TABLE OF CONTENTS The function of the gauge is to register the ullage of the tank at any given time, in particular when the liquid level in the tank is changing during the loading and discharge periods. The gauge is designed to record the readings not only at the top deck level of the tank but also remotely at a central cargo control room. A transmitter is fitted on the head of the gauge for just this purpose.
The unit is totally enclosed and various models manufactured are suitable for use aboard not only oil tankers, but chemical and gas carriers as well (Figure 5.13).
Inside the gauge housing is a calibrated ullage tape, perforated to pass over a sprocket wheel and guided to a spring-loaded tape-drum. The tape extends into the tank and is secured to a float of critical weight. As the liquid rises or falls, the tape is drawn into, or extracted out from, the drum at the gauge head. The tape-drum, being spring loaded, provides a constant tension on the tape, regardless of the amount of tape paid out. A counter window for display is fitted into the gauge head, which allows the ullage to be read on site at the top of the tank.
