Introduction to Hot Tapping in Piping

Introduction to Hot Tapping in Piping
Hot tapping is the technique used to attach a branch connection to a pipe while the system is in service, and then creating an opening in that pipe by drilling or cutting. While hot taps are most often done in piping system, they may also be done on pressure vessels and storage tanks to add nozzles. Hot tapping permit adding connections without depressurization or disruption of process operations. They may also be used to make piping connections where it would be inconvenient to prepare the system for hot work. Hot tapping is also used to isolate pipe sections for maintenance by plugging or stoppling the line.
Hot tapping is an inherently dangerous operation. Therefore, hot tapping should generally be used only when it is impractical to take the system out of service. When specifying hot tapping, care is required in inspection, design, and testing to ensure that this operation is done in a safe and reliable manner. Therefore, a hot tapping should be considered only after other options are evaluated and rejected. Each hot tapping should be properly designed, the hot tapping location thoroughly inspected, and the installation procedures reviewed.
Hot Tapping makes it possible for pipeline owners and operators to isolate and bypass sections of pipeline so they can complete their projects without shutting down the system or losing product.
Hot Tapping Procedure
Mount the hot tapping machine to the piping system.
Advance cutter/pilot assembly until it touches the parent pipe, then start the hot tap.
When cutter/pilot is completely through, stop rotation & advance to allow u-wires to drop.
Coupon and cutter are withdrawn with the coupon or cut out retained by the u-wires.
The fluid flow in the pipe is stopped between the two consecutive hot tap locations and a by-pass arrangement is made for maintaining the regular flow in piping system.
The fluid present between the two consecutive hot tap locations is drained out using a vent (for gaseous fluid) or a drain (for liquid fluid).
Modification between the two hot tap locations are completed using cutting and welding. This can be installation of any valve or a pipe piece.
Fluid is again filled between the two hot tap locations ensuring the original pressure is maintained.
Fluid flow is started again from the main pipe and by-pass arrangement and hot tapping machine is removed.
When to Avoid Hot Tapping
Hot tapping is not recommended under any of the following conditions:
Piping containing a combustible or flammable mixture.
Piping containing acids, chlorides, peroxides, or other chemicals that are likely to decompose or become hazardous from the heat of welding (e.g., sulfuric acid or acetylene).
Piping containing caustic.
Piping that contains pure oxygen or chlorine.
Air lines where the absence of hydrocarbon cannot be assured.
Monel piping handling sulfur compounds.
Stainless steel piping containing catacarb solution.

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