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1、AA Reference number ISO 10337:1997(E) INTERNATIONAL STANDARD ISO 10337 First edition 1997-12-15 Crude petroleum Determination of water Coulometric Karl Fischer titration method Ptrole brut Dosage de leau Mthode de Karl Fischer par titrage coulomtrique Copyright International Organization for Standar
2、dization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/20/2007 06:31:15 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 10337:1997(E) ISO 1997 All rights reserved. Unless otherwise specified, no part of this pub
3、lication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the publisher. International Organization for Standardization Case postale 56 CH-1211 Genve 20 Switzerland Internetcentraliso.ch X.40
4、0c=ch; a=400net; p=iso; o=isocs; s=central Printed in Switzerland ii Contents 1 Scope 1 2 Normative references 1 3 Principle. 2 4 Reagents. 2 5 Apparatus 2 6 Sampling and sample preparation. 3 6.1 General 3 6.2 Laboratory sample. 3 6.3 Preparation of the laboratory sample 3 7 Procedure. 3 7.1 Prepar
5、ation of the apparatus 3 7.2 Test portion 3 7.3 Check test 4 8 Calculation. 4 9 Expression of results. 5 10 Precision. 5 11 Test report. 5 Annex A (normative) Sample handling 7 Annex B (informative) Alternative test method using volumetric measurement of test portion size 10 Copyright International
6、Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/20/2007 06:31:15 MDTNo reproduction or networking permitted without license from IHS -,-,- ISOISO 10337:1997(E) iii Foreword ISO (the International Organization f
7、or Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has th
8、e right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. Draft In
9、ternational Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. International Standard ISO 10337 was prepared by Technical Committee ISO/TC 28, P
10、etroleum products and lubricants, Subcommittee SC 6, Bulk cargo transfer, accountability, inspection and reconciliation. Annex A forms an integral part of this International Standard. Annex B is for information only. Copyright International Organization for Standardization Provided by IHS under lice
11、nse with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/20/2007 06:31:15 MDTNo reproduction or networking permitted without license from IHS -,-,- Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards
12、1/9972545001 Not for Resale, 04/20/2007 06:31:15 MDTNo reproduction or networking permitted without license from IHS -,-,- INTERNATIONAL STANDARD ISOISO 10337:1997(E) 1 Crude petroleum Determination of water Coulometric Karl Fischer titration method WARNING The use of this International Standard may
13、 involve hazardous materials, operations, and equipment. This International Standard does not purport to address all of the safety problems associated with its use. It is the responsibility of the user of this International Standard to establish appropriate safety and health practices and determine
14、the applicability of regulatory limitations prior to use. 1 Scope This International Standard specifies a coulometric Karl Fischer titration method for the direct determination of water in crude petroleum. It covers the range 0,050 % (m/m) to 5,00 % (m/m) water in crude petroleum containing less tha
15、n 0,05 % (m/m) but more than 0,005 % (m/m) of either mercaptan sulfur or sulfide ion sulfur or both. It covers the range 0,020 % (m/m) to 5,00 % (m/m) water in crude petroleum containing less than 0,005 % (m/m) of either mercaptan sulfur or sulfide ion sulfur or both. NOTE 1A number of substances an
16、d classes of compounds associated with condensation or oxidation-reduction reactions interfere in the determination of water by Karl Fischer titration. However, the only likely interfering substances present in crude petroleum are mercaptans and ionic sulfides and providing that they are present at
17、levels less than 0,05 % (m/m), the interference is insignificant when determining water in the range 0,050 % (m/m) to 5,00 % (m/m). NOTE 2An alternative procedure is provided in annex B for the direct determination of water over the range 0,05 % (V/V) to 5,00 % (V/V) in crude petroleum containing le
