The most likely leakage of switching heat exchanger is the welding line, especially the joint of the head and the pipeline. Most of the causes of leakage are the quality problems of manufacture and installation, which are also related to maintenance. The working condition of switching heat exchanger is poor. It is not only impacted by alternating airflow, but also changes greatly in airflow temperature. In long-term operation, the weak parts are easy to leak.
Therefore, the welding quality should be strictly guaranteed during manufacture and installation. After installation, strict leak detection and pressure test must be carried out before driving, and problems should be dealt with timely to avoid passivity after driving.
There are three methods to check whether the switching heat exchanger leaks in operation:
1) flow method. When a large amount of leakage occurs between the channel of product oxygen or product nitrogen and air channel, the output of oxygen or nitrogen increases obviously. The air intake should also increase. At the same time, the air pressure decreases and the upper tower pressure increases.
2) purity method. When there is a small amount of leakage between the oxygen and nitrogen channels of the products and the air channels, it can be judged by the results of the product purity analysis, and the product purity of the switching heat exchanger decreases.
3) temperature method. When leakage occurs between the air channel and the sewage and nitrogen channel, the temperature in the middle part will change obviously, and it can be judged from the temperature change which unit has the leakage. Moreover, the air intake will also increase.
Repair welding should be conducted after identifying the leakage parts. If there is an internal leakage in a single channel, the channel can be sealed. When serious leakage can not be solved, the heat exchanger unit needs to be replaced.
