Tough plasma gouging might not be the most widely processes in place, still it plays a vital role in fabrication. As a matter of fact, any operator must master plasma gouging techniques to be considered a real professional.
In this article we are going to dig deeper on the plasma gouging topic. We are going to consider how does it work, how is related to other processes, and what are its main applications. Let’s get started by the basic definition of plasma gouging.
What is plasma gouging
Plasma gouging is an industrial metal removal process that uses a superheated plasma jet to melt and blow away metal. It’s similar to plasma cutting, but instead of severing the workpiece, it creates grooves or channels.
The plasma gouging process utilizes a plasma torch that generates an arc of extremely hot ionized gas (plasma) exceeding 20,000°C. The plasma torch uses a non-transferred arc configuration where the arc extends in open air instead of transferring the arc to the workpiece. This focused arc concentrates a lot of heat onto a small area of the metal.
Plasma gouging vs plasma cutting
While both plasma gouging and plasma cutting use a superheated plasma arc to melt metal, there are some key differences between the two processes:
Purpose: Plasma cutting aims to completely sever the workpiece, creating a clean separation, while plasma gouging focuses on removing material from the surface of the workpiece, creating grooves or channels without separating it.
Torch angle and movement: When cutting with plasma the torch is held perpendicular to the workpiece and moved along the desired cutting path. When doing plasma gouging the torch is typically held at an angle to the workpiece and manipulated side-to-side to “dig” out the groove.
Gas usage and nozzle design: For plasma cutting a higher gas flow usually is needed to expel the molten metal through the kerf (the cut path). Nozzles often have a constricting orifice to create a focused plasma stream. In the meantime, plasma gouging may use a slightly lower gas flow, focusing on directing the melt away from the groove rather than completely through the material. Nozzles often have larger openings for wider plasma streams.
Applications: Plasma cutting is used for separating metal sheets, creating intricate shapes, and other tasks requiring full penetration. Plasma gouging is useful for preparing weld joints, removing weld beads and slag, creating channels for cables or pipes, and repairing damaged metal.
Resulting groove: Plasma cutting leaves a narrow kerf with clean, square edges, while plasma gouging creates wider grooves with slightly tapered sides, depending on the torch angle and manipulation.
Speed: Plasma gouging works much faster, removing metal at higher rates than the cutting process which must cut slowly and precisely.
How does plasma gouging work
If you want to become a plasma gouging expert follow these key steps:
- Get the equipment and workpiece ready: You’ll need a plasma cutter with a dedicated gouging mode, gouging-specific consumables (torch tip, shield, nozzle), and a compressed gas source (usually air or oxygen). The metal surface should be clean and free of debris for optimal results.
- Initiating the Arc: When you activate the torch, a high-voltage pulse passes through the electrode inside the torch tip. An electric arc is generated between a tungsten cathode and copper anode inside the plasma torch head. This creates intense heat that ionizes the passing inert gas into a plasma state.
- Melting the Metal: The superheated plasma jet (over 20,000°C) exits the torch through a wide, short nozzle directed at the metal workpiece. This concentrated plasma arc melts the surface of the base metal. Compressed air is blown around the plasma arc, focused by an outer shroud. This high-velocity swirling air hits the molten metal and blows it away, creating a groove.
- Maintaining the Process: The torch head is angled about 30-60 degrees to the workpiece and slowly traversed across the area to be gouged out. The consistent plasma arc continues melting while the directed airflow keeps removing metal, digging a rough trench.
- Repeat the Process: The width, depth and shape of the gouged area can be controlled by adjusting torch angle, travel speed, gas flow levels, and current input. The molten metal gets blown away, forming a groove or channel on the workpiece surface. Wider grooves require slower travel or multiple passes. The process is repeated to obtain the desired depth and shape of the groove surface preparation that will then be exposed to welding passes.
Advantages of plasma gouging
Plasma gouging can help in many ways in some specific industrial applications. Let’s review some of its unique advantages.
Precision and Control: Plasma gouging allows for highly accurate and controlled removal of material, creating narrow and deep grooves with minimal heat-affected zones. This is especially valuable for precise beveling or detailed groove shapes.
Versatility: Unlike other specialized methods, plasma gouging works on a wide range of metals, including ferrous (steel, iron) and non-ferrous (aluminum, copper) materials. This makes it a valuable tool for various applications.
