S.I. No. 242/1950:

STANDARD SPECIFICATION (TUNGSTEN FILAMENT GENERAL SERVICE ELECTRIC LAMPS) ORDER, 1950.

STANDARD SPECIFICATION (TUNGSTEN FILAMENT GENERAL SERVICE ELECTRIC LAMPS) ORDER, 1950.

I, DANIEL MORRISSEY, Minister for Industry and Commerce, in exercise of the power conferred on me by subsection (3) of section 20 of the Industrial Research and Standards Act, 1946 (No. 25 of 1946), hereby order as follows :

1. This Order may be cited as the Standard Specification (Tungsten Filament General Service Electric Lamps) Order, 1950.

2.--(1) The specification set forth in Part II of the Schedule to this Order is hereby declared to be the standard specification for the commodity described in Part I of the said Schedule.

(2) The said standard specification may be cited as Irish Standard 25 : 1950.

SCHEDULE.

PART I.

TUNGSTEN FILAMENT GENERAL SERVICE ELECTRIC LAMPS

PART II.

SPECIFICATION.

SCOPE.

1. This specification covers Tungsten Filament General Service Electric Lamps of rated watts set out in Tables 4 and 5 respectively. The lamps shall be bayonet cap single coil filament lamps, or bayonet cap coiled coil filament lamps, or Edison screw cap single coil filament lamps.

DEFINITIONS.

2. For the purpose of this specification, the following definitions shall apply :--

Luminous Flux is the rate of emission of radiant energy evaluated according to its capacity to produce the sensation of light. It is the total visible radiant power issuing from the illuminant. The unit of luminous flux is the lumen.

The Lumen is the luminous flux radiated within unit solid angle by a uniform point source having a luminous intensity of one candle.

Luminous Intensity is the luminous flux per unit solid angle, i.e., per steradian.

The Candle is the unit of luminous intensity, and is the new Candle defined by the Bureau International des Poids et Mesures at its meeting in Paris, 1948.

Candle Power is the luminous intensity expressed in Candles.

The Mean Spherical Candle Power of a lamp is the average of its candle power in all directions in space. It is equal to the total luminous flux of the lamp in lumens divided by 4.

The Rated Volts and Rated Watts are the volts and watts marked on the lamp by the manufacturer, and their values shall be expressed in absolute units as defined by the Bureau International des Poids et Mesures at its meeting in Paris, 1948.

The Efficiency is the quotient in lumens per watt of the value of the luminous flux divided by the value of the input of power.

The Standard Deviation of a group of measurements is the square root of the number obtained by adding the squares of the differences between the individual measurements and the average of the group and dividing the sum by the number of measurements.

The Co-efficient of Variation of a group of measurements is their standard deviation expressed as a percentage of the average of the group of measurements.

Certified Lamps are lamps certified by the Institute for Industrial Research and Standards as secondary standards suitable for use in the determination of mean spherical candle power. They shall have at the time of use the Candle Power or Lumens for which they are certified.

CLASS.

3. For the purpose of this specification lamps having the same rated volts and rated watts shall be regarded as lamps of the same class.

RATED VOLTS.

4. The rated volts of lamps conforming to this specification shall be 100, 110, 200, 210, 220, 230 or 240.

CAPS.

5. (a) Designation.

Bayonet Caps shall be designated by the letter B, followed by a set of numbers, e.g., B.22/25 x 26, where the first number is the nominal outer diameter in millimetres of the cylindrical plug of the cap, the second number is the approximate overall length of the cap in millimetres, and the third number is the approximate flange diameter in millimetres.

Edison Screw Caps shall be designated by the letter E, followed by a set of numbers, e.g., E.27/25, where the first number is the nominal outer diameter in millimetres of the screw threads of the cap and the second number is the approximate overall length of the cap in millimetres.

(b) Dimensions.

The dimensions of bayonet caps shown in Fig. 1 shall conform to the values set out in Table 1. The dimensions of each type of Edison screw cap shown in Fig. 2 shall conform to the values set out in Table 2. The dimensions of the screw threads of Edison screw caps shown in Fig. 3 shall conform to the values set out in Table 3.

(c) Torque.

The caps of lamps of rated watts 15 to 200 inclusive shall be attached to the bulbs strongly enough to withstand a torque of 29 kilogram centimetres applied by the method described in Appendix A.

