Disclosure to Promote the Right To Information

Whereas the Parliament of India has set out to provide a practical regime of right to information for citizens to secure access to information under the control of public authorities, in order to promote transparency and accountability in the working of every public authority, and whereas the attached publication of the Bureau of Indian Standards is of particular interest to the public, particularly disadvantaged communities and those engaged in the pursuit of education and knowledge, the attached public safety standard is made available to promote the timely dissemination of this information in an accurate manner to the public.

इंटरनेट मानक

“!ान $ एक न' भारत का +नम-ण”Satyanarayan Gangaram Pitroda

“Invent a New India Using Knowledge”

“प0रा1 को छोड न' 5 तरफ”Jawaharlal Nehru

“Step Out From the Old to the New”

“जान1 का अ+धकार, जी1 का अ+धकार”Mazdoor Kisan Shakti Sangathan

“The Right to Information, The Right to Live”

“!ान एक ऐसा खजाना > जो कभी च0राया नहB जा सकता है”Bhartṛhari—Nītiśatakam

“Knowledge is such a treasure which cannot be stolen”

“Invent a New India Using Knowledge”

है”ह”ह

IS 3910 (1992): Requirements for rotating element currentmeters (cup type) for water flow measurement [WRD 1:Hydrometry]

( Reaffirmed 2003 )

mclnr '"I FiGf5

~~T rfTf~lfT ~ ~~ !:fGfT~ +rTtfrf - ~urT

~~T~c Cf}~c +rTc~

( qQC'fT t.! ;:rX-TeJUJ )

Indian Stadnard

REQUIREMENTS FOR WATER FLOWMEASUREMENT IN OPEN CHANNELS­

ROTATING ELEMENT CURRENT METERS

( First Revision)

UOC 681°121'8: 532"57

<0 HIS 1992

BUREAU OF INDIAN STANDARDSMANAK BHAVAN•. 9 BAHAOUR SHAH ZAFAR MARG

NEW DELHI 110002

July 1992 Price Grollp 4

Fluid Flow Measurement Sectional Committee, RVD I

FOREWORD

This Indian Standard ( First Revision) was adopted by the Bureau of Indian Standards, after thedraft finalized by the Fluid FI,)w Measurement Sectional Committee had been approved by theRiver Valley Division Council.

In the field of management of water resources, precise measurement of flow is an essential pre­requisite. Of late, this measurement has assumed new dimension in the role of flow distribution/sharing between adjacent states or neighbouring countries.

For undertaking such measurement of flow, current meters are generally deployed. In India,current meters with cup type rotating element were mostly used drawn from various makes andmodels. To provide guidance to the user as well as to the manufacturer in respect of this type ofcurrent meters, this Indian Standard was first published in 1966.

Gradually current meters with other types of rotating elements came into being in Indian use andrange of produce. Therefore, the need to update the existing standard, covering other commontypes of rotating elements a Iso was felt and therefore this revision has been formulated. Thisstandard is based on ISO 2537 : 1985 and covers the requirement based on indigenous manu­facturing practice, which is in developing stage. As and when improvement is made in undigenousmanufacturing this standard will be updated.

For the purpose of deciding whether a particular requirement of this standard is complied with. thefinal value. observed or calculated, expressing the result of a test or analysis, shall be rounded off inaccordance with IS 2 : 1960 'Rules for rounding off numerical values (revised)'. The number ofsignificant places retained in the rounded off value should be the same as that of the specified valuein this standard.

IS 3910 : 1992

Indian Standard

REQUIREMENTS FOR WATERFLOWMEASUREMENT IN OPEN CHANNELS ­ROTATING ELEMENT CURRENT METERS

( First Revision)

1 SCOPE NOTE - The axis of the rotating element may be at right anglesor it may be parallel to the direction of flow.

This standard specifies the operational requirements,constructional guidelines and maintenance of rotatingelement current meter for the measurement of flowvelocities in the open channel.

