A Basic Overview of Exothermically Welded Connections - nVent Blog

When constructing electrical protection systems, electrical grounding connections must remain dependable over the life of the system. If bonds weaken, grounding, bonding and lightning protection systems become susceptible to failures.

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Exothermic welding, often known under by our brand name nVent ERICO Cadweld, is a method that has been around since and offers a number of advantages over other types of connections.

Discover what exothermic welding is, when it should be used and how it compares to mechanical grounding connections.

What Is Exothermic Welding?

Exothermic welding is a process used for joining similar metals, such as copper to steel or copper to copper. It employs an exothermic reaction to form a molecular bond between the two pieces.

The connection is produced in a purpose-designed graphite mold. The weld employs an exothermic reaction of thermite (powdered metal) to heat the metal. Put simply, the exothermic process involves a chemical reaction that releases heat and requires no external source of heat.

Exothermic Welding Chemical Reaction that Produces Heat

3Cu2O +2Al → 6Cu + Al2O3 + HEAT
Copper Oxide + Aluminum → Copper + Aluminum Oxide (Slag) + Heat
Reaction Temperature approximately °C (°F)

When executed correctly, an exothermically welded connection is homogeneous after cooling, meaning a true weld has been formed and the elements are completely fused together. The connection is permanent, irreversible and requires no additional means to hold
it together, as shown in the image below.

In the s, Professor Charles A. “Pops” Cadwell, the namesake of nVent ERICO Cadweld, worked to improve the installation or repair of signal bonds and track power connections to electrified train rail. These welds took significant effort and equipment to complete. “Car A”, shown below, was used to transport the equipment and personnel needed to make a single connection.

In , Pops patented the Cadweld process, and enabled one man with 25 pounds of equipment to replace all of this equipment previously needed. Shortly thereafter, exothermic welding for cathodic protection applications was created, followed by high voltage power transmission and electrical grounding and bonding connections.

Over the last 80 years, the equipment has been greatly enhanced to improve ease-of-use, product safety and weld quality to increasingly justify its use and broaden its applications. Exothermic welding is a significant invention that has accounted for more than 150 million connections.

How Does Exothermic Welding Compare to Mechanical Connections for Grounding?

In general, exothermic connections are superior to mechanical connections for grounding due to the permanent bond made between two materials. Especially for use with electrical connections, a reliable connection is key.

Advantages of exothermically welded connections:

• Maintain a lower resistance over time due to the fused connection.
• Will not deteriorate with age due to a limited susceptibility to corrosion.
• Lifespan exceeds that of the conductors it connects.
• Eliminates any risk of loosening because of the molecular bonding.
• Will resist repeated faulty currents.
• Offers the lowest possible earth path resistance.
• Can be quality controlled by a visual inspection.
• Safe and easy to use with minimal training and protective requirements.
• UL® listed to UL 467.
• Exceeds the requirements of IEEE 837.

Disadvantages of mechanical connections:

• Cause a point-to-point current flow (i.e. unequal current density).
• Susceptible to corrosion, lowering resistance over time.
• Require an anti-oxidant compound in order to prolong the lifetime of the connection.

How Is an Exothermic Weld Performed?

To illustrate the exothermic welding process, below are the directions using nVent ERICO Cadweld Plus.

Components:

For more information, please visit Exothermic welding powder.

• Graphite mold
• Weld metal
• Igniter
• Mold clamps
• Cleaning tools
• Sleeves, shims, batting

Directions for performing an exothermic weld:

1. Insert Cadweld Plus cup into mold (may require use of a cover/baffle).
2. Attach control unit termination clip to ignition strip.
3. Press and hold control unit switch and wait for the ignition.
4. Open the mold and remove the expended steel cup—no special disposal required.

After learning the process, it typically only takes a few minutes to complete an exothermic connection. Between the simple process and improved performance, exothermic welding becomes the preferred method for most electrical professionals.

