Table of Contents
1. Scope
2. Deviations from the SI Units
3. Base Units
4. Multiples of SI Units
5. Table of Quantities and Units
6. Conversion Units
Attachments:
Attachment I: Deviations from the SI-Units-2-sheets
Attachment II: Table of Conversion Factors-5-sheets
1. Scope
1.1 This design guide shall be used to establish the units of measurement which are to be used for standard forms, standard specifications, etc.
The internationally accepted SI units (Système International des Unitées) are selected to be used following the recommendations as given in British Standard PD 5886.
1.2 For each job the Engineering Design Basis which forms part of the Project Procedure Manual shall refer to this Engineering Design Guide and shall contain possible additional Client’s requirements.
1.3 Calculations, which require input from textbooks in non SI units, may be performed in other units (imperial, old metric etc.) provided that end results are converted to SI units using the conversion factors given in this Design Guide.
2. Deviations from the SI Units
For practical reasons some deviations from the SI units and BS-PD5686 have been applied. See attachment I.
3. Base Units
The seven base SI units are:
|
Quantity |
Name of Base Unit |
Symbol |
|
length |
metre |
m |
|
mass |
kilogram |
kg |
|
time |
second |
s |
|
electric current |
ampère |
A |
|
thermodynamic temperature |
kelvin |
K |
|
luminous intensity |
candela |
cd |
|
amount of substance |
mole |
mol |
For the definitions of the base units see PD 5686-A.7.
4. Multiples of SI Units
It is recommended that the rule for prefixes, whereby only powers of 10 which are divisible by three are used, is followed wherever possible (an exception is the bar which is 105Pa).
|
Factor by which the unit is multiplied |
Prefix |
Symbol |
|
|
1012 |
tera |
T |
1) |
|
109 |
giga |
G |
1) |
|
106 |
mega |
M |
|
|
103 |
kilo |
k |
|
|
102 |
hecto |
h |
1) |
|
10 |
deca |
da |
1) |
|
10-1 |
deci |
d |
|
|
10-2 |
centi |
c |
|
|
10-3 |
milli |
m |
|
|
10-6 |
micro |
µ |
|
|
10-9 |
nano |
n |
2) |
|
10-12 |
pico |
p |
2) |
1) The use of these prefixes is to be avoived.
2) These perfixes shall only be used for the electrical discipline. When using these multiples, the following rules shall be observed:
a. For derived SI units, use only one perfix, i.e. use MJ/m3 not mJ/(mm)
b. Attach the prefix to the unit in the numerator, i.e., kg/m not g/mm
c. Do not use compound prefixes, i.e. use MJ not kkJ
5. Table of Quantities and Units
Following table summaries the quantities, the corresponding units to be used by Company, and the recommended multiplies of units.
|
Quantity |
Unit to be used |
Selection of multiples |
Remarks |
|
Plane angle |
º (degree) * |
* See att. I . pt 5 |
|
|
‘ (minute) * |
|||
|
‘’ (second) * |
|||
|
Length |
km |
||
|
m (metre) |
|||
|
‘’ (inch) * |
|||
|
mm |
See att. I . pt 1 |
||
|
Area |
m2 |
km2 |
|
|
cm2 * |
* to be avoided where |
||
|
mm2 |
possible |
||
|
Volume |
m3 |
||
|
1 (litre)=dm3 |
|||
|
cm3 or ml |
|||
|
mm3 |
|||
|
Time |
s (second) |
ms |
* See att. I . pt 3 |
