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 6917 (1973): Glass lenses for automobile headlights(replaceable bulb type) [CHD 10: Glassware]

IS : 6917 - 1973

Indian Standard SPECIFICATION FOR GLASS LENSES

FOR AUTOMOBILE HEADLIGHTS ( REPLACEABLE BULB TYPE )

( First Reprint MAY 1982 )

UDC 681.42 : 629.113.066 : 628.971.85

© Copyright 1973

I N D I A N S T A N D A R D S I N S T I T U T I O N MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG

NEW DELHI 110002

Gr. 4 August 1973

AMENDMENT NO. 1 JULY 2007 TO

IS 6917 : 1973 SPECIFICATION FOR GLASS LENSES FOR AUTOMOBILE HEADLIGHTS

(REPLACEABLE BULB)

(Page 4, clause 3.1.1) — Substitute the following for the existing clause:

'3.1.1 Limit of Alkalinity — The glass of the lenses shall conform to Class HGB 3 of the glass when graded and tested according to the method prescribed in IS 2303 (Part 1/Sec 1) : 1994‡.'

(Page 4, footnote marked ‡) — Substitute the following for the existing:

'‡Grading glass for alkalinity Part 1 Hydrolytic resistance, Section I Hydrolytic resistance of glass grams at 89°C Method of test and classification ( first revision ).'

(Page 5, clause 4.1.1) — Substitute the following for the existing clause:

'4.1.1 BIS Certification Mark

The lenses may also be marked with the Standard Mark.

4.1.1.1 The use of the Standard Mark is governed by the provisions of Bureau of Indian Standards Act, 1986 and the Rules and Regulations made thereunder. The details of conditions under which the licence for the use of Standard Mark may be granted to manufacturers or producers may be obtained from the Bureau of Indian Standards.'

( CHD 10 )

Reprography Unit, BIS, New Delhi, India

IS : 6917 - 1973

Indian Standard SPECIFICATION FOR GLASS LENSES

FOR AUTOMOBILE HEADLIGHTS (REPLACEABLE BULB TYPE)

© Copyright 1973 INDIAN STANDARDS INSTITUTION

This publication is protected under the Indian Copyright Act ( XIV of 1957 ) and reproduction in whole or in part by any means except with written permission of the publisher shall be deemed to be an infringement of copyright under the said Act.

Chairman SHRI K. D. SHARMA

Members DR S. KUMAR ( Alternate to

Shri K. D. Sharma ) SHRI J. P. AGARWAL

SHRI V. P. SHARMA ( Alternate ) SHRI C. G. AMIN ASSISTANT DIRECTOR ( CARRIAGE ),

RDSO, LUCKNOW SHRI L. S. BHARAJ SHRI V. R. BHIDE SHRI D. S. CHABHAL

DR S. P. SINGH DHAKAREY

Representing Central Glass and Ceramic Research Institute

( CSIR ), Calcutta

J. G. Glass Industries Pvt Ltd, Poona

Alembic Glass Industries Ltd, Baroda Ministry of Railways

Ministry of Defence ( R & D ) Kangan Pvt Ltd, Bombay Directorate General of Technical Development, New

Delhi Ministry of Defence ( DGI )

SHRI A. K. MUKHERJEE ( Alternate ) DR B. B. GAITONDE Haffkine Institute, Bombay

SHRI Y. S. NIMBRAR ( Alternate ) SHRI S. P. GUPTA

SHRI C. V. CHALAM ( Alternate ) DR M. M. KOHLI DR V. P. M A H E S W A R Y

SHRI P. C. MIDHA ( Alternate ) SHRI V. S. PADMANABHAN

SHRI S. S. CHOPRA ( Alternate ) SHRI K. H. PARIKH DR S. L. SASTRY D R J . M . SEHGAL SHRI C. N. SHAH SHRI C. K. SOMANY

SHRI B. D. KOTHARI ( Alternate ) SHRI J. A. TAKTAWALA

SHRI A. K. ROY ( Alternate )

Hindusthan-Pilkington Glass Works Ltd, Calcutta

Glass Carboys and Pressedwares Ltd, Bombay Development Commissioner ( Small Scale Industries ),

New Delhi

Export Inspection Council of India, Calcutta

Government of Uttar Pradesh Hindustan Antibiotics Ltd, Poona Indian Drugs & Pharmaceuticals Ltd, New Delhi Indian Chemical Manufacturers' Association, Calcutta Hindusthan National Glass Mfg Co Ltd, Calcutta

