Council Directive 72/306/EEC of 2 August 1972 on the approximation of the laws of the Member States relating to the measures to be taken against the emission of pollutants from diesel engines for use in vehicles
Modified by
  • Commission Directiveof 17 July 1989adapting to technical progress Council Directives 70/157/EEC, 70/220/EEC, 72/245/EEC, 72/306/EEC, 80/1268/EEC and 80/1269/EEC relating to motor vehicles(89/491/EEC), 31989L0491, August 15, 1989
  • Commission Directive 97/20/ECof 18 April 1997adapting to technical progress Council Directive 72/306/EEC on the approximation of the laws of the Member States relating to the measures to be taken against the emission of pollutants from diesel engines for use in vehicles(Text with EEA relevance), 31997L0020, May 16, 1997
  • Commission Directive 2005/21/ECof 7 March 2005adapting to technical progress Council Directive 72/306/EEC on the approximation of the laws of the Member States relating to the measures to be taken against the emission of pollutants from diesel engines for use in vehicles(Text with EEA relevance), 32005L0021, March 8, 2005
  • Regulation (EC) No 715/2007 of the European Parliament and of the Councilof 20 June 2007on type approval of motor vehicles with respect to emissions from light passenger and commercial vehicles (Euro 5 and Euro 6) and on access to vehicle repair and maintenance information(Text with EEA relevance), 32007R0715, June 29, 2007
Corrected by
  • Corrigendum to Council Directive No 72/306/EEC of 2 August 1972 on the approximation of the laws of the Member States relating to the measures to be taken against the emission of pollutants from diesel engines for use in vehicles, 31972L0306R(01), August 6, 1974
  • Corrigendum to Council Directive 72/306/EEC of 2 August 1972 on the approximation of the laws of the Member States relating to the measures to be taken against the emission of polutants from diesel engines for use in vehicles, 31972L0306R(02), November 23, 1977
Council Directiveof 2 August 1972on the approximation of the laws of the Member States relating to the measures to be taken against the emission of pollutants from diesel engines for use in vehicles(72/306/EEC) THE COUNCIL OF THE EUROPEAN COMMUNITIES,Having regard to the Treaty establishing the European Economic Community, and in particular Article 100 thereof;Having regard to the proposal from the Commission;Having regard to the Opinion of the European Parliament;Having regard to the Opinion of the Economic and Social Committee;Whereas the technical requirements which motor vehicles must satisfy pursuant to national laws relate, inter alia, to the emission of pollutants from diesel engines for use in vehicles;Whereas those requirements differ from one Member State to another; whereas it is therefore necessary that all the Member States adopt the same requirements either in addition to or in place of their existing rules, in order, in particular, to allow the EEC type approval procedure which was the subject of the Council DirectiveOJ No L 42, 23.2.1970, p. 1. of 6 February 1970 on the approximation of the laws of the Member States relating to the type approval of motor vehicles and their trailers to be applied in respect of each type of vehicle;Whereas, it is desirable to follow the technical requirements adopted by the UN Economic Commission for Europe in its Regulation No 24 (Uniform provisions concerning the approval of vehicles equipped with diesel engines with regard to the emission of pollutants by the engine), which is annexed to the Agreement of 20 March 1958 concerning the adoption of uniform conditions of approval and reciprocal recognition of approval for motor vehicle equipment and partsDoc. E/EEC/324 — E/EEC/TRANS/505, Rev 1/add 23, 23.8.1971.;HAS ADOPTED THIS DIRECTIVE:
Article 1For the purposes of this Directive "vehicle" means any vehicle with a diesel engine, intended for use on the road, with or without bodywork, having at least four wheels and a maximum design speed exceeding 25 km/h, with the exception of vehicles which run on rails and of agricultural and forestry tractors and of all mobile machinery.
Article 2No Member State may refuse to grant a vehicle EEC type approval or national type approval on the ground that pollutants are emitted by the diesel engine which drives the vehicle, if the engine complies with the requirements of the relevant Annexes to this Directive.
Article 3The Member State which has granted type approval shall take the necessary measures to ensure that it is informed of any modification of a part or characteristic referred to in item 1.1 of Annex I. The competent authorities of that Member State shall decide whether fresh tests should be carried out on the modified vehicle type and a fresh report drawn up. Where the tests reveal failure to comply with this Directive, the modification shall not be approved.
