Engineer's Zone

Alkylation :

Refining process for converting light, gaseous olefins into high-octane gasoline components (reverse of cracking).

Aromatics :

Class of hydrocarbons that have at least one benzene ring as part of their structure. Generally describes benzene and benzene derivatives.

Associated Gas :

Natural gas associated with oil accumulations, either dissolved in oil or found as a cap of free gas above oil in reservoir.

Benzene :

An aromatic hydrocarbon present to a minor degree in most crude oils. (Products manufactured from benzene include styrene, phenol, nylon and synthetic detergents.)

Butane (C₄H₁₀) :

Either of two saturated hydrocarbons, or alkanes, with chemical formula. In both compounds carbon atoms are joined in an open chain.

Carbon :

Atomic number is 6; element is in group 14 (or IVa) of periodic table. Carbon content of a hydrocarbon determines, to a degree, hydrocarbon's burning characteristics and qualities.

Carbon Dioxide (CO₂) :

Colourless, odourless, and slightly acid-tasting gas, sometimes-called carbonic acid gas, molecule of which consists of one atom of carbon joined to two atoms of oxygen. Carbon dioxide in atmosphere tends to prevent escape of outgoing long-wave radiation from Earth to outer space; as more heat is produced and less escapes, temperature of Earth increases.

Carbon Monoxide (CO) :

Chemical compound of carbon and oxygen.

Chlorofluorocarbon (CFC) :

Synthetic chemical that is odourless, non-toxic, non-flammable, and chemically inert. Released into atmosphere, chlorine-containing chemicals rise and are broken down by sunlight, whereupon chlorine reacts with and destroys ozone molecules.

Coal :

During Carboniferous period much of world was covered with vegetation growing in swamps. This vegetation died and became submerged under water. As decomposition took place, vegetable matter lost oxygen and hydrogen atoms, leaving a peat deposit with a high percentage of carbon. As time passed, layers of sand and mud settled from water over some of peat deposits. Pressure of these overlying layers, as well as movements of earth's crust and sometimes volcanic heat, acted to compress and harden deposits, thus producing coal.

Condensate :

Liquid mixture of pentane and higher hydrocarbons.

Drilling Mud / Fluid :

Mixture of base substance and additives used to lubricate drill bit and to counter act natural pressure in formation. Drilling mud provides circulation, flushing rock cuttings from bottom of well bore to surface.

Drilling Mud Nomenclature :

Oil Based Mud (OBM), Pseudo Oil Based Mud (POBM), Water Based Mud (WBM).

Dry gas :

Or Lean gas is natural gas composed mainly of methane.

Esters :

Compounds formed by combination of acids and alcohols.

Ethanol :

Chemical formed by fermentation or synthesis.

Ethene :

Or Ethylene simplest member of class of aliphatic organic compounds called alkenes, which contain at least one carbon-carbon double bond. Ethylene is a colourless, slightly sweet-smelling gas of formula H₂C=CH₂. It is slightly soluble in water and is produced in commercial amounts by cracking and fractional distillation of petroleum and from natural gas.

Gasoline :

Mixture of lighter liquid hydrocarbons used chiefly as a fuel for internal-combustion engines. Produced by fractional distillation of petroleum; by condensation or adsorption from natural gas; by thermal or catalytic decomposition of petroleum or its fractions; by hydrogenation of producer gas or coal; or by polymerisation of hydrocarbons of lower molecular weight.

Greenhouse Gases :

Gases that alter thermal properties of atmosphere (for example, water vapour, carbon dioxide, methane, nitrous oxide, CFCs, halons and ozone).

Halons :

Halogenated carbon compounds used in fire extinguishing equipment and contributing to stratospheric ozone depletion. Being phased out under Montreal Protocol.

Heavy oil :

Long chains of hydrogen and carbon atoms.

Hexane :

Petroleum liquid found in small amounts in condensates.

Hydrocarbons :

Family of organic compounds, composed entirely of carbon and hydrogen (for example, coal, crude oil and natural gas).

Hydrogen (H) :

Reactive, colourless, odourless, and tasteless gaseous element with atomic number of 1. Element is usually classed in group 1 (or Ia) of periodic table. Lightest of all gases, hydrogen combines with carbon to form a variety of gaseous, liquid and solid hydrocarbons.

Hydrogenation :

Reacting coal with hydrogen at high pressures, usually in presence of a catalyst.