Shree Vallabh Glass Works Ltd, Bombay

( Continued on page 2 )

Glassware Sectional Committee, CDC 10

IS : 6917 - 1973

( Continued from page 1 )

Members SHRI L. VASUDEVA RAO SHRI J . K. W A D

SHRI P. R. RAO ( Alternate ) SHRI D. DAS GUPTA,

Director ( Chem )

Representing The Indo-Asahi Glass Co Ltd, Calcutta Borosil Glass Works Ltd, Bombay

Director General, ISI ( Ex-officio Member )

Secretary SHRI G. P. SARASWAT

Assistant Director ( Chem), ISI

Protective Glasses Subcommittee, CDC 10: 13 Convener

DR S. N. PRASAD

Members

Central Glass and Ceramic Research Institute ( CSIR ), Calcutta

DR K. P. SRIVASTAVA ( Alternate to Dr S. N. Prasad )

SHRI D. N. AGARWAL Hindusthan Safety Glass Works Pvt Ltd, Calcutta SHRI P. N . AGARWAL ( Alternate )

D R S. R. DAS DR D. SEN ( Alternate )

SHRI D. M. DHAR SHRI SUDESH GULATI SHRI P. P . J A I N

National Physical Laboratory ( C S I R ) , New Delhi

Hindustan Steel Ltd, Durgapur Atul Glass Industries Pvt Ltd, New Delhi Mines Service Corporation, Asansol

SHRI A. P. AGARWAL ( Alternate ) SHRI S. C. JOSHI SHRI S. S. MAZUMDAR SHRI N. S. SOKHI

SHRI S. C. SHARMA ( Alternate ) SHRI A. C. SRIVASTAVA SHRI J. L. VAZ

National Instruments Ltd, Durgapur Indian Oxygen Ltd, Calcutta Hindustan Vacuum Glass Ltd, Faridabad

Director General of Mines Safety, Dhanbad Joseph-Leslie & Co, Bombay

Panel for Glass Lenses for Automobile Head Lamps, CDC 10: 13: 1 Convener

SHRI C. S. DEVAPRAGASAM

Members SHRI R. BHANDARI

T. I. Miller Ltd, Madras

J. M. A. Industries Ltd, New Delhi SHRI K. K. GAUTAM ( Alternate )

SHRI G. A. CLAYDON SHRI V. A. MURARI ( Alternate )

D R S. R. DAS SHRI K. S. SARMA ( Alternate )

SHRI S . M. JAISWAL SHRI A. S. HARSORA ( Alternate )

SHRI U. N. NAYAK

SHRI N. S. SOKHI SHRI S. C. SHARMA ( Alternate )

SHRI G. R. YEAKEY SHRI J. K. WAD ( Alternate )

Lucas-TVS Ltd, Madras

National Physical Laboratory ( CSIR ), New Delhi

Alembic Glass Industries Ltd, Baroda

Central Glass & Ceramic Research Institute ( CSIR ), Calcutta

Hindustan Vacuum Glass Ltd, Faridabad

Borosil Glass Works Ltd, Bombay

2

IS : 6917 - 1973

Indian Standard SPECIFICATION FOR GLASS LENSES

FOR AUTOMOBILE HEADLIGHTS ( REPLACEABLE BULB TYPE )

0 . F O R E W O R D

0.1 This Indian Standard was adopted by the Indian Standards Institution on 13 February 1973, after the draft finalized by the Glassware Sectional Committee had been approved by the Chemical Division Council.

0.2 Glass lenses meant for use in the replaceable bulb type automobile headlights are manufactured in large quantities in the country. These vary considerably in pattern, geometry and dimensions depending on the headlight in which they are to be used. It is, therefore, difficult to pres­cribe these in this standard. However, with a view to providing a basis for selecting or manufacturing lenses capable of withstanding normal mechanical impacts, thermal shocks and atmospheric conditions without any significant loss in clarity and output of light besides providing a properly distributed beam of light, suitable methods of sampling and test and criteria for judging the quality of lenses have been prescribed in this standard. 0.3 In clause 3.2.1 reference has been made to standard strain discs. A set of 5 such standard strain discs is available on payment from the Central Glass and Ceramic Research Institute, Calcutta 32.

