1、 g49g50g3g38g50g51g60g44g49g42g3g58g44g55g43g50g56g55g3g37g54g44g3g51g40g53g48g44g54g54g44g50g49g3g40g59g38g40g51g55g3g36g54g3g51g40g53g48g44g55g55g40g39g3g37g60g3g38g50g51g60g53g44g42g43g55g3g47g36g58ICS 17.120.20Hydrometry Rotating-element current-metersBRITISH STANDARDBS ISO 2537:2007BS ISO 2537:
2、2007This British Standard was published under the authority of the Standards Policy and Strategy Committee on 29 June 2007 BSI 2007ISBN 978 0 580 52904 7Amendments issued since publicationAmd. No. Date CommentsThis publication does not purport to include all the necessary provisions of a contract. U
3、sers are responsible for its correct application.Compliance with a British Standard cannot confer immunity from legal obligations.National forewordThis British Standard was published by BSI. It is the UK implementation of ISO 2537:2007. It supersedes BS 3680-8A:1989 which is withdrawn.The UK partici
4、pation in its preparation was entrusted by Technical Committee CPI/113, Hydrometry, to Subcommittee CPI/113/5, Measuring instruments and equipment.A list of organizations represented on this committee can be obtained on request to its secretary.INTERNATIONALSTANDARDISO2537Fourth edition2007-05-01Ref
5、erence numberISO 2537:2007(E)Hydrometry Rotating-element current-metersHydromtrie Moulinets lment rotatifBS ISO 2537:2007iiiiiContents Page1 Scope 12 Normative references 13 Terms and definitions 14 Principle of operation 15 Types of current-meters 26 Operational requirements . 27 Characteristics of
6、 cup-type and propeller-type current-meter 38 Construction features . 39 Calibration (rating) . 310 Maintenance of current-meter 611 Operational and servicing manual . 6Annex A (normative) Construction features of current-meters . 7Annex B (normative) Maintenance of current-meter . 11Bibliography .
7、13BS ISO 2537:2007ivForewordISO (the International Organization for Standardization) is a worldwide federation of national standards bodies(ISO member bodies). The work of preparing International Standards is normally carried out through ISOtechnical committees. Each member body interested in a subj
8、ect for which a technical committee has beenestablished has the right to be represented on that committee. International organizations, governmental andnon-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the InternationalElectrotechnical Commission (IEC)
9、on all matters of electrotechnical standardization.International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.The main task of technical committees is to prepare International Standards. Draft International Standardsadopted by the technical committees ar
10、e circulated to the member bodies for voting. Publication as anInternational Standard requires approval by at least 75 % of the member bodies casting a vote.Attention is drawn to the possibility that some of the elements of this document may be the subject of patentrights. ISO shall not be held resp
11、onsible for identifying any or all such patent rights.ISO 2537 was prepared by Technical Committee ISO/TC 113, Hydrometry, Subcommittee SC 5, Instruments,equipment and data management.This fourth edition cancels and replaces the third edition (ISO 2537:1988), which has been technically revised.BS IS
12、O 2537:20071Hydrometry Rotating-element current-meters1ScopeThis International Standard specifies the operational requirements, construction, calibration, and maintenanceof rotating-element devices for the measurement of flow velocities in open channels.ISO 748 gives information on the use of these
13、devices.2 Normative referencesThe following referenced documents are indispensable for the application of this document. For datedreferences, only the edition cited applies. For undated references, the latest edition of the referenced document(including any amendments) applies.ISO 772, Hydrometric d
14、eterminations Vocabulary and symbolsISO 3454, Hydrometry Direct depth sounding and suspension equipmentISO 3455, Hydrometry Calibration of current-meters in straight open tanks3 Terms and definitionsFor the purposes of this document, the terms and definitions given in ISO 772 and the following apply
15、.3.1 propeller pitchdistance the propeller current-meter relatively moves through the water during one revolution4 Principle of operation4.1 ProportionalityThe rotating element of a current-meter is driven by the fluid at an angular velocity that is proportional to thelocal velocity of the fluid at
16、the point of immersion when that velocity exceeds a critical value.4.2 Flow velocityIn order to determine the velocity of the fluid, a current-meter is placed at a point in a stream and the number ofrevolutions of the rotor during a specified time interval is counted or the time required by the roto
17、r to turn a givennumber of revolutions is observed. The velocity is obtained from the current-meter calibration table or calibrationequation(s), established experimentally during its calibration (Clause 9). The number of current-meterrevolutions (rotations) may be determined by sensing the signals e
