The liquid oxygen pump is the core low-temperature transmission equipment of the air separation unit. The labyrinth seal gas system is the key component to prevent the leakage of liquid oxygen and ensure the safe operation of the pump. It has the characteristics of non-contact, low loss and stable operation.
The whole set of seal structure is mainly composed of multi-stage labyrinth seal teeth, seal cavity, seal gas inlet channel, exhaust channel and pressure regulating components. The sealing teeth are arranged in a staggered manner between the pump shaft and the housing to form a multi-stage narrow throttling clearance and expansion cavity, which are not in contact with the rotating shaft throughout the whole process, and can adapt to the high-speed continuous operation of the liquid oxygen pump. Dry and clean nitrogen is generally used as the sealing gas source on site.
The system works on the principle of differential pressure regulation. During operation, the control system compares the medium pressure in the pump chamber and the seal gas pressure in real time, and automatically stabilizes the pressure through the pressure regulating valve, so that the seal gas pressure is always 0.1~0.4MPa higher than the working pressure in the pump chamber, and a positive seal barrier is established. After the high-pressure nitrogen enters the labyrinth structure, it is throttled through multistage slots and expanded and depressurized step by step to effectively prevent the low-temperature liquid oxygen and vaporized oxygen in the pump cavity from channeling outward along the axis. After a small amount of permeated medium is mixed with sealed nitrogen, it is drained uniformly through the exhaust pipeline. By continuously stabilizing the pressure, replenishing air and throttling the pressure relief, it can not only avoid the leakage of liquid oxygen, ice crystal frosting and impurities entering the bearing, but also prevent the seal gas from pouring back into the pump cavity, so as to ensure the long-term safe, stable and continuous operation of the liquid oxygen pump.
