API RP 2216:2003 pdf download

API RP 2216:2003 pdf download.lgnition Risk of Hydrocarbon Liquids and Vapors by Hot Surfaces in the Open Air.
Time lags of a minute or more during AlT testing are common5. Additionally, the AlT is lower if the test vessel size (or test surface area) is larger, the heat of combustion is greater, the pressure is higher, the hydrocarbon molecular weight is larger or the mixture conductivity is smaller6. All of these factors affect the ability to accurately predict conditions under which auto-ignition will occur when hydrocarbons contact heated surfaces.
3.3 STANDARD ASTM AUTO-IGNITION TEST METHODS
The majority of reported AlT data has been previously obtained by one of two standard AlT test methods, ASTM D 286 and D 2155. These two original test methods7 (which have now been withdrawn by the American Society for Testing and Materials) involved introducing small measured amounts of flammable or combustible liquids into glass flasks that are uniformly heated with air without an external source of ignition. If ignition occurred, the flask wall temperature and the time for Ignition to occur after introduction of the sample (ignition lag) were noted. The tests were repeated using different flask wall temperatures to determine the lowest temperature at which ignition would occur in less than 10 mm., which was then reported as the minimum ignition temperature of the liquid tested. Because both of these former test methods relied on visual detection of a flame, the ignition temperatures obtained were the minimum temperatures at which flame ignitions were visually observed.
The current ASTM test standards1, ASTM D 2883 and ASTM E 659, also use the heated glass flask technique. However, these ASTM tests now use thermoelectric flame detection methodology that will detect non-luminous or barely luminous reactions that are difficult or impossible to detect by sight. This thermoelectric methodology has resulted in a new series of terms used to describe ignition temperature thresholds, as follows:
Hot—flame Ignition: A rapid, self-sustaining, sometimes audible, gas phase reaction of a sample or its decomposition products with an oxidant usually accompanied by a readily visible yellow or blue flame. AlT is defined as the hot-flame reaction threshold temperature.
Cool-flame Ignition: A relatively slow, self-sustaining, barely luminous, gas phase reaction of the sample or its decomposition products with an oxidant. Cool flames are visible only in darkened areas. The Cool-flame Reaction Threshold (CFT) is the lowest temperature at which cool flame ignitions are observed.
Pre-flame Ignition: A slow non-luminous, gas phase reaction of the sample or its decomposition products with an oxidarn that it is contacting. The Pre-flame Reaction Threshold (PRT) is the lowest temperature at which an exothermic gas reaction is observed.
The ignition temperatures that are typically reported in flammable and combustible liquid hydrocarbon physical characteristic tables (such as in NFPA 325) are similar to AlT values. However, because the CFT temperature and the PRT temperature are slightly lower than the AlT, both must he considered when assessing the ignition risk of a specific hydrocarbon and a particular system or potential exposure.
3.4 OPEN AIR AUTO-IGNITION TESTS
The occurrence of hydrocarbon vapor releases in open air constitutes conditions that are very different from those experienced in the standard ASTM laboratory ignition temperature tests described above. Because actual field conditions diftér greatly from laboratory conditions, ignition of vapors in open air often requires surface temperatures considerably different from published ignition temperatures of specific hydrocarbons.
3.4.1 Open Air tests.