1、BRITISH STANDARD BS 3166:1959 Specification for Thermographs (Liquid-filledand vapour pressure types) For use within the temperature range 20 F to 220 F (30 C to 105 C)BS3166:1959 This British Standard, having been approved by the InstrumentIndustry StandardsCommittee and endorsed by the Chairman of
2、 theEngineering Divisional Council, was published under theauthority of the General Council on 30November1959 BSI 12-1999 The following BSI references relate to the work on this standard: Committee references INE/4 andINE/4/7 Draft for comment CZ(INE) 3463 ISBN 0 580 34119 4 Co-operating organizatio
3、ns The Instrument Industry Standards Committee, under whose supervision this British Standard was prepared, consists of representatives from the following Government departments and scientific and industrial organizations: Association of Scientific Workers British Ceramic Research Association Britis
4、h Clock and Watch Manufacturers Association British Electrical and Allied Industries Research Association British Electrical and Allied Manufacturers Association* British Industrial Measuring and Control Apparatus Manufacturers Association* British Iron and Steel Federation* British Nautical Instrum
5、ent Trade Association British Railways, The British Transport Commission British Scientific Instrument Research Association* Council of British Manufacturers of Petroleum Equipment Electricity Council, the Generating Board and the Area Boards in England and Wales* Engineering Equipment Users Associa
6、tion* Gauge and Tool Makers Association Institute of Physics Institution of Chemical Engineers Institution of Electrical Engineers* Institution of Heating and Ventilating Engineers* Institution of Mechanical Engineers* Iron and Steel Institute Meteorological Office Ministry of Health Ministry of Hou
7、sing and Local Government Ministry of Supply* National Coal Board National Physical Laboratory (D.S.I.R.)* Oil Companies Materials Association* Radio Industry Council Scientific Instrument Manufacturers Association* Society of Instrument Technology Water-Tube Boilermakers Association The Government
8、departments and scientific and industrial organizations marked with an asterisk in the above list, together with the following, were directly represented on the Committee entrusted with the preparation of this British Standard: Admiralty Air Ministry British Coal Utilization Research Association Gas
9、 Council Ministry of Power Ministry of Works Physical Society Refrigerated Cargo Research Council Society of Chemical Industry Individual manufacturers and users Amendments issued since publication Amd. No. Date CommentsBS3166:1959 BSI 12-1999 i Contents Page Co-operating organizations Inside front
10、cover Foreword ii 1 Scope 1 2 Materials 1 3 Design and construction 1 4 Temperature range 1 5 Accuracy 1 6 Compensation 2 7 Lag 2 8 Testing 2 9 Marking 2 10 Packaging 3 Appendix A Precautions to be taken when the twin-pen instrument is to be used as a wet and dry bulb hygrograph 4 Appendix B Testing
11、 of thermographs 5 Appendix C Recommendations for despatch by manufacturer and subsequent movement by customer from site to site 5 Figure 1 Typical identification plate 3 Table 1 Maximum error in computed per cent relative humidity 5BS3166:1959 ii BSI 12-1999 Foreword This standard makes reference t
12、o the following British Standards: BS 1133, Packaging code. BS 1986, Dimensional features of measuring and control instruments and panels for industrial purposes. BS 2548, Wood wool for general packaging purposes. BS 2770, Recommendations for the pictorial marking of handling instructions for non-da
13、ngerous goods. This British Standard is one of a series prepared under the authority of the Instrument Industry Standards Committee at the request of the Temperature Measuring Instruments Sub-committee of the Joint Equipment Standardization Committee. It is intended to cover Service requirements for
14、 a distant reading thermograph, either as a wet and dry bulb hygrograph or as a twin (or single) dry bulb thermograph, as well as requirements for certain industrial and marine uses. For determining the relative humidity of the air the instrument is used as a wet and dry bulb hygrograph and the rela
15、tive humidity is calculated using the appropriate hygrometric tables 1)or slide rule 2) . When used as a hygrograph several precautions must be taken in order to obtain accurate results; these are discussed inAppendix A. These precautions must be taken if the performance of the instrument, as laid d
16、own in the body of this specification, is to be attained. NOTEWhere metric equivalents have been given, the figures in British units are to be regarded as the standard. The metric conversions are approximate. More accurate conversions should be based on the tables in BS350, “Conversion factors and t
17、ables”. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document co