|
yr (year) or |
µs |
||
|
a (annum) * |
|||
|
d (day) * |
|||
|
h (hour) * |
|||
|
min (minute) * |
|||
|
Rotational |
rpm |
See att. I . pt 6 |
|
|
frequency |
(revolutions |
||
|
per minute) |
|||
|
Mass |
kg (kilogram) |
t (tonne) * |
* See att. I . pt 2 |
|
g |
|||
|
mg |
|||
|
Density |
kg/m3 |
For gases and vapours specify MW (molecular weight) |
|
Quantity |
Unit to be used |
Selection of multiples |
Remarks |
|
(mass) Moment of inertia |
kg.m2 |
||
|
Force |
N(newton)=kg.m/sec2 |
||
|
Moment of force (torque) |
N.m |
||
|
Pressure |
bar=105N/m2 |
mbar |
See att. I . pt 7 |
|
bar(a) |
mbar(a) |
||
|
bar(g) |
|||
|
Pa (pascal)=N/m2 |
|||
|
Stress |
N/mm2 |
||
|
Viscosity (dynamic) |
Pa.s * |
mPa.s = cPoise |
* Use mPa.s only |
|
Viscosity (kinematic) |
m2/s * |
mm2/s = cStokes |
* Use mm2/s only |
|
Surface tension |
N/m |
mN/m |
|
|
Energy (work) |
MJ |
||
|
heat quantity |
kJ |
||
|
J (joule) = Nm |
|||
|
kW.h * |
* See att. I . pt 8 |
||
|
Power, heat |
MW |
For use of VA and |
|
|
flow rate |
kW |
kvar see att. I . pt 9 |
|
|
W (watt) = N.m/sec |
|||
|
mW |
|||
|
Thermodynamic temperature |
K(kelvin) |
See att. I . pt 4 |
|
Quantity |
Unit to be used |
Selection of multiples |
Remarks |
|
Temperature |
ºC (degree Celsius) |
See att.I pt 4 |
|
|
Linear expansion coefficient |
K-1 or ºC-1 |
||
|
Thermal conductivity |
W/(m. ºC) |
||
|
Coefficient of heat transfer |
W/(m. ºC) |
||
|
Specific heat |
J/(kg. ºC) |
kJ/(kg. ºC) |
|
|
Entropy |
J/(kg. K) |
kJ/(kg. K) |
See att.I pt 14 |
|
Enthalpy |
J/kg |
kJ/kg |
See att.I pt 15 |
|
Electric current |
A (ampère) |
kA |
|
|
Electric charge, quantity of electricity |
C (coulomb) |
kC |
|
|
Voltage, potential difference, electromotive force |
V(volt) |
kV mV |
|
|
Electric field strenth |
V/m |
kV/mm |
|
Quantity |
Unit to be used |
Selection of multiples |
Remarks |
|
Capacitance |
F (farad) |
µF |
|
|
Magnetic flux density, magnetic induction |
T (tesla) |
mT µT |
|
|
Magnetic flux |
Wb (weber) |
mWb |
|
|
Self inductance, mutual inductance |
H (henry) |
mH |
|
|
Resistance |
O (ohm) |
MO |
|
|
Conductance |
S (siemens) |
µS |
|
|
Conductivity |
S/m |
MS/m kS/m |
|
|
Wavelength |
m |
||
|
Luminous intensity |
cd (candela) |
||
|
Luminous flux |
lm (lumen) |
||
|
Illuminance |
lx (lux) |
||
|
Luminous efficacy |
lm/W |
|
Quantity |
Unit to be used |
Selection of multiples |
Remarks |
|
Frequency |
Hz (herz) |
Mhz |
|
|
Sound intensity |
W/m2 |
||
|
Sound pressure level |
dB (decibel) |
B (bel) |
Ref. value 2.10-5N/m2 See att.I pt 12 & 13 |
|
Sound power level |
dB |
B |
Ref. value 10-12WSee att.I pt 12 & 13 |
|
Sound intensity level |
dB |
B |
Ref. value 10-12W/m2 See att.I pt 12 & 13 |
|
Mass flow rate |
kg/h |
t/h |
|
|
Volume flow rate (gas or liquid) Ditto (gas) |
m3/h Nm3/h * |
l/s |
* See att.I pt 10 |
|
Velocity |
m/s |
||
|
Acceleration |
m/s2 |
||
|
Corrosion rate |
mm/yr |
See att.I pt 3 and pt 1 |
|
|
Concentration |
mg/kg |
When PPM is used, indicate whether it is based on volume or weight (PPMv, PPMwt) |
|
Quantity |
Unit to be used |
