A Brief Introduction to Hot Tapping & Line Stoppling

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 that has the flowing fluid. The pipes, to which the mother pipeline could be connected are called ’branch pipelines’.

The purpose of Conducting Hot Tapping would be amongst the following:

  1. To remove a damaged or rusted section of  pipes
  2. To create a conduit for the fluid to another pipeline or avoid a certain area and reconnect to the same pipeline.

The hot-tapping machine shown below has the following components:

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

ii) Valve housing – Connected by bolts on the flange

iii) Tapping Machine – This is the actual element that 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.

iv) 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 Diagram             
Hot Tapping machine mounted on Pipe
          Welded Fittings                                            
Different Sizes of Split Tee Fittings
   Different Sizes of Split Tee Fittings

The process involves the following steps:

  1. Welding or Bolting the appropriate Joints on the Pipes to be hot-tapped in minimum numbers 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

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

k) 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  the Pipe and it is secured behind the valve gate.             
A cutter with a Pilot Drill is used to remove the Coupon from the Pipe and it is secured behind the valve gate.                                            
A Manual Hot Tapping Machine is used to drill a tape in front of  actual hot tapping position, this shall be later used for pressure relief
A Manual Hot Tapping Machine is used to drill a tape in front of the actual hot tapping position, this shall be later used for pressure relief

I) Now that both the taps are opened the pipe sections are to be connected, and 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

M) Further, the Line Stoppling Machine is attached to the valve housing 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
          The Line Stopple is inserted
on both sides of the pipe section to isolated
and the fluid in between is evacuated
and the fluid in between is evacuated

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

O) 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.

 Line Stopple Being Withdrawn    
  Line Stopple Being Withdrawn                   
  Hot Tapping Machine being withdrawn
   Hot Tapping Machine being withdrawn
 Conduit Pipe Being Withdrawn
       Conduit Pipe Being Withdrawn

P) The Completion Flanges or blanks are now bolted and the welded fittings/joints are left in place, if the joints are bolted then they are withdrawn.

Completion Flange
ensuring leakage
high pressure

Completion Flanges are placed ensuring leakages at high pressure are unlikely

Various Orientations wherein the Hot Tapping and Line Stoppling process could be carried out include the following:

Standard Tap
   Standard Tap
Offset Taps
    Offset Taps
     Lateral Taps

In Addition to Pipeline Hot Tapping /Line Stoppling on Land, it can also be performed on Pipelines underwater.

Underwater Sealed Valve Gates and Fittings and Joints

Special Underwater Sealed Valve Gates and Fittings and Joints ensure leak-free hot tapping/ line stoppling material

Leave a Reply

Your email address will not be published. Required fields are marked *

@instagram