18、mprises a front cover, an inside front cover, pages i and ii, pages1 to 6 and a back 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. 1) Meteorological Office booklet M.O. 265
19、, H.M.S.O., for non-aspirated wet bulbs with ventilation rates3 to6 ft/sec (1 to 2m/sec). Guide to current practice, Institution of Heating and Ventilating Engineers, 1959, for aspirated wet bulbs with ventilation rates greater than15ft/sec (5m/sec). 2) Meteorological Office humidity slide rule, for
20、 F or C, conforming to the current Meteorological Office specification.BS3166:1959 BSI 12-1999 1 1 Scope This British Standard relates to thermographs of the liquid-filled and vapour pressure types, suitable for general and marine use in the measurement of temperatures within the range 20 F to220 F
21、(30 C to105 C). The instrument comprises a single or twin-pen recorder with one or two capillary tubes and bulbs respectively. When one bulb is used as a wet bulb, acontainer for distilled water is provided. A louvred screen may be used to house the bulbs, but the screen is not specified in this Bri
22、tish Standard. 2 Materials The instrument shall be constructed of materials which have been selected so as to avoid the possibility of electrolysis and corrosion. The capillary tube shall be adequately protected against mechanical damage and corrosion by a sheath or sheaths of suitable material, the
23、 outer one of which may be of a plastics material. When the instrument is used as a hygrograph, the wick shall be capable of conducting from the reservoir a supply of distilled water sufficient to keep the surface of the wet bulb moist under all normal conditions. 3 Design and construction The therm
24、ograph shall preferably use one of the types of drum and chart described in BS1986 3) , thepreferred size of the drum being 126 mm in diameter and154mm high. If provision is made for a single drum to carry two charts, however, the drum height may be increased to308mm. The fixed spindle type of clock
25、 is preferred for drum chart recorders, with one of the rates of rotation given in BS1986. Alternatively, the thermograph shall be fitted with a circular chart in accordance with BS1986. When the twin-pen instrument is used as a hygrograph, the wet bulb pen shall record “low”, or have a time lag, so
26、 that it does not foul the dry bulb pen. Similar precautions shall be introduced when the twin-pen instrument is used to record two separate temperature readings. Suitable devices shall be incorporated to prevent damage to the mechanism within extremes of temperature stated by the manufacturer as sa
27、fe, or those agreed between the manufacturer and purchaser. The recorder shall be provided with a suitable cover, either with windows on at least the three sides which embrace the drum or with a single window of greater diameter than the circular chart, so arranged as to provide free access for remo
28、val and replacement of charts. These windows shall be of permanently transparent non-flammable material. A mechanism for withdrawing the pens from the chart shall also be fitted, operated from outside the cover. The instrument may be supplied with flexible capillary tubes up to150ft (50m) in length
29、as agreed between manufacturer and purchaser. 4 Temperature range The instrument shall have one or more of the following nominal ranges (or the nearest convenient equivalent in C): A liquid-filled instrument shall be provided with a zero adjustment having a range of 10degF. Avapour pressure instrume
30、nt shall be provided with a zero adjustment appropriate to the range. 5 Accuracy With the instrument set to read correctly at one point, preferably at32 F, the error at any other point on the scale shall not exceed1degF in any one range of120degF. When the temperature of the bulb is changed over any
31、 part of the range, the recorded difference in temperature shall not be in error by more than 1per cent of the interval tested or 1 / 2degF, whichever is the greater. When so ordered, the two systems of a twin-pen recorder shall be matched so that the difference in reading between them shall not exc
32、eed 1 / 2 per cent of the range, the recorder remaining at room temperature. This accuracy of range shall normally be achieved when the height of the bulb(s) differs from that of the recorder by 25ft, unless any other datum is agreed between the manufacturer and purchaser. Instruments provided with
33、a zero shift adjustment shall also comply with these requirements in regard to both range and height variation. 3) BS1986, “Dimensional features of measuring and control instruments and panels for industrial processes”. 20 to 100 F 0 to 120 F 20 to 140 F 80 to 200 F 100 to 220 FBS3166:1959 2 BSI 12-
34、1999 6 Compensation a) Capillary tube. For normal use, compensation for temperature of the capillary tube shall be such that if the bulb temperature is maintained constant and the temperature of the capillary tube is changed by 30degF over its whole length, then the change in the reading of the inst