Selection of multiples |
Remarks |
|
Humidity / moisure content |
g/kg |
For atmospheric condition RH% can be used (based upon saturation at specified temperature) |
|
|
Notch impact value |
J |
Related to a keyhole specimen, which is to be specified |
|
|
Spring constant |
N/mm |
||
|
Taper |
1:... |
Dimensionless ratio of unit diameter change per length. |
|
|
Slope |
mm/m |
||
|
Amount of substance |
mol (mole) |
kmol |
1 mol=kg mole |
|
Molar mass |
g/mol |
kg/mol |
g/mol=MW |
|
Molar volume |
m3/mol |
l/mol |
|
|
Molar internal energy |
J/mol |
kJ/mol |
|
|
Molar heat capacity |
J/(mol.K) |
||
|
Molar entropy |
J/(mol.K) |
||
|
Concentration |
mol/m3 |
kmol/m3 or mol/dm3 |
6. Conversion Units
The table in attachment summarizes the conversion factors which are to be used exclusively by Company personnel.
Attachment I
Deviations from the SI Units
1. Length The inch will be used for pipe sizes only.
2. Mass
The name tonne (t) is used instead of megagram (Mg).
3. Time
The minute, hour, day, month, year are still used instead of decimal multiples of the second. For times smaller than one second the SI system is follows.
4. Temperature
The unit for customary or operational temperature is the ºC. The use of K is confined to the use of temperatures involved in calculations based upon absolute zero.
Temperature below 0ºC will be indicated as -xºC and not in K.
5. Plane Angle
The division of the circle into 360º is still used.
Radians shall only be used in special calculations as required.
6. Rotational Frequency
For indication of the rotational frequency of rotating equipment the rpm (revolution per minute) is continued to be used.
7. Pressure and Vacuum
Gauge pressure is expressed in bar (g) (bar gauge).
Absolute pressure is expressed in bar(a) - (bar absolute), mbar(a) - (millibar abs).
Differential pressure is expressed in bar.
Vacuum:
- Specify absolute pressure where possible
- For pressures slightly under atmospheric pressure
(e.g. tanks during pump out) use - mbar (minus millibar)
The use of the expression Full Vacuum (FV) which equals 0 mbar (a) is continued for indication as design requirement.
The Pascal is to be used in the acoustic field only.
Examples
a. Compound pressure/vacuum range of instrument is -1-0-10 bar(a)
b. Design pressure of vessel is 16 bar(g)/FV
c. Operation pressure of rotating filter is 200 mbar(a).
8. The unit kWh may be used in consumption of electrical energy
9. In electric power technology ‘’apparent power’’ is expressed in volt-ampere (VA) or kVA and ‘’reactive power’’ is expressed in kVAR
10.The normal cubic metre (Nm3) will still be used.
As there is no universally accepted definition, the reference pressure and temperature shall always be spelled out when the Nm3 is used.
For Company the reference shall always be:
1013.25 mbar(a) and 0ºC.
11. The unit mpy (mils per year) may be used, but should be avoided as much possible.
12. The dB is also used in other fields, e.g. telecommunications and line transmission.
In these cases other reference values are applicable, which are to be specified.
