Why Choose An Exothermically Bonded Connection?

22nd April 2014
By: ETS Cable Components
Knowledge
Exothermically welded connections and mechanical connections are very similar in their applications, yet their performance can differ greatly. 

As UK distributors of ERICO CADWELD welding systems, we explore the benefits of a exothermic bonded connection over mechanical connectors. 

The CADWELD Weld

  • Will carry more current than the conductor.
  • Will not deteriorate with age.
  • Is a molecular bond that eliminates any risk of loosening or corrosion.
  • Will resist repeated faulty currents.
  • Can be quality controlled simply by visual inspection.

Reliability

As the molecular bond eliminates the concept of surface contact, an electrolyte cannot penetrate between the conductors and cause oxidation and deterioration in the course of time.

Corrosive Environments

This reliability is of particular interest for humid or chemical environments or for bonds directly buried in the ground.

Ability To Withstand High Current

The melting temperature of CADWELD filler material is higher than the melting temperature of copper (1082oC). For this reason, in the event of abnormal heating due to a high fault current, the conductor is destroyed before the connection.

Conductivity

The CADWELD connections form a solid bond around the conductors assuring continuity. The cross sectional area of the weld has greater current carrying capacity than the conductors.

Performance

Standard CADWELD welds have a cross section greater than that of the conductors to be joined, which compensates for the difference in resistivity between the conductor and the welding material. Consequently, under fault conditions, the weld will always remain cooler than the conductor.

If special applications do not allow for the required increase in cross section to be employed, the use of the formula:

CADWELD Resistivity Formula

Which will make it possible to define precisely the resistance of the CADWELD weld.

Comparison between CADWELD bonded connections and mechanical connections

CADWELD Weld Mechanical Crimped Connection
CADWELD Weld Molecular Bond

Mechanical Crimp Connection
Actual Contact Surface
Mechanical Crimp Connection - points of contact

The CADWELD bonded connection provides permanent conductivity over the whole of the section due to a molecular bonding between the metal surfaces. The mechanical connection presents a significant difference between the apparent contact surface and the actual surface.

Exothermic Welding Video Playlist

 

Related Products

Exothermically Welded Connections Cadweld Weld Metals Mechanical Crimp Connectors
CADWELD PLUS Exothermic Welding System CADWELD Traditional Weld Metals Mechanical and Crimp Connectors
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Electrical Resistance

Name: KRISHNA KHASANIS

From electrical point of view, exothermic weld offers most minimum contact resistance among all welds which helps in achieving lowest touch & step potential.

Compared to other welds / connections, exothermic welding connection is more durable.

CADWELD Air Freight

Name: Jamie Courtnell

Hi Albert,

Thanks very much for your comment, The points you raise are indeed valid and there are many many more advantages/drawbacks of each method which we could go into.

However, with your point on the explosive (heating) component being disallowed by air shipment, this can be remedied by using the CADWELD PLUS system (http://www.etscc.co.uk/cadweld-plus-system) which is suitable to be shipped by air, land or sea in unlimited quantities.

Large Fault Currents

Name: Douglas Sinclair

During large fault currents both types are put through extreme mechanical forces.

If a mechanical connection is not properly done (sometimes the inspector does not check them all) they will separate. Exothermic welds also can splice conductors very effectively onto building columns, rebar, etc. helping to assure that good grounding has been achieved (with a smack of the hammer you know if it is a good weld or not.)

Ground mats buried in the mud under many a nuclear plant done with exothermic welds at each crossover point of the heavy copper conductors assured low step and touch potentials of all the tanks and structures bonded to it.

Quite interesting!

Name: Sulaimon Adeyemo

In addition, i think fusion connection:

1. Affords more of contact area of conductors (most especially if welded with adequate mold) than mechanical connectors
2. Requires no future maintenance/attendance
3. Is a bit more expensive
4. Requires more safety measures (as it poses hazards of burn if not handled properly) most especially in my own part of the world.

Pros and Cons

Name: Albert Reed

Why choose exothermically bonded connections over mechanical connectors?

Pros:
1. They make better electrical connection (lower resistance).
2. They are much less prone to corrosion if metals being bonded are different.
3. They last a very long time.
4. Any imperfection caused by workmanship is obvious to the naked eye.
5. This list is just a start.

Cons:
1. In some jurisdictions, they must be made by someone with pyrotechnic qualifications.
2. For temporary bonding the cost may be higher.
3. Again if time is critical, some places will disallow shipment by air of the explosive (heating) component. Planning far enough ahead of the need is important.
4. You can’t easily buy a bunch of different sizes, and have field installers grab what they think is the best fit.
5. Again this list is just partial.

This subject should open up a lot of discussion by major hydraulically compressed connector manufacturers.

It will be fun to watch.

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