Line stopping allows for a valve cut-in while maintaining the existing system flow. The line drawing below shows that the main system line is isolated using a stopping unit, drained and cut. A cut-in valve is then installed. After the cut-in valve is installed, the stopping equipment is removed and a completion plug with a blind flange is installed.
A line stop for relocation uses two hot tap and two line stopping units on high-pressure piping. Line stop plugging machines stop the system flow in the old pipe. The new pipe (system relocation) is in place and the system flow is re-routed. The line stop machines are removed and stop fittings are installed at completion.
Hot tapping or pressure tapping is the method of making a connection to existing piping or vessels while the existing system is under pressure. This method employs a drilling or tapping machine; a full-ported valve and a pressure-contained fitting attached to the existing pressurized system. Minimal water loss occurs utilizing this process.