API RP 2216:2003(2010) pdf download

API RP 2216:2003(2010) pdf download.lgnition Risk of Hydrocarbon Liquids and Vapors by Hot Surfaces in the Open Air.
3.4.3 Effect of Wind Velocity
In open air near a hot surface, the time of contact is only seconds or a fraction of a second because convection currents and normal wind disturbances mose a flammable vapor-in-air mixture past the hot surface rapidly. Because the contact time under open-air conditions is so short, the surface tefllpcratLlrc required for ignition must be substantially higher than reported minimum AITs. The effect of wind eIocity on the surface temperature required tr ignition of kerosene AlT of 4l(TF 121(YCI) was determined in wind tunnel tests (see Table 4).
3.5 GASOLINE AND OXYGENATE BLENDS
The addition of ethanol, methanol and other oxygenates will slightly alter the ignition temperature of motor gasoline. The ignition temperatures of MTBE. alcohol and methanol fall within the range of ignition temperatures for gasoline (see Table 5). Test data indicated that the AlT of motor gasoline containing up to 10% ethanol is similar to that of straight gas. olinc. Gasoline blended with ethanol, in contact with a hot metal surface at a temperature of 475’F (265C) above the published AlT of gasoline, would not ignite. Howcver. gasoline blended with 10% methanollisobq.itanol had a tendency to ignite at about 360F (200”C) above the published AlT of gasoline (because it wetted the hot surtiacc more effectively than the gasolinelalcohol mixture)’2.
4 IGNITiON BY HOT SURFACES
4.1 EQUIPMENT SURFACES
Many small leaks and discharges of flammable and combustible liquids and vapors have occurred in process units without ignition by nearby hot equipment or uninsulated hot surfaces with temperatures several hundred degrees above minimum ignition temperatures of the hydrocarh m involved. However, ignition of hydrocarbons by heated surfaces has occurred when the liquid cornacied a tIred furnace or other similar direct source of ignition. For example. one statistical review of offshore fIres reported that during the ten year period from 1980 — 1990. 190 of 539 fires (35%) occurred from gas or liquid releases contacting extremely hot surfaces of equipment. usually the exhaust system piping of an engine or turbine drivert3. Another more recent paper, indicated that the U.S. Air Force experiences over 1(*) engine fires a year involving leaking fluidst4.
4.2 SIDES OF STORAGE TANKS
Hot surfaces may also cause lgintIons in high (lash point hydrocarbon storage tanks. Fixed (cone) roof tanks storing small amounts of fuel oil, diesel fuel and lubricants arc more likely to explode when involved in sumunding fires than are tanks containing low flash products. This is because vapors arc not usually present in thcsc tanks (above the liquid level) when fires occur. A considerable amount of time is required fir 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). II’ the side of the tank is heated sulliciently enough during the time the vapors are thnning. and if the vapor coneentr.ition reaches the explosive range at the same time that the side of the tank reaches ignition temperatures, an internal explosion is likely to occur.