Light oil :

Shorter chains of hydrogen and carbon atoms.

Liquefied Natural Gas (LNG) :

Gas, mainly methane, liquefied under pressure and low temperature.

Liquefied Petroleum Gas (LPG) :

Pressure or refrigeration liquefies lighter hydrocarbons, such as propane, butane, pentane, and mixtures of these gases.

Material Safety Data Sheet (MSDS)

Issued by manufacturer of chemical substances that sets out hazards likely to be encountered by those who come into contact with substance.

Mercaptans :

Strong-smelling compounds of carbon, hydrogen and sulphur found in oil and gas. Added to natural gas for safety reasons.

Methane (CH₄) :

Also marsh gas, gas composed of carbon and hydrogen, first member of paraffin or alkane series of hydrocarbons. Methane contributed 12% (counting both direct and indirect global warming effects) of UK national greenhouse gas emissions in 1990. Oil and gas production accounted for 2% of national emissions in 1990.

Natural Gas :

Gas, occurring naturally, often found in association with oil.

Natural Gas Liquid (NGL) :

Liquid hydrocarbons found in association with natural gas.

Nitrous Oxide (N₂O) :

Nitrous Oxide contributed 5% of direct global warming potential from UK national greenhouse gas emissions in 1990.

Oil :

Mixture of liquid hydrocarbons of different molecular weights.

Olefins :

Basic chemicals made from oil or natural gas liquids feed stocks; commonly used to manufacture plastics and gasoline. Examples are ethylene and propylene.

Ozone :

Allotropic form of oxygen having three atoms in each molecule, formula O₃. Ozone formed in atmosphere from nitrogen oxides and organic gases emitted by automobiles and industrial sources.

Pentane :

One of lighter hydrocarbons, such as propane and butane, and mixtures of these gases are liquefied and employed as fuels.

Petrolatum :

Odourless, tasteless, greasy substance, obtained as residue from petroleum after lighter and more volatile components have been boiled off. Purified residue is obtained in form of a yellowish or decolourised semisolid, known as petroleum jelly in form of a clear to faintly yellow liquid, known as mineral oil.

Petroleum :

Generic name for hydrocarbons, including crude oil, NGLs, natural gas and their products.

Petroleum products :

Gasoline, kerosene, heavy fuel oil, lubricating oils, petroleum jelly, and paraffin consist principally of mixtures of paraffin hydrocarbons, which range from lighter liquid members to solid members.

Propane (C₃H₈) :

Colourless, odourless gas of alkane series of hydrocarbons. It occurs in crude oil, in natural gas, and as a by-product of petroleum refining.

Sour gas :

Natural gas containing significant quantities of hydrogen sulphide.

Sulphur Dioxide (SO₂) :

Acts as a precursor in formation of sulphate aerosols which, unlike greenhouse gases, have a net negative radiative forcing effect and tend to cool Earth's surface.

Synthetic Natural Gas (SNG) :

Gases made from coals and other hydrocarbon-containing substances.

Wet Gas :

Natural gas having significant amounts of heavier hydrocarbons in gasoline range.

ADDENDUM (a) :

It is the height by which a tooth projects beyond the pitch circle or pitch line.

AXIAL MOVEMENT :

Endwise movement of input or output shafts, sometimes called endplay, is usually expressed in thousands of an inch.

BASE DIAMETER (Db) :

It is the diameter of the base cylinder from which the involute portion of a tooth profile is generated.

BACKLASH (B) :

It is the amount by which the width of a tooth space exceeds the thickness of the engaging tooth on the pitch circles. As actually indicated by measuring devices, backlash may be determined variously in the trans-verse, normal, or axial-planes, and either in the direction of the pitch circles or on the line of action. Such measure-ments should be corrected to corresponding values on transverse pitch circles for general comparisons.

BACKLASH :

Rotational movement of the output shaft when holding the input shaft stationary and rotating the output shaft alternately clockwise and counter clockwise. Backlash may be expressed in thousands of an inch measured at a specific radius at the output shaft.

BORE LENGTH :

It is the total length through a gear, sprocket, or coupling bore.

CENTER DISTANCE :

On a single reduction reducer, this is the distance between the center lines of the input and output shafts. Shaft center lines may be parallel or at right angles to one another. The center distance of multiple stage reducers usually refers to the lowest speed stage (last reduction).

CIRCULAR PITCH (p) :

It is the distance along the pitch circle or pitch line between corresponding profiles of adjacent teeth.