13. The reference values specified in this design guide are valid for acoustics only.
14. According ISO 1000-1973 (E) this is called ‘’specific entropy’’.
15. According ISO 1000-1973 (E) this is called ‘’specific energy’’.
Attachment II
Table of Conversion Factors
|
A: |
1 Å |
= |
1 angström = 10-10m |
|
1 acre |
= |
4 rood » 4.04686 x 103 m2 |
|
|
1 Aint |
= |
1 international ampère=1 Vint/W int |
|
|
0.99985 A |
|||
|
1 ° API |
= |
1 degree American Petroleum Institute |
|
|
1 at |
= |
1 technical atmosphere=1 kgf/cm2=0.980665 bar |
|
|
1 atm |
= |
1 physical atmosphere=1.01325 bar |
|
|
B: |
1 bar |
= |
105 Pa |
|
0 bar(g) |
= |
1.01325 bar(a) (Company std.) |
|
|
bbl |
= |
barrell |
|
|
1 dry bbl(US)=7056 in3=0.115627 m3 |
|||
|
1 oil bbl(US)=42 US gal=0.158987 m3 |
|||
|
1 oil bbl/d=6.62447 x 10-3 m3/h |
|||
|
1 ° Bé |
= |
1 degree Baumé 2) |
|
|
Btu |
= |
British thermal unit |
|
|
1 Btu=1 kcal.lb.°F/(kg.K)=1.05506 x 103 J |
|||
|
1 Btu.in/(ft2.h. °F)=0.144228 W/(m.°C) |
|||
|
1 Btu/(ft.h. °F)=1.73073 W/(m.°C) |
|||
|
1 Btu/ ft2=11.3565 x 103 J/m2 |
|||
|
1 Btu.in/(ft2.h. °F)=5.67826 W/(m2.°C) |
|||
|
1 Btu/ft3=37.2589 x 103 J/m3 |
|||
|
1 Btu/h=0.293071 W |
|||
|
1 Btu/lb=2.326 x 103 J/kg |
|||
|
1 Btu/(lb.°F)=4.1868 x 103 J/(kg.°C) |
|||
|
1 Btu/(ft3.°F)=67.0661 x 103 J/(m3.°C) |
|||
|
C: |
1 cal |
= |
1 calorie=4.1868J |
|
1 cc |
= |
1 cm3=10-6m3 |
|
|
1 centigrade(UK, US)=1 °C |
|||
|
1 CHU |
= |
1 Chu=1 centigrade heat unit=1.89910 x 103J |
|
|
1 cps |
= |
1 cycle per second= 1 Hz |
|
|
1 cSt |
= |
1 centistokes=0.01 St=10-6 m2/s |
|
|
cu |
= |
cubic, see main word |
|
|
1 CV |
= |
1 cheval vapeur=1 hp=735.499 W |
|
|
cwt |
= |
hundredweight |
|
|
1 UKcwt=112 lb=50.8023 kg |
|||
|
1 UScwt=100 lb=45.3592kg |
|||
|
D: |
1 deg F |
= |
1 deg R=1 °F=5/9 K=5/9°C |
|
1 dyn |
= |
1 dyne=1 g.cm/s2=10-5N |
|
|
1 dyn/cm2=0.1 Pa=10-6 bar |
|||
|
E: |
1 erg |
= |
1 dyn.cm=10-7J |
|
1 Erg |
= |
107erg=1J |
|
|
F: |
°F |
= |
degree Fahrenheit |
|
differential temperature: 1 °F=5/9°C=5/9°K |
|||
|
temperature level: |
|||
|
x°F=5/9(x-32) °C@ 5/9(x+764.82)°K |
|||
|
1 faraday |
= |
96.4846 x 103C |
|
|
1 fath |
= |
1 fathom=6 ft=1.8288m |
|
|
1 fbm |
= |
1 board foot=1 ft2.in=2.35974 x 10-3m3 |
|
|
1 ft |
= |