The caps of lamps of rated watts 300 to 1,500 inclusive shall be attached to the bulbs strongly enough to withstand a torque of 52 kilogram centimetres applied by the method described in Appendix A.

(d) Engagement.

Nothing in the construction of the caps shall prevent engagement in their holders.

BULBS.

6. Bulbs shall be clean, uncoloured and free from detrimental defects. They should be clear or internally frosted (" pearl ") but those of rated watts greater than 100 shall be clear.

DIMENSIONS.

7. The overall length of each lamp measured along its axis, and the greatest diameter of the bulb measured perpendicular to the axis, shall conform to the appropriate values set out in Table 4 in the case of single coil lamps, and in Table 5 in the case of coiled coil lamps.

The neck diameter of the bulbs of lamps of rated watts 15 to 100 inclusive shall be measured at a distance of 45 mm. from the contact-plates of the caps. The neck diameter of each bulb shall conform to the appropriate value set out in Table 4 for single coil lamps, and in Table 5 for coiled coil lamps.

The light-centre length of a lamp shall be regarded as the distance from the geometrical centre of the filament structure to the contact-plate of the cap, excluding the solder. The light-centre length shall conform to the appropriate value set out in Table 4 for single coil lamps and in Table 5 for coiled coil lamps. The light-centre length of lamps with internally frosted bulbs shall be determined by the method described in Appendix C.

FILAMENTS.

8. All portions of filaments uninfluenced by contact with supports shall appear uniform in brightness when run at rated or at half-rated volts.

INSULATION RESISTANCE.

9. The insulation resistance between the lamp filaments and the shells of the caps of bayonet cap lamps shall be not less than 50 megohms.

Before determining the insulation resistance, the lamps shall be removed from their wrappers, stored in warm dry surroundings for not less than 48 hours, and the external surfaces of their cap insulators wiped with a dry cloth. If, when first determined, the insulation resistance is found to be below 50 megohms, the lamps shall be stored in a warm dry atmosphere for at least a week and the insulation resistance again determined.

INITIAL RATING.

10. The initial watts and the initial efficiency of lamps shall be measured at the rated volts. The average initial watts, the average initial efficiency and co-efficient of variation of the initial efficiency of lamps of the same class shall comply with the values set out for that class in Table 6 in the case of single coil lamps and in Table 7 in the case of coiled coil lamps.

Before testing, lamps shall have been aged by running for one hour at their rated volts.

LIFE PERFORMANCE.

11. (a) The average efficiency throughout life of each of a number of lamps tested for life performance shall be determined at rated volts by the method described in Appendix B. The arithmetic mean of the values obtained for lamps of the same class shall be not less than the appropriate minimum average efficiency set out in Table 8 in the case of single coil lamps, and in Table 9 in the case of coiled coil lamps.

For the purpose of this clause the average efficiency throughout life of a lamp shall be the efficiency at 500 hours determined as the mean of the values of the efficiencies at 400 hours and at 600 hours. The average efficiency throughout life of any lamp for which the 600 hour reading is not obtainable, shall be assumed to be the same as the mean of the average efficiencies throughout life of the lamps which survived the 600 hour reading.

(b) The life of each of a number of lamps tested for life performance shall be determined at rated volts by the method described in Appendix B. The arithmetic mean of the values obtained for lamps of the same class shall be not less than the appropriate minimum average life set out in Table 10 for the number of lamps tested.

For the purpose of this clause the life of a lamp shall be the number of hours it operates until burn-out, or 1,000 hours, whichever is the shorter, but the life of any lamp of which the efficiency at 500 hours is less than 87·5 per cent. of its initial efficiency shall be regarded as the value in hours obtained by dividing 125 by the fractional reduction in efficiency.

The fractional reduction in efficiency shall be the quotient obtained by dividing the difference between the initial efficiency and the efficiency at 500 hours, by the initial efficiency.

MEASURED LUMENS FOR INTERNALLY FROSTED BULBS.

12. For the purpose of this specification measured lumens in the case of lamps with internally frosted (" pearl ") bulbs shall be increased by a percentage declared by the manufacturer. This percentage shall not exceed two.

MARKING.

13. Each lamp shall be distinctly and indelibly marked to show

(i) the rated volts,

(ii) the rated watts, and

(iii) the manufacturer's name or mark.

