The trap is also called an automatic drain or condensate drain, which is divided into steam system use and gas system use. The trap is installed at the end of the steam heated pipeline, and its function is to discharge the condensate in the steam heated pipeline to the outside of the pipeline. Most traps can automatically identify steam and water (not including thermostatic type), so as to achieve the purpose of automatic steam drainage. The trap is widely used in petrochemical, food and pharmaceutical, power plant and other industries, and plays a great role in energy saving and emission reduction.