2 REFERENCES

The Indian Standards listed below are necessaryadjuncts to this standard:

IS No. Title

1191: 1971 Glossary of terms and symbols usedin connectionwith the measurementof liquid flow with a free surface(first revision)

1192: 1981 Velocity area method formeasurement of flow of water inopen channels

3918 : 1966 Code of practice for use of currentmeter (cup type) for water flowmeasurement

3 TERMINOLOGY

For the purpose of this standard, the definitions givenin IS 1191 : 1971 shall apply.

4 PRINCIPLE OF OPERATION

4.1 Proportionality

The rotating element of a current meter is driven bythe fluid at an angular velocity which is proportionalto the local velocity of the fluid at the point of immer­sion when that velocity exceeds a critical value.

The velocity of fluid is determined by counting thenumber of revolutions of the rotor during a specifiedtime interval or by observing the time required bythe rotor to tum a given number of revolutions andconsulting the meter calibration table or rating equa­tion. The velocity of fluid movement may be deter­mined from the sensing of signals emitted (such aselectrical pulses) through the rotation of the rotor.The velocity may be determined from a direct read­ing of the speed of rotation of the rotating element bymeans of equipment designed for this purpose.

1

5 TYPES OF CURRENT METER

5.1 They have been classified according to the type ofrotating element used.

5.2 Cup Type Current Meter

A rotor (bucket wheel) generally formed out ofconical cup and curved vanes attached at equalintervals around the perimeter of the hub which willrotate when placed in the fluid flow. It is usual tomount the rotor with the axis vertical. Typical con­structional features are given in Annex A.

5.3 Propeller Type Current Meters

Assembly consistingof2 or more helical screw bladesformed around a hub or a number of flat platesattached at equal intervals around the perimeterthrough twisted spoke that will rotate around a hori­zontal axis when placed with fluid flow.

5.4 Savonious Type Current Meters

The rotor is an assembly of a number of curved vanes(of the formation of a turbine rotor) attached at equalintervals formed around a vertical axis.

NOTE - Miniature current meters generally are of cup type andpropeller type as mentioned above in 5.2 and 5.3.

6 OPERATIONAL REQUIREMENTS

6.1 Positioning

6.1.1 The longitudinal axis of the free suspensiontype current meter shall take-up stable position paral­lel to the direction of flow without excessive twistingand turning under the influence of local eddy currents.

6.1.2 It shaHdynamically balance in the stream withits longitudinal axis parallel to the water's surface andshall have sufficient freedom of movement in theverticilIplane to ensure the assumption ofthe position.

NOTE - Generally for miniature current meters, eoaditionsunder 6.1.2 are difficult to practise.

6.2 Relationship or Rotor Movement and StreamVelocity

The rotating element of the current meter shall be such

IS 3'10 : 1992

that when driven by the fluid, it rotates at an angularvelocity which has a known relation to the velocity ofthe flow within the calibrated velocity range stated bythe rating laboratory.

6.3 Umits of Use

6.3.1 VariousLiquids

The current meter shall be used only in liquid withproperties similar to those in which the meter wascalibrated. If the liquid properties are significantlydifferent, the meter shall be recalibrated in a liquidwith properties similar to that in which the meter is tobeused.

Unless otherwise indicated, the current meter shall becapable of being used in waters containing suspendedsediment and in saline waters.

6.3.2 Cup Type Current Meters

Vertical components of velocity may cause rotationof a hollow-cup type current meter. When there isconsiderable turbulence in a stream or where thereJlC otherwise significant vertical components of ve­Iocity, hollow-cup-type meters may over-register.Usually the over-registration will be small unless largevertical components of velocity relative to the hori­zontal components are encountered.

6.3.3 Savonius Type Current Meters

Under combined action of flow and wave, rotors withblades having higher curvature over-reads, usuallythe-over-registration will be small unless waves withhigh energy content are encountered.

7 FUNCTIONAL REQUIREMENTS

7.1 The meter shall respond rapidly and consistentlyto changes in velocity: the manufacturer shall state theexpected response rates.