Coiled coil lamps shall be marked as such.

SAMPLING.

14. For the purpose of testing conformity with this specification lamps of each class shall be sampled by selection at the rate of 5 lamps per 100, the lamps being taken from at least every second container. Where the number of lamps in one class is less than 400 the sample shall be not less than 20 lamps.

TABLE 1.--DIMENSIONS OF BAYONET CAPS.

DESIGNATION B. 22/25 x 26.

In Table 1 the linear dimensions given in inches agree to the nearest 0·001 in. with those adopted by the International Electro-technical Commission, except those marked*.

TABLE 2.--DIMENSIONS OF EDISON SCREW CAPS.

All dimensions are in agreement with those adopted by the International Electrotechnical Commission.

TABLE 3.--DIMENSIONS OF SCREW THREADS OF EDISON SCREW CAPS.

(All dimensions are in agreement with those adopted by the International Electrotechnical Commission).

TABLE 4.--DIMENSIONS OF SINGLE COIL FILAMENT LAMPS.

TABLE 5.--DIMENSIONS OF COILED COIL FILAMENT LAMPS.

TABLE 6.--INITIAL RATING OF SINGLE COIL FILAMENT LAMPS.

TABLE 7.--INITIAL RATING OF COILED COIL FILAMENT LAMPS.

TABLE 8.--EFFICIENCY OF SINGLE COIL FILAMENT LAMPS.

TABLE 9.--EFFICIENCY OF COILED FILAMENT LAMPS.

TABLE 10.--LIFE.

Appendix B.

DETERMINATION OF LIFE PERFORMANCE.

The lamps to be tested shall be selected evenly from the sample taken in accordance with Clause 14. and shall be not less than 7 in number plus 9 per cent, to the next highest integer of the number of lamps contained in that sample. The lamps selected shall be such that their average initial efficiency shall not differ by more than plus or minus 1 per cent. from the average initial efficiency set out in Table 6 for single coil lamps or set out in Table 7 for coiled coil lamps, and the efficiency of individual lamps shall not differ from that average by more than an amount equal to the coefficient of variation thereof as set out in Table 6 for single coil lamps or set out in Table 7 for coiled coil lamps.

Each lamp shall be operated throughout the life test at its rated volts in a pendant position. The momentary fluctuations from the test voltage during the life test shall not exceed plus or minus 1 per cent and there shall be no sensible departure of the mean value of the test voltage from its correct value. Records shall be kept throughout the life test by a recording voltmeter. All lamps shall be switched off twice daily for periods of not less than 15 minutes during this test. A record shall be kept of the number of lamp failures and the number of hours run by each lamp before failure, each lamp being measured for lumens and watts at the rated volts at 400 hours and 600 hours with a tolerance of plus or minus 24 hours.

Appendix C.

DETERMINATION OF LIGHT-CENTRE LENGTH OF LAMPS WITH INTERNALLY FROSTED BULBS

A projection lamp, a convex lens, and a metal plate with a pinhole aperture shall each be set up in a vertical position so that an image of the filament of the projection lamp is focussed on the pinhole aperture. A cross wire or sight vane shall be set up at a distance from the plate slightly greater than the diameter of the bulb of the lamp under examination, and in the same straight line as the pinhole aperture and the centre of the filament of the projection lamp. The lamp to be examined shall be placed in a vertical position between the cross wires and the pinhole aperture and shall be moved vertically until the geometrical centre of the shadow of the filament appears at the intersection of the cross wires. The light-centre length required is the distance between the line joining the pinhole to the centre of the cross wires and the sole plate of the lamp cap. The lamp shall be rotated about its axis so as to obtain the mean value of the light-centre length for the whole of the filament.

GIVEN under my Official Seal this 15th day of September, 1950.

DANIEL MORRISSEY,

Minister for Industry and Commerce.

Appendix A.

TORSION TEST

Test--

The cap of the lamp shall be inserted in the appropriate metal socket adaptor of the dimensions set out above and the metal socket adaptor shall be fixed to a torsion-testing machine. The torque specified in Clause 5 (c) shall be applied to the lamp by twisting the bulb. This torque shall not be applied suddenly but shall be increased continuously from zero to the value specified in Clause 5 (c).