18、mitted (such as electrical pulses) through therotation of the rotor by using a suitable counting device. The velocity can be determined from a direct reading ofthe speed of rotation of the rotating element by means of equipment designed for this purpose.BS ISO 2537:200725 Types of current-meters5.1
19、GeneralThe current-meters are generally classified depending upon the type of rotating element used, i.e. vertical axiscup-type and horizontal axis propeller-type.5.2 Cup-type current-meterThe rotor of the cup-type current-meter is constructed out of conical cups, or curved vanes attached at equalin
20、tervals around the perimeter of a hub, which rotates when placed in a fluid flow. Usually, the rotor is mountedwith the axis vertical.5.3 Propeller-type current-meterThe propeller-type current-meter is an assembly consisting of a number of straight or angled vanes attached atequal intervals around t
21、he perimeter of a hub, or two or more helical screw blades formed around a hub thatrotates about a horizontal axis when placed in a fluid flow.6 Operational requirements6.1 PositioningThe current-meter shall maintain alignment with the flow in such a way that the rotating element responds toflow mov
22、ement as intended. It shall balance in the stream with its longitudinal axis parallel to the water surface.If a pivoted suspension is incorporated within the current-meter, it shall permit freedom in the vertical plane toensure correct alignment with the stream flow. Alignment in the horizontal plan
23、e may be affected by the correctchoice of suspension equipment (see ISO 3454).Current-meters of conventional construction are intended to operate in a horizontal or near-horizontal position.Current-meters designed to operate in other positions are not covered by this International Standard.6.2 Resis
24、tance to flowThe current-meter shall offer minimum resistance to the force of the flow.6.3 Limits of useThe rotating element of the current-meter shall be such that, when driven by the fluid, it rotates at an angularvelocity, which has a known relation to the velocity of the flow within the calibrat
25、ed velocity range stated by themanufacturer or rating laboratory. The suspension system shall be used as specified by the manufacturer.The current-meter shall respond rapidly and consistently to the changes in velocity. The manufacturer shallstate the expected response rates.The current-meter shall
26、be used only in liquids with properties similar to those in which it was calibrated. If theliquid properties are significantly different, the current-meter shall be recalibrated in a liquid with propertiessimilar to that in which the current-meter is to be used.Unless otherwise indicated, the curren
27、t-meter shall be capable of being used in waters containing suspendedsediment and in saline waters.The manufacturer shall state the maximum hydrostatic pressure to which the instrument may be subjected.BS ISO 2537:20073The manufacturer shall also furnish information on the temperature limits as appl
28、icable to the use of current-meter with oil-lubricated bearings.7 Characteristics of cup-type and propeller-type current-meter7.1 GeneralThere is no significant difference between the accuracies of the velocities registered by cup-type and propeller-type current-meters. Their characteristics can be
29、summarized as follows.7.2 Cup-type current-metera) This is a robust instrument requiring less maintenance; the rotor is replaceable in the field without affectingthe calibration.b) It operates at lower velocities than the propeller-type current-meter.c) The bearings are well protected from silty wat
30、er.d) A single rotor serves for the entire range of velocities.e) When held rigidly by rod suspension and pointing upstream at right angles to the measuring section, thecurrent-meter may over- and under-register oblique flows with error generally increasing as the velocity andangle of the flow incre
31、ases.f) Vertical components of velocity may cause rotation of a hollow cup-type current-meter. When there isconsiderable turbulence in a stream or where there are otherwise significant vertical components of velocity,hollow cup-type current-meters may over-register. Usually, the over-registration wi
32、ll be small unless largevertical components of velocity relative to the horizontal components are encountered.7.3 Propeller-type current-metera) This current-meter disturbs flow less than the cup-type current-meter.b) The propeller is less likely to become entangled with debris than the cup-type cur
33、rent-meter.c) Bearing friction is less than for vertical shaft rotors because any bending moment on the rotor is eliminated.d) The commonly used propeller-type current-meter may give correct registration of velocity in oblique flow forincidence angle less than with an error about . For precise measu