7.2 Spare parts shall be fully interchangeable, so as tohave uniform functional characteristics to cause lessthan 2% divergence from the normal rating curve andto facilitate easy replacement of worn of damagedelements.

7.3 The current metershall offer minimum resistanceto flow.

7.4 The constructionshall be simple to admit all partsbeing taken but easily cleaned and refitted and alsosufficiently rugged to maintain calibration under con­ditions normally encountered in the final.

7.5 The current meter shall be provided with facili­ties for dynamic balancing (see 6.1.1 and 6.1.2) in theform of a counterweight adjustment.

7.6 It shall be provided with facilities for mounting ona cable suspension as well as on a hanger bar or awading rod.

7.7 It shall be provided with facilities for attaching toit sounding (fish) weight.

2

8 CONSTRUCTION FEATURES OF CURRENTMETERS

8.1. General

8.1.1 Cup Type

A cup type current meter shall generally consistof:

a) a rotor revolving about a vertical shaft;b) a hub assembly;c) bearings;d) a main frame or yoke;e) a chamber containing the signal generation

mechanism;t) tail fin; andg) a means of attaching the instrument to the

suspension equipment.

8.1.2 Propeller Type (Including Savonius TypeRotors)

a) a rotor that is either a propeller revolvingabout a fixed axis or a revolving set composedof the propeller and axis;

b) two bearings;c) a device giving a signal indicating movement

of the rotor;d) a means of attaching the instrument to the

suspension equipment;e) a streamlined body (not applicable to savonius

type);1) tail fin; andg) a means of attaching the instrument to the

suspension equipment.

NOTE -Ameans of providing directional control to the meter inthe current meter in the current will generally be provided. Thismay be either a pan of the suspension equipment or an integralpan of the meter.

8.2 Rotor

8.2.1 Cup Type

The rotor will generally be constructed of six hollowconical cups, fixed in the same horizontal plane atequally spaced intervals (equal angles) to a framemounted on a vertical shaft. The assembly shall beretained in the yoke by means of the upper shaftbearing and a lower pointed bearing consisting of acentral pivot and a bearing cup.

8.2.2 Propeller Type

The current meter may be provided with a single pro­peller type rotor or with several interchangeable oneseach having a different pitch and/or diameter. Eachpropeller shall consist of multiple vanes or helicalscrew blades that generally rotate about a horizontalaxis. The propellers should be made from materialwhich will not allow them to be easily distorted.

8.2.3 Savonius Type

The rotor consists ofan assembly ofabout six to eightturbine type curved vanes (or straight blades) built

around a vertical axis.Therotors shallbemade fromamaterial whichwillnotallowittobeeasilydistorted orcorroded evenin salinewaters.

8.3Bearings

The resisting torqueof the bearings shallbe as smallas possible and shall be constant duringuse. Bear­ingsshallbe lubricated as statedbythemanufacturer.Provisionshallbe made toensure thatsiltandwaterdonot enter the bearings except as required for water­lubricated bearings.

8.4 MeaDS of Registering Rotor Revolutions

8.4.1 Signals

The revolutions of the rotor shall, by means of me­chanical contacts or by means of optical or otherdevices, generate a clear and positive signals at allvelocities withintheeffective range of the meter. It ispermissible to provide a means of multiplying ordividing the signal pulse rate to suit counting equip­ment with a limited range of operation. If electricalconnections are used in the equipment, theyshouldbe appropriately protected against short-circuitingand appropriately waterproofed.»

8.4.2 Registration Device

Arrangements shallbeprovided to indicate byaudiblenote or visual display or resistrati~n on a suitsblemedia (printer/magnetic tape) number of revolutionsor revofution rate or velocity of flow.

8.5 Dlrec:tlonal Control

Directional control shallbe provided by means of tailfinsor otherdevices to enable the meterto alignitaelfwith the stream flow and to remain stable in thatposition throu,hout the full range of calibrated ve­locitiea. The directional control may be either pro­vided by the auspension syatem or provided by tailfins or other devices that are attached to or are anintegral part of the meter.