18、ss than 0,05 % (V/V) of either mercaptan sulfur or ionic sulfide sulfur or both. The limitations under which this alternative volume measurement may be used are listed in annex B. The volume measurement may also be used to determine water in the range 0,02 % (V/V) to 5,00 % (V/V) if the above interf
19、ering substances are present at levels of less than 0,005 % (V/V) as either mercaptan sulfur or ionic sulfide sulfur or both. NOTE 3For the purposes of this International Standard, the terms “% (m/m)“ and “% (V/V)“ are used to represent the mass and volume fractions respectively. 2 Normative referen
20、ces The following standards contain provisions which, through reference in this text, constitute provisions of this International Standard. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this International Stan
21、dard are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. Members of IEC and ISO maintain registers of currently valid International Standards. ISO 3170:1988, Petroleum liquids Manual sampling. ISO 3171:1988, Petroleum liquids Automatic
22、 pipeline sampling. ISO 3696:1987, Water for analytical laboratory use Specification and test methods. ISO 3733:1976, Petroleum products and bituminous materials Determination of water Distillation method. ISO 3734:1997, Petroleum products Determination of water and sediment in residual fuel oils Ce
23、ntrifuge method. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/20/2007 06:31:15 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 10337:1997(E) ISO 2 3 Prin
24、ciple After homogenizing the crude oil with a mixer, a weighed portion is injected into the titration vessel of a coulometric Karl Fischer apparatus in which iodine for the Karl Fischer reaction is generated coulometrically at the anode. When all the water has been titrated, excess iodine is detecte
25、d by an electrometric end point detector and the titration is terminated. Based on the stoichiometry of the reaction, one mole of iodine reacts with one mole of water. Thus the quantity of water is proportional to the total integrated current according to Faradays Law. 4 Reagents 4.1 Xylene, reagent
26、 grade. 4.2 Karl Fischer reagents Use commercially available reagents that meet the performance requirements described in 7.3. 4.2.1 Anode electrolyte solution (anolyte) Mix 6 parts by volume of commercial Karl Fischer anode solution with 4 parts by volume of reagent grade xylene. Other proportions
27、of Karl Fischer anode solution and xylene may be used providing they meet the performance criteria of 7.3. 4.2.2 Cathode electrolyte solution (catholyte) Use commercially available Karl Fischer cathode solution. 4.3 Water, conforming to grade 3 of ISO 3696. 5 Apparatus 5.1 Automatic coulometric Karl
28、 Fischer titrator NOTE There are presently available a number of commercial instruments. Instructions for operating these devices are provided by the manufacturers and are not described herein. 5.2 Non-aerating mixer, capable of meeting the homogenization efficiency requirements given in annex A. NO
29、TE Both insertion mixers and circulating external mixers, such as those used with automatic crude petroleum sampling systems, are acceptable providing they comply with the principles of annex A. 5.3 Syringes Add test portions to the titration vessel by means of glass syringes with Luer fittings and
30、hypodermic needles of suitable length such that the tip can reach under the surface of the anolyte when inserted through the inlet port septum. The bores of the needles used shall be kept as small as possible, but large enough to avoid problems arising from back pressure or blocking whilst sampling.
31、 NOTE 1Needles with bores between 0,5 mm and 0,8 mm have been found suitable. NOTE 2Recommended syringe sizes are: a) 10 l with fixed needle for periodic addition of water to check the titrator performance; b) 250 l and 1 ml for crude petroleum samples. 5.4 Balance, capable of weighing to 0,1 mg. 5.
