of operation, i.e., in catalytic cracking the factor used is catalyst to oil ratio divided by the weight hour space velocity.
Shell Side
The space between the tube bundle and the outer shell of a heat exchanger. The shell side liquid is that which flows through this space.
Shielded Section
A group of furnace tubes which, by their position in the furnace, are shielded either by other tubes or by a bridgewall from direct sight of the flame.
Side Stream
A stream taken from any intermediate plate in a fractionating tower, i.e., from the side rather than the top or bottom of the tower.
Single Pass
When used in conjunction with heat transfer equipment (usually reboilers and condensers), single pass means that the medium on the tube side flows in one direction. Multiple passes may be had on both shell and tube sides by a baffle arrangement.
Skimmer
A device for allowing oil to be separated from water by removing the shallow layer of oil.
Slip Stream
A portion of a stream which is removed, subjected to a separate operation, and returned to the main stream i.e., no recycle.
Slop
A term rather loosely used to denote odds and ends of oil produced at various places in the plant, which must be rerun or further processed in order to be brought into suitable conditions for use.
Slurry
Any mixture of solids and liquids. Most commonly used on FCCU in reference to fractionator bottoms oil containing catalyst.
Soak
Hold on oil at an elevated temperature to allow a reaction to proceed to desired point.
Sour
Gasoline, naphthas, and refined oils are said to be "sour" if they show a positive "doctor test". Sourness is directly connected with odour, it being usual for a "sour" gasoline to have a bad odour while a "sweet" gasoline has a good odour. (See "Sweet").
Space Velocity (Various Units)
A factor used in catalytic reforming and cracking processes giving the relative amounts of reacting material and catalyst; common units are volume per hour per volume of catalyst and weight per hour per weight of catalyst.
S.S.U.
Saybolt Seconds, Universal. A measure of viscosity.
Stabilizer
A fractionating column and heat exchanger system operating under pressure which is used to remove and recover the volatile light hydrocarbons always present in distillate and absorption plant.
Stock
In general, any oil which is to receive further treatment before going into finished products. Used also in a more restricted sense, meaning any oil which is finished as far as refining operations
are concerned but which must still be mixed, blended, or compounded with some other oil before becoming a finished product. More properly spoken of in this sense as "Finished Stocks".
Strapping of Tank
Calibrating the volume of a tank.
Stripper
A fractionating device used to remove relatively low - boiling materials from a liquid stream made up mostly of higher boiling components. This is accomplished by counter-current scrubbing with
a stream of gas, such as fuel gas or steam, or may be accomplished by heating the liquid in the bottom of the fractionator.
Stripping Steam
Steam used in a stripper to remove low-boiling components from a liquid stream.
Superheat
Heat added to a vapour to raise its temperature above the dew point at the pressure existing. The term is also applied to the temperature difference between the vapour and its dew point.
Surface Condenser
A condenser in which the cooling medium and the vapour to be condensed are separated by metal surfaces.
Sweet
Gasoline, naphthas, and refined oils are said to be sweet if they show a negative " doctor " test.
Sweetening
The process of treating a hydrocarbon stock for the purpose of removing or converting to a less undesirable form the sulphur compounds present.
A gauge taken with a tapeline.
Tar
Heavy bottoms which did not distill overhead.
Tetraethyl Lead (TEL)
A gasoline additive used to increase octane number. This material is highly toxic and must be handled with special precautions.
Topped Crude
See " Reduced Crude ".
Torch Oil
This term refers to oil which is burned for the purpose of keeping a torch lighted. In the case of fluid catalytic cracking unit it refers to oil burned in the regenerator for the purpose of keeping
the unit in heat balance or for startup.
Tower
Vessel containing fractionating trays or packing in which fractional distillation takes place.
Transfer Line
Refers to a line carrying oils and/or gases at some elevated temperature (usually from a furnace) to some other equipment i.e., line from outlet of a furnace to a reactor or reboiling system.
Troy
Also termed " bubble place ". In petroleum refining, usually refers to a part of a fractionating tower the purpose of which is to contact liquid and vapour in a counter-current manner.
Trickle Valve
A check valve on the bottom of cyclone diplegs to prevent backflow of catalyst into the cyclones.
Tube Sheet
The section in a heat exchanger which separates the liquid flowing through the tubes from the liquid in the shell and holds the tubes in place. In a furnace, a sheet or metal wall into which the
tubes are secured by tube rolling.
Tube Side
Pertains to material flowing through the tubes of a heat exchanger.
Turnaround
The shut-down period for an operation unit usually for mechanical reconditioning. The period from the end of one run to the beginning of the next, i.e., off—stream to on—stream period.
A patented catalytic process for the removal of sulphur, nitrogen, and oxygen compounds from naphthas or distillates.
A substance in the gaseous state which can be condensed by cooling or compression.
Vapour Line
The pipe through which the oil vapours are led from the still to the condenser.
Vapour Phase
In the gaseous state.
Vapour Pressure
The pressure exerted by a vapour which is in a state of equilibrium with a solid, liquid, or solution at a specified temperature.
Virgin Stock
Oil derived directly from crude oil and which contains no cracked material.
Viscosity
The resistance to flow displayed by a fluid (liquid or gas). In the petroleum industry, the viscosity of liquids is usually measured by
the Saybolt viscosimeter.
Volatility
The tendency of a liquid to turn to vapour.
A weir is a flat or notched dam or obstruction to liquid flow and is normally used for either the measurement of fluid flows or to maintain a given depth of fluid as on a tray of fractionating
tower.
Wet Gas
Wet gas is a gas containing important amounts of heavier hydrocarbons such as butane, pentane, etc., useful as gasoline components.