Hot tapping or pressure tapping is the method of making a connection to existing piping or pressure vessels without the interrupting or emptying that section of pipe or vessel. This means that a pipe or tank can continue to be in operation whilst maintenance or modifications are being done to it. The process is also used to drain off pressurized casing fluids and add test points or various sensors such as temperature and pressure.
Hot tapping is also the first procedure in line stopping, where a hole saw is used to make an opening in the pipe, so a line plugging head can be inserted.
Line stopping or line plugging is a means of isolating a piping system to provide a shut off where none exists. This process serves as a control, or temporary valve, that can be removed after alterations or valve replacements have been made. With a hot tap previously made on a line, a line stopper is attached to a temporary valve, and the valve is opened. The line stopper is hydraulically or mechanically pushed into the line to seal the pipe. The main is supported by the line stop sleeve. After performing the necessary service, the stop is removed, and a blind flange is installed on the sleeve.