Hot tapping is a specialist method of connecting to a live, pressurised pipeline or vessel without shutting it down. It allows operators to add branches, valves or monitoring equipment while maintaining the flow of oil, gas or another product.
Oil and gas pipelines often need to be modified, repaired or expanded while they remain in operation. A new branch may be required, monitoring equipment may need to be installed, or part of a pipeline network may need to be redirected.
The traditional approach would be to shut down the affected system, isolate it, remove the product, reduce the pressure and prepare the equipment for work. Although this may be the safest option in many situations, shutting down a major pipeline or processing system can interrupt production, delay customer supplies and create significant operational costs.
This specialist engineering technique allows a controlled opening to be made in an operating pipeline, tank or pressure vessel. A new connection can then be added without completely emptying or shutting down the existing system.
However, hot tapping should never be treated as ordinary drilling or welding. The work may involve flammable, toxic or high-pressure materials. A minor error can lead to a leak, fire, equipment failure or serious injury.
For that reason, hot tapping requires detailed engineering assessments, suitable equipment, competent personnel, controlled operating conditions and carefully approved procedures.
What Is Hot Tapping in Oil and Gas?
Hot tapping, sometimes called pressure tapping, live tapping or line tapping, is the process of creating a new connection to equipment that remains pressurised and in service.
The connection may be made to:
- An oil pipeline
- A natural gas pipeline
- A fuel line
- A storage tank
- A pressure vessel
- A refinery process pipe
- A water or utility line
- A petrochemical system
TWI describes hot tapping as a way of connecting to a pressurised system by drilling or cutting into a pipeline or pressure vessel without taking it out of service.
The term “hot” does not necessarily mean that the pipeline contains a product at a high temperature. It generally refers to the fact that the equipment is active, pressurised or carrying a live product while the connection is being created.
Hot tapping may involve welding a fitting onto the outside of a pipe, installing a valve and using a specialised tapping machine to cut through the pipe wall. The cut section, often called a coupon, is normally retained by the machine rather than being allowed to fall into the pipeline.
Once the opening has been created, the cutting tool is withdrawn, the valve is closed and the new branch can be connected to the required equipment.
Why Is Hot Tapping Used?
Hot tapping is mainly used when shutting down a pipeline would be difficult, expensive or disruptive.
Oil and gas systems may operate continuously for long periods. Closing an important pipeline can affect production facilities, refineries, storage terminals, power stations, industrial customers and distribution networks.
A properly planned hot tap can allow work to proceed while the original system continues operating.
Common reasons for hot tapping include:
- Adding a new branch connection
- Installing a valve
- Connecting a bypass line
- Adding pressure or temperature instruments
- Installing flow-monitoring equipment
- Connecting a new customer or facility
- Diverting product around damaged equipment
- Preparing for pipeline isolation
- Expanding an existing network
- Modifying a refinery or processing plant
Hot tapping can also support maintenance work when a damaged or ageing section of pipeline must eventually be isolated.
How Does Hot Tapping Work?
The hot tapping process involves more than simply drilling through a pipe.
The exact method depends on the pipeline material, diameter, wall thickness, pressure, temperature, product and operating environment. However, the general concept involves several controlled stages.
First, engineers assess whether the pipeline is suitable for hot tapping. They examine the pipe material, condition, operating limits, contents and previous inspection information.
A fitting is then secured to the outside of the pipe. Depending on the design, this fitting may be welded or mechanically attached.
A valve is installed onto the fitting. The valve creates a controlled barrier between the live pipeline and the external environment.
The tapping machine is mounted onto the valve. Its cutting tool passes through the open valve and cuts into the pipe wall.
Once the opening has been completed, the cutter and pipe coupon are withdrawn into the tapping machine. The valve is then closed.
The tapping machine can be removed, leaving a secure valve and branch connection attached to the original pipeline.
This is a simplified explanation rather than an operating procedure. Each hot tap must be supported by project-specific engineering, inspection, risk assessment and approved work instructions.
Main Components Used for Hot Tapping
Several pieces of specialised equipment are required to complete a hot tap safely.
Hot Tap Fitting
The fitting creates the structural connection between the existing pipeline and the new branch.
Common designs include:
- Full-encirclement split tees
- Welded branch fittings
- Mechanical fittings
- Reinforced nozzles
- Saddles
The fitting must be designed for the pipe diameter, pressure, temperature, material and expected loads.