0.4 For judging the resistance of lenses to weathering and solarization, a test based on artificial weathering and solarization cycle has been pres­cribed in this standard. For assessing suitability a new product is com­pared with an approved sample which is also subjected to the test simul­taneously. It is, however, to be expected that the onset and degree of deterioration of the lenses on natural weathering and solarization will show some variations because of the variations of day-light (intensity and spectral distribution), air temperature, relative humidity, rainfall, periods during which the lenses remain wet and atmospheric contaminants.

0.5 This standard contains clauses 4.1, 4.2, B-1.1 and B-3.0 which call for agreement between the purchaser and the supplier. 0.6 In the formulation of this standard due weightage has been given to international co-ordination among the standards and practices prevailing in different countries in addition to relating it to the practices prevailing

3

IS : 6917 - 1973

in the field in this country. This has been met by basing the standard on investigations carried out at the Central Glass and Ceramic Research Institute, Calcutta and also deriving assistance from the following publications:

BS 3900: Part F 3:1971 Resistance to artificial weathering ( enclosed carbon arc ). British Standards Institution.

ASTM Standard C-148-1965 Polariscopic examination of glass containers. American Society for Testing and Materials.

0.7 For the purpose of deciding whether a particular requirement of this standard is complied with, the final value, observed or calculated, express­ing the result of a test or analysis, shall be rounded off in accordance with IS : 2-1960*. The number of significant places retained in the rounded off value should be the same as that of the specified value in this standard.

1. SCOPE 1.1 This standard prescribes the requirements and the methods of sampling and test for glass lenses meant for use in replaceable bulb type headlights of automobiles.

2. TERMINOLOGY

2.1 For the purpose of this standard, definitions given in IS : 1382-1961† in addition to the following shall apply.

2.1.1 Light Unit — comprising of a lamp, holder, reflector and a lens.

2.1.2 Headlight — The light unit of a vehicle intended to illuminate road ahead.

3. REQUIREMENTS

3.1 Material — The lenses shall be made of colourless glass. They shall be clear, bright in appearance and shall have no objectionable tint.

3.1.1 Limit of Alkalinity — The glass of the lenses when tested in accord­ance with 2 of IS : 2303-1963‡, shall show a titre value not exceeding 4.1 ml of 0.01 N hydrochloric acid.

3.2 Workmanship and Finish — The lenses shall be free from bubbles, deformities, stains, chips, foreign particles, surface cracks, wrinkles, scratch marks or any other defect that may affect the optical characteristics or obviously spoil the appearance.

*Rules for rounding off numerical values ( revised ). †Glossary of terms relating to glass industry. ‡Method of grading glass for alkalinity.

4

IS : 6917 - 1973

3.2.1 Annealing — T h e lenses shall be well annealed so that the residual strain in them shall not be more than that of one standard strain disc corresponding to 22.8 ± 1.0 nm of optical retardation.

3.2.1.1 T h e residual strain may be determined by the method prescribed in Appendix A using a polarirneter or by a polariscope in conjunction with one standard strain disc ( see 0.3 ) which has an optical retardation of not less than 21.8 nm nor more than 23.8 nm.

3.3 Pat tern , G e o m e t r y and D i m e n s i o n s — The pattern, geometry and dimensions of lenses shall be such that when they are fitted in a light unit, they shall meet the photometric requirements for automobile headlights prescribed in IS : 3563-1966*.

3.3.1 T h e lens design shall preclude inadvertent shifting with respect to the light unit.

3.4 R e s i s t a n c e to Weather ing a n d Solar izat ion — T h e lenses shall pass the test for resistance to weathering and solarization when tested in accordance with the method prescribed in Appendix B.

3.5 R e s i s t a n c e to T h e r m a l Shock — The lenses shall withstand a thermal shock of 55°C when tested in accordance with method D of IS : 6506-1972†.

4 . MARKING A N D PACKING

4.1 M a r k i n g — The lenses shall be marked legibly and indelibly with the following in places which do not affect the optical performance:

a) Manufacturer 's name or recognized trade-mark, if any; and b) Symbols as desired by the purchaser.