CIRCULAR THICKNESS (t) :

It is the length of arc between the two sides of a gear tooth on the pitch circle, unless other-wise specified.

CLEARANCE-OPERATING (c) :

It is the amount by which the dedendum in a given gear exceeds the addendum of its mating gear.

CONTACT RATIO (mc) :

In general, the number of angular pitches through which a tooth surface rotates from the beginning to the end of contact.

DEDENDUM (b) :

It is the depth of a tooth space below the pitch line. It is normally greater than the addendum of the mating gear to provide clearance.

DIAMETRAL PITCH (P) :

It is the ratio of the number of teeth to the pitch diameter.

EFFICIENCY :

The amount of output power of the reducer as compared to the amount of input power. It is usually stated as a percentage.

FACE WIDTH (F) :

It is the length of the teeth in an axial plane.

FILLET RADIUS (rf) :

It is the radius of the fillet curve at the base of the gear tooth.

FULL DEPTH TEETH :

Are those in which the working depth equals 2.000 divided by the normal diametral pitch.

GEAR :

It is a machine part with gear teeth. When two gears run together, the one with the larger number of teeth is called the gear.

HUB DIAMETER :

It is outside diameter of a gear, sprocket or coupling hub.

HUB PROJECTION :

It is the distance the hub extends beyond the gear face.

INPUT HORSEPOWER :

The amount of power applied to the input shaft of a reducer by the prime mover is its input horsepower. It is often used as a selection basis for power transmission components, and it appears in the rating tables of drive manufacturer’s published data. Remember that input horse-power ratings represent the maximum amount of power that the reducer can safely handle

INVOLUTE TEETH :

Of spur gears, helical gears and worms are those in which the active portion of the profile in the transverse plane is the involute of a circle.

KEYWAY :

It is the machined groove running the length of the bore. A similar groove is machined in the shaft and a key fits into this opening.

LONG AND SHORT-ADDENDUM TEETH :

Are those of engaging gears (on a standard designed center distance) one of which has a long addendum and the other has a short addendum.

MECHANICAL RATING :

The maximum power or torque that a speed reducer can transmit, based on the strength and durability of its components, is it’s mechanical rating. Obviously, the reducer may be rated no higher than the strength or durability of its weakest component. Reducers typically have a safety margin of two to three on their mechanical ratings. Thus, a reducer can withstand momentary overloads of 200-300% of its mechanical rating during a startup or other brief overload situations.

MOUNTING POSITION :

The relationship of the input and output shafts relative to the floor line.

NORMAL DIAMETRAL PITCH (Pn) :

It is the value of the diametral pitch as calculated in the normal plane of a helical gear or worm.

NORMAL PLANE :

It is the plane normal to the tooth surface at a pitch point and perpendicular to the pitch plane. For a helical gear this plane can be normal to one tooth at a point laying in the plane surface. At such point, the normal plane contains the line normal to the tooth surface and this is normal to the pitch circle.

NORMAL PRESSURE ANGLE (øn) :

In a normal plane of helical tooth.

OUTPUT HORSEPOWER :

The amount of power avail-able at the output shaft of a reducer is its output horsepower. Due to losses caused by inefficiency, output horsepower is always less than input horse-power.

OUTSIDE DIAMETER (Do) :

It is the diameter of the addendum (outside) circle.

OVERHUNG LOAD :

The input or the output shaft of a speed reducer can be subject to an overhung load; that is, to a force applied at right angles to the shaft, beyond its outermost bearing. Such a force is a shaft bending load resulting from a gear, pulley, sprocket or other external drive member. Besides the tendency to bend the shaft, the overhung load (that is, the radial force on the shaft) is reacted to by the shaft in it’s bearings. Therefore, the overhung load creates loads that the bearings must be able to support without damage.

PITCH CIRCLE :

It is the circle derived from a number of teeth and a specified diametral or circular pitch. Circle on which spacing or tooth profiles is established and from which the tooth proportions are constructed.

PITCH CYLINDER :

It is the cylinder of diameter equal to the pitch circle.

PINION :

It is a machine part with gear teeth. When two gears run together, the one with the smaller number of teeth is called the pinion.

PITCH DIAMETER (D) :

It is the diameter of the pitch circle. In parallel shaft gears, the pitch diameters can be determined directly from the center distance and the number of teeth.