It must also support the valve, tapping machine and new connection without overstressing the original pipe.
Isolation Valve
A valve is installed between the fitting and the tapping machine.
It remains open while the cutting tool enters the pipeline. After the cut has been completed and the cutter has been withdrawn, the valve is closed.
This allows the tapping machine to be removed without releasing the pipeline contents.
The valve must be compatible with the product, pressure and operating temperature.
Tapping Machine
The tapping machine contains the equipment used to cut through the pipe wall.
It generally includes:
- A pressure-containing body
- A boring bar
- A cutting tool
- A drive mechanism
- Seals
- A coupon-retention device
- Pressure-control connections
The machine must maintain containment throughout the operation.
Cutter and Pilot Drill
The cutter creates the circular opening in the pipe wall.
A pilot drill may guide the cutter and help retain the coupon. Preventing the coupon from entering the live pipeline is important because a loose metal section could damage valves, pumps or other downstream equipment.
Pressure-Testing Equipment
Before the pipeline wall is cut, the new fitting, valve and tapping assembly may be tested to confirm their integrity.
The test method must be suitable for the operating system and should not expose the original pipeline to damaging pressure.
Which Pipelines Can Be Hot Tapped?
Hot tapping may be used on pipelines carrying:
- Crude oil
- Natural gas
- Refined petroleum products
- Diesel
- Heating oil
- Water
- Steam
- Certain chemicals
- Compressed air
However, not every live pipeline is suitable.
The decision depends on factors such as:
- Pipe material
- Wall thickness
- Corrosion
- Cracking
- Operating pressure
- Product temperature
- Flow rate
- Chemical composition
- Weldability
- Internal deposits
- Previous repairs
- Pipeline accessibility
Certain contents or operating conditions may make hot tapping unacceptable. Some products may decompose, ignite or react when exposed to welding heat. Others may create severe health risks if containment is lost.
API RP 2201 is an established industry reference specifically concerned with safe hot tapping practices on equipment operating within petroleum and petrochemical facilities.
What Is In-Service Welding?
In-service welding is the process of welding onto a pipeline or vessel that remains operational.
It is often part of a hot tapping project because a branch fitting may need to be welded around or onto the existing pipeline.
The flowing product inside the pipe can remove heat rapidly from the weld area. Although this cooling effect may reduce the chance of excessive internal heating in some circumstances, it can also create hard and brittle areas in the weld or surrounding metal.
TWI notes that making a welded connection to a live pipeline or vessel is commonly known as hot tapping or in-service welding and requires controls established through suitable standards and procedures.
The welding procedure must therefore account for:
- Pipe material
- Carbon equivalent
- Wall thickness
- Product flow
- Heat input
- Cooling rate
- Electrode type
- Preheating requirements
- Hydrogen control
- Residual stress
A welding procedure that works on an empty pipe may not be suitable for an operating pipeline.
What Are the Main Risks of Hot Tapping?
Hot tapping can prevent a disruptive shutdown, but it introduces serious technical and safety risks.
Burn-Through
Burn-through occurs when welding heat weakens or melts through the remaining pipe wall.
If this happens on a live hydrocarbon pipeline, oil or gas may escape directly into the welding area and ignite.
The risk is affected by wall thickness, heat input, welding technique, internal pressure and product flow.
Hydrogen Cracking
Rapid cooling can create hard areas in certain pipeline steels. Combined with hydrogen and welding stress, this may lead to cracking.
Some cracks may not be immediately visible. They can develop during or after the welding operation and weaken the connection.
Product Ignition
The pipeline may contain flammable oil, gas or vapour.
A leak, failed seal or damaged pipe wall could expose the product to welding arcs, hot surfaces or other ignition sources.
Loss of Containment
Loss of containment may occur because of:
- Seal failure
- Incorrect equipment assembly
- Valve leakage
- Fitting failure
- Cutting-tool problems
- Pipeline movement
- Excessive pressure
- Poor welding
- Existing pipe defects
The consequences depend on the product, pressure, location and nearby ignition sources.
Incorrect Coupon Retention
The circular section cut from the pipe should normally be retained by the tapping tool.
If it falls into the pipeline, it may travel downstream and obstruct or damage valves, pumps, meters and processing equipment.
Pipeline Instability
The fitting, valve and tapping machine add weight and mechanical loads to the pipe.
Engineers must consider whether the existing pipeline and its supports can carry these loads safely.
