Gaining the Best Performance When Cleaning Pipeline Welds
By Igor Dobravc Mesarec, production line leader, and Tony Hufford, category manager – Metal Fabrication, Weiler Abrasives
Multipass welds used in oil and gas pipeline construction are critical since weld failure can be catastrophic.
In addition to being subject to stringent quality requirements, pipeline construction is often completed in challenging environments. And due to tight project timelines and the need to ensure proper penetration between weld passes, operators and helpers typically must grind and clean the welds while they are still hot.
All these factors make proper weld preparation and interpass cleaning crucial to the success of the overall process.
Knowing the common mistakes to avoid and which abrasive products can help get the work done is important to maintaining quality and staying on production timelines.
P
ipeline welding challenges
As mentioned above, the sometimes-difficult environment and stringent quality and timeline demands of pipeline welding introduce challenges into weld preparation and cleaning.
In midstream pipeline construction, full-length pipe is often laid out in the right-of-way already beveled. The pipe gang preps the pipe by cleaning the rust and pits off of this bevel. They then face the land to a nickel thickness and set two ends of pipe together, leaving an 1/8-inch gap between the 37-degree bevels on each end of the pipe. The first pass, called the root pass or bead pass, is the most critical because it creates the foundation for the remaining passes to be added on top of that bead. The welder or helper cleans the root pass with a 1/8-inch grinding wheel to create a “U” in preparation for the hot pass.
After the root pass, the second pass (the hot pass) helps ensure full penetration of the weld. The hot pass must be completed quickly after the root pass to avoid the pipe temperature falling below allowable levels. This means grinding the root pass on a hot weld before laying down the hot pass. If the pipe diameter is larger than 12 inches, two welders and two helpers work simultaneously to quickly lay and grind the root and hot pass and ensure there is no distortion during the welding process.
The hot pass and all subsequent passes — the number of passes depends on pipe diameter and wall thickness — are typically cleaned with a knot wire brush known as a stringer bead brush. These products remove inclusions or impurities that rise to the surface of the weld without removing base material. If inclusions aren’t removed, they can cause a weld to fail X-ray inspection later — resulting in costly repairs or rework.
One challenge in multipass welding, especially during root pass grinding, is the space constraint involved in the V-groove. It’s important to choose abrasive products designed to fit deep into the bevel so there is no accidental grinding of the pipe sidewall, which could cause potential rework or failures.
In addition, because the root pass is ground while it is still hot, operators may be grinding a weld that is up to 500 degrees Fahrenheit (260 degrees Celsius). The hot weld will cause some grinding wheels to glaze over. When a product glazes, the wheel is not removing material effectively from the root pass. This can cause operators to push harder on the wheel or to chip the edge of the wheel in an attempt to get it to grind better. However, chipping the wheel is an unsafe practice that can result in the wheel breaking apart at high speeds. To avoid this, look for a wheel specifically designed to grind hot welds without glazing.
Chatter is another challenge during pipeline root grinding. A wheel that has a lot of chatter and vibration can cause the operator’s arm or hand to become numb over time, which creates an ergonomic issue. Too much chatter can also cause the wheel to bounce out of the bevel, and the operator may accidentally scar the pipe. This can require costly repair.
Avoid these 5 common mistakes
Addressing some common mistakes in pipeline weld preparation and interpass cleaning can help improve efficiency and safety — and produce better results.
- Improper cleaning: The more preparation done upfront in the process, the fewer problems an operator will face when it’s time for weld inspection. If the weld cleaning and preparation aren’t done correctly, it can result in weld inclusions or even costly weld failure. Ensure that all of the pits and rust are removed from the pipe bevels just prior to the pipe being set and tacked for prep of the root pass.
- Using the wrong product: At the start of the day, welders and welders’ helpers often get a bucket of products before they head to the right-of-way. If they aren’t provided with the right products for the job, they will attempt to make them work due to their distance from the supply station. However, using tools and products that aren’t designed for the job introduces safety risks and can result in poor weld quality. Be aware that not all 1/8-inch-thick wheels are the same. Some wheels are designed only to be used vertically, while other products are designed to be used for grinding as well. Make sure to look at the manufacturer’s recommendations and never use a wheel designed only for vertical use to face the land or transition pipe.
