172.240—Permeability of spaces.
When doing the calculations required in § 172.225 ,
(a)
The permeability of a floodable space, other than a machinery or cargo space, must be assumed as listed in Table 172.240;
(b)
Calculations in which a machinery space is treated as a floodable space must be based on an assumed machinery space permeability of 85% unless the use of an assumed permeability of less than 85% is justified in detail; and
(c)
Calculations in which a cargo space that is completely filled is considered flooded must be based on an assumed cargo space permeability of 60% unless the use of an assumed permeability of less than 60% is justified in detail. If the cargo space is not completely filled, a cargo space permeability of 95% must be assumed unless the use of an assumed permeability of less than 95% is justified in detail.
| Spaces and tanks | Permeability (percent) |
|---|---|
| Storeroom spaces | 60 |
| Accommodations spaces | 95 |
| Voids | 95 |
| Consumable liquid tanks | 1 95 or 0 |
| Other liquid tanks | 2 95 or 0 |
| Cargo (completely filled) | 60 |
| Cargo (empty) | 95 |
| Machinery | 85 |
| 1 Whichever results in the more disabling condition. | |
| 2 If tanks are partially filled, the permeability must be determined from the actual density and amount of liquid carried. | |