4.1.1 T h e lenses may also be marked with the ISI Certification Mark.

NOTE — The use of the ISI Certification Mark is governed by the provisions of the Indian Standards Institution ( Certification Marks ) Act and the Rules and Regulations made thereunder. The ISI Mark on products covered by an Indian Standard conveys the assurance that they have been produced to comply with the requirements of that standard under a well-defined system of inspection, testing and quality control which is devised and supervised by ISI and operated by the producer. ISI marked products are also continuously checked by ISI for conformity to that standard as a further safeguard. Details of conditions under which a licence for the use of the ISI Certification Mark may be granted to manufacturers or processors, may be obtained from the Indian Standards Institution.

4.2 P a c k i n g — T h e lenses shall be packed as agreed to between the purchaser and the supplier.

*Specification for automobile headlights ( replaceable bulb type) . †Methods for thermal shock tests on glassware.

5

IS : 6917 - 1973

5. SAMPLING

5.1 The method of drawing representative samples and criteria for con­formity to this specification shall be as prescribed in Appendix C.

A P P E N D I X A ( Clause 3.2.1.1 )

DETERMINATION OF RESIDUAL STRAIN IN GLASS LENSES

A-0. GENERAL

A-0.1 Two methods are prescribed; method A is based on measurement of strain with a polarimeter, and method B on comparison with standard strain discs using a polariscope. Any one of these methods may be used depending on availability of equipment.

A-1. METHOD A

A-1.1 Apparatus A-1.1.1 Polarimeter — conforming to the following requirements:

a) The high brightness of the field shall be at least 30 cd/cm2 at the edge of the field, as observed with the polarizing element and protecting element in operating position;

b) The degree of polarization of the field at all points shall not be less than 99.0 percent;

c) The field shall be of sufficient size to permit the examination of the whole lens at one viewing;

d) The source of light shall consist of 75 or 100 W incandescent lamp bulbs so arranged as to satisfy the brightness requirements stated in (a) above;

e) A quarter-wave plate with an optical retardation of 141 nm shall be inserted between the polarizer and the analyzer with its slow axis at 90° to the plane of polarization of the polarizer; and

f) The analyzer shall be so mounted that it can be rotated with respect to the polarizer and quarter-plate, and the angle of rotation determined.

A-1.2 Procedure — Rotate the analyzer initially so as to have its plane of polarization perpendicular to that of the polarizer. This is the ' 0 ' position and the field should be black. Introduce the lens and view the

6

IS : 6917 - 1973

face of the lens through the analyzer. A dark cross will appear in the field between the areas which shall show colour in a tint plate polariscope. In a lens with low strain, this cross will be hazy and indistinct. Rotating the analyzer causes the dark cross to separate into 2 arcs which proceed outward in opposite directions towards the edges of the lens. As these dark areas move outward, they develop a blue-grey colour on the concave side and a brown colour on the convex side. In measuring the birefringence at a selected point, rotate the analyzer until the blue-grey colour is just displaced by the brown colour at the selected point. Rotate the lens itself about its own axis to determine if the region of maximum birefringence has been selected. If not, rotate the analyzer further to displace the blue-grey colour with the brown colour in the region of maximum birefringence. Convert the angle of rotation of the analyzer to optical retardation.

NOTE — One degree of rotation of the analyzer is equivalent to about 3.14 nm of optical retardation when a white light source as specified in ( d ) above is used ( effective wave length approximately 565 nm ).

A-1.2.1 The lens shall be taken as having satisfied the requirement of the test if the strain does not exceed optical retardation of 23.8 nm.

A-2. METHOD B

A-2.1 Apparatus A-2.1.1 Polariscope — conforming to the following requirements:

a) The high brightness of the field shall be at least 30 cd/cm2 at the point where the lens is held for examination and at least 17 cd/cm2

at the edge of field as observed with the polarizing element and protective element in operating position,

b) The degree of polarization of the field at all points shall not be less than 99.0 percent,

c) The field shall be of sufficient size to permit the examination of the whole lens at one viewing, and

d) A sensitive tint plate standardized to give an optical retardation of 565 nm shall be used.

A-2.1.2 Standard Strain Disc — One. Such a disc shall be a circular plate of glass between 7.5 and 10 cm in diameter and having nominal residual strain ( about 6 mm from the edge ) corresponding to not less than 21.8 nm nor more than 23.8 nm of optical retardation.

NOTE 1 — In standardizing such discs for measurement or calibration, error shall not exceed 0.7 nm.

NOTE 2 — A set of 5 such discs is generally available which could be useful in covering the range of annealing of commercial glass containers also.

