1、DEUTSCHE NORM SeDtember 2000 Natural gas Sampling guidelines (IS0 1071 5 : 1997) Enalish version of DIN EN IS0 10715 I DIN - IEN IS0 10715 ICs 75.060 Erdgas - Probenahmerichtlinien (IS0 1071 5 : 1997) Supersedes parts of DIN 51853, November 1995 edition. European Standard EN IS0 10715 : 2000 has the
2、 status of a DIN Standard. A comma is used as the decimal marker. National foreword This standard has been published in accordance with a decision taken by CEN/CS to adopt, without alteration, International Standard IS0 1071 5 as a European Standard. The responsible German body involved in its prepa
3、ration was the Normenausschuss Materialprfung (Materials Testing Standards Committee), Technical Committee 622 Anforderungen an und Prfung von Prfgasen. Amendments DIN 51 853, November 1995 edition, has been superseded by the specifications of EN IS0 1071 5, which is identical to IS0 1071 5. Previou
4、s editions DIN 51853: 1960-02, 1979-01, 1995-11 EN comprises 42 pages. No pari of this standard may be reproduced without the prior permission of Ref. No. DIN EN IS0 1071 5 : 2000-0 Y Deutsches Institut fr Normung e. V., Berlin. Beuth Verlag GmbH, 10772 Berlin, Germany, s the exclusive right of sale
5、 for German Standards (DIN-Normen). English price group 15 Sales No. 11 15 o1 .o1 EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN IS0 10715 January 2000 ICs 75.060 English version Natural gas Sampling guidelines (IS0 1071 5 : 1997) Gaz naturel - Lignes directrices pour lchantillonnage (IS0 1071
6、 5 : 1997) Erdgas - Probenahmerichtlinien (IS0 1071 5 : 1997) This European Standard was approved by CEN on 1999-1 1-26. CEN members are bound to comply with the CENKENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without
7、 any alteration. Up-to-date lists and bibliographical references concerning such national stand- ards may be obtained on application to the Central Secretariat or to any CEN member. The European Standards exist in three official versions (English, French, German). A version in any other language mad
8、e by translation under the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the official versions. CEN members are the national standards bodies of Austria, Belgium, the Czech Republic, Denmark, Finland, France, Germany, Greece, Icel
9、and, Ireland, Italy, Luxembourg, the Netherlands, Norway, Portugal, Spain, Sweden, Switzerland, and the United Kingdom. CEN European Committee for Standardization Comit Europen de Normalisation Europisches Komitee fr Normung Central Secretariat: rue de Stassart 36, B-1050 Brussels O 2000. CEN - All
10、rights of exploitation in any form and by any means reserved worldwide for CEN national members. Ref. No. EN IS0 10715 : 2000 E Page 2 EN IS0 1071 5 : 2000 Foreword International Standard IS0 10715 : 1997 which was prepared by ISO/TC 193 Natural gas of the International Organization for Standardizat
11、ion, has been adopted by CEN/CS as a European Standard. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, and conflicting national standards withdrawn, by July 2000 at the latest. In accordance with the CENKENELEC I
12、nternal Regulations, the national standards organizations of the follow- ing countries are bound to implement this European Standard: Austria, Belgium, the Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, the Netherlands, Norway, Portugal, Spain, Sweden
13、, Switzerland, and the United Kingdom. Natural gas - Sampling guidelines, Endorsement notice The text of the International Standard IS0 1071 5 : 1997 was approved by CEN as a European Standard without any modification. Contents 1 Scope 4 2 Definitions 4 3 Principles of sampling 6 4 Safety precaution
14、s . . . . . . . . . . 8 5 Technical considerations 10 6 Materials used in sampling . . . . . 13 7 General preparation of equipment . 14 8 Sampling equipment . 15 9 Spot sampling 21 10 Direct sampling 22 11 incremental sampling 24 Annexes A Use of a block valve in direct sampling 26 B Cleaning of ste
15、el sampling cylinders . 28 C Procedure for low-pressure sampling into glass cylinders 29 D Procedure for sampling by the fill-and-empty method . 31 E Procedure for sampling by the controlled-rate method 33 F Procedure for sampling by the evacuated-cylinder method . 35 G Guidelines for the calculatio
16、n of the residence time 37 H Students t-table 41 J Bibliography . . . . . 42 Page 3 EN IS0 1071 5 : 2000 Introduction This International Standard provides guidance on all aspects of the sampling of processed natural gas. Unless otherwise stated, all pressures up to 15 MPa in this International Stand
17、ard are given as gauge pressures. The determination of the composition and the properties of the gas is highly dependent on the sampling technique. Also of great importance are the design, construction, installation and maintenance of the sampling system as well as the conditions of sample transfer
18、and transport. These guidelines cover sampling strategy, details of sampling methods, the choice of sampling method and sampling equipment. This document is intended for use in those cases where sampling is not described as part of the analytical procedure. This document concentrates on sampling sys
19、tems and procedures. Analyses from the samples collected using these systems and procedures may be utilized in many different ways, including calculations to determine the calorific value of the gas stream, identification of contaminants contained in the gas stream, and compositional information to
20、determine whether or not the stream meets contractual specifications. Page 4 EN IS0 1071 5 : 2000 WARNING - The use of this International Standard may involve hazardous materials, operations and equipment. This standard does not purport to address all of the safety problems associated with its use.
