Metal ring gaskets originated in the 1920s, and were first applied in the boiler field in the United States, used for sealing manhole covers, auto clips, and other containers. Later, they received special attention in the petroleum production and refining industry. With the increase in temperature and pressure of steam power units, metal ring gaskets are more and more widely used. The metal ring gasket contacts with the inner and outer side (mainly the outer side) of the flange trapezoidal groove through the gasket, and is pressed tightly and sealed. The metal ring pad is divided into an octagonal ring pad and an elliptical pad. Metal ring gaskets can be divided into octagonal and elliptic structures according to section shape. Octagonal ring pad and flange groove match, mainly for surface contact. Compared with the oval ring pad, although it is not easy to fit the flange groove, it can be used again, and because the section is made of straight lines, it is easy to process. The oval ring gasket is in line contact with the flange groove, and sealing is good, but the processing accuracy is high, thus increasing the manufacturing cost, and the oval ring gasket can not be reused.