- Too much pressure: When using a wire brush for interpass weld cleaning, too much pressure can cause problems. Pushing too hard will bend the wires of the brush so that the sides — rather than the wire tips — are hitting the weld. This reduces cleaning power and efficiency and also increases the likelihood of long wire breakage. Let the brush do the work to make sure the ends are striking the weld to remove inclusions.
- Poor product storage: For abrasive products, proper storage and handling are critical to performance and product life. Store the products in a clean, dry place overnight and avoid laying them on the ground in snow, mud or puddles. While pipeline welding is rarely done in perfect conditions, keeping the products out of dirt, mud and water goes a long way toward optimizing results. Often, welders mount the grinding wheel and products on their rigs so they can hang them up when they’re not in use.
- Not using the tool guard: For safe use of a grinding wheel, the tool guard should always be in place. If an operator feels the guard gets in the way when grinding or cleaning tight spaces, look for a floating guard that can be easily adjusted.
Products for pipeline weld cleaning
From flap discs and grinding wheels to wire brushes, there are a range of abrasive products available for pipeline weld prep and interpass cleaning. One product will not cover the needs for all the necessary steps in the process, so it’s important to choose the right product for each job.
For grinding the root pass, look for a grinding wheel that is balanced to reduce chatter and provide better control to stay in the weld groove. Weiler® Tiger pipeline grinding wheels are designed specifically for pipeline notching and grinding, so they can be used for facing the land and transitioning, as well as grinding the root pass. These wheels are also designed to break down and grind hot welds, which eliminates glazing. And they deliver bite right out of the box, so operators won’t feel the need to chip the wheel to improve performance.
Weiler Abrasives visited several right-of-way jobsites and worked directly with contractors to develop the Tiger pipeline grinding wheels to ensure the products meet pipeline needs. Because they are specifically designed to grind hot welds without glazing and to deliver immediate bite, the wheels optimize performance and efficiency in pipeline welding.
Tiger aluminum-backed flap discs are another product typically used during weld repair and bevel grinding. These products have less flex for more control and are good for grinding pits and rust from pipe bevels without rounding the edge. They can also be used to smooth out welds during repair work in tight spaces.
For cleaning the hot pass and any subsequent passes, a variety of wire brushes can be used to do the job.
Weiler stringer bead brushes — the industry standard — are designed to fit into the base of the V-groove and be aggressive enough to remove inclusions on the first pass. Encapsulated brushes provide increased aggression in tight spaces and eliminate wire breakage.
Filler pass brushes can be used to clean filler and cap passes since they have a wider footprint to clean larger surface areas toward the top of the V-groove.
Weiler Abrasives also offers Dually stringer bead brushes, which have a hex nut on each side of the wheel that allows operators to easily remove the brush from a right-angle grinder and flip it. The design provides adequate tool clearance so there is no need to remove the tool guard to flip the wheel. This allows operators to take advantage of the natural self-sharpening feature by wearing the brush tips in the opposite direction to increase cleaning speed.
No matter which product is chosen for the job, be sure to follow best practices for safe and efficient use. Pay attention to these factors and think SPOT:
- Speed and size: Make sure the product fits the tool and has an rpm rating that meets or exceeds the tool rpm rating.
- Pressure: To get the most efficient and safe performance, use proper pressure and don’t push too hard.
- Orientation: The angle to the workpiece at which an abrasive is used plays a role in safe operation. Different tools may require different orientations, so the proper angle can vary.
- Time: Don’t dwell or grind in one area too long, which can result in grinding through the weld.
Putting it all together
Using the right products for the job and following best practices in weld prep and interpass cleaning can help operators avoid failed X-rays or other inspections and produce high-quality welds in these challenging environments. It can also help keep projects on time and on budget by introducing efficiencies and preventing downtime and costs for rework.
This article was featured in the March 2022 issue of World Pipelines magazine.
Igor Dobravc Mesarec- Production Line Leader
Tony Hufford - Category Manager: Metal Fabrication
