ISO 91-2:1991 pdf free download – Petroleum measurement tables
1 Scope
This part of ISO 91 refers to Computer implemen- tation procedures for the correction of densities and volumes to the reference temperature of 20 “C (see note 1 ). The implementation procedures referred to do not cover the full range of tables referred to in patt 1 of this International Standard, but provide for those tables designated in part 1 as being for pri- mary use. In addition, reference is made to im- plementation procedures for use with lubricating oils that are not included in ISO 91 -1:1982 (see note 2). This part of ISO 91 provides for the reference tem- perature of 20 OC, using the Same expansion data as used for the tables referred to in ISO 91 -1 . NOTES 1 Although the Standard reference temperature for pet- roleum measurement adopted in ISO 5024 is 1 5 T and should be used in international trade, it is recognized that its use is not yet universally accepted and that the refer- ence temperature of 20 OC is still widely used. 2 Tables relating to lubricating oils and the reference temperatures of 15 “C and 60 OF are proposed for adoption in a revision of ISO 91 -1 in course of preparation.
2 Normative reference
The following Standard contains provisions which, through reference in this text, constitute provisions of this part of ISO 91 . At the time of publication, the edition indicated was valid. All Standards are sub- ject to revision, and Parties to agreements based on this part of ISO 91 are encouraged to investigate the possibility of applying the most recent edition of the Standard indicated below. Members of IEC and ISO maintain registers of currently valid International Standards. ISO 91 -1 :1982, Petroleum measurement tables – Part 1: Tables based on reference temperatures of 1 5 “C and 60 degrees F.
3 Source of Computer implementation procedures
3.1 The Computer implementation procedures have been published by the Institute of Petroleuml) as Petroleum measurement Paper No. 3: Computer implernen ta tion procedures for correc fing densities and volumes to 20 C, October 1 988.
Such publications are reprinted from time to time. If corrections are included in such reprints, the IP has agreed to advise ISO of them and an amendment will be issued to this part of ISO 91 referring to the corrections and to the date of the reprint. Users should then ensure that they have the most recent reprint. a temperature of 20 OC. If the input variable is ob- served density rather than an observed hydrometer reading, Steps 3 and 4 shall be omitted. The series of tables 60A, 60B and 60D shall be used to calculate the volume correction factor for the correction of a volume at an observed temperature entering with the density at 20 OC. The procedures in these tables make use of the procedures for tables 53A and 53B, as referred to in ISO 91 -1 , to which reference shall also be made. A list of errata was published by the IP in Januar-y 1989 and supplied with all copies of Petroleum measurement paper No. 3. Users of this part of ISO 91 shall ensure that the corrections in the errata Slip are used.
3.2 Of the tables referred to above, the series of tables 59A, 59B and 590 shall be used to convert from observed hydrometer readings, or observed densities, at an observed temperature, to density at NOTE 3 In the implementation procedures relating to the conversion of hydrometer readings, the coefficient of thermal cubic expansion for glass of 23 x 1 0e6 OC-’ has been used. This value is marginally below the conven- tional value quoted in ISO 1 768, i.e. 25 x 10-’ OC-‘. This differente in coefficient is not significant for most tem- perature differentes found in practice. It may be corrected for by subtracting 0,000002 R’ ((3 – 20) from the hydrom- eter reading, before entering tables 59A, 59B and 590 with readings made using hydrometers complying with ISO 649-1 , where X’ is the hydrometer reading and 0 the observed temperature, if it is agreed between the inter- ested Parties that the temperature differente (8 – 20) is sufficient for the error to be otherwise significant.