Article 4The amendments necessary for adjusting the Annexes so as to take account of technical progress shall be adopted in accordance with the procedure laid down in Article 13 of the Council Directive of 6 February 1970 on the approximation of the laws of the Member States relating to the type approval of motor vehicles and their trailers.
Article 51.Member States shall put into force the provisions needed in order to comply with this Directive within eighteen months of its notification and shall forthwith inform the Commission thereof.2.Furthermore, once notification of this directive has been effected the Member States shall ensure that the Commission is informed, in time for it to submit its comments, of the most important laws, regulations and administrative provisions which they envisage adopting in the field covered by this Directive.
Article 6This Directive is addressed to the Member States.
nullLIST OF ANNEXESAnnex I:Definitions, application for EC type-approval, granting of EC type-approval, symbol of the corrected absorption coefficient, specifications and tests, modifications of the type, conformity of productionAppendix 1:Information documentAppendix 2:Type-approval certificateAnnex II:Example of the symbol of the corrected absorption coefficientAnnex III:Test at steady speeds over the full load curveAnnex IV:Test under free accelerationAnnex V:Limit values applicable in the test at steady speedsAnnex VI:Characteristics of opacimetersAnnex VII:Installation and use of the opacimeterANNEX 1The text of the Annexes is similar to that of Regulation No 24 of the UN Economic Commission for Europe; in particular the breakdown into items is the same. For this reason, where an item of Regulation No 24 has no counterpart in this Directive, its number is given in brackets as a token entry.DEFINITIONS, APPLICATION FOR EC TYPE-APPROVAL, GRANTING OF EC TYPE-APPROVAL, SYMBOL OF THE CORRECTED ABSORPTION COEFFICIENT, SPECIFICATIONS AND TESTS, MODIFICATIONS OF THE TYPE, CONFORMITY OF PRODUCTION(1.)1.DEFINITIONSFor the purposes of this Directive:(2.1.)1.1."Vehicle type as regards the limitation of the emission of pollutants from the engine" means motor vehicles which do not differ in such essential respects as the vehicle and engine characteristics defined in Appendix 1;1.2."Diesel engine" means an engine which works on the compression-ignition principle;1.3."Cold-start device" means a device which by its operation temporarily increases the amount of fuel supplied to the engine and is intended fo facilitate the starting of the engine;1.4."Opacimeter" means an instrument for continuous measurement of the absorption coefficients of the light by the exhaust gases emitted by vehicles.2.APPLICATION FOR EEC TYPE APPROVAL2.1.The application for EC type-approval pursuant to Article 3 (4) of Directive 70/156/EEC of a vehicle type with regard to its emission of pollutants from diesel engines shall be submitted by the manufacturer.2.2.A model for the information document is given in Appendix 1.3.2.1.A description of the engine type including all the particulars referred to in Annex II:3.2.2.Drawings of the combustion chamber and of the upper face of the piston.2.3.An engine and the equipment prescribed in Appendix 1 for fitting to the vehicle to be approved shall be submitted to the technical service conducting the approval tests defined in item 5. However, if the manufacturer so requests and the technical service conducting the approval tests agrees, a test may be carried out on a vehicle representative of the vehicle type to be approved.3.GRANTING OF EC TYPE-APPROVAL3.1.If the relevant requirements are satisfied, EC type-approval pursuant to Article 4 (3) and, if applicable, Article 4 (4) of Directive 70/156/EEC shall be granted.3.2.A model for the EC type-approval certificate is given in Appendix 2.3.3.An approval number in accordance with Annex VII to Directive 70/156/EEC shall be assigned to each type of vehicle approved. The same Member State shall not assign the same number to another type of vehicle.4.SYMBOL OF THE CORRECTED ABSORPTION COEFFICIENT(4.1.)(4.2.)