8.6 Response Behaviour

The manufacturer shatlspecify the minimum speedof response which is defined II the lowest lpeed atwhich the current meter will initiate and maintainsteady motion. The manufacturer Ihall also lta~ theconsistency of response together with tolerances tochanges in velocity.

8.7 Hydrostatic: Preslun

Themanufacturerahallstate themaximumhydrostaticpreasure to which the instrument maybe subjected.

••• Conduc:tlvlty of Water

The manufacturer ahall stipulate the maximum con­ductivity of water in whichthe metercan be uled.

, CONSTRUCTIONAL MATERIALS

'.1 The meter.haJJ be constructed of corrolion-resil­tant materiall throupout or of material. that are

3

183'10 : 1m

effectively protected against conditions encounteredin natural medium wheremeasurement are proposedto be taken. The use of the meter in silty. or salinewatersmayreduce the life of the meter.

'.2 The rotors preferably be constructed of suchmaterial whose specificgravity shouldbe as closetothatof the fluid whose flowvelocityis intended to bemeasured (toenable theenergytransference fromthefluid to the rotorwith leastdelay).

10 CALIBRATION (OR RATING)

10.1 General

10.1.1 Thecalibration of currentmete1'l involves ex­perimental determination of the relationship betweenvelocity of flow and rate of revolution of rotor(usually expressed as revolutions per second) aDdprovided as a calibration curveor calibration (rating)relationship.

10.1.2 Thecalibration (rating) of a currentmetcrwiJInormall>.> be validonlyfor that range of vclocities forwhich It has been manufactured and calibrated andforuse witha similarliquid to thatwhichwas uaed initacalibration. Extrapolation is permissible to highervelocities provided that sufficient calibration dataexist for metera of a similar type at these bighervelocities and that a greater unce.rtainty is accepted.Anr. current meter new or old requires periodicalcalibration.

10.2 Conronnlty

10.Z.1 AU calibration shall be carried out in accor­dance withrelevant IndianStandard on calibration.

103 Type or CaUbl'8tfon (RatlnS>

A current metershallhaveindividual calibration (1'It­ing)where the relation of velocity to response isbaaedona 1'Itingofthatparticular meter. Eachmetershallbecalibrated to produce individual1'ltinp.

lOA Equation

1004.1 Fromthecalibration data,manufacturer or 1'It­ing laboratories shall supplya 1'Iting table for con­venience for ule in the-field and Iball allo lpecifytheequation of the ratingcurvederived fromthedataand tbe minimum speeCi necessary to produce a rep­resentative selllingof the fluid motion. Thi. speed isthe loweltspeedat whichthecurrentmeterwilliniti­ate and maintain steadymotion. The actuailimita ofthe 1'ItinS shall be stated.

10,5 Rec:aUbratlon

Each'mete1'llhall be fCcalibrated (re-rated) wheneverita~rformance is doubtful. Recalibration on routinebailS "ballbe carried out at yearly intervals or after300 h of Ule, whichever il the shorter.

10.6 Type of Su.peDllon

The performance of a meter may be affected by itamode of ,ulpension and the .oundinl welSht uletl.

IS 3910 : 1992

For individual ratings, it is advisable that the calibra­tion be carried out using the means of suspension andthe sounding weight intended to be used during ameasurement. The distance from the bottom of thesounding weight to the meter, for the calibration con­figuration, shal1 be specified by the rating laboratoryor manufacturer.

It is possible to derive by experimental coefficientswhich can be applied to gauging data to correct for theeffects (ifany) ofdifferent sounding weight and differ­ent means, size and shape of suspension.

Such coefficients are applicable only to the specificcombination for which data have been experimentallyobtained.

attention should be paid to equipment which has beenin storage for a long period of time.