7

IS : 6917 - 1973

A-2.2 Procedure — Rotate the analyzer initially so as to have its plane of polarization perpendicular to that of the polarizer. The field should look black. Introduce the lens in the field of vision and view its face through the analyzer. Compare the maximum broad colour pattern in the lens with the maximum colour produced with the standard strain disc to determine whether the maximum amount of colour with the lens is less than that produced in the standard strain disc.

A-2.2.1 The lens shall be taken as having satisfied the requirement of the test if the intensity of colour produced by it does not exceed that produced by one standard strain disc.

A P P E N D I X B ( Clause 3.4 )

RESISTANCE TO WEATHERING AND SOLARIZATION

B-0. GENERAL

B-0.1 The action of atmosphere and sunlight on the lenses in due course of time results in weathering and solarization which brings about loss of transparency and discoloration ( usually brownish ). This test is, there­fore, prescribed to ensure that the performance of new lots of lenses is not inferior to that of the approved samples under actual conditions of use.

B-1. PREPARATION OF THE TEST SPECIMENS

B-1.1 Take the required number of samples and 4 approved samples, unless otherwise agreed to between the purchaser and the supplier. Wash the pieces with tap water to remove any adhering dirt or dust. Finally rinse with distilled or demineralized water and dry.

NOTE — If the normal drying conditions arc specified, these should be interpreted as a temperature of 27 ± 2°C and a relative humidity of 60 to 70 percent with free circulation of air and without exposure to direct sunlight.

B-2. APPARATUS

B-2.1 A suitable apparatus is illustrated diagrammatically in Fig. 1 and 2 and consists of the following.

B-2.1.1 Drum — 1.2 m in diameter; so mounted that it rotates about its axis which is vertical; with a lid fitted over the top of the drum but not rotating with it; and so arranged that the lid can be lowered or raised. The drum should rotate continuously, completing 1 revolution every 20 minutes.

8

IS : 6917 - 1973

B-2.1.2 Frame — consisting of 2 galleries for mounting lenses under test. T h e galleries are designed to hold the lenses at an angle of 10 to 15° to the vertical and have provision for drainage.

B-2.1.3 Enclosed DC Arc Lamp — mounted with its axis vertical, 215 ± 15 mm from the axis of the drum, and at such a height that the centre of the arc is approximately 25 mm above the centre of the lenses on the upper gallery. T h e arc is enclosed in a clear borosilicate glass cylin­der 178 mm long, 127 mm in diameter and 1.5 to 3 mm in wall thickness ( see Fig. 1 ).

B-2.1.3.1 The arc is formed between two uncovered carbons, each 15 mm in diameter, the upper (pos i t ive) carbon being 305 mm long when fitted. T h e power consumption across the arc is 6 000 ± 50 W, the voltage being controlled between 130 and 145 V. The burning rate for the positive carbon should not exceed 4 m m / h . A burning rate in excess of this figure can usually be traced to an air leak in the lamp.

B-2.1.3.2 Care should be taken to ensure that the base of the lamp does not cast a shadow on the test lenses on the lower gallery.

B-2.1.4 Assembly of Two Water Atomizers — centrally placed, by means of which the panels are sprayed with fresh distilled or demineralized water which shall be drained away from the bottom of the drum and not recir­culated. Each atomizer discharges about 1 500 ml of water per hour at an air pressure of approximately 4 kN/m 2 in such a way that the whole of the surface of each lens is evenly wetted with a fine spray approximately a quar ter of a revolution before it comes in closest proximity to the lamp. A suitable assembly is illustrated in Fig. 2.

B-2.1.4.1 In storage and in passage to the atomizers, the water shall not come in contact with any material other than stainless steel, glass polymethyl methacrylate, polythene or other inert material. The water issuing from the jets shall comply with the following limits:

Total solids Not more than 5 ppm Iron ( as Fe ) Not more than 0.25 ppm Copper ( as Cu ) Not more than 0.20 ppm Silica Not detectable pH 6 to 7

T h e temperature of water in the atomizers should not exceed 30°C. NOTE — The water system should be cleaned regularly to ensure that the jets and the

water flow systems are free from algal growth and bacterial slime.

B-2.1.5 Ventilating Fan — fitted in the lid and so arranged as to blow air into the d rum at a rate of approximately 500 m 3 /h . The fan is fitted into the lid diametrically opposite to the direction of the sprays, with its axis 300 to 350 mm from the axis of the drum ( see Fig. 1 ).