(4.3.)4.1.To every vehicle conforming to a vehicle type approved under this Regulation there shall be affixed, conspicuously and in a readily accessible place specified in the Addendum to the type-approval certificate shown in Appendix 2, a symbol being a rectangle surrounding a figure expressing in m-1 the corrected absorption coefficient obtained, at the time of approval, during the test under free acceleration, and determined at the time of approval by the method described in item 3.2 of Annex IV.4.2.The symbol must be clearly legible and indelible.4.3.Annex II gives an example of the symbol.5.SPECIFICATIONS AND TESTS5.1.GeneralThe components liable to affect the emission of pollutants shall be so designed, constructed and assembled as to enable the vehicle, in normal use, despite the vibration to which it may be subjected, to comply with the provisions of this Directive.5.2.Specifications concerning cold-start devices5.2.1.The cold-start device shall be so designed and constructed that it cannot be brought into or kept in action when the engine is running normally.5.2.2.The provisions of item 5.2.1 above shall not apply if at least one of the following conditions is met:5.2.2.1.The light absorption coefficient of the gases emitted by the engine at steady speeds when measured by the method described in Annex III with the cold-start device operating is within the limits prescribed in Annex V.5.2.2.2.Keeping the cold-start device in operation causes the engine to stop within a reasonable time.5.3.Specifications concerning the emission of pollutants5.3.1.The emission of pollutants by the vehicle type submitted for approval shall be measured by the two methods described in Annexes III and IV, relating respectively to tests at steady speeds and to tests under free acceleration.A test under free acceleration shall be carried out, especially in order to provide a reference figure for administrations which use this method to check vehicles in use.5.3.2.The emission of pollutants, as measured by the method described in Annex III, shall not exceed the limits prescribed in Annex V.5.3.3.In the case of engines with an exhaust-driven supercharger the absorption coefficient measured under free acceleration shall not exceed the limit prescribed in Annex VI for the nominal flow value corresponding to the maximum absorption coefficient measured during the tests at steady speeds, plus 0·5 m-1.5.4.Equivalent measuring instruments shall be allowed. If an instrument other than those described in Annex VI is used, proof of its equivalence for the engine considered shall be required.6.MODIFICATIONS OF THE TYPE AND AMENDMENTS TO APPROVALS6.1.In the case of modifications of the type approved pursuant to this Directive, the provisions of Article 5 of Directive 70/156/EEC shall apply.7.CONFORMITY OF PRODUCTION7.1.Measures to ensure the conformity of production shall be taken in accordance with the provisions laid down in Article 10 of Directive 70/156/EEC.(7.2.)7.2.In particular, conformity of the vehicle with the approved type as regards the emission of pollutants from diesel engines shall be verified on the basis of the results listed in the Addendum to the type-approval certificate shown in Appendix 2. In addition:7.2.1.Where a check is carried out on a vehicle taken from the series, the tests shall be carried out as follows:7.2.1.1.A vehicle which has not been run in shall be subjected to the test under free acceleration described in Annex IV. The vehicle shall be deemed to conform to the approved type if the absorption coefficient determined does not exceed by more than 0·5 m-1 the figure shown in the approval mark.7.2.1.2.If the figure determined in the test referred to in item 7.2.1.1 above exceeds by more than 0·5 m-1 the figure shown in the approval mark, a vehicle of the type considered or its engine shall be subjected to the test at steady speeds over the full-load curve, as described in Annex III. The emission levels shall not exceed the limits prescribed in Annex V.(8.)(9.)ANNEX IIANNEX IIEXAMPLE OF THE SYMBOL OF THE CORRECTED ABSORPTION COEFFICIENTThe above symbol shows that the corrected absorption coefficient is 1·30 m-1.ANNEX IIITEST AT STEADY SPEEDS OVER THE FULL-LOAD CURVE1.INTRODUCTION1.1.This annex describes the method of determining emissions of pollutants at different steady speeds over the full-load curve.1.2.The test may be carried out either on an engine or on a vehicle.2.MEASUREMENT PRINCIPLE2.1.The opacity of the exhaust gases produced by the engine shall be measured with the engine running under full load and at steady speed. Six measurements shall be made at engine speeds spaced out uniformly between that corresponding to maximum power and the higher of the following two engine speeds:45 per cent of the engine speed corresponding to maximum power; and1000 rpm.The extreme points of measurement shall be situated at the limits of the interval defined above.2.2.In the case of diesel engines which are fitted with an air supercharger which can be engaged at will, and in which engines the entry into operation of the air supercharger automatically brings about an increase in the quantity of fuel injected, the measurements shall be made both with and without the supercharger working.For