Line stopping is a process used to modify a line in a pipe system or make repairs without interrupting service to the rest of the system or depressurizing the line. It reduces the amount of time the line is out of service and avoids having to drain the system, which can be expensive, messy and slow. The basics of a line stop are as follows:
Step 1: A Hot Tap makes a hole in the pipe and a Line Stopping machine is bolted to the tapping valve.
Step 2: Once secure, the valve is opened and the machine is filled with whatever flows in the pipe.
Step 3: The Line Stop machine inserts a steel Plugging Head down through the open valve and into the pipe through the tapped hole.
Step 4: Then a sensor touches the inside wall of the pipe, and the Plugging Head moves and turns into the sealing position.
Step 5: The flow is then stopped and the pipe can depressurize and modifications or repairs can be made. Once the changes are complete, the pipe
is repressurized and the plugging tees are blanked.
When you just can not interrupt service of a line to make repairs of modifications there is a way to keep continuous flow in the line and still do the
work. This process is called a bypass.
What is a bypass? When you need to make a change in an existing system without interrupting the flow, a bypass is a great method. The process
has several steps.
First, a set of bypass tees are attached to the pipe on either side of the area to be valved or repaired. Then a set of stop tees are attached on the
pipe outside of where the pipe will be cut to add new valve or repair work. Then, on the very inside, vent holes are made to release the pressure in the portion of the pipe that will be cut.
Second, temporary sandwich type valves are installed on each of the tees and each one is hot tapped.
Then, the bypass pipe work is commissioned and installed and the up stream and down stream plugging machines are inserted into the fittings.
Once the bypass is functioning, the plugging machines are lowered and the pipe is plugged. The center section is ready to be de-pressurized through the
vent hole fittings and that section can the be cut and altered in whatever way you need.
When the repair or modifications are finished, the center section is re-pressurized through the vent holes. Then the plugging machines are withdrawn
and the main line becomes the line of flow.
To finish things off, the sandwich valves are removed, the fittings are all blinded and blanked off and the job is complete.