(a) Each cargo tank must have a secondary barrier that meets Table 3 and except as allowed in Table 3, the hull must not be the secondary barrier.
(b) If the Commandant (CG-ENG) specially approves an integral tank for a design temperature at atmospheric pressure lower than −10 °C (14 °F), the integral tank must have a complete secondary barrier that meets § 154.460.
(c) If the Commandant (CG-ENG) specially approves a semi-membrane tank under the requirements of an independent tank type B, the semi-membrane tank may have a partial secondary barrier specially approved by the Commandant (CG-ENG).
(d) If Table 3 allows the hull to be a secondary barrier, the vessel's hull must:
(1) Meet §§ 154.605 through 154.630; and
(2) Be designed for the stresses resulting from the design temperature.
Table 3—Secondary Barriers for Tanks
| Tank type
| Cargo temperature (T) at atmospheric pressure
|
|---|
| T≥−10 °C (14 °F)
| T<-10 °C (14 °F)≥55 °C (−67 °F)
| T<−55 °C (−67 °F)
|
|---|
| Integral | No secondary barrier required | Tank type not usually allowed
1 | Tank type not allowed.
|
| Membrane | ......do | Complete secondary barrier
1 | Complete secondary barrier.
|
| Semi-membrane | ......do | ......do | Do.
|
| Independent:
| | | |
| Type A | ......do | ......do | Do.
|
| Type B | ......do | Partial secondary barrier
1 | Partial secondary barrier.
|
| Type C | ......do | No secondary barrier required | No secondary barrier required.
|
source: CGD 74-289, 44 FR 26009, May 3, 1979, unless otherwise noted.
cite as: 46 CFR 154.459