At present, the main connection methods of fire pipes are: groove connection, flange connection, welding and threaded connection. In-pipe threading is to turn the end of galvanized steel pipe into a threaded outlet through a threading machine, and connect the two pipes together in the form of threaded connection through cast iron wire connectors. Groove pressing is a process of groove connection. The end of galvanized steel pipe is pressed out of a circle of grooves by a groove pressing machine for installing groove fixtures.