By October 17, 2007, single hull tank vessels (U.S. Flag and foreign Flag) will be required to have a Tank Level of Pressure Monitoring Systems
(TLPM) device permanently installed on each cargo tank which meets the following requirements:
- is intrinsically safe as per 46 CFR 111.105;
- indicates any loss of power or failure of the tank level or pressure monitoring device and monitors the condition of the alarm circuitry and sensor by an electronic self-testing feature;
- sets off an alarm at or before the cargo in the cargo tank either increases or decreases by a level of one percent from the cargo quantity in the tank after securing cargo transfer operations;
- operates in conditions up to sea state 5 (corresponding to Beaufort 6, i.e. winds between 22 and 27 knots and waves height between 2.5 to 4 metres), moisture, and varying weather conditions; and
- has audible and visual alarm indicators which are distinctly identifiable as cargo tank level or pressure monitoring alarms that can be seen and heard on the navigation bridge of the tank ship or towing vessel and on the cargo deck area.
Double-hull tank vessels and vessels carrying asphalt are exempt from the requirements.