32、5 Thermometer, capable of measuring the sample temperature to the nearest 1 C. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/20/2007 06:31:15 MDTNo reproduction or networking permitted
33、 without license from IHS -,-,- ISOISO 10337:1997(E) 3 6 Sampling and sample preparation 6.1 General Sampling is defined as all the steps necessary to obtain a representative sample of the contents of any pipe, tank or other system and to place the sample into the laboratory test container. 6.2 Labo
34、ratory sample Only representative samples obtained as specified in ISO 3170 or ISO 3171 shall be used for this International Standard. 6.3 Preparation of the laboratory sample The following sample handling procedure shall apply in addition to 6.2. 6.3.1 Record the temperature of the sample in degree
35、s Celsius immediately before mixing. 6.3.2 Mix the laboratory sample immediately before analysis to ensure complete homogeneity. Mix the laboratory sample in the original container with the mixing time, mixing power (speed) and mixer position relative to the bottom of the container found to be satis
36、factory for the crude petroleum being analyzed as established by the procedure given in clause A.3.3. The volume and water content of the crude petroleum shall not exceed the maxima validated in clause A.3.3. 6.3.3 Record the temperature of the laboratory sample in degrees Celsius immediately after
37、mixing. The rise in temperature between this reading and the reading in 6.3.1 shall not exceed 10 C otherwise loss of water may occur or the emulsion may be destabilized. 7 Procedure 7.1 Preparation of the apparatus 7.1.1 Follow the manufacturers directions for preparation and operation of the titra
38、tion apparatus. 7.1.2 Add the anolyte to the outer compartment of the titration cell to the level recommended by the manufacturer. 7.1.3 Add the catholyte to the inner compartment of the titration cell to a level 2 mm to 3 mm below the level of the anolyte. 7.1.4 Seal all joints and connections to t
39、he titration cell to prevent atmospheric moisture from entering. 7.1.5 Turn on the titrator and stirrer. Allow the residual moisture in the titration cell to be titrated until the end point is reached. Do not proceed beyond this stage until the background current (or background titration rate) is co
40、nstant and less than the maximum recommended by the manufacturer of the instrument. NOTE High background current for a prolonged period may be attributable to moisture on the inside walls of the titration cell. Gentle shaking of the cell (or more vigorous stirring action) will wash the inside with e
41、lectrolyte. Also check all fittings to ensure atmospheric moisture does not enter the cell. It is recommended that the titrator be permanently switched on to stabilize to a low background current. 7.2 Test portion Mix the sample as specified in 6.3.1 to 6.3.3. 7.2.1 Immediately after mixing use a cl
42、ean, dry syringe of suitable capacity (see table 1 and the note following table 1) to withdraw at least 3 portions of the laboratory sample and discard to waste. Immediately withdraw a test portion of sample, clean the needle with a paper tissue and weigh the syringe and contents to the nearest 0,1
43、mg. Insert the needle through the inlet port septum, start the titration and, with the tip of the needle just below the liquid surface, inject the entire test portion. Withdraw the syringe, wipe the needle with a clean tissue and reweigh the syringe, to the nearest 0,1 mg. After the end point is rea
44、ched, record the water titrated from the display on the titrator. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/20/2007 06:31:15 MDTNo reproduction or networking permitted without lice
45、nse from IHS -,-,- ISO 10337:1997(E) ISO 4 Table 1 Test portion size based on expected water content Expected water content % (m/m) Test portion size g Water titrated g 0,02 to 0,11200 to 1 000 0,10 to 0,50,5500 to 2 500 0,50 to 50,251 250 to 12 500 NOTE If the concentration of water in the laborato
46、ry sample is completely unknown it is advisable to start with a small trial test portion to avoid excessive titration time and depletion of the reagents. Further adjustment of the portion size may be made as necessary. 7.2.2 When the background current or titration rate returns to a stable reading a
47、s outlined in 7.1.5 an additional test portion shall be taken to give a duplicate determination. Duplicates shall be taken and injected within the period for which the sample is known to be homogeneous and stable as determined in clause A.3.3. Duplicates shall agree to within the repeatability limit
48、 of 10.1.1. 7.3 Check test The water titrated is a direct function of the coulombs of electricity consumed. However, reagent performance deteriorates with use and shall be regularly monitored by accurately injecting 10 l of water. Suggested intervals are initially with fresh reagents and then after every 10 test portion injections. Replace the anolyte and catholyte solutions whenever one of the following occurs: the result from a 10 l injection of water is outside 10 000 g 200 g; persist