Code of Federal Regulations Title 46. Shipping § 46.154.407 Cargo tank internal pressure head

(a) For the calculation required under § 154.406(a)(1) and (b), the internal pressure head (h_eq), must be determined from the following formula:

h_eq=10 P_o+(h_gd) _max

where:

h_gd (the value of internal pressure, in meters of fresh water, resulting from the combined effects of gravity and dynamic accelerations of a full tank)=aβ Zβ Y;

where:

aβ =dimensionless acceleration relative to the acceleration of gravity resulting from gravitational and dynamic loads in the β direction (see figure 1);

Z  =largest liquid height (m) above the point where the pressure is to be determined in the β direction (see figure 2);

Y=maximum specific weight of the cargo (t/m ³) at the design temperature.

(b) The (h_gd) _max is determined for the β direction, on the ellipse in Figure 1, which gives the maximum value for h_gd.

(c) When the longitudinal acceleration is considered in addition to the vertical transverse acceleration, an ellipsoid must be used in the calculations instead of the ellipse contained in Figure 1.