A Brief Introduction to Hot Tapping & Line Stoppling

6 min readOct 19, 2022

Pipelines are a conveyance medium for various fluids that are necessary to keep civilization functional. To keep these critical pieces of infrastructure functional, several tools, accessories and machinery are needed to keep up with the requirements of their maintenance, repair and overhaul cycles.

Productivity is critical for maintaining profitability for the large economies of scale plants that, to provide an example: refine crude oil into various petrochemical products. Various pipeline fluid mediums such as steam, flare gas, crude oil, water, etc. require careful handling while the pipelines carrying them are drilled into and the flow is redirected to a conduit and then to its original destination.

A main pipeline called a ‘mother pipeline’ is the one which has the flowing fluid. The pipes, which the mother pipeline could be connected to are called ’branch pipelines’.

Purpose of Conducting Hot Tapping would be amongst the following:

To remove a damaged or rusted section of pipes

2. To create a conduit for the fluid to another pipeline or avoiding a certain area and reconnecting to the same pipeline.

The Hot tapping machine shown below has the following components:

a) Full Encirclement Fitting or Joints — usually have a pipe flange attached to them.

b) Valve housing — Connected by bolts on the flange

c) Tapping Machine — This is the actual element which shall perform the cutting, it has a drive component or motor that is electrically or hydraulically driven and rotates the Boring Bar that moves back and forth using a hydraulic mechanism. Here the feed and speed can be controlled.

d) Cutter — The Cutting Element has a Pilot Drill which cuts and retrieves a cut section of the pipe called a coupon with a set of prongs that stop the cut section from falling back into the pipe.

Pilot Drill With Cutter Hot Tapping Machine Diagram Hot Tapping machine mounted on Pipe

Welded Fittings Different Sizes of Split Tee Fittings

The process involves the following steps:

e) Welding or Bolting the appropriate Joints on the Pipes to be Hot Tapped in minimum number to carry out to the line stopping after hot tapping is conducted.

Examples include: Bolted or Welded Split Tee, Weld-O-Let, and Reinforcement (RF) pads

Split Tee Joint being welded Welded Tees on the Pipes where hot tapping and stoppling is to be

carried out and the new conduit is to be connected

f) Bolting of the Valve housing onto the joint is carried out which shall allow the tapping machine to be mounted on the same with smaller valves being fastened on the joints and correct measurements are made for the fittings.

Valve Housing being mounted on the relevant Split Tee Joint Smaller Tap with its own valve housing

g) The Tapping Machine is mounted on the valve housing and the tapping is initiated using manual machines for the smaller taps and larger machines for the main taps

Cutter with a Pilot Drill is used to remove the Coupon from A Manual Hot Tapping Machine is used to Drill a tap in front of the

the Pipe and it is secured behind the valve gate. actual hot tapping position, this shall be later used for pressure relief

Now that both the taps are opened the pipe sections to be connected, the conduit is inserted and bolted on the valve housings of both, hence continuing the flow of the working fluid.

The Conduit Piping Connects the mother pipeline and ensures that the flow does not stop

Further, the Line Stoppling Machine is attached to the valve housing and the Stopple is extended into the pipe and the flow is obstructed. In Some cases an inflatable bag is used to stop the effervescent fumes from escaping to prevent an explosive environment or asphyxiating gasses from harming workmen or stopping their work. The excess pressure is released from the pipe which is now effectively cordoned off using line stopples.

The Line Stopple is inserted on both sides of the pipe section to isolated and the fluid in between is evacuated

The Damaged or rusted section of the pipe or the desired pipeline modification is initiated.

The evacuated pipeline allows for safe working with the isolated section and new pipe section can thus be added without loss of productivity.

The Line Stopple is now Withdrawn behind the valve gate and the excess gas (if any) is released. The fluid is now free to move through the pipe and hot tapping/line stoppling machines are now withdrawn.