1、ICS 75.080Prfung von Minerallkohlenwasserstoffen Bestimmung derZndtemperaturIn keeping with current practice in standards published by the International Organization for Standardization(ISO), a comma has been used throughout as the decimal marker.Ref. No. DIN 51794 : 2003-05English price group 07 Sa
2、les No. 010702.04DEUTSCHE NORM May 200351794Continued on pages 2 to 7. No part of this translation may be reproduced without the prior permission ofDIN Deutsches Institut fr Normung e.V., Berlin. Beuth Verlag GmbH, 10772 Berlin, Germany,has the exclusive right of sale for German Standards (DIN-Norme
3、n).Determining the ignition temperature ofpetroleum productsTranslation by DIN-Sprachendienst.In case of doubt, the German-language original should be consulted as the authoritative text.SupersedesJanuary 1978 edition.All dimensions are in millimetres.ForewordThis standard has been prepared by Techn
4、ical Committee Prfung von flssigen Kraftstoffen und Heizlenof the Fachausschuss Minerall- und Brennstoffnormung of the Normenausschuss Materialprfung(Materials Testing Standards Committee).It should be borne in mind that the ignition temperature of flammable substances is not a physico-chemicalconst
5、ant but depends on the prevailing conditions in a particular case. However, since the method ofmeasurement makes it possible to grade the ignitability of flammable liquids and gases exposed to hotsurfaces, the standard does provide a basis for establishing appropriate safety measures for flame-proof
6、electrical and nonelectrical equipment.In the case of mixtures, particularly of oils, further ignitions of the sample material introduced into the ignitionvessel may be observed even at temperatures below the ignition temperature (determined as specified inthis standard) if air gets into the vessel
7、after introducing the sample. This post-ignition temperature maybe more than 100 K lower than the ignition temperature determined. For safety reasons, a check is alwaysto be made as to whether there is a post-ignition temperature 1 when determining the ignition temperature.AmendmentsThis standard di
8、ffers from the January 1978 edition as follows:a) sampling details have been changed;b) other materials have been specified instead of asbestos;c) the standard has been editorially revised.Previous editionsDIN 51794: 1961-07, 1978-01.1 ScopeThis standard specifies a method of determining the ignitio
9、n temperature of flammable liquids and gases,and of petroleum products and their mixtures at temperatures between 75 C and 650 C. The ignitiontemperature is a measure of the tendency of flammable substances to ignite in contact with hot bodies whenmixed with air and makes it possible to classify the
10、m from a safety point of view.Page 2DIN 51794 : 2003-052 Normative referencesThis standard incorporates, by dated or undated reference, provisions from other publications. Thesenormative references are cited at the appropriate places in the text, and the titles of the publications are listedbelow. F
11、or dated references, subsequent amendments to or revisions of any of these publications apply to thisstandard only when incorporated in it by amendment or revision. For undated references, the latest edition ofthe publication referred to applies.DIN 17470 Heating conductor alloys Technical delivery
12、conditions for round and flat wireDIN 51610 Sampling of liquefied petroleum gasesDIN 51750-1 Sampling of petroleum products GeneralDIN 51750-2 Sampling of liquid petroleum productsDIN 51794 Determination of the ignition temperature of petroleum productsDIN EN 61010-1 Safety requirements for electric
13、al equipment for measurement, control and laboratory use Part 1: General requirements (IEC 1010-1 : 1995)DIN EN ISO 4259 Petroleum products Determination and application of precision data in relation tomethods of test (ISO 4259 + Corr 1 : 1993)DIN ISO 1773 Laboratory glassware Narrow-necked boiling
14、flasks (ISO 1773 : 1997)3 Concepts3.1 Ignition temperatureThe lowest temperature at which combustion of a flammable substance can be initiated under the conditionsdescribed in this standard.3.2 IgnitionThe reaction of a mixture in an ignition vessel with marked flame development or deflagration if t
15、his occurswithin five minutes.3.3 Ignition delayThe time between the introduction of a sample into an ignition vessel and the start of combustion.NOTE: The ignition delay may take a fraction of a second to minutes, but it is generally less than three minutes.4 UnitThe unit in which the ignition temp
16、erature is reported shall be C.5 PrincipleIn every ignition test, a small portion of the flammable substance under test is introduced into an open conicalflask. The flask is heated in an electric furnace and it is observed whether ignition takes place at the prevailingtemperature. Finally, any vapor
17、izable components left in the flask are blown out with air.The lowest ignition temperature is determined from a series of ignition tests in which temperature and samplesize are varied. The ignition temperature is then reported as the result of a selection from the lowest valuesobtained in a number o
