Why does the water seal tank in a chemical plant need to be continuously replenished with water, and why is water constantly drained from it?

It is mainly to prevent the water level in the water seal groove from dropping after water escapes, so that the water seal function is not lost

Ensure that the water in the water seal tank overflows properly, as this is necessary to maintain the function of the safety seal and prevent gas from escaping inside the equipment due to a lack of water in the seal.

The water in the tank rises and falls due to the action of gas. If no water is added and the overflow mechanism is not maintained, after the water in the tank overflows several times, the water level inside the tank will drop, or even gas leakage may occur, thereby losing its water-sealing function.

It is also possible that the gas contains a certain amount of substances soluble in water, leading to the contamination of the water seal

The water in the water seal tank rises and falls as the gas phase pressure changes. Without adding water, it is difficult to maintain a certain water level after overflow, which would result in a water seal pressure relative to atmospheric pressure. This causes the pressure of the water in the water seal tank to be lower than the gas phase pressure, leading to leakage from the tank and the loss of its sealing function.

Common structures of liquid seals include the liquid seal tank type, U-tube liquid seal device, Type II tube liquid seal device, and automatic drainage liquid seal device. I’ve used them all, and I really haven’t thought carefully about why they all need to overflow by running. It seems that the reasons were basically covered by the friends upstairs; as a supplementary point: it’s probably not the reason mentioned by the friend on floor 6 – when designing the liquid seal, a safety margin is taken into account based on pressure. There are also requirements for the diameter of the inlet and outlet pipes. For details, see \"HG-T 20570.17-95 Installation of Liquid Seals.\" The main reason seems to be to prevent evaporation and failures caused by a lack of water after the liquid seal moves up or down. Evaporation is easy to understand. A typical example of liquid-sealed lifting is the wet screw-guided gas storage tank. After the gas holder is raised or lowered, the water seal height changes significantly, which can lead to a lack of water and result in gas leaks or even catastrophic accidents such as the sudden collapse of the gas holder. Another reason is that many liquid seals use circulating water, which makes the injection pipes and valves prone to clogging, preventing the establishment of a liquid seal. Therefore, even as a liquid seal device for draining condensate (which overflows at any time), it is necessary to operate the water injection valve periodically. Automatic drainage type liquid seal devices also require the water injection pipe to remain dripping.

What the people upstairs said makes sense, but it’s just my personal opinion. If it is merely to prevent water vapor from escaping and sealing is not sufficient, checking it after some time will meet the requirements. Our previous company did the same thing. If it’s like this in winter, is it related to anti-freezing? . .

I agree with what was said above; we still need to take into account the issue of freezing in winter

Maintaining the water seal at an appropriate level serves two purposes: 1. To ensure the reliability of the water seal and prevent it from being damaged due to evaporation; 2. To carry away the impurities that evaporate from the container, preventing their accumulation within the water seal over time

1. Maintain a constant static pressure, usually a slight positive pressure. 2. If no water is added, it will evaporate, causing the water level to drop. As a result, the pressure in the equipment being protected exceeds the static pressure, allowing gases (usually inert gases such as nitrogen) to escape and be wasted. 3. If the static pressure is too high, it can cause overpressure or underpressure in equipment designed for normal pressure conditions. 4. During routine inspections, the lower valves can be opened to release some water in order to check for any nitrogen leakage and to ensure that this pipeline is functioning properly or is under a slight positive pressure.