What is the fundamental purpose of using a two-chamber equilibrium vessel for measuring the drum liquid level?

The purpose of a two-chamber balanced vessel is to eliminate the effects caused by the difference in density between the drum and that in the level gauge.

In simple terms, it ensures that the temperature of the liquid in the positive and negative pressure transduction tubes is the same; this results in a consistent density of the liquid in those tubes, thereby eliminating measurement errors caused by temperature differences.

It seems that for drum liquid levels at high pressures, dual-chamber balance vessels aren’t used; generally, single-chamber vessels are employed, with temperature and pressure compensation algorithms for high-temperature and high-pressure conditions

The main function of the dual-chamber balance container is to ensure that the differential pressure level gauge measures the actual liquid level. In a boiler, there is a boiling interface and no clear boundary between water and steam; by using a dual-chamber balance container, the water in the boiler can be drawn out, and this container ensures that the substance inside remains in liquid form. The differential pressure level gauge then measures the level of liquid in the dual-chamber balance container. The most important aspect of using a two-chamber equilibrium vessel is to make a hole at the bottom of the device, connecting it to the bottom of the two-chamber equilibrium vessel; this ensures good fluidity and guarantees that the level indicated is the actual liquid level, rather than a false level caused by vapor. For reference only; that’s the principle behind it. I’m not sure if I explained it clearly.