Hot Taps and Line Stops are “under pressure” drilling operations, meaning that a pipe or other pressure vessel is drilled into, while the system remains in service, and under pressure. There are many reasons to do this, and by the same token, there are many good reasons to not do this, if a system can be shut down, in order to perform the drilling operation.Hot taps and line stops involve the use of specialized equipment and highly trained technicians, in order to cut a hole in a pipe, without taking the pipe out of service, or lowering the pressure. This is most often done in Chemical Plants, Refineries, Power Plants, Manufacturing Plants, Nuclear Power Plants, or any other location, where loss of service, is not acceptable. This technical paper is intended to be a primer of the hot tap and line stop operation, primarily intended for those who have little if any prior knowledge of the process. This work is highly technical, requires years of training, highly specialized equipment, and should not be attempted without proper training. Iran API has the ability of HOT TAPPING up to 56″ pipelines.