STANDARD HANDBOOK OF PETROLEUM & NATURAL GAS ...

Derricks and Portable Masts 513
When pipe or tubing is racked in more than one area, the minimum area of
setback shall be no less than 120% of the area on one side; when rods are racked
on more than one area, the minimum area of rods shall be no less than 150%
of the area of one side to account for the effect of wind on the leeward area
(Figure 4-4).
The pressure due to wind is
P = 0.00338 (V;)(C,)(C,) (4-3)
where P = pressure in. lb/ft4
V, = wind velocity in knots
C, = height coefficient
Height (ft) c,
0- 50 1 .o
50-1 00 1.1
100-1 50 1.2
150-200 1.3
200-250 1.4
NOTE: In calculating the value of A,
If R is greater than lSa, use R. If not, use 1.5a.
If T is greater than 1.2b, use T. If not, use 1.2b.
Figure 4-4. Diagram of projected area [9].