When pipeline modifications, repairs, or maintenance are required, the traditional approach of complete system shutdown can be prohibitively expensive and disruptive. Fortunately, modern engineering has provided two sophisticated alternatives: hot tapping and line stopping. Whilst both techniques allow work on pressurised systems without full depressurisation, they serve distinctly different purposes and excel in different scenarios. Understanding the nuances of each method is crucial for selecting the right approach for your specific operational needs.
Understanding Hot Tapping Pipework
Hot tapping, also known as pressure tapping, is a technique that enables the creation of new connections on live, pressurised pipelines. This method is primarily used when you need to add branch lines, install new valves, attach monitoring equipment, or create additional outlets without interrupting service.
The hot tapping process involves welding a fitting onto the exterior of the pipeline, installing a valve, and then using specialised drilling equipment to penetrate the pipe wall whilst maintaining full system pressure. The cut section—called a coupon—is safely captured and removed, leaving a new opening for connections.
Commercial hot tapping has become increasingly sophisticated, with equipment capable of working on pipes ranging from small diameter service lines to large transmission mains. The technique is widely used across oil and gas, petrochemical, water distribution, and industrial processing sectors where uninterrupted flow is essential.
Key Advantages of Hot Tapping
Hot tapping offers several compelling benefits that make it the preferred choice for many pipeline modification projects. The most obvious advantage is continuity of service—your pipeline continues operating normally throughout the entire procedure, eliminating revenue loss associated with shutdowns.
From a safety perspective, hot tapping eliminates many risks associated with depressurisation and repressurisation cycles. There’s no need to drain or purge the system, which reduces environmental concerns and waste disposal costs. The technique also minimises exposure to potentially hazardous materials, as the system remains sealed throughout the operation.
Installation speed is another significant benefit. Once preparations are complete, the actual drilling operation is remarkably quick—often taking just hours rather than the days required for traditional shutdown methods. This efficiency translates directly to cost savings and reduced project timelines.
Hot tapping also provides excellent flexibility for system expansion. As your infrastructure needs grow, new connections can be added without disrupting existing operations, making it ideal for phased development projects or responding to unexpected demand increases.
Limitations of Hot Tapping
Despite its advantages, hot tapping isn’t suitable for every situation. The technique requires adequate pipe wall thickness to safely accommodate drilling operations—pipes that are severely corroded or have insufficient wall thickness aren’t good candidates. There are also practical size limitations; whilst equipment exists for a wide range of diameters, extremely small or exceptionally large pipes may present challenges.
Hot tapping creates a permanent opening in the pipeline, so it’s specifically designed for situations where you intend to add something—whether that’s a branch line, valve, or instrument connection. If your goal is temporary isolation for maintenance or repair work on a specific section, hot tapping alone won’t achieve that objective.
Understanding Line Stopping
Line stopping, sometimes called line plugging, serves a fundamentally different purpose than hot tapping. This technique provides temporary isolation of a pipeline section, creating a zero-leak seal that allows maintenance, repairs, or modifications to be performed on isolated segments whilst the rest of the system remains operational.
The line stopping process typically begins with hot tapping to install the necessary fittings and valves. Once these access points are established, a specially designed plugging head is inserted through the valve into the flowing pipeline. This head contains a sealing mechanism—often an inflatable bag or mechanical plate—that is expanded or deployed to completely block flow through the pipe.
With the line stopped, the isolated section can be drained, depressurised, and opened for work whilst upstream and downstream sections continue normal operations. Once repairs or modifications are complete, the pipeline section is restored, pressure-tested, and the plugging device is removed.
Key Advantages of Line Stopping
Line stopping shines in situations where work must be performed inside the pipeline or where complete isolation of a section is necessary. It’s particularly valuable for tie-in operations when connecting new pipeline segments to existing infrastructure, allowing welding and integration work without shutting down the entire system.
For urgent repair scenarios—such as addressing leaks, replacing corroded sections, or fixing valve failures—line stopping enables rapid response without waiting for scheduled shutdowns. This capability can prevent small problems from escalating into major incidents.
The technique offers precise control over which sections are isolated. Multiple line stops can be deployed simultaneously to isolate exactly the working area needed, minimising the scope of interrupted service. This precision is particularly valuable in complex pipeline networks where different sections serve different customers or facilities.
Line stopping also provides a contingency option during planned shutdowns. If unexpected issues arise or repairs take longer than anticipated, line stops can maintain isolation whilst the rest of the system is brought back online, reducing the duration of service interruption.
Limitations of Line Stopping
Line stopping is inherently a temporary measure rather than a permanent solution. The plugging devices must be removed once work is complete, and they cannot remain in place indefinitely. The technique also requires sufficient straight pipeline length both upstream and downstream of the stopping point to properly seat and seal the plugging device.
