API RP 2216:2010 pdf download

API RP 2216:2010 pdf download.lgnition Risk of Hydrocarbon Liquids and Vapors by Hot Surfaces in the Open Air.
4.2 SIDES OF STORAGE TANKS
Hot surfaces may also cause ignitions in high flash point hydrocarbon storage tanks. Fixed (cone) roof tanks storing small amounts of fuel oil, diesel fuel and lubricants are more likely to explode when involved in surrounding fires than are tanks containing low flash products. This is because vapors are not usually present in these tanks (above the liquid level) when fires occur. A considerable amount of time is required for the radiant heat of a fire impacting on the side of one of a high flash point hydrocarbon storage tank, to produce enough vapors to fill the empty space above the liquid level with a concentration that is too rich to burn (above the upper explosive limit). If the side of the tank is heated sutilciently enough during the time the vapors arc forming. and if the vapor concentration reaches the explosive range at the same time that the side of the tank reaches ignition temperatures. an internal explosion is likely to occur15.
4.3 IGNITION OF HEAVY OILS BY HOT SURFACES
Hot surface fires have occurred involving heavy oils such as hydraulic oil, motor oil, lubricating oil and gear oil. One example of such an ignition would be the release of a fine spray or oil mist from a broken or leaking hydraulic line, against an overheated surfice, such as that caused by a bearing failure. Allowing a spill or stream of heavy oil to contact a hot surface for a period of time (depending on the surface temperature) that is long enough for decomposition (cracking) to occur, will result in ignition. An example of this would be a motor oil spill on the hot manifold of an automobile engine.
5 SUMMARY
5.1 GENERAL
All of the testing (to date) indicates that surface temperatures must be several hundred degrees (Fahrenheit) above the laboratory measured minimum A1Ts to ignite flammable vapors in the open air. However, it should be recognized that both pre-flame ignition and cool-flame ignition may occur at temperatures lower than the AlT (see 3.3). In addition, both wind velocity and ignition lag time will impact the AlT (see 3.4).
The size of the heated surface also affects the ability to cause ignition. Heated surfaces may be too small (in size) to cause ignition whereas a flame or large, ignitable spark (suchas an electrical spark) could be the source of ignition in anidentical situation (same hydrocarbon，same temperature,etc.). In fact, a heated surface may be so small that noincrease in temperature will compensate for volume (such asthe size of a small piece of hot sparking metal that resultsfrom the use of hand tools on steel surfaces).
lt appears that a number of other factors also influence theAIT of a hydrocarbon when contacting hot surfaces.Theseinclude the rate of liquid spread on the hot surface, the rate ofheat transfer between the heated surface and the hydrocarbon,the temperature and molecular changes within the liquid andthe ambient temperature, rate of vaporization and diffusion ofthe liquid. These factors affect the ability to accurately predictconditions under which auto-ignition will occur when hydro-carbons contact heated surfaces.
5.2CONCLUSION
The identification of a heated surface as the cause of igni-tion can often lead to an incorrect analysis of the real sourceof ignition. In general, ignition of hydrocarbons by a hot sur-face should not be assumed unless the surface temperature isapproximately 360°F (182°C) above the accepted minimumignition temperature of the hydrocarbon involved.Test dataand field experience both indicate that the ignition of flamma-ble hydrocarbon vapors by hot surfaces in the open airrequires temperatures considerably above the reported mini-mum AITs of the hydrocarbons involved.