1、INTERNATIONAL STANDARD IS0 4795 First edition 1996-12-15 Glass for thermometer bulbs Verre pour rbservoirs de thermomktres This material is reproduced from IS0 documents under International Organization for Standardization (ISO) Copyright License number IHSllCC11998. Not for resale. No part of these
2、 IS0 documents may be reproduced in any form, electronic retrieval system or otherwise, except as allowed in the copyright law of the country of use, or with the prior written consent of IS0 (Case postale 58,121l Geneva 20, Switzerland, Fax +41 22 734 IO 79), IHS or the IS0 Licensers members. Refere
3、nce number IS0 4795:1996(E) IS0 4795:1996(E) Foreword IS0 (the International Organization for Standardization) is a worldwide federation of national standards bodies (IS0 member bodies). The work of preparing International Standards is normally carried out through IS0 technical committees. Each memb
4、er body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. IS0 collaborates closely with the International Ele
5、ctrotechnical Commission (IEC) on all matters of electrotechnical standardization. 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 least 75 % of the member bodies castin
6、g a vote. This International Standard IS0 4795 has been prepared by Technical Committee lSO/rC 48, Laboratory glassware and related apparatus, Subcommittee SC 3, Thermometers. Annex A forms an integral part of this International Standard. Annexes B, C and D are for information only. Q IS0 1998 All r
7、ights reserved. Unless otherwise specified, no part of this publication 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 pos
8、tale 56 l CH-1211 Geneve 20 l Switzerland Internet: centralisocs.iso.ch X.400: c=ch; a=400net; p=iso; o=isocs; s=central Printed in Switzerland ii INTERNATIONAL STANDARD 0 IS0 IS0 4795: 1996(E) Glass for thermometer bulbs 1 Scope This International Standard specifies the physical and chemical charac
9、teristics and the marking of thermometric glass and the test methods to be used for the selection of glass for the manufacture of the bulbs of liquid-in-glass thermometers. It is not applicable to the glass used in parts of the thermometer other than the bulb (e.g. the stem). However, the glass used
10、 for the other parts can be identical to that used for the bulb. The coefficient of linear thermal expansion of the bulb glass should not differ from that of the glass intended for the stem by more than 0,2 x lo6 K-. 2 Normative references The following standards contain provisions which, through re
11、ferences 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 Standard are encouraged to investigate the possibility of applying
12、the most recent editions of the standards indicated below. Members of IEC and IS0 maintain registers of currently valid International Standards. IS0 719:1985, G/ass - Hydrolytic resistance of glass grains at 98 “C - Method of test and classification. IS0 7884-7:1987, G/ass - Viscosity and viscometri
13、c fixed points - Part 7: Determination of annealing point and strain point by beam bending. 3 Definitions For the purposes of this International Standard, the following definitions apply. 3.1 strain point, O,: The temperature determined in accordance with IS0 7884-7. NOTE - By the beam-bending metho
14、d, the viscosity of glass at the strain point may be evaluated as 10“dPa.s. 3.2 zero-point correction, K: Correction of the thermometer at 0 “C: where find is the temperature indicated. 1 IS0 4795:1996(E) 0 IS0 3.3 zero-point depression: Change of the zero-point correction after heating and fast coo
15、ling of the thermometer. 4 Maximum temperature of use The maximum temperature recommended for use shall not exceed (0, -130) “C, where 8, is the strain point determined in accordance with the method given in IS0 7884-7. 5 Requirements 5.1 Stability The indication at 0 “C of a suitable test thermomet
16、er having a bulb made of the glass under consideration shall not change by more than 2 “C after exposure to the maximum temperature recommended for use (see clause 4) for 500 h. This stability requirement can be determined in accordance with annex B. 5.2 Zero-point depression When tested in accordan
17、ce with the procedure given in annex A, a thermometer having a bulb made of the glass under consideration shall have an average zero-point depression not exceeding 0,05 “C for “normal glass” or 0,03 “C for borosilicate glass. NOTE -The zero-point depression of some types of thermometric glass is giv
18、en in annex C. 5.3 Chemical resistance When tested according to the procedure and classification given in IS0 719, the glass shall comply with the requirements of class HGB 3 or better. 6 Marking 6.1 Thermometric glass complying with this International Standard shall be identified according to eithe
19、r of the schemes given in 6.2 and 6.3. 6.2 The manufacturer of the thermometric glass shall incorporate an identification stripe or stripes in accordance with the approved list shown in table D.l (see annex D). 6.3 The manufacturer of the thermometer shall mark it with an identification alphanumeric
20、 code in accordance with the approved list shown in table D.l (see annex D) and shall, on request, supply a certificate of conformity provided by the manufacturer of the thermometric glass. NOTE 1 The list of approved identification stripes and identification codes will be maintained under the respo
21、nsibility of the secretariat for this International Standard, on the basis of data provided by the national test authorities or notified bodies responsible for testing and certification of thermometric glass. NOTE 2 Manufacturers wishing to claim, for a thermometric glass not listed in table D.l, co