Vibration, ground movement and thermal expansion may also affect the connection.
Exposure to Hazardous Substances
The pipeline contents may be toxic, corrosive, extremely hot or capable of displacing oxygen.
Hydrogen sulphide is a particular concern in sour oil and gas systems because exposure can be rapidly fatal.
Why Is Pipeline Inspection Necessary?
The pipe must be inspected before a hot tap is approved.
A pipeline that appears sound externally may contain internal corrosion, laminations, cracking or previous damage.
Inspection may include:
- Visual examination
- Ultrasonic thickness testing
- Weld inspection
- Material verification
- Magnetic particle testing
- Radiographic examination
- Review of corrosion records
- Examination of previous repairs
- Pipeline integrity data
Wall thickness must be sufficient to support welding, tapping and future operating loads.
The inspection should cover more than the exact tapping point. The surrounding area must also be capable of carrying the new fitting and branch connection.
HSE guidance places responsibility on pipeline operators to manage pipeline integrity, maintenance and safe operating limits throughout the life of the system.
Engineering Assessment Before Hot Tapping
A formal engineering assessment helps determine whether hot tapping is technically possible and whether it is preferable to shutting down the system.
The assessment may consider:
- Pipeline design pressure
- Current operating pressure
- Operating temperature
- Product composition
- Pipe diameter
- Wall thickness
- Material grade
- Corrosion allowance
- Flow rate
- Welding heat input
- Branch size
- External loads
- Environmental conditions
- Emergency isolation options
The assessment should also identify conditions under which the work must stop.
For example, operations may need to be suspended if pipeline pressure changes, product flow becomes unstable, gas is detected, equipment leaks or weather conditions become unsafe.
The Role of Risk Assessment
A hot tapping risk assessment should examine the complete operation rather than only the cutting stage.
Hazards may arise during:
- Site preparation
- Excavation
- Pipeline exposure
- Inspection
- Welding
- Pressure testing
- Valve installation
- Machine assembly
- Cutting
- Machine removal
- Branch commissioning
The assessment should identify who may be affected, how an incident could escalate and which preventive or emergency controls are required.
Controls may include:
- Permit-to-work systems
- Gas monitoring
- Fire protection
- Restricted work areas
- Emergency shutdown arrangements
- Pressure monitoring
- Communication systems
- Rescue planning
- Spill containment
- Competent supervision
Hot tapping should only proceed when the risks have been reduced as far as reasonably practicable and the work complies with applicable legal, engineering and company requirements.
Benefits of Hot Tapping
When it is suitable and professionally controlled, hot tapping can provide several operational benefits.
Reduced Shutdown Time
The main advantage is that the pipeline can usually remain in operation.
This reduces production interruption and helps maintain supply to customers or connected facilities.
Lower Product Loss
A conventional shutdown may require a long section of pipeline to be emptied, vented or drained.
Hot tapping can reduce the amount of product that must be removed or disposed of.
Reduced Emissions
Avoiding depressurisation may reduce the release or flaring of natural gas.
However, the environmental benefit depends on the specific pipeline, product and alternative shutdown method.
Faster Network Expansion
A new branch can be connected without waiting for a major planned shutdown.
This can support new facilities, customers, monitoring systems or production areas.
Support for Pipeline Isolation
Hot tapping can be combined with specialist isolation methods to create a safe work zone around damaged or ageing equipment.
This may allow a particular pipeline section to be replaced while the wider network remains operational.
Limitations of Hot Tapping
Hot tapping is not automatically the best choice simply because it avoids a shutdown.
Its limitations include:
- High specialist costs
- Complex engineering
- Strict material requirements
- Serious fire and leak hazards
- Limited suitability for damaged pipelines
- Need for specialist equipment
- Dependence on accurate records
- Restricted working space
- Weather and access constraints
- Potential long-term stress at the branch connection
A planned shutdown may be safer and more practical when the pipeline condition is uncertain or when the product creates unacceptable hot-work risks.
The decision should be based on risk and engineering evidence rather than production pressure alone.
Hot Tapping and Line Stopping
Hot tapping and line stopping are related but different operations.
Hot tapping creates an opening in a live pipeline.
Line stopping uses that opening to insert a temporary plugging device into the pipeline. The plug restricts or stops product flow, allowing a section of the system to be isolated.
A typical isolation project may use two line stops with a bypass between them. Product is redirected through the bypass while the isolated pipeline section is repaired or replaced.