34、rement of flow in oblique orconvergent flow, a special type of component (self-compensating) propeller-type current-meter is usedwhich measures directly the axial component of velocity with an error less than for greater angle ofincidence up to .e) Propeller-type current-meters are not as susceptibl
35、e to vertical currents as cup-type current-meters andtherefore give better results when used for stream flow measurement in large rivers by moving boat method(ISO 4369) to minimize errors created by the pitching or vertical motion of the boat.8 Construction featuresSee Annex A.9 Calibration (rating)
36、9.1 GeneralIn order to determine the velocity of the stream from the revolution of the rotor of the conventional current-meter,a relation between the angular velocity of the rotor and the velocity of the water that spins the rotor has to beestablished experimentally. The relation so established expe
37、rimentally is known as calibration (rating) of the51%1%45BS ISO 2537:20074current-meter. The results of the calibration are provided in the form of a calibration table. In addition, acalibration curve with calibration equation(s) may be provided.The calibration of the current-meter shall normally be
38、 valid only for that range of velocities for which it has beenmanufactured and calibrated, and for use with a similar liquid to that which was used in its calibration.Extrapolation is permissible to higher velocities provided that sufficient calibration data exist for current-metersof a similar type
39、 at these higher velocities and that a greater uncertainty is accepted.Attention shall be paid to possible variation in the calibration due to liquid density and viscosity.9.2 Conformity of calibrationCalibration of new current-meter and recalibration of old current-meter in use shall be carried out
40、 at therecognized rating laboratory in accordance with the ISO 3455.9.3 Minimum speed of responseThe minimum speed of response (also called the threshold, or stall velocity) of a rotating-element current-meteris defined as the minimum speed at which the rotor of the current-meter attains continuous
41、and uniform angularmotion during calibration. This speed shall be determined in the rating laboratories. The lower the speed ofresponse of a current-meter, the lower the speed of flow that is measurable with confidence. However, theuncertainties of measurement at the minimum speed of response are hi
42、gh. It is therefore desirable that thecurrent-meter shall be used in the field for stream velocities greater than twice its minimum speed of response.9.4 Calibration tableFor the new current-meter, the manufacturer shall supply the calibration table based on the calibration testsconducted at the rat
43、ing laboratory. The calibration table shall be in the form suitable to the gauging technique inuse. It shall also specify the calibration equation(s) and the following information:a) the name and address of the rating laboratory;b) the date of calibration;c) the calibration job number;d) the make an
44、d type of current-meter;e) the serial number of the current-meter and each rotor;f) spin time of cup-type current-meter;g) type of suspension of current-meter on carriage (cable or rod suspension);h) the details of sinker weight if used during calibration;i) the position of the current-meter in the
45、cross-section of the tank;j) a statement indicating the minimum speed of response;k) the limits of calibration;l) any remarks regarding modifications made to the current-meter;m) the water temperature during calibration;n) the viscosity of the bearing oil;o) standard deviation and percentage deviati
46、on indicating accuracy of calibration equation(s);p) the signature of a responsible member of the staff at the rating laboratory.BS ISO 2537:200759.5 Types of calibration9.5.1 GeneralThe current-meters are calibrated individually or a group (standard) calibration is established from a group ofcurren
47、t-meters of uniform manufacture.9.5.2 Individual calibrationIn the case of individual calibration, the relationship of velocity and rate of rotor revolutions is established for aparticular current-meter. Individual calibration is necessary when a very high standard in manufacture is notguaranteed.9.
48、5.3 Group (standard) calibrationGroup calibration shall be based on the calibration of a group of current-meters of uniform manufacture. Thesample of current-meters calibrated shall be adequate in number and shall comprise, if possible, both newcurrent-meters and well-maintained used current-meters.
49、 The manufacturer shall make available a descriptionof the original calibration and of the current-meters used in the calibration. In addition, they shall check thevalidity of the standard calibration on a sample comprising at least of newly manufactured meters selectedat random, and again shall give similar details of the check calibration. The cost saving in adopting a groupcalibration is significant but the confidence levels are lower than for an individual calibration. Strict control ofmanufactures tolerances is an essent
