What is the purpose of the dip pipe on a vehicle mounted LPG tank?

The dip pipe in a vehicle-mounted LPG (Liquefied Petroleum Gas) tank serves the critical role of determining the actual quantity of liquid gas present within the tank. When inserted into the tank, the dip pipe allows for accurate measurement of the liquid level by providing a direct path for liquid to flow to the gauge or measuring instrument. This ensures that operators can ascertain how much LPG is available for use, which is vital for both safety and operational efficiency.

This function is particularly important in understanding the tank's capacity, as it allows for real-time monitoring of fuel levels, ensuring that the tank is neither overfilled nor excessively depleted during use. Accurately gauging the contents of an LPG tank is essential for preventing accidents related to overpressure or gas starvation.

The other options do not reflect the primary function of the dip pipe. For example, internal pressure measurement and temperature indication involve different components and sensors not associated with the dip pipe's purpose, and relieving excess vapor typically requires different mechanisms, such as pressure relief valves. Thus, the correct answer emphasizes the importance of measuring the liquid capacity of the LPG tank effectively.