9

IS : 6917 - 1973

FIG. 1 DIAGRAM OF APPARATUS FOR ARTIFICIAL WEATHERING AND SOLARIZATION

10

IS : 6917 - 1973

NOTE — The distance between the two atomizers is shown as 150 mm, but this distance should be such that the panels are uniformly wetted when the sprays are operating.

FIG. 2 DETAILS OF ASSEMBLY OF WATER ATOMIZERS

11

IS : 6917 - 1973

B-3. PROCEDURE

B-3.0 It is preferred if the full test period is carried out as a continuous exposure but where breaks occur due to failure of the equipment and diffi­culties in operating over the week end, the required number of hours should be added on to make up for the time lost. The use of the equip­ment as an interrupted cycle may be permitted subject to agreement between the parties. B-3.1 Maintain the temperature of the room in which the apparatus is operated at 27 ± 2°C Fit the lamp with a new pair of carbons and a clean borosilicate glass cylinder free from cracks and chips. Arrange the samples on the frame with the concave side of lenses facing the wall of the drum. Start the apparatus and expose the lenses for the specified period, operating the apparatus in cycles of 24 hours as follows:

a) 4 hours with atomizers on and fan off, b) 2 hours with atomizers off and fan on, c) 10 hours with atomizers on and fan off, d) 2 hours with atomizers off and fan on, e) 5 hours with atomizers on and fan off, and f) 1 hour with atomizers off and fan off and apparatus stopped.

During the last period of 1 hour, change the carbons, clean the glass cylin­der and prepare to recommence the cycle.

B-3.1.1 At intervals of 7 days, remove the lenses, allow to dry, and compare with approved samples for difference in transparency and colour. If the samples under test show any change of colour or loss of trans­parency in relation to approved samples, stop further testing and reject the samples.

B-3.1.2 After the specified period of 21 days of exposure, remove the lenses, allow to dry, repeat the examination and report the results.

A P P E N D I X C ( Clause 5.1 )

SAMPLING OF GLASS LENSES FOR AUTOMOBILE HEADLIGHTS

C-1. SCALE OF SAMPLING

C-1.1 In any consignment, all glass lenses of the same pattern, geometry and dimensions manufactured from the same material under relatively simi­lar conditions of manufacture shall be grouped together to constitute a lot.

12

IS : 6917 - 1973

C-1.2 For ascertaining the conformity to the requirements of this speci­fication the tests shall be carried out separately for each lot.

C-1.3 T h e number of glass lenses to be sampled from a lot for ascertain­ing conformity to the requirements of this specification shall be according to Table 1.

C-1.3.1 Glass lenses to be included in the sample shall be selected at random from the lot. In order to ensure the randomness of selection, procedures given in IS : 4905-1968* may be followed.

C-2. N U M B E R OF TESTS AND CRITERIA FOR CONFORMITY

C-2.1 Charac ter i s t i c s Requ ir ing Non-des t ruc t ive T e s t i n g ( See 3.2 and 3.3 ) — In respect of workmanship and finish, annealing, pat tern, geometry and dimensions, sample lenses selected according to col 3 of Table 1 shall be examined. A glass lens failing to satisfy any one or more of these requirements shall be regarded as defective.

C-2.1.1 T h e lot shall be accepted without further t o t i n g if the number of defective glass lenses in the sample does not exceed the corresponding acceptance number ( see col 5 of Table 1 ).

C-2.1.2 T h e lot shall be rejected without further testing if the number of defective glass lenses in the sample is found to be greater than or equal to the corresponding rejection number ( see col 6 of Table 1 ).

C-2.1.3 If the number of defective glass lenses found in the sample is between the corresponding acceptance and rejection numbers, another sample of the same size as given in col 3 of Table 1 shall be tested. The lot shall be accepted if the total number of defective glass lenses in the cumulative sample does not exceed the corresponding acceptance number given in col 5 of T a b l e 1 and rejected if this number equals or exceeds the corresponding rejection number given in col 6 of Table 1.

C-2.2 C h a r a c t e r i s t i c s Requir ing D e s t r u c t i v e T e s t i n g ( See 3 .1 .1 , 3.4 and 3.5 ) — In respect of limit of alkalinity, resistance to weathering and solarization, and thermal shock, the samples of lenses shall be selected according to column 7 of Table 1 from out of those which have passed non-destructive tests as above.