each engine speed, the result of the measurement shall be the higher of the two figures obtained.3.TEST CONDITIONS3.1.Vehicle or engine3.1.1.The engine or the vehicle shall be submitted in good mechanical condition. The engine shall have been run in.3.1.2.The engine shall be tested with the equipment described in Appendix 1 to Annex I.3.1.3.The settings of the engine shall be those described by the manufacturer and by Appendix 1 to Annex I.3.1.4.The exhaust device shall not have any orifice through which the gases emitted by the engine might be diluted.3.1.5.The engine shall be in the normal working condition prescribed by the manufacturer. In particular, the cooling water and the oil shall each be at the normal temperature indicated by the manufacturer.3.2.FuelThe reference fuel specified in Annex IV of Directive 88/77/EEC, as last amended, and which is appropriate to the emission limits against which the vehicle or engine is being type-approved, shall be used.3.3.Test laboratory3.3.1.The absolute temperature T of the laboratory, expressed in degrees Kelvin, and the atmospheric pressure H, expressed in torr, shall be measured, and the factor F shall be determined by the formulaF = 750H0·65 × T2980·53.3.2.For a test to be recognized as valid, the factor F shall be such that 0·98 ≤ F ≤ 1·02.3.4.Sampling and measuring apparatusThe light-absorption coefficient of the exhaust gases shall be measured with an opacimeter satisfying the conditions laid down in Annex VI and installed in conformity with Annex VII.4.LIMIT VALUES4.1.For each of the six engine speeds at which the absorption coefficient is measured pursuant to paragraph 2.1 above, the nominal gas flow G, expressed in litres per second, shall be calculated by means of the following formulae:
— for two-stroke engines
— for four-stroke engines
where:Vis the cylinder capacity of the engine expressed in litres; andnis the engine speed in revolutions per minute.4.2.For each engine speed the absorption coefficient of the exhaust gases shall not exceed the limit value given in the table in Annex V. Where the value of the nominal flow is not one of those given in that table, the limit value applicable shall be obtained by interpolation on the principle of proportional parts.ANNEX IVTEST UNDER FREE ACCELERATION1.TEST CONDITIONS1.1.The test shall be carried out on the vehicle or engine which has undergone the test at steady speeds described in Annex III.1.1.1.If the engine is tested on a bench the test shall be carried out as soon as possible after the test for measurement of opacity under full load at steady speed. In particular, the cooling water and the oil shall be at the normal temperatures indicated by the manufacturer.1.1.2.If the test is carried out on a stationary vehicle, the engine shall first be brought to normal operating condition by a road run. The test shall be carried out as soon as possible after completion of the road run.1.2.The combustion chamber shall not have been cooled or fouled by a prolonged period of idling preceding the test.1.3.The test conditions described in Annex III, items 3.1, 3.2 and 3.3, shall apply.1.4.The conditions described in Annex III, item 3.4, with regard to the sampling and measuring apparatus shall apply.2.TEST METHODS2.1.If the test is a bench test, the engine shall be disconnected from the brake, the latter being replaced either by the rotating parts driven when no gear is engaged or by an inertia substantially equivalent to that of the rotating parts.2.2.If the test is carried out on a vehicle, the gear-change control shall be set in the neutral position and the engine in gear.2.3.With the engine idling, the accelerator control shall be operated quickly, but not violently, so as to obtain maximum delivery from the injection pump. This position shall be maintained until maximum engine speed is reached and the governor comes into action. As soon as this speed is reached the accelerator shall be released until the engine resumes its idling speed and the opacimeter reverts to the corresponding conditions.2.4.The operation described in item 2.3 above shall be repeated not less than six times in order to clear the exhaust system and to allow for any necessary adjustment of the apparatus. The maximum opacity values read at each successive acceleration shall be noted until stabilized values are obtained. No account shall be taken of the values read while the engine is idling after each acceleration. The values read shall be regarded as stabilized when four consecutive readings are situated within a band width of 0·25 m-1 and do not form a decreasing sequence. The absorption coefficient XM to be recorded shall be the arithmetic