1、BRITISH STANDARD BS ISO 8573-3:1999 Compressed air Part 3: Test methods for measurement of humidity ICS 71.100.20BSISO8573-3:1999 This British Standard, having been prepared under the directionof the Engineering SectorCommittee, was publishedunder the authority ofthe Standards Committee andcomes int
2、o effect on 15August1999 BSI 04-2000 ISBN 0 580 32898 8 National foreword This British Standard reproduces verbatim ISO8573-3:1999 and implements it as the UK national standard. The UK participation in its preparation was entrusted to Technical Committee MCE/8, Compressors, pneumatic tools, pneumati
3、c machines and vacuum technology, which has the responsibility to: aid enquirers to understand the text; present to the responsible international/European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; monitor related international and Eur
4、opean developments and promulgate them in the UK. A list of organizations represented on this committee can be obtained on request to its secretary. Cross-references The British Standards which implement international or European publications referred to in this document may be found in the BSI Stan
5、dards Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Find” facility of the BSI Standards Electronic Catalogue. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible
6、for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, the ISO title page, pages ii to iv, pages 1 to 10, an inside back cover and a ba
7、ck cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Amendments issued since publication Amd. No. Date CommentsBSISO8573-3:1999 BSI 04-2000 i Contents Page National foreword In
8、side front cover Foreword iii Text of ISO 8573-3 1ii blankBSISO8573-3:1999 ii BSI 04-2000 Contents Page Foreword iii Introduction 1 1 Scope 1 2 Normative references 1 3 Terms and definitions 1 4 Units 1 5 Selection guide and available methods 1 6 Sampling techniques 2 7 Measurement methods 2 8 Evalu
9、ation of test results 4 9 Conversions from non-standard humidity units to standard format and vice versa 4 10 Uncertainty 4 11 Expression of results 4 12 Test report 4 Annex A (informative) Example of compressed air humidity statement 6 Annex B (informative) Calculation of vapour pressure 6 Annex C
10、(informative) Preferred methods of humidity measurement 7 Annex D (informative) Non-preferred methods of humidity measurement 9 Bibliography Inside back cover Table 1 Methods available for measuring humidity 1 Table 2 Spectroscopic methods Laser diode 2 Table 3 Chilled mirror (condensation) with man
11、ual thermometer reading 2 Table 4 Chilled mirror (condensation) with automatic mist detection and temperature-measuring device 3 Table 5 Chemical reaction method using direct-reading (glass) tubes with hygroscopic content 3 Table 6 Measurement with electrical sensor based on capacitance 3 Table 7 Me
12、asurement with electrical sensor based on conductivity 3 Table 8 Measurement with electrical sensor based on resistance 3 Table 9 Psychrometer (wet and dry bulb thermometers) 3 Table B.1 Values for factor F i 7BSISO8573-3:1999 BSI 04-2000 iii Foreword ISO (the International Organization for Standard
13、ization) 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 the right to
14、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. International Stand
15、ards are drafted in accordance with the rules given in the ISO/IEC Directives, Part3. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least75% of the member bodies casti
16、ng a vote. International Standard ISO8573-3 was prepared by Technical Committee ISO/TC118 Compressors, pneumatic tools and pneumatic machines, Subcommittee SC4, Quality of compressed air. ISO 8573 consists of the following parts, under the general title Compressed air Part 1: Contaminants and qualit
17、y classes; Part 2: Test methods for aerosol oil content; Part 3: Test methods for measurement of humidity; Part 4: Test methods for solid particle content; Part 5: Test methods for oil vapour and organic solvent content; Part 6: Test methods for gaseous contaminant content; Part 7: Test methods for
18、viable microbiological contaminant content. Annex A, Annex B, Annex C and Annex D are for information only.iv blankBSISO8573-3:1999 BSI 04-2000 1 Introduction This part of ISO8573 is one in a series of International Standards (planned or published) with the aim of harmonizing air contamination measu
19、rements. It is also intended to be used for reference when stating air purity class according to ISO8573-1. 1 Scope This part of ISO8573 provides guidance on selection from the available suitable methods for measurement of humidity in compressed air and specifies the limitations of the various metho