PRESSURE ANGLE (ø) :

It is the angle at a pitch point between the line of pressure which is normal to the tooth surface, and the plane tangent to the pitch surface. In involutes teeth, pressure angle is often described also as the angle between the line of action and the line tangent to the pitch circle. Standard pressure angles are established in connection with standard gear-tooth proportions.

PRESSURE ANGLE—OPERATING (ør) :

It is determined by the centre distance at which the gears operate. It is the pres-sure angle at the operating pitch diameter.

PRIME MOVER :

The machine that provides power to a drive is its prime mover. The most frequently encountered prime movers include electric motors, internal combustion engines, hydraulic motors and air motors. The type of prime mover used can affect the speed reducer during operation. For example, an electric motor runs relatively smoothly in comparison to an internal combustion engine.

ROOT DIAMETER (Dr) :

It is the diameter at the base of the tooth space.

SERVICE FACTORS :

Numbers which modify the loads which must be considered in selecting a speed reducer are called service factors. They vary with the type of service in which the reducer is to be used, the kind of prime mover involved and the duty cycle. The service factor can be a multiplier applied to the known load, which redefines the load in accordance with the conditions at which the drive will be used, or it can be a divisor applied to catalogue reducer ratings, thus redefining the rating in accordance with drive conditions. The service factor is usually applied to the speed reducer, but can also be applied to the name plate rating of the prime mover.

THERMAL RATING :

The maximum power or torque that a speed reducer can transmit continuously, based on its ability to dissipate heat generated by friction, is called its thermal rating.

TIP RELIEF :

It is an arbitrary modification of a tooth profile whereby a small amount of material is removed near the tip of the gear tooth.

THRUST LOAD :

Forces imposed on a shaft parallel to the shaft axis. Such a force is called a thrust load. It is often encountered on shafts driving mixers, fans, blowers and similar machines. When a thrust load acts on a speed reducer, you must be sure that the thrust load rating of the reducer is high enough that it’s shafts and bearings can absorb the load.

UNDERCUT :

It is a condition in generated gear teeth when any part of the fillet curve lies inside a line drawn tangent to the working profile at its point of juncture with the fillet.

WHOLE DEPTH (ht) :

It is the total depth of a tooth space, equal to addendum plus addendum, equal to the working depth plus variance.

WORKING DEPTH (hk) :

It is the depth of engagement of two gears; that is, the sum of their addendums.

Plasticity:

The property of a material, which does not regain its original position on the removal of external forces, is called plasticity.

Ductility:

It is the property of a material, which enables it to be drawn into wires without rupture.

Brittleness:

It is the property of a material, which enables it to fail by rupture due to some external force with little permanent deformation. E.g. cast iron.

Malleability:

It is the property of a material, which enables it to be flattened into thin sheets without cracking by pressing.

Strength:

It is the ability of a material to resist the external applied forces without breaking or yielding.

Stiffness:

It is the ability of a material to resist deformation under stress. The modulus of elasticity is the measure of stiffness.

Elasticity:

It is the property of a material to regain its original shape under deformation when external forces are

removed.

Toughness:

It is the property of a material to resist fracture due to high impact load like hammer blows. The toughness of material decreases when it is heated.

Machinability:

It is the property, which refers to a relative case with which a material can be cut. It may be noted that brass can be easily machined than steel.

Resilience:

It is the property of a material to absorb energy and to resist shock and impact loads. It is measured by the amount of energy absorbed per unit volume within elastic limit.

Creep:

When a point is subjected to a constant stress at higher temperature for a long period of time, it will undergo a slow and permanent deformation called creep. This property is considered in designing

I.C. Engines, boilers and turbines.

Fatigue:

When a material is subjected to repeated stresses, it fails at stresses below the yield point stresses. Such a type of failure of a material is known as fatigue. This property is considered in designing shafts, connecting rods, springs, gears etc.

Hardness:

It is the property of a metal and has a wide variety of meanings. It embraces many different properties such as resistance to wear, scratching, deformation, machinability etc. It also means that ability of a metal to cut another metal.

The hardness is usually expressed in numbers, which are dependent on the method of making the test.

i. Brinell hardness

ii. Rockwell hardness

iii. Vickers hardness (diamond pyramid)

iv. Shore scleroscope

Endurance limit:

It is the limit up to which a member can withstand the repeated stress when applied ten million cycles. This limiting stress is also called fatigue limit.

Difference between Hardness and Toughness