21、It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability or regulatory limitations prior to use. All sampling activities shall comply with local safety regulations. 1 Scope The purpose of this document is to provide co
22、ncise guidelines for the collection, conditioning and handling of representative samples of processed natural gas streams. It also contains guidelines for sampling strategy, probe location and the handling and design of sampling equipment. It considers spot, composite (incremental) and continuous sa
23、mpling systems. This document gives consideration to constituents such as oxygen, hydrogen sulfide, air, nitrogen and carbon dioxide in the gas stream. This document does not include sampling of liquid streams or streams with multiphase flow. Traces of liquid, such as glycol and compressor oil, if p
24、resent, are assumed to be intrusive and not a pari of the gas to be sampled. Their removal is desirable to protect the sampling and analytical equipment from contamination. This document can be used for custody transfer measurement systems and allocation measurement systems. 2 Definitions For the pu
25、rposes of this International Standard, the following definitions apply: 2.1 direct sampling: Sampling in situations where there is a direct connection between the natural gas to be sampled and the analytical unit. 2.2 floating-piston cylinder: A container which has a moving piston separating the sam
26、ple from a buffer gas. The pressures are in balance on both sides of the piston. 2.3 flow-proportional incremental sampler: A sampler which collects gas over a period of time and at a rate that is proportional to the flow rate in the sampled pipeline. 2.4 high-pressure natural gas: Natural gas with
27、a pressure exceeding 0,2 MPa. NOTE - The maximum for this International Standard is 15 MPa. Page 5 EN IS0 1071 5 : 2000 2.5 hydrocarbon dew point: The temperature, at a given pressure, at which hydrocarbon vapour condensation begins. 2.6 incremental sampler: A sampler which accumulates a series of s
28、pot samples into one composite sample. 2.7 indirect sampling: Sampling in situations where there is no direct connection between the natural gas to be sampled and the analytical unit. 2.8 liquid separator: A unit, in the sample line, used to collect liquid fall-out. 2.9 low-pressure natural gas: Nat
29、ural gas having a pressure between O and 0.2 MPa. 2.10 purging time: The period of time during which a sample purges a piece of equipment. 2.1 1 representative sample: A sample having the same composition as the natural gas sampled when the latter is considered as a homogeneous whole. 2.12 residence
30、 time: The time it takes for a sample to flow through a piece of equipment. 2.13 retrograde condensation: Retrograde behaviour describes the non-ideal phase properties of hydrocarbon gas mixtures, such as natural gas. Retrograde condensation is the production of a liquid phase of heavy hydrocarbons
31、at a particular pressure and temperature where, at that same temperature, the gas stays in a single phase at a higher pressure as well as at a lower pressure. NOTE - See also 5.2. 2.14 sample container: A container for collecting the gas sample when indirect sampling is necessary. 2.15 sample line:
32、A line provided to transfer a sample of the gas to the sampling point. It may include devices which are necessary to prepare the sample for transportation and analysis. 2.16 sample probe: A device inserted into the gas line to be sampled and to which a sample line is connected. 2.17 sampling point:
33、A point in the gas stream where a representative sample can be collected. 2.18 spot sample: A sample of specified volume taken at a specified place at a specified time from a stream of gas. 2.19 transfer line: A line provided to carry the sample to be analysed from the sample point to the analytical
34、 unit. 2.20 water dew point: The temperature, at a given pressure, at which water vapour condensation begins. Page 6 EN IS0 1071 5 : 2000 3 Principles of sampling 3.1 Sampling methods The main function of sampling is to take an adequate sample that is representative of the gas. The main distinction
35、in sampling is between direct and indirect sampling methods. In the direct sampling method, the sample is drawn from a stream and directly transferred to the analytical unit. In the indirect sampling method, the sample is stored before it is transferred to the analytical unit. The main classificatio
