Manual Tank Gauging
For manual gauging, a dip tape or dipstick is used. A graduation is applied to read the measurement. An acceptable measuring tape is made of steel with a weight on the end. Often, special paste is used, which changes color when it is in contact with the product. At underground tanks at gas stations, dipsticks are used, which are calibrated for a certain tank and have readout in volume. An official measuring tape or dipstick must be calibrated regularly against an accepted standard and may not be buckled. Accurate hand dipping is more complicated than it looks and, therefore, requires training.
Under good conditions, it is possible to measure with accuracies approaching 1mm. Wind, precipitation, cold and lack of light have a negative effect on measuring results. When employees have to perform a hand dip on an above ground tank, they must climb the tank, which is an additional safety risk and time consuming. Hand dipping is not recommended with toxic or dangerous products. Even with these factors, this method is still accepted worldwide.
Once a manual measurement is taken, it may need to be included into the tank gauging system's software. FuelsManager® allows the operator to input manual measurements to be used in inventory calculations.
For further information, please refer to the API standards as set out in the Manual of Petroleum Measurement Standards Chapter 3 - Tank Gauging, Section 3.1B.4 "Field Calibration of Automatic Tank Gauges".