18、f test series.6 SamplingSamples shall be collected as specified in DIN 51750-1 and DIN 51750-2. In the case of nonhomogeneoussubstances, measures shall be taken to prevent the composition of the sample being substantially altered byevaporation prior to the test since any change in the composition of
19、 the mixture will affect the ignitiontemperature.Samples of liquefied gases shall be collected as specified in DIN 51610 using a type A1 sample flask.7 Apparatus7.1 GeneralThe lowest safe ignition temperature shall be determined using the test assembly shown in figure 4, which isto comply with the r
20、equirements given in subclauses 7.2 to 7.10. It should be noted, however, that the valuefound will depend on the design (e.g. on the volume and the shape of the surface) of the ignition vessel.The following equipment shall be used.Page 3DIN 51794 : 2003-057.2 Electric resistance furnace, having a me
21、tal insert and designed for 220 V for heating the ignition vessel(see figure 1). It may be operated by alternating current using a variable-voltage transformer or by direct currentusing variable resistors.Preferably, the control system shall switch only a fraction of the heating current on and off,
22、the unregulatedfraction being used to set the furnace to the required test temperature.The ceramic tube shall have CrAl 255 heating wire as in DIN 17470, 35,8 m long and 1,2 mm in diameter,wrapped round it with a spacing of 1,2 mm between the turns. The heating coil shall be held in place with a hig
23、h-temperature cement and covered with aluminium oxide powder thermal insulation about 20 mm thick. Astainless-steel cylindrical metal insert having a cover plate made of the same material shall be inserted into thetube learing as small a gap as possible. The cover plate shown in figure 2, which can
24、also be used to suspendthe ignition vessel, is to consist of an upper plate and a split lower plate, with a split ring made of heat-resistantinsulating material in between.The ignition vessel shall be inserted into the cover plate using a heat-resistant sealing strip and firmly joinedto the cover pl
25、ate after pushing the split rings together by tightening the two nuts.It is advisable to heat the furnace to the temperature for starting the preliminary test as in subclause 8.2, usingthe maximum heating current of about 6 A. If a temperature controller is used, the heating and cooling periodsshall
26、 be approximately of equal length.Key1 Thermocouple2 Fixing bushings3 Heat-resistant sealing strip4 Ignition vessel (of capacity 200 ml)5 Ceramic sheath6 Upper cover plate7 Split ring, made of heat-resistant insulatingmaterial8 Lower cover plate9 Thermal insulation10 Heating coil11 Ceramic tube12 Me
27、tal insert13 High-temperature cement14 220 V connection with earthing contact15 Thermocouple junction16 Disc, made of heat-resistant insulatingmaterial17 Metal baseFigure 1: Resistance furnacePage 4DIN 51794 : 2003-05Key1 Upper cover plate2 Split ring, made of heat-resistantinsulating material3 Cove
28、r plate4 Fixing bushingFigure 2: Cover for resistance furnaceIt is recommended that some form of device be fitted to the cover plate that can be used as a support for thepipette when introducing the substance into the ignition vessel.Any other similar furnace may be used to heat the ignition vessel
29、provided the ignition temperatures of 99,9 %n-heptane and benzene are (219t2,5) C and (558t5) C, respectively.CAUTION. Because of the health risk involved in handling benzene, it is recommended that acetonehaving an ignition temperature of (540t 5) C be used as an alternative.7.3 Ignition vessel, co
30、mprising a narrow-neck conical flask having a nominal capacity of 200 ml and thedimensions shown in figure 3, made of refractory laboratory glass as in DIN ISO 1773.Page 5DIN 51794 : 2003-05Figure 3: 200 ml narrow-neck conical flask7.4 Thermocouple7.4.1 Iron/constantan thermocouple (of wire diameter
31、 0,5 mm), for temperature measurements. The leadsof the thermocouple shall be passed through ceramic sheaths fitted to the cover plate, within 1 mm of the vesselwall. The thermocouple wires shall be clamped so that the junction is in close contact with the outer wall of thevessel, (25t2) mm above it
32、s bottom. They shall be held in position by the fixing bushings above the ceramicsheaths. The thermocouple voltage shall be measured with a compensation circuit; if the Lindeck-Rothe circuitis used, it is advisable to use an instrument of class 0,5 (as in DIN EN 61010-1). It is recommended thattherm
33、ocouples that have been in service for a prolonged period be checked using the same measuring systemand a calibrated thermocouple (of wire diameter 0,2 mm), whose junction is attached to the junction to betested.7.4.2 Optional second thermocouple, passed through the base of the furnace into the vess