Speed and Efficiency: Compared to grinding or chipping, plasma gouging is significantly faster, providing increased productivity and reducing labor costs. The high removal rate is perfect for large projects or repetitive tasks.
Safety: Compared to methods like oxyfuel or carbon arc gouging, plasma gouging produces less flame and sparks, reducing the risk of fire and explosions. Additionally, the use of compressed air or oxygen instead of flammable gases further enhances safety.
Cleanliness: Plasma gouging creates minimal dross and slag compared to other methods, reducing the need for extensive cleaning and post-processing work. This translates to faster completion and lower overall project costs.
Lower distortions: Compared to arc-air gouging, plasma gouging introduces less heat into the workpiece leading to reduced warping.
Narrower grooves: The precise plasma arc allows creating narrow, deep grooves for welding joints designs requiring high depth-to-width ratios.
Disadvantages of plasma gouging
Of course, we must acknowledge that plasma gouging has also some disadvantages, like the folllowing:
Higher Initial Cost: Setting up equipment for plasma gouging requires an initial investment in the plasma cutter, consumables, and compressed air source. This may be a drawback for infrequent or one-time use compared to alternative methods.
Skill Requirements: While not overly complex, operating a plasma gouging torch effectively requires training and practice to achieve optimal results. Inexperience can lead to inconsistent groove depths, slag formation, and potential damage to the workpiece.
Noise and Fumes: While safer than some alternatives, plasma gouging still generates significant noise and fumes during operation. Proper ventilation and personal protective equipment are essential for operator safety and comfort.
Limited Thickness: Compared to thicker material cutting methods like oxyfuel or plasma cutting, plasma gouging generally excels in shallower groove creation (typically up to 25 mm). Deeper gouging might require specific equipment or multiple passes.
Other gouging processes
Besides plasma gouging, there are several other processes available for gouging metal, each with its own advantages and limitations. These can be grouped according to its type, like mechanical or thermal gouging. Here’s a rundown of some common options:
Mechanical Gouging
Grinding: This versatile method uses abrasive wheels to remove material through friction. It offers good control and precision but can be slow and generate dust.
Hand Milling and Routing: Similar to grinding, these methods use rotating cutters to remove material. They offer precision and flexibility but require specialized equipment and can be noisy.
Chipping and Hammering: Traditional methods using chisels and hammers are effective for removing slag or weld beads but are slow and labor-intensive.
Thermal Gouging
Oxyfuel Gouging: This process uses a high-pressure oxygen jet to burn and remove metal preheated by a fuel gas flame. It’s cost-effective for thick steel but creates slag and is limited to ferrous metals.
Air Carbon Arc Gouging (ACAG): This arc welding process uses a carbon electrode and compressed air to melt and blow away metal. It’s faster than oxyfuel gouging but produces fumes and has limited control over gouge shape.
Manual Metal Arc Gouging (MAG): This arc welding process uses a flux-coated electrode to melt and remove metal. It’s versatile and works on various metals but can be less precise than plasma gouging.
Other Gouging Methods
High-Velocity Water Jetting: This method uses a high-pressure stream of water mixed with abrasives to cut and remove metal. It’s ideal for sensitive materials or areas with limited access but requires specialized equipment and can be noisy.
Laser Gouging: This advanced method uses a focused laser beam to melt and vaporize metal. It offers high precision and minimal heat-affected zone but requires expensive equipment and specialized skills.
Equipment for plasma gouging
Plasma gouging, while similar to plasma cutting, requires its own specific equipment setup. Here’s a breakdown of the essential elements:
Power Source or Plasma Cutter
You will need a plasma cutting equipment with a dedicated gouging mode. This mode typically provides higher amperage and optimized settings for effective groove creation. Common plasma cutter amperage ranges for gouging include 40-200 amps, depending on the material thickness and desired depth. The plasma cutter draws its power from a generator or a wall outlet. Choose a power supply with adequate capacity to match the maximum amperage of your plasma cutter.
Gas Supply
Plasma gouging commonly uses compressed air, nitrogen, or oxygen as the gouging gas. Air provides a wider, shallower groove, while oxygen creates a narrower, deeper cut. Some materials might require specific gas choices, so consult the manual for recommended settings. You will also need a regulator to control the gas pressure and hoses to connect the gas source to the torch.
