(a) For the calculation required under §154.406(a)(1) and (b), the internal pressure head (heq), must be determined from the following formula:
heq = 10 Po + (hgd)max
where:
hgd (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);
Zβ = 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/m3) at the design temperature.
(b) The (hgd) max is determined for the β direction, on the ellipse in Figure 1, which gives the maximum value for hgd.
(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.
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