34、el interior so thatits junction touches the bottom of the ignition vessel, to enable the test temperature to be adjusted with acontroller.7.5 1 ml graduated pipette, capable of delivering 35 to 40 drops at ambient temperature from 1 ml of distilledwater.7.6 1 ml injection syringe, made of glass, wit
35、h 0,75 mm cannula.7.7 Calibrated gastight piston-operated pump, made of glass, with a swept volume of 200 ml, having athree-way stopcock and a connecting hose that is not attacked by the substance to be tested.7.8 Hand-operated bulb pump, having a cottonwool filter, blowpipe and connecting hose (see
36、 figure 4).Key1 Cottonwool filter2 Hand-operated bulb pump3 Connecting hose4 Blowpipe5 Angled tube6 Mirror7 Connecting hose8 Three-way stopcock9 Piston-operated pump10 Pressure regulator11 Sample containerFigure 4: Assembly for determining the ignition temperature of gaseous substancesPage 6DIN 5179
37、4 : 2003-057.9 Mirror, mounted above the ignition vessel at about 250 mm from the cover plate. This is recommendedfor enabling the processes in the ignition vessel to be reliably observed from the side.7.10 Additional cover plate, fitted with ignition vessel and thermocouple, kept as a replacement.
38、This willmake it easier to perform several consecutive tests.8 Procedure8.1 Transferring the sample to the ignition vessel8.1.1 Transfer liquid samples with a pipette or viscous liquids having a dynamic viscosity of more than50 mPas with an injection syringe in a rapid but still readily countable se
39、quence of drops to the ignition vessel.Cool samples having an initial boiling point of less than 60 C as well as the pipette or the injection syringe toat least 30 C below the boiling point before the transfer. Protect the samples and the equipment fromatmospheric moisture while doing this.8.1.2 Col
40、lect gaseous samples only from the vapour space of the sample container and inject them as followsinto the ignition vessel: first remove an aliquot of the sample from the sample container, if necessary via apressure reducer, through the side attachment connection using a piston-operated pump and exp
41、el it via theelbow situated outside the ignition vessel. Once all the lines and the elbow have been filled with the gas undertest by flushing several times, transfer the elbow to the position shown in figure 4 and force the required quantityof the gas under test into the ignition vessel at a flow ra
42、te of about 25 ml/s.8.2 Preliminary testFirst make a rough preliminary test of the ignition temperature by heating the ignition vessel at a rate of 3 Cto 5 C/min, introducing five drops of liquid or 50 ml of the gaseous substance into the vessel every time thetemperature rises about 20 C. Determine
43、whether ignition occurs at each temperature. Always clean the vesselby blowing it out using a hand-operated bulb pump before introducing new sample material. The temperatureat which ignition is first observed under these conditions shall be regarded as the initial temperature for the maintest.8.3 Ma
44、in test8.3.1 Lowest value of first test seriesStarting at the initial temperature for the main test, introduce the sample in the same quantity as for thepreliminary test into the ignition vessel, lowering the temperature in steps of 5 C until a temperature is reachedat which, for the first time, no
45、ignition occurs. Then continue the ignition tests by varying the sample size at thistemperature.If ignition occurs in this process, repeat the ignition test after lowering the temperature of the ignition vessela further 5 C and record the ignition delay and the amount of substance introduced. In thi
46、s way, establish thetemperature that does not result in ignition for any of the quantities of sample material used. Now performfurther tests between this temperature and a temperature 5 C higher, altering the temperature and the samplesize introduced in small quantities. In doing this, it is advisab
47、le to start from the higher temperature and varythe quantity found most favourable at the next highest temperature by small amounts at every temperaturestage (reduced by about 2 C).The lowest temperature at which ignition is still observed under these conditions shall be taken as the lowestvalue of
48、the first test series.8.3.2 Lowest value of main testThe lowest value of the first test series may be affected by residues in a frequently used ignition vessel and shallconsequently not be regarded as a final result. The final lowest value shall be determined by a second test seriesat the end of the
49、 main test in the temperature range of the lowest value of the first test series using a fresh, cleanignition vessel or a used ignition vessel dried after carefully removing any impurities from the inside walls bywashing with water, if necessary after using acid or other solvents. In addition, after every ignition test, theignition vessel shall be cleaned with the bulb pump. The slight cooling of the vessel due to blowing cold air inshall be allowed to correct itself before starting the next ignition test.8.4 Repeating the testPerform further test seri