mean of these four values.2.5.Engines fitted with an air supercharger shall be subject, where appropriate, to the following special requirements:2.5.1.In the case of engines with an air supercharger which is coupled with or driven mechanically by the engine and is capable of being disengaged, two complete measurement cycles with preliminary accelerations shall be carried out, the air supercharger being engaged in one case and disengaged in the other. The measurement result recorded shall be the higher of the two results obtained;2.5.2.In the case of engines with an air supercharger which can be cut out by means of a driver-operated bypass, the test shall be carried out with and without the bypass. The measurement result recorded shall be the higher of the results obtained.3.DETERMINATION OF THE CORRECTED VALUE OF THE ABSORPTION COEFFICIENT3.1.NotationXMvalue of the absorption coefficient under free acceleration measured as described in item 2.4 of this Annex;XLcorrected value of the absorption coefficient under free acceleration;SMvalue of the absorption coefficient measured at steady speed (Annex III, item 2.1.) which is closest to the prescribed limit value corresponding to the same nominal flow;SLvalue of the absorption coefficient (Annex III, item 4.2.) for the nominal flow corresponding to the point of measurement which gave the value SM;Leffective length of the light path in the opacimeter.3.2.When the absorption coefficients are expressed in m-1 and the effective length of the light path in metres, the corrected value XL is given by the smaller of the following two expressions: orANNEX V
TECHNICAL CHARACTERISTICS OF REFERENCE FUEL PRESCRIBED FOR APPROVAL TESTS AND TO VERIFY CONFORMITY OF PRODUCTIONCEC reference fuel RF-03-A-84Equivalent ISO methods will be adopted when issued all properties listed above.The figures quoted show the evaporated quantities (percentage recovered + percentage loss).The values quoted in the specification are "true values". In establishment of their limit values the terms of ASTM D 3244 "Defining a basis for petroleum product quality disputes" have been applied and in fixing a maximum value, a minimum difference of 2R above zero has been taken into account; in fixing a maximum and minimum value, the minimum difference is 4R (R = reproducibility).Notwithstanding this measure, which is necessary for statistical reasons, the manufacturer of fuel should nevertheless aim at a zero value where the stipulated maximum value is 2R and at the mean value in the case of quotations of maximum and minimum limits. Should it be necessary to clarify the question as to whether a fuel meets the requirements of the specification, the terms of ASTM D 3244 be applied.The range for cetane is note in accordance with the requirement of a minimum range of 4R. However, in cases of dispute between fuel supplier and fuel user, the terms of ASTM D 3244 can be used to resolve such disputes provided replicate measurements, of sufficient number to achieve the necessary precision, are made in preference to single determinations.This fuel should be based on straight run and cracked hydrocarbon distillate components only; desulphurization is allowed. It must not contain any metallic additives or cetane improver additives.Even though oxidation stability is controlled, it is likely that shell life will be limited. Advice should be sought from the supplier as to storage conditions and life.If it is required to calculate thermal efficiency of an engine or vehicle, the calorific value of the fuel can be calculated from:Specific energy (calorific value) (net) MJ/kg =(46,423 - 8,792d2 + 3,170d) (1 - (x+y+s)) + 9,420s - 2,499xwhere:dthe density at 15 o C,xthe proportion by mass of water (%/100),ythe proportion by mass of ash (%/100),sthe proportion by mass of sulphur (%/100).
Limits and unitsASTM method
Cetan numbermin 49D 613
max 53
Density 15 oC (Kg/l)min 0,835D 1298
max 0,845
Destillation50 %min 245 oCD 86
90 %min 320 oC
max 340 oC
FBPmax 370 oC
Flash pointmin 55 oCD 93
CFPPmin —EN 116 (CEN)
max - 5 oC
Viscosity 40 oCmin 2,5 mm2/SD 445
max 3,5 mm2/S
Sulphur contentmin (to be reported)D 1266/D 2622
D 2785
max 0,05 % mass
Copper corrosionmax 1D 130
Conradson carbon residue (10 % DR)max 0,2 % massD 189
Ash contentmax 0,01 % massD 482
Water contentmax 0,05 % massD 95/D 1744
Neutralization (strong acid) numbermax 0,2 mg KPH/g
Oxidation stabilitymax 2,5 mg/100 mD 2274
Additives
Carbon-hydrogen ratio(to be reported)
ANNEX VLIMIT VALUES APPLICABLE IN THE TEST AT STEADY SPEEDS
Note: Although the above values are rounded to the nearest 0·01 or 0·005, this does not mean that the measurements need to be made to this degree of accuracy.
