High level alarms
Certain cargoes require tanks to be fitted with high level alarms which are independent of any alarms fitted to the closed gauging system. The alarm may be activated by either a float operated switch, a capacitive pressure transmitter, or an ultrasonic device.
The activation point should be set to when the cargo is approaching the normal full condition. Typically this limit will be set at 95%.
Tank overflow control systems (high-high level alarms)
Tank overtlow control systems should be set to alarm when the level in the tank reaches 98% of capacity.
All high level and overflow alarms should be tested in accordance with the manufacturers’ instructions to ensure correct operation prior to cargo operations. This will ensure that the alarms are working correctly and can be relied upon.