20、ds. It does not provide methods for measurement of water content in states other than vapour. This part of ISO8573 specifies sampling techniques, measurement, evaluation, uncertainty considerations and reporting for the air contamination parameter humidity. It gives guidance for the conversion of hu
21、midity statements to the standard format. 2 Normative references The following normative documents contain provisions which, through reference in this text, constitute provisions of this part of ISO8573. For dated references, subsequent amendments to, or revisions of, any of these publications do no
22、t apply. However, parties to agreements based on this part of ISO8573 are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. For undated references, the latest editions of the normative documents referred to applies. Members of
23、ISO and IEC maintain registers of currently valid International Standards. ISO 3857-1, Compressors, pneumatic tools and machines Vocabulary Part1: General. ISO 5598, Fluid power systems and components Vocabulary. ISO 7183:1986, Compressed air dryers Specifications and testing. ISO 8573-1, Compressed
24、 air Part 1: Contaminants and purity classes. 3 Terms and definitions For the purposes of this part of ISO8573, the terms and definitions given in ISO3857-1 and ISO5598 and the specific humidity terms and definitions given in ISO7183 apply. 4 Units For the purposes of this part of ISO8573, the follo
25、wing non-preferred SI units are used: 1 bar = 100000Pa NOTEBar(e) is used to indicate effective pressure above atmospheric. 1 l (litre)= 0,001 m 3 5 Selection guide and available methods The methods available for measuring humidity, their grade of uncertainty and their preferred range of use are lis
26、ted inTable 1. Table 1 Methods available for measuring humidity Methods in order of increasing uncertainty Uncertainty C Range for humidity level expressed as pressure dew point c , C Remarks Method Table 80 60 40 20 0 +20 +40 +60 Spectroscopic Table 2 a Detection limit for water vapour is about 0,1
27、 10 6to 1 10 6 b Condensation Table 3 and Table 4 0,2 to 1,0 Chemical Table 5 1,0 to 2,0 Electrical Table 6, Table 7 and Table 8 2,0 to 5,0 Psychrometer Table 9 2,0 to 5,0 a The uncertainty is not yet available in C. b Volume fraction. c Pressure dew point is defined in ISO7183.BSISO8573-3:1999 2 BS
28、I 04-2000 6 Sampling techniques 6.1 General Dew point can be measured at atmospheric pressure or under actual pressure conditions. The pressure to which the dew point is referred shall be stated. It is important that the air flow is controlled within the upper and lower limits to prevent damage to t
29、he probe and to ensure that a representative measurement is made. 6.2 Probe installation 6.2.1 Full flow measurement The probe is inserted in the main air flow stream, but protected against free water and other contaminants and used within the stated lower and upper limits of flow velocity for the m
30、easurement system. 6.2.2 Partial flow measurement 6.2.2.1 Bypass The probe is installed in a small bypass tube. In this way the flow velocity to which the probe is exposed may be controlled. 6.2.2.2 Extraction The probe is installed in a small extraction tube which conducts an air sample from the ma
31、in air flow stream into the measurement chamber, where the measurement is made under system pressure. 6.2.3 Reduced-pressure measurement The probe is installed in a chamber into which an air flow is fed from the main air stream. Before measurement, the pressure is reduced to a suitable measuring pre
32、ssure (normally atmospheric). 6.3 Requirements on sampling and measurement conditions 6.3.1 The measurements carried out depend on the reproducibility of the method and the experience of the parties involved in the provision of measurement facilities. 6.3.2 Materials used for conducting the air into
33、 the sampling system shall not affect the water vapour content of the sample. SeeC.2 inAnnex C. 6.3.3 The sampling system pressure shall be recorded during measurement. 6.3.4 The sampling system temperature shall be higher than the measured dew point. 6.3.5 The measurement system shall have reached
34、a steady state before any measurement takes place and shall be kept steady during measurement. The readings from two consecutive measurements taken with at least20min interval shall not differ by more than the accuracy of the measuring system. 7 Measurement methods Table 2 toTable 9 list a number of