Nominal flow Glitres/secondAbsorption coefficient Km-1
422·26
452·19
502·08
551·985
601·90
651·84
701·775
751·72
801·665
851·62
901·575
951·535
1001·495
1051·465
1101·425
1151·395
1201·37
1251·345
1301·32
1351·30
1401·27
1451·25
1501·225
1551·205
1601·19
1651·17
1701·155
1751·14
1801·125
1851·11
1901·095
1951·08
2001·065
ANNEX VICHARACTERISTICS OF OPACIMETERS1.SCOPEThis annex defines the conditions to be met by opacimeters used in the tests described in Annexes III and IV.2.BASIC SPECIFICATION FOR OPACIMETERS2.1.The gas to be measured shall be confined in an enclosure having a non-reflecting internal surface.2.2.In determining the effective length of the light path through the gas, account shall be taken of the possible influence of devices protecting the light source and the photoelectric cell. This effective length shall be indicated on the instrument.2.3.The indicating dial of the opacimeter shall have two measuring scales, one in absolute units of light absorption from 0 to ∞ (m-1) and the other linear from 0 to 100; both scales shall range from 0 at total light flux to full scale at complete obscuration.3.CONSTRUCTION SPECIFICATIONS3.1.GeneralThe design shall be such that under steady-speed operating conditions the smoke chamber is filled with smoke of uniform opacity.3.2.Smoke chamber and opacimeter casing3.2.1.The impingement on the photoelectric cell of stray light due to internal reflections or diffusion effects shall be reduced to a minimum (e.g. by finishing internal surfaces in matt black and by a suitable general layout).3.2.2.The optical characteristics shall be such that the combined effect of diffusion and reflection does not exceed one unit on the linear scale when the smoke chamber is filled with smoke having an absorption coefficient near 1·7 m-1.3.3.Light sourceThe light source shall be an incandescent lamp with a colour temperature in the range 2800 to 3250 K or a green light emitting diode (LED) with a spectral peak between 550 and 570 nm. The light source shall be protected against sooting by means that do not influence the optical path length beyond the manufacturer’s specifications.3.4.Receiver3.4.1.The receiver shall consist of a photoelectric cell with a spectral response curve similar to the photopic curve of the human eye (maximum response in the range 550/570 nm; less than 4 per cent of that maximum response below 430 nm and above 680 nm).3.4.2.The construction of the electrical circuit, including the indicating dial, shall be such that the current output from the photoelectric cell is a linear function of the intensity of the light received over the operating-temperature range of the photoelectric cell.3.5.Measuring scales3.5.1.The light-absorption coefficient k shall be calculated by the formula Φ = Φo · e-kL, where L is the effective length of the light path through the gas to be measured, Φo the incident flux and Φ the emergent flux. When the effective length L of a type of opacimeter cannot be assessed directly from its geometry, the effective length L shall be determinedeither by the method described in item 4 of this Annex; orthrough correlation with another type of opacimeter for which the effective length is known.3.5.2.The relationship between the 0-100 linear scale and the light absorption coefficient k is given by the formulak = - 1L loge1 - N100where N is a reading on the linear scale and k the corresponding value of the absorption coefficient.3.5.3.The indicating dial of the opacimeter shall enable an absorption coefficient of 1·7 m-1 to be read with an accuracy of 0·025 m-1.3.6.Setting and testing of the measuring apparatus3.6.1.The electrical circuit of the photoelectric cell and of the indicating dial shall be adjustable so that the pointer can be reset at zero when the light flux passes through the smoke chamber filled with clean air or through a chamber having identical characteristics.3.6.2.With the lamp switched off and the electrical measuring circuit open or short-circuited, the reading on the absorption-coefficient scale shall be ∞, and it shall remain at ∞ with the measuring circuit reconnected.3.6.3.An intermediate check shall be carried out by placing in the smoke chamber a screen representing a gas whose known light-absorption coefficient k, measured as described in item 3.5.1. is between 1·6 m-1 and 1·8 m-1. The value of k must be known to within 0·025 m-1. The check consists in verifying that this value does not differ by more than 0·05 m-1 from that read on the opacimeter indicating dial when the screen is introduced between the source of light and the photoelectric cell.3.7.Opacimeter response3.7.1.The response time of the electrical measuring circuit, being the time necessary for the indicating dial to reach 90 per cent of full-scale deflection on insertion of a screen fully obscuring the photoelectric cell, shall be 0·9 to 