C-2.2.1 Limit of Alkalinity — A test sample shall be prepared from any 3 lenses taken at random from out of those selected as in col 7 of Table 1 for carrying out the alkalinity test. The lot shall be accepted if the material passes the alkalinity test, otherwise the lot shall be rejected.

*Methods for random sampling.

13

IS : 6917 - 1973

C-2.2.2 Resistance to Weathering and Solarization and Thermal Shock — Out of the remaining samples, selected according to C-2.2 and column 7 of Table 1 equal number of samples shall be tested for (a) resistance to weathering and solarization and (b) resistance to thermal shock. The lot shall be accepted if all the selected glass lenses pass the corresponding tests.

14

TABLE 1 SCALE OF SAMPLING AND PERMISSIBLE NUMBER OF DEFECTIVES

( Clauses C-1.3 and C-2 )

No. OF GLASS LENSES IN THE LOT

(1) Up to 500

501 to 1 000

1 001 and above

NON-DESTRUCTIVE TESTING

Stage of No. of Cumula- Accept- Rejec-Sampling Glass tive No. ance tion

Lenses of Glass No. No. in the Lenses Sample in the

Sample

(2)

First Second First Second First Second

(3) 13 13 20 20 32 32

(4) 13 26 20 40 32 64

(5) 0 1 0 3 1 4

(6)

2 2 3 4 4 5

DESTRUCTIVE TESTING,

No. OF GLASS LENSES IN THE SAMPLE

(7)

13 – 19 – 29 –

INTERNATIONAL SYSTEM OF UNITS ( SI UNITS )

Base Units

QUANTITY Length Mass Time Flectric current Thermodynamic

temperature Luminous intensity Amount of substance

Supplementary Units

QUANTITY Plane angle Solid angle

Derived Units Q U A N T I T Y

Force Energy Power Flux Flux density Frequency Electric conductance Electromotive force Pressure, stress

U N I T metre kilogram second ampere kelvin

candela mole

U N I T radian steradian

U N I T newton joule watt weber tesla hertz siemens volt pascal

SYMBOL m kg s A K

cd mol

SYMBOL rad sr

SYMBOL

N J W Wb

T Hz

s V Pa

DEFINITION 1 N 1 J 1 W 1 Wb 1 T 1 Hz 1 S 1 V 1 Pa

= 1 kg.m/s2

= 1 N.m = 1 J/s = 1 V.s = 1 Wb/m2

= 1 c/s (s -1) = 1 A/V = 1 W/A = 1 N/m 2

INDIAN S T A N D A R D S INSTITUTION

M a n a k Bhavar i , 9 B a h a d u r S h a h Zafar Marg , NEW DELHI 110002

T e l e p h o n e s : 26 60 2 1 , 27 01 31

Reg iona l Offices:

W e s t e r n : Novelty C h a m b e r s , Gran t R o a d E a s t e r n : 5 C h o w r i n g h e e A p p r o a c h S o u t h e r n : CIT C a m p u s N o r t h e r n : B69, P h a s e VII

Branch Offices: ' P u s h p a k ' , N u r m o h a m e d S h a i k h M a r g , K h a n p u r 'F ' B lock , Unity Bldg, N a r a s i m h a r a j a S q u a r e G a n g o t r i C o m p l e x , B h a d b h a d a R o a d , T . T . N a g a r 22E K a l p a n a A r e a 5-8-56C L . N . G u p t a Marg R 14 Y u d h i s t e r Marg , C S c h e m e 117/418 B S a r v o d a y a N a g a r P a t l i p u t r a I ndus t r i a l E s t a t e H a n t e x Bldg ( 2 n d F loo r ) , Rly S t a t i o n R o a d

T e l e g r a m s : M a n a k s a n s t h a

T e l e p h o n e

B O M B A Y 400007 37 97 29 C A L C U T T A 700072 27 50 90 M A D R A S 600113 41 24 42 S . A . S . N A G A R –

( M O H A L I ) 160051

A H M A D A B A D 380001 2 03 91 B A N G A L O R E 560002 22 48 05 B H O P A L 462003 6 27 16 B H U B A N E S H W A R 751014 5 36 27 H Y D E R A B A D 500001 22 10 83 J A I P U R 302005 6 98 32 K A N P U R 208005 4 72 92 P A T N A 800013 6 28 08 T R I V A N D R U M 695001 32 27

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