35、 methods for humidity measurement, including limitations on application, measurement pressure and temperature. Descriptions of the different methods can be found inAnnex C. Some non-preferred methods are described inAnnex D. Consideration shall be given to the measurement system integrity and the ca
36、libration requirements of the measurement equipment which shall be used as described in applicable instructions and International Standards. It shall be proven that the equipment used is capable of achieving the uncertainty required within the specified range and tolerance. Any method shall only be
37、used within the upper or lower limits of its range of operation. Check and consider calibration records. Table 2 Spectroscopic methods Laser diode Table 3 Chilled mirror (condensation) with manual thermometer reading Characteristic applications Atmospheric air and compressed air Humidity range 80 C
38、to +60 C pressure dew point Pressure range Atmospheric pressure Temperature range 0 C to +40 C Contamination tolerance Good Characteristic applications Atmospheric air and compressed air Humidity range 20 C to +25 C pressure dew point Pressure range 0 bar(e) to 200 bar(e) Temperature range 0 C to +5
39、0 C Contamination tolerance PoorBSISO8573-3:1999 BSI 04-2000 3 Table 4 Chilled mirror (condensation) with automatic mist detection and temperature-measuring device Table 5 Chemical reaction method using direct-reading (glass) tubes with hygroscopic content Table 6 Measurement with electrical sensor
40、based on capacitance Table 7 Measurement with electrical sensor based on conductivity Table 8 Measurement with electrical sensor based on resistance Table 9 Psychrometer (wet and dry bulb thermometers) Characteristic applications Atmospheric air and compressed air Humidity range 80 C to +25 C pressu
41、re dew point Pressure range 0 bar(e) to 20 bar(e) Temperature range 0 C to +50 C Contamination tolerance Poor Characteristic applications Atmospheric air and compressed air Humidity range 65 C to +35 C pressure dew point Pressure range Atmospheric pressure Temperature range 0 C to +40 C Contaminatio
42、n tolerance Average Characteristic applications Atmospheric air and compressed air Humidity range 80 C to +40 C pressure dew point Pressure range 0 bar(e) to 20 bar(e) Temperature range 30 C to +50 C Contamination tolerance Average Characteristic applications Atmospheric air and compressed air Humid
43、ity range 40 C to +25 C pressure dew point Pressure range 0 bar(e) to 20 bar(e) Temperature range 30 C to +50 C Contamination tolerance Average Characteristic applications Atmospheric air and compressed air Humidity range 40 C to +25 C pressure dew point Pressure range 0 bar(e) to 20 bar(e) Temperat
44、ure range 0 C to +50 C Contamination tolerance Average Characteristic applications Atmospheric air Humidity range 5% to 100% relative humidity Pressure range Atmospheric pressure Temperature range 0 C to +100 C Contamination tolerance PoorBSISO8573-3:1999 4 BSI 04-2000 8 Evaluation of test results 8
45、.1 Reference conditions Unless otherwise agreed, the reference conditions for humidity statements are: 8.2 Recalculation for deviating pressure When necessary, the obtained value can be referred to another pressure (reference pressure) using the absolute pressure values and partial pressures. SeeAnn
46、ex B. 8.3 Recalculation for deviating temperature Normally not required except in the case of relative humidity. 8.4 Recalculation for influence of other contaminants Some contaminants, particularly molecules which have a structure similar to water molecules, may disturb the measurements. Therefore
47、these shall be eliminated from the sample before measurement takes place. If this is not possible, then an evaluation shall be made to determine the uncertainty caused by these contaminants. 9 Conversions from non-standard humidity units to standard format and vice versa 9.1 Relative humidity The re
48、lative humidity value for a known air sample at a known temperature can be recalculated to a dew point temperature using the table in ISO7183:1986, Annex C, which gives values for saturation pressures and densities of water vapour at different temperatures. Read the saturation vapour pressure for th
49、e actual temperature and multiply this by the percentage relative humidity. In the table, read the dew point temperature corresponding to the actual partial vapour pressure. 9.2 Dew point Dew point at atmospheric pressure (1 bar absolute) is erroneously but commonly referred to as “atmospheric dew point”. It represents an imaginary dew point and is not an acceptable term for describing the water content. 9.3 Mixing ratio (or specific humidity) W
