When electrical protection systems are installed, grounded electrical connections must remain stable throughout the life of the installation. As connections break, mechanisms for grounding, locking, and lightning defense become vulnerable to failures.
A method that connects similar metals and has been around since the 1930s, Cad welding offers several advantages over the other types of connections. So, what is Cad welding? It is a welding process that utilizes an increasingly exothermic thermite contact between a metal like aluminum and copper oxide, which helps transfer uncontaminated copper into the weld. Here, we will discuss everything there is to know what about Cad welding.
What is CAD Welding?
Cad welding has a growing use when it comes to connecting steel reinforcing bars. A large wall pipe-like sleeve acts as a vortex and is positioned over the connection which has a space between the edges. Thermite powder is pumped via a hole, which also acts as the point of combustion. The thermite is ignited by an oxyacetylene torch, which appears to burn at a rapid rate, which binds the bars together.
The effect is a complete section splice with force equal to or greater than that of the reinforcing steel. It is assumed that rail tracks are done in a similar way except that there is a mold that acts as a vortex to hold the thermite that the finished weld does not include. The same is performed for cables like underground grids on a far smaller scale to create a permanent joint, as mechanical contraction joints may fail over time.
What is Cadweld?
You’ve probably heard the term ‘Cadweld’ before. But what is it exactly, and how does it work? These are questions that we will look to answer here. Used as a brand name for a process called exothermic welding, Cadweld is utilized to tie together copper conductors to create stable and minimum-impedance electrical joints at physical connections.
If exothermic welding is not used to strengthen ground contact joints, then over time the connection strength would increase and will risk the reliability of the ground route due to corrosion and the effects of high currents at structurally-weak connection sites. That may lead to a significant safety risk.
The Cadweld welding process is a way of exothermically welding various components made of metal together in an electrically sound molecular-bonded contact, resistant to temperature differences, and not susceptible to the corrosion problems associated with compression or mechanical components.
The welding method combines metals with a current that carries power equal to the resting conductor, allowing for lower resistivity and thus a stronger earth-path for future short-circuit hits. An almost metal-metal exothermic connection can be achieved with a wide range of mold-bodies, welding tools, and starting equipment for the welding process.
When it comes to connections that are exothermically connected, the most commonly recommended and installed are the Erico Cadweld connections. This is because they can be used for the following:
- Welded High-voltage cable attachments, – for example exothermically welding markedly different conductors inside clear joints of transmission
- Cable attachments, like perpendicular links, tees, intersections, several ties, and tap-offs
- Flat busbar/band attachment to binding pin, including cessation and tee contact via the conductors
- The cable connection to the binding pin, including cessation and tee link via conductors
- Flat busbar/band on metallic surfaces, – for example for steel manufacturing and grounding
- Cable to metallic surfaces, for example for the settling of steel structures and manufacturing
- Flat busbar/tape link, like perpendicular joints, tees, hybrids, and tap-offs or the development of systems for earthing
- Cable to strengthening concrete bar or metal pipework
- Busbar cable links or links to flatband earthing networks, cable termination lugging
How Hot Does Cadweld Get?
An exothermic mixture, the welding material responds to temperatures approaching 1400 ° C or 2500 ° F and a focused discharge of smoke to create hot molten steel. While these materials are not dangerous, the ignition temperatures for the welding material can reach 900 ° C or 1650 ° F.
By sticking to the Cadweld welding protocols, the possibility of burns and fire caused by spillage of hot molten material would be minimized. The utilization of water or CO2, in the event of a fire, can assist in containing blazing containers. Large amounts of water will assist in managing a fire should the exothermic materials become involved. The application of water should be performed from a distance, and the following should be ensured:
- Ensure the mold fit is appropriate and the equipment is properly assembled.
- Avoid the chemicals and moisture in welded mold and materials. The connection between hot molten metal and moisture or pollutants may cause hot material to eject
- The thickness of the base material must be adequate for the volume and form of connection to avoid melting and leak of hot molten metal
No matter how hot the Cadweld gets, you can ensure your safety during the exothermic welding process by following the steps mentioned above.
How Do You Perform Exothermic Welding?
Also referred to as exothermic bonding or thermite welding, exothermic welding is a method in which lightning safety or earthing (grounding) conductors are firmly connected together.
For joining different metals, an exothermic weld can be particularly useful. An advantage that this method has over other similar processes is that it does not need any outward heat source. Instead, it functions by using a thermite composition’s chemical exothermic reaction to heat the conductors to a level where, once cooled, a low-resistance, mechanically solid molecular link can develop. Here, the thermite composition is weld powder.
Producing an exothermic weld joint is a simple process involving exothermic welding equipment, handle clamps, welding powder, and moulding. Connections are resistant to recurrent fault currents, incredibly conductive, durable and they show outstanding tolerance to erosion. The majority of the exothermic connections have at minimum the cross-sectional area of the joined earth conductors.
How is an Exothermic Connection Made?
Creating an exothermic welding joint is a simple process involving, as described below, various tools, handle clamp, welding powder, mold, and cleaning accessories.
- Place washed conductors in the exothermic mould after drying it. This can be done through pre-heating or creating a test joint
- Use a handle clamp to secure the mould and position the metal retaining disk at the base of the exothermic mould vortex
- Load the welding powder into the mould and add a small portion of welding powder at the edge of the mould for quick combustion
- Fasten the mold cover tightly
- Spark initial powder with flint gun
- To solidify before opening the mould, wait at least a few seconds after the exothermic welding reaction takes place
- Clear the weld and wipe mould properly before creating the next connection
What is Exothermic Welding Used for Electrical?
For a number of projects, engineers rely on electrical connectors. Linking and grounding provide the basis for all electrical safety systems. Regardless of the project, it is of critical importance that the electrical grounding and connecting links work reliably over a facility’s life. It is not appropriate to increase tolerance over time and have a lack of connection due to transients.
Electrical engineers can minimize the risk of exothermic links causing ground bonding and grounding system failures. Made in a purpose-designed graphite mold, exothermic connections avoid elevated electrical resistance, help minimize oxidation, and remove vibration-related weakening of the connections.
Compared to mechanical connections, exothermic weld connections are far more effective. They create a strong, permanent connection between those conductors that:
- Will neither weaken nor deform
- Needs little instruction, and can be evaluated visually
- Keeps resistance low
- Has the ability to endure recurrent fault currents without loss of operation
- Gives the same maximum holding power as the conductor itself
- Does not need external heat source or power
All in all, exothermically welded attachments achieve a high degree of durability over a facility’s life as opposed to mechanical connections.
Final Thoughts
By now, we know Cad welding is the same thing as exothermic welding. It is simply a brand name for the latter. So, what have we found so far about exothermic welding? We have found that to establish a molecular connection between two metal parts, it utilizes an exothermic reaction.
The link is made in a graphite mold which has been purposely designed. The metal is heated by the welding using a thermite exothermic reaction. In simple words, the exothermic method entails a chemical reaction that emits heat and needs no external source of heat.
After cooling, an exothermically welded bond is homogeneous if performed correctly, which means a true weld is created and the components are fully fused together. The relation is irreversible, immutable, and doesn’t need any extra means to keep it joined together.
“Cad Weld” flickr photo by pv411 https://flickr.com/photos/pv411/6159857740 shared under a Creative Commons (BY) license