Learn More About Exothermically Welded Connections

When you have a project that requires grounded connections, will you use Burndy HYGROUND® compressions or nVent ERICO Cadweld exothermic welds? Both connections are high-quality and long-lasting, so how do you select the best option for your location?

In this article, we’ll provide an overview of nVent ERICO Cadwelds and demonstrate when they are the most suitable option.

What is a nVent ERICO Cadweld?

nVent ERICO Cadweld is the brand name of an exothermic weld, which means that it uses molten metal to permanently join conductors. Typically, thermite powder (powdered aluminum and iron oxide) is poured into a graphite mold, then ignited. The thermite becomes molten, reaching temperatures in excess of °F. When the metal cools, you remove the mold and are left with an exothermically welded joint.

Click here to see exothermic welding in action.

Modern exothermic welds have been an industry standard since the late 19th century. Like all exothermic welds, nVent ERICO Cadwelds create a low-impedance, durable connection that resists corrosion. It’s a common weld because it is relatively easy to complete, it lasts decades, and you don’t need any outside heat or power to create it.

Advantages of a nVent ERICO Cadweld

Exothermic welds are suitable for connecting copper to copper or connecting copper to steel, cast iron, brass, and bronze. It’s especially useful when connecting two different types of metal because it resists galvanic corrosion. When welding two dissimilar metals, they often corrode preferentially, meaning that one metal corrodes quicker than the other. nVent ERICO Cadwelds help limit preferential corrosion, which is just one reason that they’re used frequently.  

Without an exothermic weld to reinforce connection joints, the connection can degrade from soil corrosion. With an exothermic weld, the joint resists corrosion from soil so it can be buried underground or under concrete with no risk of deterioration. In fact, the weld may even outlast the wire.

The applications for nVent ERICO Cadwelds are nearly endless. With the right graphite mold, you can use exothermic welds to join multiple copper wires to each other. They can be used to connect wire to rebar or ground rods. You can also use nVent ERICO Cadwelds to install ground grids or to connect new equipment to existing grids.

nVent ERICO Cadwelds won’t loosen over time. They can carry electrical currents at the same capacity as the conductor, sometimes more. When done properly, they can withstand multiple fault currents without failing. They’re so sturdy that they can withstand natural and manmade vibrations without loosening, so Cadwelds are an excellent option in many different circumstances.

Disadvantages of nVent ERICO Cadweld

The primary disadvantage of a nVent ERICO Cadweld is that environmental conditions must be ideal for a successful weld. It’s not safe to do exothermic welds in explosive environments or near flammable components. When used outdoors, exothermic weld completion can be limited by weather. Exothermic welds cannot be completed when there is high wind, rain or other moisture in the vicinity of the connection. However, the conditions won’t suffer from exposure to moisture after a successful installation.

If you need a connection done immediately, an exothermic weld may prove to be a challenge in some locations and climates. Unfortunately, delays to your project can be costly. However, if you have flexibility in your schedule, you can wait and create the nVent ERICO Cadweld when the conditions are suitable.

Compared to compression welds, exothermic welds take quite a bit more time. It’s likely that your labor costs will be much higher for a project with nVent ERICO Cadwelds than one with Burndy HYGROUND® connections. It’s also difficult to inspect the quality of an exothermic weld to be sure that there are no “pits” in the weld interior. The quality of the weld can also vary from one installer to another.

Get a nVent ERICO Cadweld with Wetherbee

High-quality, durable connections are essential to the safety of your employees and facility. Choosing the right weld for your location helps avoid liability issues, plus it reduces the time and money that you have to spend on maintenance. If you’re not sure which type of weld is best for your location, get in touch with Oklahoma’s Certified nVent ERICO Cadweld Installers. We can discuss your options and then move forward with creating expert welds that will last for decades. 

Contact us to discuss your requirements of Electrolytic ion grounding electrode. Our experienced sales team can help you identify the options that best suit your needs.