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18 CHARACTERIZATION AND PROPERTIES OF PETROLEUM FRACTIONS
birth of the computer and its expansion, more analytical
prefixes are not used in conjunction with the English units.
methods in the form of equations were developed in the 1960s As an example 1 000 000 Pa can be expressed as 1 MPa. These
and mainly in the 1970s and 1980s. Nearly all correlations However, in the English system of units when volumetric
and graphical methods that were developed until the early quantities of gases are presented in large numbers, usually
1980s are in English units. However, starting from the 1980s every 1000 units is expressed by one prefix of M. For ex-
many books and handbooks appeared in the SI units (from Le ample, 2000 scf of gas is expressed as 2 Mscf and similarly
Systeme International d’Unites). The general trend is to unify 2 000 000 scf is written as 2 MMscf. Other symbols usu-
all engineering books and documents in SI units to be used ally used to express large quantities are b for billion
9
by the international community. However, many books, re- (1000 million or 10 ) and tr for trillion (one million millions
12
ports, handbooks, and equations and figures in various publi- or 10 ).
cations are still in English units. The United States and United
Kingdom both officially use the English system of units.
Therefore, it is essential that engineers be familiar with both 1.7.3 Units of Mass
unit systems of English and SI. The other unit system that
is sometimes used for some properties is the cgs (centimeter, The mass is shown by mand its unit in SI is kg (kilogram), in
gram, second) unit, which is derived from the SI unit. cgs is g (gram), and in the English unit system is lb m (pound-
Since the book is prepared for an international audience, mass). On many occasions the subscript m is dropped for lb
the primary unit system used for equations, tables, and fig- when it is referred to mass. In the English unit system, units
ures is the SI; however, it has been tried to present equivalent of ounce (oz) and grains are also used for mass units smaller
of numbers and values of properties in both SI and English than a pound. For larger values of mass, unit of ton is used,
units. There are some figures that are taken from other ref- which is defined in three forms of long, short, and metric.
erences in the literature and are in English units and they Generally the term ton is applied to the metric ton (1000 kg).
have been presented in their original form. There are some The conversion factors are as follows:
special units that are commonly used to express some spe-
cial properties. For example, viscosity is usually expressed in 1kg = 1000 g = 2.204634 lb = 35.27392 oz
centipoise (cp), kinematic viscosity in centistoke (cSt), den-
sity in g/cm , specific gravity (SG) at standard temperature 1lb = 0.45359 kg = 453.59 g = 16 oz = 7000 grain
3
of 60 F, or the GOR in scf/stb. For such properties, these pri- 1g = 0.001 kg = 0.002204634 lb = 15.4324 grain
◦
mary units have been used throughout the book, while their 1 ton (metric) = 1000 kg = 2204.634 lb
respective equivalent values in SI are also presented.
1 ton (short) = 2000 lb = 907.18 kg
1 ton (long) = 2240 lb = 1016 kg = 1.12 ton (short)
1.7.2 Fundamental Units and Prefixes = 1.1016 ton (metric)
Generally there are four fundamental quantities of length (L),
mass (M), time (t), and temperature (T) and when their units
are known, units of all other derived quantities can be deter- 1.7.4 Units of Length
mined. In the SI system, units of length, mass, and tempera- The unit of length in SI is meter (m), in cgs is centimeter
ture are meter (m), kilogram (kg), and Kelvin (K), respectively. (cm), and in English unit system is foot (ft). Smaller values
In English units these dimensions have the units of foot (ft), of length in English system are presented in inch (in.). The
pound mass (lb m ), and degrees Rankine ( R), respectively. The conversion factors are as follows:
◦
unit of time in all unit systems is the second (s), although
in English unit, hour (h) is also used for the unit of time. −3 6
From these units, unit of any other quantity in SI is known. 1m = 100 cm = 10 km = 1000 mm = 10 microns ( m)
10
2
For example the unit of force is SI is kg·m/s which is called = 10 angstroms ( ˚ A) = 3.28084 ft = 39.37008 in.
Newton (N) and as a result the unit of pressure must be = 1.0936 yd (yard)
2
N/m or Pascal (Pa). Since 1 Pa is a very small quantity, 1ft = 12 in. = 0.3048 m = 30.48 cm = 304.8mm
larger units such as kPa (1000 Pa) or mega Pascal (MPa) = 3.048 × 10 −4 km = 1/3yd
are commonly used. The standard prifixes in SI units are as 1cm = 10 −2 m = 10 −5 km = 10 mm = 0.0328084 ft
follows: = 0.393701 in.
4
1km = 1000 m = 3280.48 ft = 3.93658 × 10 in.
Giga (G) = 10 9
Mega (M) = 10 6 1in. = 2.54 cm = 0.0833333 ft = 0.0254 m = 2.54×10 −5 km
Kilo (k) = 10 3 1 mile = 1609.3m = 1.609 km = 5279.8ft
Hecto (h) = 10 2
Deka (da) = 10 1
Deci (d) = 10 −1 1.7.5 Units of Time
Centi (c) = 10 −2
Milli (m) = 10 −3 The unit of time in all major systems is the second (s); how-
Micro (μ) = 10 −6 ever, for large values of time other units such as minute (min),
Nano (n) = 10 −9 hour (h), day (d), and sometimes even year (year) are used
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