12.1.2 Inspection

For inspection, it shal1 be possible to dismantle andreassemble the current meter assembly in the field,without specialized workshop facilities and by per­sonnel without specialist training. Such tools as arerequired to carry out this operation shall be suppliedas standard accessories.

On-site removal and replacement of the rotor on itsshaft shal1 be possible with minimum disturbance tothe bearing assembly, and preferably without re­moving the bearing assembly from the instrument.

11 TOLERANCE

Attention should be paid to possible variations in therating due to changes in liquid density or viscosity.

Maximum permissible tolerances in the velocitymeasurement with new current meters shal1 be asfollows:

The scatterofthe points about the rating curve for eachvelocity class shall be approximately normal so thatthe errors will be compensating.

10.8 Operating Conditions

12;1.3 Signal Test

Before use, the meter shall be tested for correct op­eration. By turning the rotor slowly, the number of ro­tations shall be compared with the number of pulsesreceived. For current meters with a generator it shallbe checked that output varies with rotor speed.

12.2 Spin Test

12.2.1 Current Meters with Ball Bearings or with aPivot Bearing

If no, special instruments are provided by the manu­facturer, the test described below may be carried outafter the meter has been lubricated and assembledready for use. For a new cup type current meter thespin time shal1 be a minimum of 75 seconds.

Place the meter in the normal operatingift~s,withthe rotor protected from air currents. Spin the rotor byhand. As it nears its stopping point, observe itsmotion carefully to see whether the stop is abrupt orgradual. If the stop is abrupt, the cause shall be foundand corrected before the meter is used. A pre-specifiedminimum spin time should be observed for a meter ingood condition.

12.2.2 Current Meters Without Ball Bearings

The design of meters without ball bearings preventsthe meter from working properly in air. The manufac­turer shall recommend a simple check procedure toensure proper operation.

12.3 Cleaning and Lubrication

After each discharge measurement, or more fre­quently for extended measurements, all bearing sur­faces (including any pivot) shall be thoroughlycleaned and, where appropriate, lubricated. Ifbearingsrequire lubrication to be applied for. use of thecurrent meter in the field, the lubricant used shaJlhave the same viscosity characteristics as the lubricantused at the time ofcalibration; this lubricant shall havethe same or equivalent specifications as that recom­mended by the manufacturer.

12.4 The history sheet of the current meter shall bemaintained in the proforma given below:

± 1 percent± 0"5 percent

Velocity around 0·3 mlsVelocity greater than 0"3 mls

10.7 Uncertainty

As a check for goodness of fit of the rating curve, themanufacturer or rating laboratories shall state the stan­dard error of the data for the lower and upper limits ofcalibration, and for at least two intermediate points.The standard errorsha II be stated as a percentage ofthevelocity class and shall be related to the 95% confi­dence limits.

12.1 General

Under conditions of normal operation, the user shouldfol1ow recommended check procedures before andafter each discharge measurement, as laid down inthe manufacturer's operation and servicing manuaI:Inthe event of more comprehensive instructions notbeing provided the procedures specified in 12.1.1to 12.1.3 should be fol1owed.

12 MAINTENANCE

12.1.1 Examination

The meter shall be examined before and after eachdischarge measurement for worn or damaged bear­..proPer shaft alignment, correct operation ofcontactpoints and deformation ofthe yoke or cup-wheel in thecase ofcup type meters or as rotor assembty in case ofsavonius type meters. All moving parts should becarefully inspected and checks performed to ensureoperation iJiaccordance with specifications. Particular

4

IS 3910 : 1991

HISTORY SHEET AND CALIBRATION DATA

Name of manufacturer .

Date of manufacture .

Serial number '" .

Source of manufacture : .

SlNo.

Date of Startand Stoppage ofUse and Re-use

Date of Place ofCalibra- Calibra-

tion tion

Resultof

Test

Equa­tions

Remarks GivingCondition of

Meter, Repair IfAny,Reason for Stoppage,Use and Re-use, etc

(1) (2) (3) (4) (5) (6) (7)

11.5 Transport and Storage

A suitable protective instrument case shall be pro­vided by the manufacturer in which the current metermay be stored when not in use. Suitable storageshall also be provided in the case for the toolsrequired for instrument maintenance.