36、ns of the indirect sampling method are spot sampling and incremental sampling. b Direct 0 Indirect Incremental 9 Figure 1 - Survey of direct and indirect sampling methods The information needed from the analysis of natural gas falls into two basic categories: averaged and limit values. 3.1.1 Average
37、d values A typical example is the calorific value. Custody transfer requires the time- or flow-averaged calorific value. Commercial agreements determine the period and method of averaging. 3.1.2 Limit values Most gas custody transfer contracts contain specification limits on composition or on gas pr
38、operties. Direct sampling can be applied, but often the requirements are such that also indirect sampling has to be applied. 3.2 Sampling frequency This subclause gives guidelines for the establishment of the sampling frequency. Mostly the sampling frequency is a matter of common sense. Information
39、on the properties of the gas stream in the past and about expected (systematic) future changes determines the sampling frequency. Generally, pipeline gas composition will have daily, weekly, monthly, semi-annual and seasonal variations. Compositional variations will also occur because of gas treatme
40、nt equipment and reservoir changes. All of these environmental and operational considerations shall be taken into account when selecting a sampling interval. The statistical approach in this paragraph is only intended to support the common-sense approach. In this context, the required sampling frequ
41、ency is the number of samples to be taken in a certain period of time in order to obtain meaningful results. Page 7 EN IS0 1071 5 : 2000 The formula for calculating the number of samples is: - s n2 =tx- d where d is the error margin required; n is the number of samples; s is the standard deviation;
42、t is Students r-factor (see table H.l in annex H) This equation shall be solved by iteration: an initial value of t is estimated, and used to calculate a revised value of n, which is used, in turn, to give a new value of t. The error margin, the number of samples and the standard deviation shall be
43、taken over the same period of time. 3.2.1 Error margin There are two different cases of error margins. One case is related to the determination of averaged values. In most custody transfer contracts, these values are given as an indication of the accuracy. The other is related to the determination o
44、f limit values. Custody transfer contracts specify the limits but rarely give an indication of the accuracy. In these cases, the difference between the last measured value, or the last years average, and the limit value is the error margin. 3.2.2 Number of samples The number of samples is the number
45、 of samples to be taken in a defined period. It is equivalent to the number of partial samples in incremental sampling. 3.2.3 Students :-factor Students t-factor allows for the finite sample size, and is to be found in standard statistical tables. The value depends on the claimed certainty (typicall
46、y 95 %) and the “degrees of freedom“, here to be taken as the number of measurements minus one (n-1). EXAMPLE 1 Determination of the monthly average caloric value d = 0,4 % (error margin required from custody transfer contract for monthly averaged value) s = 0,6 Oh (estimated variation over a one-mo
47、nth period) First estimate, taking n = 7: t = 2,45 for 6 degrees of freedom and a certainty of 0,975 single-sided (equals 0,95 double-sided) - Of6 n2 = 2,45 x- Of4 1 n=14 First iteration, taking n = 14: Page 8 EN IS0 1071 5 : 2000 recalculate for t= 2,16 for 13 degrees of freedom, and a certainty of
48、 0,975 single-sided (equals 0,95 double-sided) n=11 Second iteration, taking n = 11 : recalculate for t= 2,23 for 1 O degrees of freedom, and a certainty of 0,975 single-sided (equals 0,95 double-sided) 11=11 EXAMPLE 2 Total sulfur determination Last measured concentration 20 rng/m3 and the contract
49、 limit value 50 mg/m3. d= 30 mg/m3 (difference between limit value from custody transfer contract and last measured value) s = 10 mg/m3 standard deviation in spot sample results (in the past year) t = 4,30 n - 1 taken as 2, level of certainty 95% 10 112 =4,3x- 30 1 - 11 = 2 Three samples are enough. Recalculation indicates that two samples are not enough. 4 Safety precautions 4.1 General Sampling and sample handling shall follow all relevant national and company-related safety regulations. In the case of inadequate regulations, those responsible for sampling shall esta
