(a) Refrigerated and semirefrigerated tanks shall be filled so that there is an outage of at least 2 percent of the volume of the tank at the temperature corresponding to the vapor pressure of the cargo at the safety relief valve setting. A reduction in the required outage may be permitted by the Commandant when warranted by special design considerations. Normally then, the maximum volume to which a tank may be loaded is:
VL = 0.98dr V/dL
where:
VL = maximum volume to which tank may be loaded.
V = volume of tank.
dr = density of cargo at the temperature required for a cargo vapor pressure equal to the relief valve setting.
dL = density of cargo at the loading temperature and pressure.
(b) Nonrefrigerated tanks shall be filled so that their filling densities shall not exceed the ratios indicated in table 38.15-1(b).
(c) The “filling density” is defined as the percent ratio of the weight of the gas in a tank to the weight of water the tank will hold at 60 °F.
Table 38.15-1(b)—Maximum Permissible Filling Densities for Tanks Operating At or Near Ambient Temperature
| Specific gravity at 60 °F. |
Maximum permitted filling density | ||
|---|---|---|---|
| Unlagged tanks—water capacity | Lagged tanks—all capacities | ||
| 1,200 gal. and under | Over 1,200 gal. | ||
| 0.473-0.480 | 38 | 41 | 42 |
| 0.481-0.488 | 39 | 42 | 43 |
| 0.489-0.495 | 40 | 43 | 44 |
| 0.496-0.503 | 41 | 44 | 45 |
| 0.504-0.510 | 42 | 45 | 46 |
| 0.511-0.519 | 43 | 46 | 47 |
| 0.520-0.527 | 44 | 47 | 48 |
| 0.528-0.536 | 45 | 48 | 49 |
| 0.537-0.544 | 46 | 49 | 50 |
| 0.545-0.552 | 47 | 50 | 51 |
| 0.553-0.560 | 48 | 51 | 52 |
| 0.561-0.568 | 49 | 52 | 53 |
| 0.569-0.576 | 50 | 53 | 54 |
| 0.577-0.584 | 51 | 54 | 55 |
| 0.585-0.592 | 52 | 55 | 56 |
| 0.593-0.600 | 53 | 56 | 57 |
| 0.601-0.608 | 54 | 57 | 58 |
| 0.609-0.617 | 55 | 58 | 59 |
| 0.618-0.626 | 56 | 59 | 60 |
| 0.627-0.634 | 57 | 60 | 61 |
Note: Increase in filling densities to provide for seasonal changes may be considered by the Commandant upon presentation of factual evidence that safe operation can be effected.
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