Provision shall be made for the storage and transpor­tation of the current meter and its components insuch a manner that the bearings and other ~rts ofthe meter can be protected from wear and fromdamage resulting from vibration or shock.

13 OPERATIONALAND SERVICING MANUAL

A comprehensive operational and servicing manualshould be supplied with each instrument, It shouldpresent full instructions, illustrated where necessaryand include appropriate circuit diagrams with compo­nentvalues. The manual should containsectionson thefollowing:

a) normal maintenance, servicingon site, check­ing procedure including recommended screwtorques;

b) spares list, including a list of contributingmanufactuIeIS;

s

c) lubricant and sealant details, including lubri­cant and compound specifications;

d) preparations necessary for transport and stor­age;

e) details ofpowersource, ifany and appropriaterates and duration of recharge;

f) details of electrical and (or) electroniccircuitry (including component values) withcircuit diagrams and test procedures.

14 ACCESSORIES AND SPARES

14.1 Essential site spares and maintenance spares forat least two years, as well as accessories are to be pro­vided as per recommendation of the manufacturer.

14.1 Appropriate fish weights shall be provided tocover the velocity ranges for which it is expected to beused.

15 MARKING

Current meter shall be engraved with source ofmanufacture, trade mark, year of manufacture and theserial number for each delivery.

IS 3'10 : 1992

ANNEXA(Clause S.2)

TYPICAL DETAILS OF A STANDARD SIZE CUP TYPE CURRENT METERWITH FRONT HOOP

A-OGENERAL

A-O.l Details of various parts and theirarrangementof the such type of current meter are shown inFig. I, 2, 3, 4. Thecounter is of electronic type. Thesignal generating system hasmagnet and read switchassemtily.

A-O.2 Material to be Vied

A-O.2.1 'The meter shallbeconstructed of non-corro­sivematerials andfor:

a) Yoke (Main Frame) - Manganese bronzecalting.

b) Bucket Wheel Cups - Brailiheet.c) Pivot- RUlt proof, hardened, and tempered

closegrained tccl steelwith minimum Vicatadiamond"'pyramid hardness No. 640 (Rock­well C-S7).

d) Pivot Bearing - Rust proof, hardened andtempered steelwith minimumVieats diamondpyramid hardness No.720(Rockwell C-61).

e) Contact Chamber - Brass sheet.t) Contact Point - Platinum.g) Contact Spring

NOTS - ThoCODIwctloa ofmlalature (PIIJDY), whichIawith·out froathoop1IIImilarexcept for:

I) ThoI!zeofthebucketwheella, emIDitead of 12'7emladIII otherpartalre lultablydlmlnlahed.

b) CoatactdllmtJerbell11lD latell'll partof theyoke.

c) Tllere belDlDOprovlaloa formouatln, on I cablelupea­.Ioa_It IaIlwly' mounted oa I wldla, rodor baa,er bar.

d) ThereIre DOtill f1D1.

e) Somedm. It may Dot bavebucketwheelnlallll aut laduaderthoae coDdltloDillOft metallic p1ua ahould bepro­vided to replace thepivotwhile the meterII belDltn..­ported or .tered.

1, luoketoWhMl oup I, CIp ~r oontaat 11. Iuoket~1I 22. Tilltin2. Yolce ohlmber locknut 23. Tilltin NOUrln; pinI. IplncIle 1O, Contaat 'Pring 1•• Pivot lock nut 24. Tilltin ooum.r-welght4, Upper epInc1le blaring l'. Inlulatecl oontaat bIr 17. Pivot hoIcter 21. Contact to MrthI. PIYGt '2, Oontaat breaker 'I, Bucketorlilln; level 21. Platinum 00lUCtI10 ""'Ingoup allmpln; ring ,.. EIrth wmlnli 27. Vulc.n1t8 mount7, Oontaot cNmMr 11. Terlmlnli knob 20, e.ntrll adaptor pivot 21. Inlulatltd oontaot-bIrI. ....lngwllMr 14, Iplndll ooIw 11• Adaptor allmP l.aurln; lorew

