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Welding for the Long Haul: Ensuring Durability and Reliability in Pipeline Construction

October 05, 2023 · Leave a comment · Red-D-Arc
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Pipelines transporting oil, natural gas and water are multi-billion dollar projects that ensure a reliable energy supply and vital infrastructure to function. Any weld failure can lead to devastating environmental damage, risk to human life, and extreme capital loss. So, welding pipelines requires utmost precision and weld integrity.

You can only lay pipes in sequence, to extend the existing line. So, maximum productivity is a must for any pipeline project. Welding efficiency and speed must not compromise weld quality, which makes pipe welding challenging, especially in harsh conditions and remote areas. However, modern welding technology and automation allow high productivity with maximum weld reliability. 

Pipe Preparation For Reliable Welding Operation

Pipe preparation is a crucial step to ensure weld reliability. It’s impossible to make highly durable, resilient welds with bad prep work. Ensuring pipe joint cleanliness, consistent joint dimension, and high-quality cut and bevel is paramount. The importance of pipe preparation cannot be overstated. A single weld discontinuity resulting from inadequate joint preparation could lead to weld failure, significant environmental damage, and loss of resources.

Pipe Cutting And Beveling

Pipe cutting and beveling procedures need maximum dimensional stability for consistent weld quality. It’s vital to create a consistent and precise bevel angle, as instructed by the welding procedure specifications (WPS). 

It’s very challenging to achieve absolute accuracy when manually cutting and beveling, even if a highly skilled operator uses the torch. Automated pipe cutting and beveling solutions, like the H&S Tool AFC-12 Split-Frame Pipe Saw and H&M Band-Type Pipe Bevelers are the best way to produce accurate cuts and precise bevel angles. They are exceptionally easy to use, fast, and highly efficient. The motorized cutting/beveling head rotates around the pipe, producing the desired joint shape with exceptional accuracy, which helps reduce re-work and welds that fail inspection.

The bevel angle and shape depend on the pipe thickness, material type, welding process, filler metal, and the forces the joint will be exposed to, among other factors. If the bevel isn’t consistent, the heat input, expanding and contracting forces, filler metal deposition, and filler metal dilution may also be inconsistent, which may lead to unpredictable weld quality. Simply put, if the pipe bevel is consistent across its circumference, the welding procedure will have a consistent effect on the weld joint. In addition, a poorly executed bevel may remove too much material, which could lead to burn-through and other weld discontinuities. 

Heat Treatment

Preheating the pipe joint area before welding is crucial to prevent or minimize negative metal microstructure and property changes in the heat affected zone (HAZ) and partially melted zone (PMZ). Depending on the pipe material, the joint could lose corrosion resistance, develop hydrogen cracking, or become brittle and crack from internal weld stresses if not preheated.

Welding causes sudden heating and cooling. As a result, the weld metal and molten base metal will start pulling the surrounding material as they cool. Unless this process is controlled with slow cooling, some materials, like high-strength steels, can crack as the cooling weld pulls the surrounding metal. 

Preheating the pipe joint elevates the temperature, which allows for a slow, controlled weld cooling process and helps prevent stress cracking. In addition, preheating reduces the amount of moisture in the base metal, which directly helps avoid hydrogen weld cracking. 

There are several methods for pipe preheating: open flame, resistance, and induction heating. 

Open flame heating poses safety risks, requires a lot of fuel, and you need to store large batches of propane. In addition, an open flame might not provide a uniform temperature gradient, which could lead to cracking and reduced weld quality. In contrast, induction heating offers consistent heat treatment, has a faster time-to-temperature, and is safer for the operators. For example, Miller ProHeat 35 can output up to 35 kW at a 100% duty cycle to preheat large pipes quickly and uniformly. It’s easy to use, can be air or liquid-cooled, and supports a built-in temperature control for manual or temperature-based programming.