1 foot=(1/3)yd=0.3048m |
|
|
1 ft.lbf |
= |
1.35582 N.m |
|
|
1 ft.lbf/h |
= |
0.376616 x 10-3W |
|
|
1 ft.lbf/lb |
= |
2.98907J/kg |
|
|
1 ft.pdl |
= |
42.1401 x 10-3N.m |
|
|
1 ft/h |
= |
84.6667 m/s |
|
|
1 ft/min |
= |
5.08 x 10-3m/s |
|
|
1 ft2 |
= |
92.90304 x 10-3m2 |
|
|
1 ft3 |
= |
28.3168 x 10-3m3 |
|
|
1 ft3/h |
= |
28.3168 x 10-3m3/h |
|
|
1 ft3/lb |
= |
62.4280 x 10-3m3/kg |
|
|
1 ft3/min |
= |
1.6990 m3/h |
|
|
1 ft H2O |
= |
29.8907 mbar |
|
G: |
gal |
= |
gallon |
|
1 UKgal=4.54609 x 10-3m3 |
|||
|
1 UKgal/d=189.4205 x 10-6 m3/h |
|||
|
1 UKgal/h=4.5460 x 10-3m3/h |
|||
|
1 UKgal/lb=10.0224 x 10-3 m3/h |
|||
|
1 UKgal/min=0.2727m3/h |
|||
|
1 USgal=3.78541 x 10-3m3 |
|||
|
1 USgal/d=0.1577 x 10-3m3/h |
|||
|
1 USgal/h=3.7854 x 10-3m3/h |
|||
|
1 USgal/lb=8.34541 x 10-3m3/kg |
|||
|
1 Usgal/min=0.2271 m3/h |
|||
|
1 gcal |
= |
1 gramcalorie=1cal |
|
|
1 gf |
= |
1 gramforce=9.80665 x 10-3N |
|
|
1 gr |
= |
1 grain=64.79891 x 10-6kg |
|
|
1 gr/ft3=2.28835 x 10-3kg/m3 |
|||
|
1 gr/UKgal=14.2538 x 10-3kg/m3 |
|||
|
1 gr/USgal=17.1181 x 10-3kg/m3 |
|||
|
H: |
1 ha |
= |
1 hectare=100 a=104m2 |
|
1 hl |
= |
1 hectoliter=0.1 m3 |
|
|
1 hp |
= |
1 horsepower=550 ft.lbf/s=745.7 W |
|
|
1 hph |
= |
1 horsepower hour=2.68452 x 106J |
|
|
1 metric hp |
= |
1 pk=735.499 W |
|
|
I: |
imp |
= |
imperial=UK, see main word |
|
in |
= |
inch |
|
|
1 in=25.4 x 10-3m 4) |
|||
|
1 in2=0.64516 x 10-3m2 |
|||
|
1 in2/h=0.6452 x 10-3m2/h |
|||
|
1 in3=16.3871 x 10-6m3 |
|||
|
1 in3/lb=36.1273 x 10-6m2/kg |
|||
|
1 inH2O=2.49089 mbar |
|||
|
1 in.Hg=33.8639 mbar |
|||
|
J: |
1 Jint |
= |
1 Vint2.s/W int=1.00019 J |
|
K: |
1 kcal |
= |
1 kilocalorie=4.1868 x 103J |
|
1 kcal/h=1.163 W |
|||
|
1 kcal/min=69.78 W |
|||
|
1 kgf |
= |
1 kgf=1 kp=9.80665 N |
|
|
1 kgf.h/m2=35.3039 x 103 Pa.s |
|||
|
1 kgf/cm2=0.980665 bar |
|||
|
1 kgf/mm2=98.0665 bar=9.80665 N/mm2 |
|||
|
1 kp |
= |
1 kilopond=1 kgf=9.80665 N |
|
|
1 kWh |
= |
1 kilowatt hour=3.6 x 106 J |
|
|
L: |
lb |
= |
pound |
|
1 lb=0.45359237 kg |
|||
|
1 lb.ft/s=0.138255 kg.m/s |
|||
|
1 lb.ft2=42.1401 x 10-3kg.m2 |
|||
|
1 lb.in=292.640 x 10-6kg.m2 |
|||
|
1 lb/acre=0.112085 x 10-3kg.m2 |
|||
|
1 lb/ft=1.48816 kg/m |
|||
|
1 lb/ft2=4.88243 kg/m2 |
|||
|
1 lb/UKgal=99.7763 kg/m3 |
