Before closing the throttle valve, the conditions for closing the valve should be created: the liquid oxygen liquid level is close to the normal liquid level, and the liquid level has an upward trend. The temperature in front of section-1 valve should be kept at-155 ~ Between-165℃. The low pressure should be controlled at 0.05MPa, and the medium pressure should be less than 0.3MPa (surface pressure ).
When you start to close the valve, you should master the speed of closing the valve. If it is closed too fast, it will cause liquid suspension; if it is closed too slowly, it will cause the liquid oxygen level gauge to be too full. The speed of closing valve is based on the principle of stable liquid oxygen level. If the liquid oxygen level rises fast, the valve can be closed faster; if the liquid oxygen level rises slowly, it will close slowly. If the liquid oxygen level has a downward trend, then the valve should be stopped. If the liquid level drops quickly and the medium pressure rises obviously, the throttle valve should be opened again, and it should be shut down after the liquid level rises. Pay attention to the change of medium pressure when closing the valve. As the two valves close smaller, it is normal for medium pressure to rise. But the rising speed should not be too fast. Generally, it is better to rise 0.1MPa in half an hour. If sometimes the medium pressure rises faster, while the liquid oxygen level does not drop temporarily or even rises, in this case, the valve can not be closed again, and it will be closed when the medium pressure is stable and the liquid level does not drop.
When starting, the liquid air and liquid nitrogen throttle valve are opened respectively 12 ~ 15 circles. At the beginning of closing the valve, close the two valves 2 circles respectively. Every 3 ~ After 5 minutes, turn it off for another 2 circles according to the situation of liquid oxygen level and medium pressure. After two valves are closed to 8 circles, each time it can only be closed at the speed of half a circle. After the two valves are closed to 6 circles, first close the liquid nitrogen throttle to 1.5 ~ 2 circles. The speed in the future should be slower, and it can only be reduced at the speed of 90 °, 60 ° and 30 °. When the liquid-air throttle is closed to 4 circles and the liquid nitrogen throttle is closed to 2 circles, it should be closed according to the analysis results of the purity of the liquid-air and liquid nitrogen. When the purity of liquid air and liquid nitrogen is close to normal requirements, first control the liquid level gauge to 1.0 ~ 1.5 kPa, and then adjust the purity of liquid air and liquid nitrogen with liquid nitrogen throttle to achieve the best working condition. At this time, the switch amplitude of the valve is only 1 ° ~ Adjust within the range of 5 °.
