What is the most accurate method to determine the amount of propane in a large storage tank?

The most accurate method to determine the amount of propane in a large storage tank is through the use of a roto gauge or slip tube gauge. This type of gauge is designed specifically to provide a reliable measurement of the liquid level within the tank by using a mechanical system that allows for precise readings.

Roto gauges operate on the principle of displacement and give a direct readout of the propane level, which translates into the volume of gas contained within the tank. They are effective even when tank pressure changes, as they are less affected by vapor pressure compared to other gauges. This accuracy is crucial for safety and for maintaining the proper functioning of the gas system, especially in large commercial or industrial applications.

In contrast, a float gauge measures the level of liquid based on a floating device, which can be subject to inaccuracies due to variations in liquid density or buoyancy issues, especially if the tank is not uniformly filled. A pressure gauge indicates the pressure of the vapor above the liquid and can help infer the liquid level only under specific conditions, but it does not directly measure the liquid quantity and can lead to errors if the temperature changes. A fixed liquid level gauge might involve more complex systems and can be subject to calibration issues, making it less accurate under certain conditions compared