Plo. 1CuuBNT MlTIIll (CuP 1'YPB)

«5

j~'81-.. _. 137---------4

IS 3910 : 1992

Sl;:CTION XX

FINS (3.QFF)

X /

,J

r-E?--'-I -+II

x

FIN WITH SLOT (1.QFF)

All dimensions in millimetres.

FIG. 2 DETAILS OF FIN

7

IS 3910 : 1992

SUCKJT

BUCKET WHEEl ASSEMBLY

--'H-1-8

SECTION XX

All dimensiollS in millimetres.

FIG•. 3 BUCKET WHEEL FOR CuRRENT METER

. 25'4 -I 2·97 MAX

12'7 ----j 19-5--1

E-3-i=SJ,~0,""

~4A PIVOT

4 B PIVOT CUP

All dimensions in millimetres.

FIG. 4 PIvOT AND PIvOT CuP

8

Standard Mark

The use of the Standard Mark IS governed by the provisions of the Bureau oj indianStandards Act, i986 and the Rules and Regulations made thereunder. The Standard Mark. onproducts covered by an Indian Standard conveys the assurance that they have been producedto comply with the requirements of that standard under a well defined system of inspection,tesnng and quality control which IS devised and supervised by BIS and operated by theproducer. Standard marked products are also continuously checked by HIS for conformityto that standard as a further safeguard. Details of conditions under which a licence for tbeuse of the Standard Mark may be granted [0 manufacturers or producers may be obtainedfrom the Bureau of Indian Standards,

Bureau of Indian Standards

BIS is a statutory institution established under the Bureau of Indian Standards Act, 1986 to promoteharmonious development of the activities of standardization. marking and quality certification of goodsand attending to connected matters in the country.

Copyright

BIS has the copyright of all its publications. No part of these publications may be reproduced Inany form without the prior permission in writing of BIS. This does not preclude the free use, in thecourse of implementing the standard, of necessary details. such as symbols and sizes, type or gradedesignations. Enquiries relating to copyright be addressed to the Director ( Publications ), BIS.

Revision of Indian Standards

Indian Standards are reviewed periodically and revised, when necessary and amendments, if any, areissued from time to time. Users of Indian Standards should ascertain that they are in possession ofthe latest amendments or edition. Comments on this Indian Standard may be lent to BIS giving thefollowing reference:

Doc: No. RVD 1 (47)

Amendments Issued Since Publication

Amend No.

Headquarters:

Date of Issue

BUREAU OF INDIAN STANDARDS

Text Affected

Manak Bhavan, 9 Bahadur Shah Zafar Marg, New Delhi 110002Telephones: 33101 31. 331 13 7'

Regional Offices:

Central: Manak Bhavan, 9 Bahadur Shah Zafar MargNEW DELHI 110002

Eastern: 1/14 C. I. T. Scheme VII M, V. I. P. Road, ManiktolaCALCUTTA 700054

Northern: SCO 445-446, Sector 35-C, CHANDIGARH 160036

Southern: C. I. T. Campus, IV Cross Road, MADRAS 600113

Western: Manakalaya, E9 MIDC, Marol, Andheri ( East)BOMBA Y 400093

Telegrams: Manaksanstha( Common to all Offices)

Telephone

{33 1 01 31331 1375

378662

S3 3843

23502 16

612 92 95

Branches: AHMADABAD. BANGALORE. BHOPAL. BHUBANESHWAR. COIMBATORE.FARIDABAD. GHAZIABAD. GUWAHATI. HYDERABAD. JAIPUR. KANPUR.LUCKNOW. PATNA. SRINAGAR. THIRUVANANTHAPURAM.

Printed at Printrade, New Delhi, India