Welding Processes Employed For Pipeline Construction

Historically, manual SMAW welding was predominantly used to weld oil and gas pipelines worldwide. Today, wire welding processes like GMAW and FCAW offer higher productivity and weld quality thanks to highly advanced, modern power sources that can provide varying arc functions for different materials and thicknesses; however, due to environmental conditions and other limiting factors, manual SMAW is still frequently used to construct pipelines. 

Manual GTAW has some innate challenges for joining pipelines, like the need for highly skilled operators, slow welding speed, and shielding gas coverage loss in outdoor conditions. Fortunately, automated GTAW solutions overcome most of these challenges, allowing the production of the highest quality welds for pipelines whenever automated GTAW can be employed.

Regardless of the applied welding process, the power source must be highly reliable. The settings must do exactly as expected, and the machine cannot fail or behave erratically. It’s imperative to use high-end and rugged power sources out in the field to ensure operation productivity and efficiency. If one operator stalls out due to the machine’s failure, the entire operation’s workday may suffer. In the demanding and fast-paced pipeline environment, welders rely on their equipment to produce code and inspection-passing welds.

Pipeline construction often takes place in harsh conditions and remote areas where power is unavailable. So, rugged diesel-powered welders or diesel generators are needed to perform the job. For example, our Dual Maverick 200/200X is a diesel-powered heavy-duty rugged welder that supports dual-power output, allowing two operators to weld on one pipe, which is often necessary to prevent pipe distortion from uneven heat input. Besides GMAW, FCAW, and GTAW support, Maverick 200/200X supports standard SMAW and Downhill Pipe SMAW mode that allows welding pipe “downhill” where the operator can adjust the arc force for a more digging arc for root and hot passes and a softer arc for fill and cap passes. 

Pipelines sometimes need to be cladded on the inside with corrosion resistant alloys (CRA) to prevent corrosion from highly aggressive chemicals like organic acids, chlorides, carbon dioxide, and hydrogen sulfide. This is done using automated TIG cladding systems in the shop before the pipes are delivered on-site.  

Automated Orbital Pipe Welding

Whenever possible, employing automated orbital GTAW pipe welding offers unmatched productivity, joint quality, accuracy, and most importantly, consistency. 

Welding automation can also help you take on more jobs despite the shortage of the welding workforce. As it becomes increasingly more challenging to recruit welding talent, businesses can turn to automation to maximize the productivity of their operators. In addition, orbital welding has a reduced learning curve compared to manual TIG and provides a highly consistent weld quality, allowing a high ROI on operator training. 

Orbital welding systems rotate the torch around the pipe joint with a consistent torch distance and speed. As a result, the torch always stays at an optimal position. In addition, orbital systems can be programmed to change welding parameters automatically depending on whether the torch is moving overhead, uphill, downhill, or flat. Our Axxair SATO-220E4x open orbital weld heads can accommodate a wide pipe diameter range, support inclination and axial adjustment of the electrode, and have a compact design for making high quality welds at minimum space. 

Rent Or Lease Pipe Welding Equipment From Red-D-Arc

Whether you are a seasoned pipeline contractor or looking to enter this industry, Red-D-Arc is here for you. We can provide expert pipeline equipment recommendations ranging from pipe bevelers and cutters to high-end welding power sources and pre and post-weld heating solutions. No matter the pipe material and thickness, we can offer suitable welding processes and the necessary equipment.

Renting or leasing pipe welding equipment saves significant resources. Buying heavy-duty welding power sources can be a considerable investment, which may not pay off if the job scales down in the future. In addition, maintenance and storage can take an additional draw on your resources. Our massive fleet of welding and cutting equipment is ready for you no matter the job, allowing you to scale in and out and only allocate resources to the equipment you presently need. Contact us today, and our team will match you with the most suitable pipeline welding equipment for the job at hand. 

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Airgas, an Air Liquide company, is the nation's leading single-source supplier of gases, welding and safety products. Known locally nationwide, our distribution network serves more than one million customers of all sizes with a broad offering of top-quality products and unmatched expertise.