|||
|
1 lb/USgal=119.826 kg/m3 |
|||
|
1 lb/h=0.4536 kg/h |
|||
|
1 lb/in=17.8580 kg/m |
|||
|
1 lb/in3=27.6799 x 103 kg/m3 |
|||
|
1 lbf=1 poundforce=4.44822 N |
|||
|
1 lbf.ft=1.35582 N.m |
|||
|
1 lbf.ft/in=53.3787 N |
|||
|
1 lbf.h/ft2=172.369 x 103 Pa.s |
|||
|
1 lbf.in=0.112985 N.m |
|||
|
1 lbf/ft2=0.478803 mbar |
|||
|
1 lbf/in2=68.9476 mbar |
|||
|
1 lbf/ft3=16.0185 kg/m3 |
|||
|
M: |
1 mh4O |
= |
98.0665 mbar |
|
1 mil |
= |
1 milli-inch=25.4 x 10-6m |
|
|
1 circular mil=(P /4)mil2=0.506707x10-9 m2 |
|||
|
mi |
= |
mile |
|
|
1 (statute) mile=1.609344 x 103m |
|||
|
1 UK nautical mile (knot)=1853.184 m |
|
1 mmHg |
) = |
1 mm mercury=1.33322 mbar | |
|
1 mmQS (G) |
) = |
||
|
1 mwk |
) = |
1 mh4O=98.0665 mbar | |
|
1 mWS (G) |
) = |
||
|
O: |
oz |
= |
ounce |
|
1 oz=(1/16)lb=28.3495 x 10-3kg |
|||
|
1 oz/ft2=0.305152 kg/m2 |
|||
|
1 oz/UKgal=6.23602 kg/m3 |
|||
|
1 oz/USgal=7.48915 kg/m3 |
|||
|
1 oz/in3=1.72999 x 103kg/m3 |
|||
|
P: |
1 p |
= |
1 Poise=1 dyn.s/cm2=0.1 Pa.s |
|
1 pole |
= |
1 rod=5.0292 m |
|
|
1 ppb |
= |
1 part per billion=10-9 |
|
|
1 ppm |
= |
1 part per million=10-6 |
|
|
1 psi |
= |
1 pound per square inch=0.0689476 bar |
|
|
R: |
1 r |
= |
1 rev=1 revolution=360° |
|
1 ° R |
= |
1 degree Rankine=(5/9)K=0.555556 K |
|
|
1 ° R |
= |
1 degree Réamur |
|
|
differential temperature: 1 ° R=0.8° C=0.8K |
|||
|
temperature level: x ° R=0.8 x ° C=(0.8x+273.15)K |
|
S: |
1 St |
= |
1 stokes=1 cm2/s=10-4m2/s=100 mm2/s |
|
T: |
1 t |
= |
1 ton=1000 kg, see ton |
|
ton |
= |
1 t=1 (metric) ton-1 tonne(UK, US)=103kg |
|
|
1 UKton=1 long(or ‘gros’) ton=1016.05 kg |
|||
|
1 USton = 1 short(or’’nett’’) ton=2000 lb=907.185 kg |
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|
1 tf |
= |
1 tonforce=9.80665 x 103N |
|
|
1 UKtonf |
= |
1 UKton=9.96402 x 103N |
|
|
1 UStonf |
= |
1 USton=8.89644 x 103N |
|
|
1 (standard) (comercial) ton of refrigeration=3.51685 x 103 W |
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|
1 registerton |
= |
2.83286 m3 |
|
|
1 Torr |
= |
1 torr=133.322 Pa |
|
|
W: |
1 Wh |
= |
3.6 x 103J |
|
Y: |
1 yd |
= |
1 yard=0.9144 m |
|
Z: |
Zoll(G) |
= |
in, see inch |
Abbreviations
G = Germany
F = France
UK = Great Britain
US = United States
D = Dutch