Flame center

Figure 13. Flame center for flares and ignited vents.

These coordinates locate the flame center, which is treated as the source of all radiation from the flame. 

Step 6 Calculate the location of the flame center, which is treated as the source of all radiation from the flame. Only flames bent over by the wind are considered, since for nearly vertical flames (calm air) the effective center of flame radiation is higher off the ground and therefore not limiting for spacing purposes. 

Credit for additional height of the flame center for multiple valve installations may be taken by clustering the safety valve discharge pipes to the atmosphere. The following procedure should be used for determining equivalent diameter and exit velocity to be used in the flame center calculation. Diameter and velocity are based on the total acmal area of the clustered vents. 

Xj = Downwind distance from flare stack to flame center, m... 

Height of flame center above flare tip, m h = Height of flare tip above grade, m F = Fraction of heat release radiated from the flame m = Mass flaring rate, kg/s H = Lower heating value of the flare gas, MJ/kg r = Relative humidity, percent The following are the calculation steps ... 

Step 5 Calculate K from the following equation. K is incident on a surface normal to a line from point (x, z) to the flame center. This is the maximum value of K at that location and is the value used when personnel exposure is being considered. 

R = distance from flame center to point X on ground (see Figure 7-77)... 

Worst condition of gas flow and tvind velocities, vertically below flame center ... 

A flame under the influence of wind will tilt in the direction that the wind is blowing and will change the location of the flame center. API RP 521 (2007) presents two methods for estimating the required flare height when the flame is tilted. 

E. Meeks, A. Ting, J.F. Grcar, and R.J. Kee. Flame-Centered Grid Transformation for Numerical Simulation of Strained Flames. Combust, and Flame, 96 179-185,1994. 

The shortest stack is obtained when Qmax- 3,300 Btu/hr. sq. ft. (Figure 6-4) which allows for zero escape time. The limiting radial distance from the flame center, X (feet), see Figure 6-5, is... 

The controversy around the rapid spread of the flames centers around whether blame lies primarily with the use of hydrogen gas for lift or the flammable coating used on the outside of the envelope fabric. 

Heat the glass tubing of appropriate length with the flame centered where you want the bend, supporting the tubing lengthwise in the upper zone of the flame. Be careful to rotate it slowly in the flame to insure uniform... 

Remove the flame, center the cover on the crucible, and allow them to cool to room temperature. Begin another run during this period of cooling. Finally, weigh the cooled crucible, cover, and dehydrated sample on the analytical balance, and record the mass in TABLE 8.3. Use a spatula to scrape the dehydrated sample from the crucible into a bottle on the reagent bench marked DEHYDRATED BaCl2. 

D = minimum distance from flame center, m X = fraction of heat intensity transmitted F = fraction of heat radiated Q = heat release, kW K = allowable radiation, kW/m ... 

A different approach is used to estimate the vertical and horizontal distances of the flame center from the top of the flare stack. 

Figure 4.19 Flame center for flares and ignited vents vertical distance (SI units). (Courtesy American Petroleum Institute, 1220 L Street, NW, Washington, D.C.)...

Total heat released (Equation 4.93) = 1.49 W kW Minimum distance from flame center (Equation 4.92) = 53 m Flare stack diameter (Equation 4.94) = 0.496 m... 

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