46 CFR §153.440

1. (a)Except as prescribed in paragraph (c) of this section, when Table 1 refers to this section, the containment system must meet the following requirements:
   1. (1)A heated or refrigerated cargo tank must have a remote reading thermometer sensing the temperature of the cargo at the bottom of the tank.
   2. (2)A refrigerated tank must have a remote reading second thermometer near the top of the tank and below the maximum liquid level allowed by § 153.981.
   3. (3)Unless waived under § 153.491(a), a cargo tank endorsed to carry a Category A, B, or C NLS cargo must have a thermometer whose temperature reading is no greater than the temperature of the cargo at a level above the tank bottom at least one-eighth but no more than one-half the height of the tank if the cargo is—
      1. (i)A Category A NLS or a Category B NLS having a viscosity of at least 25 mPa.s at 20 °C;
      2. (ii)A Category C NLS having a viscosity of at least 60 mPa.s at 20 °C; or
      3. (iii)A Category A, B, or C NLS that has a melting point greater than 0 °C.
2. (b)A readout for each remote thermometer required by this section must be at the point where cargo transfer is controlled.
3. (c)A portable thermometer may be substituted for the equipment required in paragraphs (a) and (b) of this section if—
   1. (1)Table 1 allows open gauging with the cargo; or
   2. (2)Table 1 allows restricted gauging with the cargo, and the portable thermometer is designed to be used through the containment system's restricted gauging system.