Hot tapping

Hot Tapping is a means by which access is made to the inside of an operational pipeline, using either a drill or a circular cutter, it is the process of drilling a hole in an on-stream operational piping system without spilling its contents or interrupting its flow. A hot tap is performed when it is not feasible or impractical to take piping or equipment out of service.

Hot Tap Applications include:

  • Attachment of a branch connection to the line,
  • Installation of an internal probe or monitor,
  • To stop or redirect flow in a line for maintenance or repair purposes.
  • Implies positioning a branch fitting on an operating pressurised line, flowing or stagnant. Followed by cutting a hole in the header through the branch to allow connection to the flowing media. Normally implies using a welded fitting,
  • Can also be applied as a repair method to remove defects, i.e. dents.

Hot Tap Fittings

Hot Tap fittings are either bolted or welded to the existing header pipeline. A tapping/drilling machine is attached to the valve, which is attached to the hot tap fitting. A cutter, attached to the tapping machine is inserted into the hot tap fitting through the valve and the tap is made. In the case of a permanent valve, a branch connection can be made, allowing flow through the outlet.

Selection of Hot Tap Fittings

 For reduced-branch taps, weld neck flanges on a weld-o-let can be used, but the size of the branch must not exceed 50% of the header diameter, to ensure remaining strength is not compromised. It also compensates for the material that is cut out of the header and provides strength to support the Hot Tap valve and Hot Tap Machine. Where the branch will exceed 50% of the header diameter, Hot Tap fittings are full-branch or reduced-branch split tees, designed for use with Tapping Machines.

Where unlisted material under ASME is used to manufacture a Hot Tap Fitting, or where listed ASME Material is modified, there shall be an Approved Mechanical Design in accordance with the applicable ASME code, signed off by an Engineer and AIA.  For South African Legislative Compliance the Pressure Equipment Regulations under the OHS Act No 85 of 1993, as well as SANS347 shall comply. The design must be signed off by a registered Professional Engineer.


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