1·1 second.3.7.2.The damping of the electrical measuring circuit shall be such that the initial overswing beyond the final steady reading after any momentary variation in input (e.g. the calibration screen) does not exceed 4 per cent of that reading in linear scale units.3.7.3.The response time of the opacimeter which is due to physical phenomena in the smoke chamber is the time between the entry of the gas into the measuring apparatus and the complete filling of the smoke chamber; it shall not exceed 0·4 second.3.7.4.These provisions shall apply solely to opacimeters used to measure opacity under free acceleration.3.8.Pressure of the gas to be measured and of scavenging air3.8.1.The pressure of the exhaust gas in the smoke chamber shall not differ by more than 75 mm (water gauge) from the atmospheric pressure.3.8.2.The variations in the pressure of the gas to be measured and of the scavenging air shall not cause the absorption coefficient to vary by more than 0·05 m-1 in the case of a gas having an absorption coefficient of 1·7 m-1.3.8.3.The opacimeter shall be equipped with appropriate devices for measuring the pressure in the smoke chamber.3.8.4.The limits of pressure variation of gas and scavenging air in the smoke chamber shall be indicated by the manufacturer of the apparatus.3.9.Temperature of the gas to be measured3.9.1.At every point in the smoke chamber the gas temperature at the instant of measurement shall be between 70 oC and a maximum temperature, specified by the opacimeter manufacturer, such that the readings over this temperature range do not vary by more than 0·1 m-1 if the chamber is filled with a gas having an absorption coefficient of 1·7 m-1.3.9.2.The opacimeter shall be equipped with appropriate devices for measuring the temperature in the smoke chamber.4.EFFECTIVE LENGTH "L" OF THE OPACIMETER4.1.General4.1.1.In some types of opacimeter the gas between the light source and the photoelectric cell, or between transparent parts protecting the source and the photoelectric cell, is not of constant opacity. In such cases the effective length L shall be that of a column of gas of uniform opacity which gives the same absorption of light as that obtained when the gas is admitted in a normal way into the opacimeter.4.1.2.The effective length of the light path is obtained by comparing the reading N of the opacimeter operating normally with the reading No obtained with the opacimeter modified so that the test gas fills a well defined length Lo.4.1.3.It will be necessary to take comparative readings in quick succession to determine the correction to be made for shifts of zero.4.2.Method of assessment of L4.2.1.The test gas shall be exhaust gas of constant opacity or a light-absorptive gas of a gravimetric density similar to that of the exhaust gas.4.2.2.A column of length Lo of the opacimeter, which can be filled uniformly with the test gases, and the ends of which are substantially at right angles to the light path, shall be accurately determined. This length Lo shall be close to the presumed effective length of the opacimeter.4.2.3.The mean temperature of the test gas in the smoke chamber shall be measured.4.2.4.If necessary, an expansion tank of compact design and of sufficient capacity to damp the pulsations may be incorporated in the sampling line as near to the probe as possible. A cooler may also be fitted. The addition of the expansion tank and of the cooler must not unduly disturb the composition of the exhaust gas.4.2.5.The test for determining the effective length shall consist of passing a sample of test gas alternately through the opacimeter operating normally and through the same apparatus modified as indicated in item 4.1.2.4.2.5.1.The opacimeter readings shall be recorded continuously during the test with a recorder whose response time is equal to or shorter than that of the opacimeter.4.2.5.2.With the opacimeter operating normally, the reading on the linear scale of opacity is N and that of the mean gas temperature expressed in Kelvin degrees is T.4.2.5.3.With the known length Lo filled with the same test gas, the reading on the linear scale of opacity is No and that of the mean gas temperature expressed in Kelvin degrees is To.4.2.6.The effective length will be4.2.7.The test shall be repeated with at least four test gases giving readings evenly spaced between the 20 and 80 on the linear scale.4.2.8.The effective length L of the opacimeter will be the arithmetic mean of the effective lengths obtained as stated in item 4.6 with each of the gases.ANNEX VIIINSTALLATION AND USE OF THE OPACIMETER1.SCOPEThis annex specifies the installation and use of opacimeters for the tests described in Annexes III and IV.2.SAMPLING OPACIMETER2.1.Installation for steady-speed tests2.1.1.The ratio of the cross-sectional area of the probe to that of the exhaust pipe shall not be less