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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 interestto the public, particularly disadvantaged communities and those engaged in the pursuit ofeducation and knowledge, the attached public safety standard is made available to promote thetimely dissemination of this information in an accurate manner to the public.

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I S 39 : 994

Indian Standard

SURFACE FLOATS -FUNCTIONALREQUIREMENTS

irst Revision

UDC 5325731

Q BI S 1994

BUREAU OF INDIAN STANDARDS

MANAK BHAVAN 9 BAHADUR SHAH ZAFAR MARG

NE W DELHI 110002

une Price Gr oup 2

( Reaffirmed 2004 )

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Fluid Flow Measurement Sectional Committee, RVD 1

FOREWORD

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

While current meters should be used as a rule for the measurement of velocity of flow in openchannels, in certain circumstances it may not be possible or advisable to use current meters. Thesemay be:

a) velocities of flow being beyond the calibrated range of the current meters.

b) the flow being such that there is the danger of losing the current meter, and

c) there being lack of facilities for the use of current meter.

In the above circumstances it may be suitable to use surface floats. However, while using surfacefloats the following disadvantages should be kept in mind:

a) Evolving and applying a non-constant coefficient for obtaining the correct mean velocity ina reach; and

b) Values obtained by surface floats are affected by longitudinal and cross winds.

This standard was first published in 1966. This revision has been prepared to incorporate thelatest practices in this field, mainly in respect of functional requirements.

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SURFACE

IS 3911: 1994

I ndi an St andard

FLOATS- FUNCTIONALREQUIREMENTS

i r st Revi si on1 SCOPE

This standard specifies the functional requirements, performance tests and materials to be usedfor surface floats.

2 REFERENCES

The following Indian Standards are necessaryadjuncts to this standard:

IS No.

1191 : 1971

Title

Glossary of terms and symbolsused in connection with themeasurement of liquid flow witha free surface first r evision 1

1192 : 1981 Velocity area methods formeasurement of flow of water inopen channels first revision

3 TERMINOLOGY

For the purpose of this standard, the definitionsgiven in IS 1191 : 1971 shall apply.

4 FUNCTIONAL REQUIREMENTS

4.1 The float shall be sufficiently heavy or weight-ed so that its greater part would be submergedin water to reduce interference due to wind. Atthe same time the float should be light enough toattain the velocity of the current within a shortdistance after being introduced into the river andit shall be sufficiently stable.

4.2 The paint on the float shall be such, that it isconspicuously identifiable from a distance withalternate bands of paint which are durable in orunder water ( black and white or red and white).

4.3 If a flag is used with the float, it shall be ofa permanent color, conspicuously identifiable,and provision shall be made to prevent it fromsliding down.

5 TESTS

5 1 The test given in 5.1.1 shall be made beforethe floats are used in the field. The tests shall bemade on three floats for every 24 of identicalshape, materials and dimensions.

5.1.1 The surface velocity in a canal as obtainedby a standard cup type current meter placed asnear the surface as possible (without any of itsrotar components being exposed ) and the surface

1

velocity as obtained by the float when windinterference is negligible shall not vary by morethan 5 percent.

5.2 In the selected reach, measurements shall bemade at as near a stage as possible by currentmeter, preferably by the integration methodaccording to IS 1192 : 1981, and the coefficientfor obtaining the mean velocity in the verticalworked out for the float. In the absence of a

more reliable figure a reduction coefficient of85 may be adopted.

NOTE -The reduction coefficients generally vary from079 to 092. This reduction coefficient is not a con-stant even for a particular channel, since it varieswith depth, slope, and relative roughness of the chan-nel boundary. It may also be obtained from VonKarmans logarithmic velocity distribution law.

MATERIALS

6 1 Depending upon the nature and conditions,

surface floats may be mado of almost any distin-guishable article that floats, such as woodendesks, bottles, etc. Floating ice cakes or adistinguishable piece of drift may also be used.Wooden floats are meant to be used in riversunder moderate velocity conditions wilh lessturbulence, whilst metallic floats are meant forlarge turbulent rivers. Bottle floats weighted withcement mortar may also be used in conditions ofrelatively smooth flow.

Typical examples for materials to be used fordifferent components are given in 6.2 to 6.4,however these do not preclude the use ofalternative materials having characteristicsequivalent to or superior to those specified.Typical illustration of wooden and metallic floatsare given in Annex A.

