NBN ISO 91:2021

This document refers to temperature volume correction factors, which allow users to convert volumes,
measured at ambient conditions, to those at reference conditions for transactional purposes. This
document also refers to compressibility factors required to correct hydrocarbon volumes measured
under pressure to the corresponding volumes at the equilibrium pressure for the measured
temperature.
Table 1 shows the defining limits and their associated units of correction factors referenced in this
document for crude oil, refined products and lubricating oils. These values are shown in bold italics.
Also shown in the table are the limits converted to their equivalent units (and, in the case of the densities,
other base temperatures). Table 2 shows defining limits of correction factors for light hydrocarbons
(natural gas liquids and liquefied petroleum gases).
Table 1 — Defining limits of correction factors for crude oil, refined products and lubricating oils
Crude oil Refined products Lubricating oils
Density, kg/m3 @ 60 °F 610,6 to 1 163,5 800,9 to 1 163,5
Relative density @ 60 °F 0,611 2 to 1,164 64 0,801 68 to 1,164 6
API gravity @ 60 °F 100 to –10 45 to –10
Density, kg/m3 @ 15 °C 611,16 to 1 163,79 611,16 to 1 163,86 801,25 to 1 163,85
Density, kg/m3 @ 20 °C 606,12 to 1 161,15 606,12 to 1 160,62 798,11 to 1 160,71
Temperature, °C –50,00 to 150
Temperature, °F –58,0 to 302
Pressure, psig 0 to 1 500
Pressure, kPa (gauge) 0 to 1,034 × 104
Pressure, bar (gauge) 0 to 103,4
60 °F thermal expansion
factor (a60), per °F 230,3 × 10-6 to 930,0 × 10
-6
a60, Per °C 414,0 × 10-6 to 1 674,0 × 10
-6
Table 2 — Defining limits of correction factors for light hydrocarbons (natural gas liquids and
liquefied petroleum gases)
Density, kg/m3 @ 60 °F
Density, kg/m3 @ 15 °C
Density, kg/m3 @ 20 °C
350,0 to 688,0
351,7 to 687,8
331,7 to 683,6
Temperature °C
Temperature °F
-46,0 to 93,0
-50,8 to 199,4
Pressure Saturation conditions (bubble point or saturation vapour
pressure) (see Note 2 to 4.1)
This document also specifies standard reference conditions of pressure and temperature for
measurements carried out on crude petroleum and its products, including liquefied petroleum gases
(see Annex B).
© ISO 2017 – All rights reserved 1

ISO 91:2017(E)
This document excludes specifying standard reference conditions for natural gas which are given in
ISO 13443[15].