Flow characteristics matter significantly—line stopping is more challenging in systems with high flow velocities or where the fluid contains large amounts of debris or solid particles that might interfere with proper sealing. Additionally, the technique requires careful pressure management; the pressure differential across the plug must be within equipment specifications to ensure safe operation.
The initial investment for line stopping can be substantial, as it typically requires the preliminary step of hot tapping to install access points if they don’t already exist. However, this cost must be weighed against the alternative of complete system shutdown.
When to Choose Hot Tapping
Hot tapping is your optimal choice when your objective is permanent system modification. If you’re adding new branch connections to supply a new facility, installing permanent isolation valves to improve system sectionalisation, or adding monitoring instrumentation for better operational control, hot tapping provides the most direct and cost-effective solution.
The technique excels in situations where maintaining continuous flow is absolutely critical—think refineries where shutdown costs measure in hundreds of thousands of pounds per day, or municipal water systems where service interruption affects thousands of residents. Hot tapping also makes economic sense when you need multiple new connections, as each tap can be completed relatively quickly once equipment is mobilised.
Consider hot tapping when working with relatively new pipelines in good condition with adequate wall thickness. The technique is also ideal for systems containing non-hazardous fluids where the drilling operation presents minimal risk, though with proper precautions, it’s routinely performed on hydrocarbon systems as well.
When to Choose Line Stopping
Line stopping becomes the method of choice when you need to perform work inside the pipeline that requires complete isolation. Replacing valve internals, removing pipeline obstructions, installing internal pig launchers or receivers, or cutting out and replacing corroded or damaged pipe sections all require the zero-flow conditions that line stopping provides.
Emergency repair situations often demand line stopping capabilities. When a critical pipeline develops issues that cannot wait for scheduled shutdowns, line stopping allows immediate response whilst maintaining service to unaffected areas. This capability can be literally invaluable when equipment failure threatens production, safety, or environmental compliance.
The technique is also ideal for major tie-in projects where new pipeline segments must be welded to existing infrastructure. Line stopping allows these connections to be made under controlled, depressurised conditions whilst the system continues operating around the work area.
Choose line stopping when you need maximum flexibility in planning maintenance activities. Rather than coordinating organisation-wide shutdowns, you can isolate specific sections as needed, allowing different teams to work on various system segments without conflicting schedules.
Combining Both Techniques: Integrated Solutions
In practice, hot tapping and line stopping frequently work as complementary techniques rather than competing alternatives. Many projects require both: hot tapping to install the fittings and valves needed for access, followed by line stopping to create the isolation necessary for internal work.
This integrated approach offers the best of both worlds. Consider a project where you need to replace a failing valve in an operational pipeline. Hot tapping installs temporary bypass connections around the faulty valve, then line stopping isolates the valve from both directions, allowing safe removal and replacement whilst the bypass maintains system flow.
Similarly, when connecting a new pipeline branch, you might use hot tapping to create the initial access point and install a valve, then employ line stopping to isolate the section whilst performing the final welded connection between the branch and the main line.
Making the Right Choice for Your Project
Selecting between hot tapping pipework and line stopping—or determining the optimal combination of both—requires careful evaluation of several factors. Start by clearly defining your project objective: are you adding something permanently or temporarily isolating for maintenance?
Assess your pipeline condition, including wall thickness, corrosion levels, and material specifications. Evaluate operational constraints such as allowable service interruption duration, pressure and flow requirements, and safety considerations related to the fluid being transported.
Budget and timeline also play important roles. Whilst both techniques avoid the massive costs of full shutdowns, they have different cost structures and time requirements that should align with your project parameters and urgency.
RDS Pipeline: Your Partner for Complete Pipeline Isolation Solutions
At RDS Pipeline, we don’t believe in one-size-fits-all approaches. Our comprehensive service portfolio encompasses both commercial hot tapping and line stopping capabilities, supported by state-of-the-art equipment and extensively trained personnel. This dual expertise means we can objectively recommend the best solution for your specific situation—or design integrated approaches that leverage both techniques for optimal results.
Our team brings decades of combined experience across diverse industries and applications. We’ve executed countless projects ranging from routine modifications to complex emergency interventions, always prioritising safety, efficiency, and minimal disruption to your operations. Whether you’re planning system expansions, responding to unexpected failures, or implementing preventive maintenance programmes, we have the technical capabilities and practical experience to deliver results.
From initial engineering assessment through final commissioning, RDS Pipeline provides end-to-end project support. We work closely with your team to understand operational constraints, develop detailed execution plans, and implement solutions that meet your technical requirements and business objectives.
Don’t compromise your operations with extended shutdowns when advanced isolation techniques can keep you running. Contact RDS Pipeline today to discuss your pipeline isolation needs. Let our expertise in both hot tapping and line stopping help you choose the right approach—or the right combination—to keep your infrastructure performing whilst we deliver the modifications and maintenance your systems require.
