Pipeline welding applications in the oil and gas industry typically have stringent code requirements, which makes proper surface preparation and cleaning a key part of completing high-quality welds. Because pipeline welding is often completed in the field or in a yard, the outdoor conditions can pose challenges that also have an impact on productivity and quality. Selecting appropriate tools that are best-suited for the job — and following guidelines and best practices for proper usage of those tools — is critical for addressing the environmental challenges and quality demands involved in pipeline welding applications.
While surface preparation and cleaning is just one part of the large process of oil and gas pipeline welding, it’s a step that can have a significant impact on the productivity, quality and efficiency of the job.
COMMON TOOLS IN PIPELINE APPLICATIONS
For most surface conditioning and cleaning jobs in pipeline welding applications, there are three common tools that are most often used: stringer bead brushes, flap discs and grinding wheels. Sometimes encapsulated wire brushes — those molded to hold the wire in place — are also used. When it comes to tool sizes, 4-1/2 in, 7 in and 9 in right angle grinders are commonly used in the United States for this type of work. Each tool is designed for different applications in pipeline welding, such as interpass and post-weld cleaning and finishing, or facing of the land. The bottom line of the entire process is to achieve a strong, clean weld with full penetration and no inclusions or porosity. The work must be precise due to the demands on oil and gas pipelines.
Typically, pipes are in 40 ft sections that range from 10 in to 48 in ID. Often, the pipe ends are beveled so that when the sections are put end to end, it forms a V-joint to be filled by welding. In preparing the bevels, the flat face of a grinding wheel is used to do facing, which squares off the land (where the pipe bevel ends and the face of the pipe is still flat). Flap discs are used to take out any pitting or rough edges on the beveled ends when preparing the bevels. Typically, aluminum-backed flap discs are used because they have less flex, which offers more control for the operator and allows them to be more precise in removing imperfections.
After a root pass is laid in the weld joint, a 1/8 in or slightly thicker bonded wheel is typically used to grind out the area to remove excess buildup and reshape the face of the root. Once it’s ensured there is proper penetration in the weld, the second pass — or the hot pass — is laid, followed by numerous filler passes and the final cap pass.
Stringer bead brushes are used to clean the slag from the weld bead between passes. A root pass stringer bead brush has smaller, thinner knots, making it better suited to penetrate the smaller space of the root pass weld. There are also brushes designed for the filler pass; these brushes are slightly wider and allow for faster cleaning of the filler and cap passes. Encapsulated wire brushes are sometimes chosen for their extended life and elimination of long wire breakage as the product wears, but they are more costly than traditional stringer bead brushes.
For all of these common tools used in pipeline applications, it’s important to choose high quality products that can hold up to the rigors of the process and environment and remove inclusions after the first pass. When choosing a wire brush or stringer bead brush, look for a wire that’s been heat-treated and has trimmed ends, which eliminates any “break-in” period for the wire brush to clean to its maximum effectiveness. When selecting coated abrasives, consider one made from zirconia alumina, which offers more durability. For bonded abrasives, products made from a mixture of zirconia alumina and/or ceramic with a harder bond typically hold up well under high pressures. Durability for heavy use is key in pipeline welding applications.
KEEP TOOLS IN GOOD CONDITION
Choosing high-quality, durable tools is an important part of getting the most out of them in rigorous pipeline applications. Proper storage and maintenance of those tools on the jobsite is another key step in getting the best performance and results. When working outside, keep in mind that tools should be kept clean, so avoid placing them in water or mud. This helps minimize environmental effects that could degrade the performance of the tool or cause the product to crack or wear faster. Clean, dry storage helps keep tools in safe working condition, free from rust and damage. Also, be sure to inspect the tool prior to each use to check for any damage or wear.
The field conditions of pipeline applications, such as extreme hot or cold weather or rain, can present additional challenges in getting the best performance from surface conditioning tools. Follow these best practices regarding tool usage to help improve safety, productivity and tool life.
KNOW THE BEST PRACTICES FOR EACH TOOL
Each tool has different best practices regarding pressure, tool angle to workpiece and orientation. It’s important to know how to best handle and use each tool in order to get the best performance — and longer tool life. For example, wire brushes are designed to let the wire tips do the work. When an operator puts excessive pressure on the brush, each individual wire filament is bent, causing the sides of the wires to strike the workpiece, rather than the sharp tips. This leads to stress areas in the wires that can eventually cause breakage. Not only does using too much pressure damage the wires of the brush, it also means the operator is working harder than necessary.
Because the tips of a stringer bead brush do the work, the angle at which the welding operator holds the brush in relation to the work surface is also important. When using a stringer bead brush, the tips should be perpendicular to the weld being cleaned to minimize the amount of flex in the wires and reduce the likelihood of wire breakage. A wire brush should not be used at the same angle as flap discs or grinding wheels.
New stringer bead brush technology on the market is specifically designed for pipeline applications to make flipping the accessory easier and to maximize wire life and safety as the brush wears. This technology features a hex nut on each side of the wheel and allows operators to easily remove the brush from the tool and flip it. That way they can use the other side of the tips, which become razor-sharp as the opposite side wears. The design of the hex nut has the appropriate profile to provide adequate tool clearance, so there is no temptation to remove the guard from the tool in order the change the position of the wheel.
When using a flap disc in pipeline applications, use it at a right angle to ensure complete contact with the abrasive side of the disc being used on the surface, and not just the edge. This maximizes the life of the disc and also the productivity of the disc while the operator is using it. It is important to always follow the manufacturer’s recommendations for tool and accessory speed and usage and personal protection equipment guidelines.
INSPECT FOR WEAR
Along with proper storage to help maintain clean tools and accessories, it’s important to inspect the tool or accessory each time it’s used for any signs of damage or wear. Know the signs of wear — and know when it’s time to change a brush or flap disc. Using a brush or flap disc for too long is a mistake made by many welding operators. Any sign of long wire breakage in a power wire brush means it should be replaced, because long wire breakage can throw the brush out of balance and pose significant safety hazards.
With a flap disc, when the epoxy on the underside of disc starts to become exposed, it means the disc has been fully used and should be replaced. As bonded wheels are used down to a smaller diameter, the wheel becomes harder to control and also may not fit into the necessary spaces for pipeline applications, which can create pinch points or damage to the wheel. Replace the wheel as it becomes worn down to avoid these issues.
BEST PRACTICES FOR MAXIMUM PERFORMANCE
Following these best practices for the tools used for surface preparation and cleaning in pipeline welding applications can help extend tool life, benefit operator safety and improve productivity and efficiency. Surface preparation and cleaning is just one part of the overall process in pipeline welding applications, but it plays a significant role in completed weld quality.
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