When a leak is generated in an air separation plant, the cooling capacity is insufficient and the main cooling liquid level keeps falling. In the case of a large gas leak, an increase in pressure in the cold box can be observed. If the cold box is not tight, a large amount of cold gas will come out from the gap. In the case of low temperature liquid leakage, no obvious pressure rise and gas escape can be observed, and the base temperature can often be measured to have dropped significantly.
In order to have a preliminary judgement on the leakage site and leakage before shutdown for maintenance, in order to shorten the downtime. Comprehensive use of the following methods of judgement: (1) the purity of the gas escaping from the cold box. When the nitrogen or liquid nitrogen leakage, cold gas nitrogen volume fraction of up to 80% or more; oxygen or liquid oxygen leakage, the volume fraction of oxygen can be tested to a significant increase. (2) Observe the cold box wall ‘sweat’ or ‘frost’ parts. This time to note that the cryogenic liquid leakage, ‘frost’ part of the partial leakage point below. (3) Observe the regularity of the escaping gas. The main judgement switching type heat exchanger switching channel leakage. If the container is used alternately, the leakage can be further judged by switching the use of the container.
In order to judge the accuracy of the leakage, accumulate experience in actual operation practice, but also be familiar with the structure of the cold box and each container, pipeline, valve space location.