After the work is completed, the line-stop equipment is removed and the pipeline is returned to its normal configuration.
Because line stopping introduces additional loads, sealing requirements and operating risks, it requires separate engineering and planning.
Where Is Hot Tapping Commonly Used?
Hot tapping is used across several parts of the oil and gas industry.
Oilfields
Operators may use it to connect new wells, flowlines, gathering systems or monitoring equipment.
Natural Gas Networks
Gas transmission and distribution companies may create new branches or prepare sections for isolation.
Oil Refineries
Refineries use extensive networks of process piping. Hot tapping may support modifications when shutting down an entire processing unit would cause major disruption.
Fuel Storage Terminals
New transfer lines, valves or measurement systems may be connected to operating terminal infrastructure.
Offshore Installations
Hot tapping can be used on offshore and subsea pipelines, although access, pressure, water depth and emergency response make the work especially complex.
TWI has developed inspection procedures for hot tap connections, including work relating to subsea oil and gas pipelines under hyperbaric conditions.
Who Can Carry Out Hot Tapping?
Hot tapping must be completed by trained and authorised specialists.
The team may include:
- Pipeline engineers
- Welding engineers
- Qualified welders
- Inspection specialists
- Hot tap machine operators
- Process engineers
- Safety professionals
- Site supervisors
- Emergency response personnel
Each person should understand their responsibilities and the conditions that require the operation to stop.
Competence must cover the specific equipment, product, pipeline material and operating environment involved. General welding or mechanical experience alone may not be sufficient.
What Happens After a Hot Tap?
The completed connection must be inspected, tested and documented.
Post-work activities may include:
- Checking for leaks
- Inspecting welds
- Confirming valve operation
- Removing temporary equipment
- Applying corrosion protection
- Updating pipeline drawings
- Recording the new fitting
- Establishing inspection intervals
- Monitoring the connection
- Reviewing the completed work
The branch fitting becomes part of the permanent pipeline system and must be included in future integrity-management and maintenance programmes.
Accurate records are essential because future operators need to know the fitting’s location, design, material, pressure rating and inspection history.
Hot Tapping in the Wider Fuel Supply Chain
Pipelines, terminals and processing facilities must often be modified as demand, equipment and distribution networks change.
Hot tapping can support these changes while helping maintain the movement of fuels through critical infrastructure.
Further along the supply chain, companies such as 123 Oil rely on dependable storage, transport and pipeline systems to help deliver fuel to domestic, commercial, agricultural and industrial customers.
Although customers may never see the engineering work behind fuel distribution, specialist operations such as hot tapping can help keep complex supply networks functioning during upgrades and maintenance.
Conclusion
Hot tapping in oil and gas is a specialist method of creating a new connection to a live, pressurised pipeline, tank or vessel without completely shutting down the system.
The process can be used to install branches, valves, monitoring instruments and temporary isolation systems. Its main advantage is the ability to reduce shutdown time, product loss and disruption.
However, hot tapping involves substantial risks. Welding and cutting near pressurised hydrocarbons can lead to burn-through, cracking, fire, leakage and equipment failure.
A successful hot tap depends on accurate pipeline information, material verification, inspection, engineering calculations, qualified procedures, competent workers and effective emergency arrangements.
It is not a routine shortcut around a shutdown. It is a carefully controlled engineering operation that should only be selected when its safety and technical suitability have been fully demonstrated.
Frequently Asked Questions
Hot tapping allows a new connection to be added to a pressurised pipeline, tank or vessel without completely stopping the system or draining its contents.
Yes, hot tapping can be performed on certain natural gas pipelines. However, the pipe condition, material, pressure, gas composition and emergency controls must first be carefully assessed.
Many hot taps use a welded branch fitting, but mechanical fittings may also be available. The suitable method depends on the pipeline material, service conditions and engineering design.
Hot tapping creates an opening in a live pipeline. Line stopping uses that opening to insert a temporary plug that restricts or stops flow within a section of the pipeline.
Hot tapping is a high-risk activity because it may involve welding and cutting into equipment containing pressurised, flammable or toxic products. It requires specialist procedures and trained personnel.
The coupon is the circular piece removed from the pipe wall. It should normally be retained by the cutting tool to prevent it from falling into and damaging the pipeline system.
No. Severely corroded, cracked, thin-walled, unsuitable or poorly documented pipelines may not be safe for hot tapping. An engineering assessment is required before work begins.