46 CFR §39.2007

1. (a)Each cargo tank of a tankship must be equipped with an intrinsically safe high-level alarm and a tank overfill alarm.
2. (b)If installed after July 23, 1990, the high-level alarm and tank overfill alarm required by paragraph (a) of this section must—
   1. (1)Be independent of each other;
   2. (2)Activate an alarm in the event of loss of power to the alarm system;
   3. (3)Activate an alarm during the failure of electrical circuitry to the tank level sensor; and
   4. (4)Be able to be verified at the tank for proper operation prior to each transfer. This procedure may be achieved with the use of an electronic self-testing feature that monitors the condition of the alarm circuitry and sensor.
3. (c)The high-level alarm required by paragraph (a) of this section must—
   1. (1)Activate an alarm once the cargo level reaches 95 percent of the tank capacity or higher, but before the tank overfill alarm;
   2. (2)Be identified with the legend “High-level Alarm” in black letters at least 50.8 millimeters (2 inches) high on a white background; and
   3. (3)Activate a visible and audible alarm so that it can be seen and heard on the vessel where cargo transfer is controlled.
4. (d)The tank overfill alarm required by paragraph (a) of this section must—
   1. (1)Be independent of the cargo gauging system;
   2. (2)Be identified with the legend “TANK OVERFILL ALARM” in black letters at least 50.8 millimeters (2 inches) high on a white background;
   3. (3)Activate a visible and audible alarm so that it can be seen and heard on the vessel where cargo transfer is controlled and in the cargo deck area; and
   4. (4)Activate an alarm early enough to allow the person in charge of transfer operations to stop the cargo transfer before the tank overflows.
5. (e)If a spill valve is installed on a cargo tank fitted with a vapor collection system, it must meet the requirements of 46 CFR 39.2009(a)(3).
6. (f)If a rupture disk is installed on a cargo tank fitted with a vapor collection system, it must meet the requirements of 46 CFR 39.2009(a)(4).