than 0·05. The back pressure measured in the exhaust pipe at the intake of the probe shall not exceed 75 mm (water gauge).2.1.2.The probe shall be a tube with an open end facing forwards in the axis of the exhaust pipe, or of the extension pipe if one is required. It shall he situated in a section where the distribution of smoke is approximately uniform. To achieve this, the probe shall be placed as far downstream in the exhaust pipe as possible, or, if necessary, in an extension pipe so that, if D is the diameter of the exhaust pipe at the outlet, the end of the probe is situated in a straight portion at least 6 D in length upstream of the sampling point and 3 D in length downstream. If an extension pipe is used, no air shall be allowed to enter the joint.2.1.3.The pressure in the exhaust pipe and the characteristics of the pressure drop in the sampling line shall be such that the probe collects a sample substantially equivalent to that which would be obtained by isokinetic sampling.2.1.4.If necessary, an expansion tank of compact design and of sufficient capacity to damp the pulsations may be incorporated in the sampling line as near to the probe as possible. A cooler may also be fitted.The design of the expansion tank and cooler shall not unduly disturb the composition of the exhaust gas.2.1.5.A butterfly valve or other means of increasing the sampling pressure may be placed in the exhaust pipe at least three 3 D downstream from the sampling probe.2.1.6.The connecting pipes between the probe, the cooling device, the expansion tank (if required) and the opacimeter shall be as short as possible while satisfying the pressure and temperature requirements described in Annex VI, items 3.8 and 3.9. The pipe shall be inclined upwards from the sampling point to the opacimeter, and sharp bends where soot might accumulate shall be avoided. If not embodied in the opacimeter, a bypass valve shall be provided upstream.2.1.7.A check shall be carried out during the test to ensure that the requirements of Annex VI, item 3.8, concerning pressure and those of Annex VI, item 3.9, concerning the temperature in the measuring chamber are observed.2.2.Installation for tests under free acceleration2.2.1.The ratio of the cross-sectional area of the probe to that of the exhaust pipe shall not be less thas 0·05. The back pressure measured in the exhaust pipe at the intake of the probe shall not exceed 75 mm (water gauge).2.2.2.The probe shall be a tube with an open end facing forwards in the axis of the exhaust pipe, or of the extension pipe if one is required. It shall be situated in a section where the distribution of smoke is approximately uniform. To achieve this, the probe shall be placed as far downstream in the exhaust pipe as possible or, if necessary, in an extension pipe so that, if D is the diameter of the exhaust pipe at the outlet, the end of the probe is situated in a straight portion at least 6 D in length upstream of the sampling point and 3 D in length downstream. If an extension pipe is used, no air shall be allowed to enter the joint.2.2.3.The sampling system shall be such that at all engine speeds the pressure of the sample at the opacimeter is within the limits specified in Annex VI, item 3.8.2. This may be checked by noting the sample pressure at engine idling and maximum no-load speeds. Depending on the characteristics of the opacimeter, control of sample pressure can be achieved by a fixed restriction or a butterfly valve in the exhaust pipe or extension pipe. Whichever method is used, the back pressure measured in the exhaust pipe at the intake of the probe shall not exceed 75 mm (water gauge).2.2.4.The pipes connecting with the opacimeter shall be as short as possible. The pipe shall be inclined upwards from the sampling point to the opacimeter, and sharp bends where soot might accumulate shall be avoided. A bypass valve may be provided upstream of the opacimeter to isolate it from the exhaust-gas flow when no measurement is being made.3.FULL-FLOW OPACIMETERThe only general precautions to be observed in steady-speed and free-acceleration tests are the following:3.1.Joints in the connecting pipes between the exhaust pipe and the opacimeter shall not allow air to enter from outside.3.2.The pipes connecting with the opacimeter shall be as short as possible, as in the case of sampling opacimeters. The pipe system shall be inclined upwards from the exhaust pipe to the opacimeter, and sharp bends where soot might accumulate shall be avoided. A bypass valve may be provided upstream of the opacimeter to isolate it from the exhaust-gas flow when no measurement is being made.3.3.A cooling system may also he required upstream of the opacimeter.ANNEX IXEXAMPLE OF THE SYMBOL OF THE CORRECTED ABSORPTION COEFFICIENTThe above symbol shows that the corrected absorption coefficient is 1·30 m-1.ANNEX X