6.2 Base and Stem

Sal wood of the best quality or any other heaviertype of wood available locally shall be used. Itshall be well seasoned. Specific gravity shall notbe less than 05.

6.3 Metallic Sheet

Gl sheet, stainless steel sheet or any other suitablematerial.

6.4 Paint

Paint shall be colour fast, durable and as specifiedby the purchaser.

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IS 3911 : 1994

ANNEX AC l a u se 6 1 )

TYPICAL ILLUSTRATION OF SURFACE FLOATS

A-l WOODEN FLOATS

A-l.1 General Descrip:ionGenerally the wooden floats consist of (a) circulardisc, (b) cylindrical stem and hooks, and c) flag.The circular disc is either streamlined at theedges (Type A, Fig. 1 ) or cylindrical in shape( Type B, Fig. 1 ).

A-l.2 Type A ( Streamlined ) Wooden Float

A-1.2.1 ircular Disc

The circular disc ( streamlined at the edges) shall

be carved out of one single solid wooden pieceof suitable thickness so as to correspond to therequired dimensions as shown in Fig. 1 withoverall dimensions of approximately 150 and40 mm. At the top centre of the streamlined disca square shaped recess approximately 40 x 40 mmand 25 mm deep shall be made centrally to engagethe lower end of the vertical rod or stem, whichshould fit squarely in this recess.

A-l .2.2 Stem

The sfem or the rod shall be circular in the upper

portion and approximately 20 mm diameter and200 mm long. The lower end of the stem shall becut square to the size of the recess so as to fitsquarely in the same. The base of the stem isthus approximately square shaped 40 x 40mmand 25 mm deep and should fit tightly in therecess. To hold it securely, two brass screwsshould be screwed from the bottom of the disc tothe square hole of the stem. On the top of thestem a hook shall be screwed as shown in Fig. 1,Type A for lowering and lifting the float.

A-l .2.3 Flag

The upper end of the stem shall be provided witha rectangular flag about 100 x50 mm size toensure visibility of the float. It should be closedat one end so as to tightly fit in the top portionof stem. A screw should be provided in the stemto hold the flag in position and prevent it fromsliding down.

A-1.2.4 Painting

For improved visibility of the float, the stemshould be painted in alternate bands, each 20 mmwide, of black and white enamel paint and theentire surface of the disc should be painted inwhite paint.

A-l .2.5 Sizes

Surface floats of wooden Type A may be made ofvarious sizes depending upon the width of theriver, the size of the central disc varying from150 mm to 300 mm and that of the stem from20 mm to 40 mm.

A-l.3 Type B Cylindrical) Wooden Floats

The details of Type B floats are identical to thatof Type A tloats except that the circular disc isnot streamlined but it is vertical at the edges( see Fig. 1, Type B ).

A-2 SURFACE FLOAT TYPE C METALLIC

A-2.1 Details of Type C Surface Floats ( Metallic )

The surface float shall be barrel shaped. It shouldhave a diameter of approximately 300 mm at thecentre decreasing uniformly to about 200 mm atthe two ends which should be sealed so as to makethe drum water-tight. The length of the barrelshould be approximately 300 mm. The exposedsurface of the sealed ends should form a plainsurface and be normal to the axis of the barrel.The barrel may be made of GI sheet approxi-mately 063 mm thick. It shall be duly weightedfor stability while floating. On the top end ofthe float an iron book should be screwed forlowering and lifting as shown in Fig. 1, Type C.

A-2.1.1 Painting

The drum shall be painted in alternate band8 ofred and white enamel paint approximately 50 mmin width along the circumference of the barreland the exposed surface of the sealed ends .shallbe painted red.

2

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IS 3911 1994

4RGN HOOK

-STEM STEM

Type A Streamlined ) Type t3 Cylindrical ) Type C Metallic )

All dimensions in millimetres and approximate.

FIG. 1 DETAILS OF SURFACE FLOATS

3

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Bureau of Indian Standards

BIS is a statutory institution established under the Bur eau of I ndian Standards Act 1986 to promoteharmonious development o 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 grade

designations. 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.

This Indian Standard has been developed from Dot : No. RVD 1 ( 5 )

Amendments Issued Since Publication

Amend No. Date of Issue Text Affected

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