Plasma Torch and Consumables
Gouging Torch: Choose a torch specifically designed for gouging, as it might have a different nozzle design or angle compared to a cutting torch. Some torches offer interchangeable components for flexibility.
Nozzle: The nozzle constricts the plasma arc and directs the gas flow. Gouging nozzles often have larger openings compared to cutting nozzles to accommodate wider plasma jets for groove creation.
Electrode: The electrode conducts the electricity to create the plasma arc. Specific electrode types might be recommended for particular gouging applications.
Shield: The shield protects the nozzle and operator from sparks and molten metal. Different shield designs can offer varying levels of coverage and cooling.
Safety Gear
Helmet: A suitable auto-darkening welding helmet is essential to protect your eyes from the bright plasma arc and flying debris.
Gloves and Protective Clothing: Wear welding gloves and fire-resistant clothing to shield your hands and body from heat and sparks.
Respiratory Protection: Use a respirator certified for welding fumes and airborne particulates to avoid inhaling harmful smoke and dust.
Additional Equipment
Cables: Flexible cables safely transmit and handle the very high currents between the power supply and plasma torch. These maintain electrical conductivity.
Ground Clamp: Secure a ground clamp to the workpiece to complete the electrical circuit and ensure safe operation.
Magnetic Angle Gauge: This tool helps maintain the optimal torch angle for consistent gouge depth and profile.
Cleaning Tools: Wire brushes or grinding discs can be used to clean slag and debris after gouging.
Compressed Air Source: Plasma gouging requires high-flow rate (2-5 bar or 30-70 psi) clean & dry compressed air to create the swirl airflow around the arc to eject the molten metal.
Air Filter & Hose: An in-line filter is used to remove dust, dirt, oil and moisture from the air stream which would contaminate the surface. Air is delivered through plasma-rated hoses.
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Applications for plasma gouging
The versatility of plasma gouging shines in various applications across different industries. Here are some of the most common uses:
Weld Preparation and Repair
Bevel cutting: Creating angled edges for easier weld penetration.
Removing weld beads and slag: Cleaning up after welding for improved weld quality.
Backing out or “gouging out” defective welds: Excising flawed weld sections for repair.
Repairing cracks and damaged metal: Removing cracks and preparing them for filling with new material.
Metalworking and Fabrication
Groove cutting: Creating channels for pipes, wires, or other fixtures.
Removing unwanted metal: Cutting off tabs, lugs, or temporary weldments.
Preparing for joining: Creating grooves for mechanical fittings or brazing.
Scrap removal: Cutting up scrap metal for recycling or sorting.
Maintenance and Refurbishment
Removing corrosion or damaged areas: Cleaning up metal surfaces before repair or coating.
Disassembling welded structures: Safely separating welded components for maintenance or replacement.
Modifying existing structures: Adjusting openings or creating new features without complete disassembly.
Some specific uses
While plasma gouging can be used in the beforementioned processes, there are some specific uses that can help us to see how important for any welding and cutting operator to master its technique. Let’s see a few of these examples.
Pipeline and Vessel Fabrication: Gouging thick sections of pipe and tank materials to prep for root and fill welding passes. Achieves deep penetration and removal rates.
Railway and Shipbuilding: Gouging worn parts, castings and fabricated components to sound metal before welding repairs of critical transportation equipment.
Construction and Mining: For field work repairing and maintaining heavy machinery equipment at mining, oil drilling, and construction sites where portability is less critical.
Orbital Tube Welding: Automated tube mills use plasma gouging to precision prep and bevel pipe ends for consistent high-quality welds.
Nuclear Power: Used extensively in nuclear plant construction and maintenance for the reliability and control it affords when removing thick specialty alloy metals.
Remanufacturing: Salvaging worn parts by gouging away damaged material and rebuilding components to original design specs via welding versus full replacement.
Get some help to get started with plasma gouging
If you are part of the mining, energy, automotive, and manufacturing industries, to name just a few, you need to know everything about plasma gouging. We can help you with that, because our experts have decades of experience in plasma cutting and plasma gouging.
We distribute the equipment, accesories, and consumables needed for plasma gouging. Contact us whenever possible to talk about your plasma cutting and gouging needs.