35、rument shall not exceed 1 / 2degF for the30 degF change. The compensation for special conditions of use shall be the subject of agreement between manufacturer and purchaser. b) Recorder. With the bulb(s) and capillary tube(s) at a uniform temperature a change of temperature of the whole recorder by3
36、0 degF shall not produce a perceptible change in reading. 7 Lag With the thermometer bulb at equilibrium room temperature, the bulb shall be plunged into a well-stirred water bath differing in temperature by at least30 degF. The instrument shall take up at least two-thirds of the difference in tempe
37、rature within15 seconds. 8 Testing Certification of thermographs shall normally be carried out by a recognized testing station, but periodic checks on performance and examination for general compliance with this specification may be conducted in the manner described inAppendix B. 9 Marking The follo
38、wing shall be permanently marked on the upper surface of the base plate, e.g.as inFigure 1: a) The manufacturers name or trade mark. b) A serial number. c) The number of this British Standard, i.e.“BS3166. d) The nominal range of the instrument. e) The “safe” temperature limits. f) The chart referen
39、ce number. g) The designed difference in height between the bulb(s) and recorder. The mark “BS3166” on a product is an indication bythe manufacturer that it purports to comply with the requirements of this British Standard. The British Standards Institution is the owner of the registered certificati
40、on trade mark shown below. The presence of the certification mark on a product is an additional independent assurance that the product does comply with the requirements of the relevant British Standard. This certification mark may be used by the manufacturer only under licence from the BSI and parti
41、culars of the conditions under which licences are granted may be obtained from the Director, British Standards Institution, 2 Park Street, London, W.1.BS3166:1959 BSI 12-1999 3 10 Packaging The instrument shall be packed for transit in such a manner as to minimize the possibility of accidental damag
42、e 4) . Detailed recommendations are given inAppendix C. Figure 1 Typical identification plate 4) General guidance on methods of packaging and packaging materials is given in BS1133, “Packaging code”.BS3166:1959 4 BSI 12-1999 Appendix A Precautions to be taken when the twin-pen instrument is to be us
43、ed as a wet and dry bulb hygrograph The principal errors in humidity determinations which occur when this instrument is used as a hygrograph arise from the use of an incorrect value for the wet bulb temperature and therefore, in general, of the wet bulb depression. Common causes of error in the wet
44、bulb temperature are inadequate ventilation or an imperfect wet bulb. Inadequate ventilation is most likely to be a source of error when the instrument is used indoors, or outdoors on a calm sunny day. It cannot be overstressed that for good results adequate ventilation is essential, and wherever po
45、ssible it is recommended that the bulbs be artificially ventilated. This may be achieved by drawing a stream of air over them, care being taken that the direction of air flow is not from the wet to the dry bulb. For naturally ventilated bulbs exposed in a louvred screen the ventilation rate is assum
46、ed to be3 to6ft/sec (1to2m/sec), while for artificially ventilated bulbs the ventilation rate should be more than15ft/sec (5m/sec). Aspirated or non-aspirated hygrometric tables should be used as appropriate. The tables should state the speed for which they are applicable; the slide rule can be used
47、 for either case. Coupled with the errors arising from inadequate ventilation are those caused by conduction along the wet bulb capillary to the wet bulb. Errors due to this cause are greater when the wet bulb depression is large and they also depend on ventilation; they can be reduced to negligible
48、 proportions by extending the wet bulb covering for a short distance along the capillary. The errors due to an imperfect wet bulb arise from many different causes; some of the commonly occurring ones are listed below. It should be remembered that this list is not exhaustive and great care should be
49、taken when planning any installation that all foreseeable sources of error are circumvented, e.g.fortuitous radiation or unrepresentative exposure. a) Faulty irrigation of the wet bulb. i) Dressing in the wick the wick should be clean and free from oil or starch and should be changed frequently. ii) Bacteriological action on the wick this is particularly prevalent at ambient temperatures above about95 F; it can be inhibited without affecting the wet bulb temperature by adding 1 / 2per cent by volume of saturated mercuric chlo