22、mpliance with the requirements of this International Standard, should apply to their national standards body, who will register the glass with the secretariat for this International Standard. A certificate from a national test authority or notified body that the thermometric glass to be registered c
23、orresponds to the requirements of this International Standard is recommended. 2 0 IS0 IS0 4795:1996(E) Annex A (normative) Determination of the average zero-point depression NOTE - This annex is based on annex B of International Recommendation OIML R7:1978, Clinical thermometers - Mercury-in-glass w
24、ith maximum device. A.1 Fabrication of test thermometers Using the glass under consideration for the bulb, make test thermometers with the following specifications. Scale range at least: - 3,0 “C to + 3,0 “C. Graduation: 0,02 “C, 0,05 “C, or 0,l “C. Distance between consecutive graduation lines: at
25、least 0,7 mm for enclosed-scale thermometers or at least I,0 mm for solid-stem thermometers. Expansion chamber: of sufficient volume that the thermometer can be heated 50 “C above the maximum recommended temperature without damage. Stabilization: thermometers stabilized (see A.2). A.2 Confirmation o
26、f stabilization A.2.1 Heat the thermometer in a liquid bath or metal block oven from room temperature to the maximum recommended temperature of use + 5 “C and keep it at this temperature for at least 5 min. A.2.2 Cool the thermometer to 50 “C at a rate between 10 “C/h and 15 “C/h. A.2.3 Remove the t
27、hermometer from the bath or oven, determine the correction at 0 “C and record its value (K,). A.2.4 Heat the thermometer again to the maximum recommended temperature of use + 5 “C, using the same immersion depth as that employed in A.2.1 and keep it at this temperature for 24 h. A.2.5 Cool the therm
28、ometer as specified in A.2.2. A.2.6 Redetermine the correction as specified in A.2.3 and record its value (K,). A.2.7 If the difference between K, and K, exceeds 0,15 “C, reject the samples. Carry out the stabilization of fresh samples and repeat the procedures described in A.2.1 to A.2.6. If the di
29、fference between K, and K, is 0,15 “C or less, carry out the depression of zero test (A.3). 3 IS0 4795:1996(E) 0 IS0 A.3 Depression of zero test A.3.1 Select m stabilized test thermometers (where m 2 31, tested according to A.2, which have not subsequently been heated above room temperature. A.3.2 K
30、eep each thermometer at a temperature of between 20 “C and 25 “C for 7 days. Determine the correction at 0 “C and record its value (4). A.3.3 Heat each thermometer to (100 + I) “C. Keep it at this temperature for 30 min, then remove it from the test bath and allow it to cool to room temperature with
31、out the bulb touching any object. Determine the correction at 0 “C within 15 min of its removal from the test bath and record its value (K,). A.3.4 Repeat step A.3.2 and determine KS; repeat step A.3.3 and determine &; repeat step A.3.2 and determine K,; repeat step A.3.3 and determine m is the tota
32、l number of test thermometers; n is the number of zero depressions obtained. A.4.2 If the standard deviation of the m x n values of zero depression obtained is not greater than 0,Ol “C, report the average depression of zero as calculated in A.4.1. 4 0 IS0 IS0 4795:1996(E) Annex 6 (informative) Stabi
33、lization test Heat a suitable test thermometer to a temperature equal to the maximum recommended temperature of use (see clause 4) of the glass under consideration and keep it at this temperature for 5 min. Allow the thermometer to cool in the test bath or furnace to 50 “C at a rate between 10 “C/h
34、and 15 “C/h and then determine the correction at 0 “C. Heat the thermometer again to the maximum recommended temperature and keep it at this temperature for 500 h. Allow the thermometer to cool to 50 “C at the same rate as before, and redetermine the correction under the same conditions as before. R
35、eport the difference between the two corrections in degrees Celsius. Is0 4795:1996(E) 0 IS0 Annex C (informative) Zero-point depression of some types of thermometric glass Type of glass Manufacturer Zero-point depression “C DURAN NG 360 SCHOTT GLASWERKE Russia 0,011 0,011 N16B SCHOTT ROHRGLAS 0,013
36、2954 III SCHOTT GLASWERKE 0,02 B49T Choisy-le-Roi 0,02 GGI 860 Saale-Glas 0,024 0 IS0 IS0 4795:1996(E) Annex D (informative) Type of glass and identification The types of thermometric glass listed in table D.l are certified by the following national testing authorities as complying with the particul
37、ar requirements of this International Standard: National testing authorities: CNAM: LNE Paris, France NML: National Measurement Laboratory, Sydney, Australia PTB: Physikalisch-Technische Bundesanstalt, Braunschweig und Berlin, Germany NPL: National Physical Laboratory, Teddington, United Kingdom NPL
38、I: National Physical Laboratory, New Delhi, India CsMo: Slovak Laboratory for Metrology, Bratislava, Slovakia su: Glass Institute, Hradec Kralove, Czech Republic IS0 4795:1996(E) 0 IS0 Table D.l- Certified thermometric g ilass IDENTIFICATION STRIPE(S) OR APPROVED ABBREVIATION GLASS (NAME OR TYPE) MA
39、NUFACTURER SINGLE RED STRIPE SCHOTT N 16B SCH0l-T ROHRGLAS GMBH, THERMOMETRIC NORMAL BAYREUTH, DE GLASS SINGLE BLUE STRIPE NORMAL GLASS WHITEFRIARS GLASS LTD, LONDON, GB DOUBLE BLUE STRIPE NORMAL GLASS DIAL PLOWDEN 81.040.30 Descriptors: laboratory equipment, laboratory glassware, thermometers, tanks (containers), specifications, materials specifications, marking. Price based on 8 pages
