Pressing al cable lugs

Aluminium cable lugs
Light-weight and special processing qualities: aluminium cable lugs and connectors
  • The benefit of aluminium conductors: their light weight and comparatively easy handling.
  • According to the standards in place, aluminium conductors are available in four different designs that require different processing methods in places.
  • The contact lubricant in aluminium connecting material improves the contact properties, thus enabling a smooth electrical connection. 

While special cable lugs ensure perfect connections even under tough conditions, there are also situations that necessitate the choice of particularly light-weight materials. Aluminium cable lugs are characterised by their light weight. However, aluminium requires even greater care in processing compared to copper: it is worth noting that aluminium has reduced conductivity.

Aluminium is used in an increasing number of sectors. One such sector is energy distribution, for example. Due to their light weight, excellent flexibility and resulting ease of cable handling, power supply network operators are increasingly turning to aluminium cables – such as for circular pipes used for urban utility supply purposes.

Aluminium compression cable lugs with tube dimensions according to DIN 46329 as well as aluminium connectors with tube dimensions according to DIN 46267 Part 2 are a good choice if you opt to process aluminium conductors. The aluminium compression cable lugs and connectors with a standardised tube are all compatible with single and stranded round shaped and sector shaped conductors according to DIN EN 60228 and aluminium stranded conductors according to DIN EN 50182. The compression cable lugs and connectors are not designed for fine and superfine stranded conductors as these conductor types are not standardised.

The constant material thickness, exact diameter and precise fit make aluminium connectors stable and secure.

Aluminium compression cable lugs are manufactured in a barrier type according to DIN 46329 – thus allowing oil-soaked and paper-insulated cables to be processed without the oil escaping.  

However, there are also simpler variations made from a single tube and, as a result, without any longitudinal tightness. Nevertheless, the quality of the connection is the same in both instances. In any case, however, the tube dimensions are however aligned with those stated in DIN 46329. This means the same crimping dies can always be used.

Aluminium cable lugs and connectors from Klauke:

Aluminium compression joints according to DIN

Aluminium reduction-compression joints

Aluminium compression joints, full tension

Overview of aluminium conductors
Aluminium conductors are sold in four different variants, which sometimes require special processing methods in places:

  • Class 1 single-stranded round shaped conductors (re)
  • Class 1 single-stranded sector shaped conductors (re)
  • Class 2 stranded round shaped conductors (rm)
  • Class 2 stranded sector shaped conductors (rm)

These abbreviations can be found on the connectors and cable lugs along with other details. You will be able to use these details to work out which aluminium conductor is suitable for which connector and/or cable lug.

The marking on the aluminium compression cable lugs are roughly in line with those that can also be found on copper cable lugs. An example of this is as follows: “KL22 12-120 rm/ sm 150 re/se”

  • KL: Manufacturer code (Klauke in this particular instance)
  • 22: Tool code
  • 12: Metric bolt dimensions of the connecting bolt bore (in this case M12 bolt)
  • 120: Nominal cross-section of conductor in mm² (rm/sm)
  • rm/sm: For stranded round shaped conductors and pre-rounded multi-stranded sector shaped conductors
  • 150: Nominal cross-section of conductor in mm² (re/se)
  • re/se: For single-stranded round shaped conductors and pre-rounded single-stranded sector shaped conductors

You may already have noticed that the nominal cross-sections of the se and re conductors are always one unit of measurement higher than the nominal cross-sections of the sm and rm conductors. The reason for this is quite simple: single-stranded conductors take up less volume than stranded conductors.

In order to maintain a secure connection, we recommend that you use hexagonal crimping dies according to DIN 48083 Part 4 or the EKM60ID indent crimping tool when processing compression cable lugs.

With regard to aluminium, there are special crimping dies whose crimp width is 7mm, which is 2mm wider than the crimp width of the crimping dies for copper connecting material. These larger crimp widths generate a larger contact surface that offsets the reduced conductivity of aluminium.
A contact lubricant for aluminium connecting materials
Commercially-available connecting material for aluminium conductors are coated ex-works with a special contact lubricant. During crimping, this destroys the non-conductive oxide layer, which forms on the surface of the aluminium after a short time. The lubricant improves the contact properties. The lubricant also prevents oxygen from penetrating the contact points. Re-oxidation is therefore avoided. The result is a flawless electrical connection. The majority of cable lugs are sealed with a plastic plug, which prevents the contact lubricant from drying out or leaking, and increases the durability of the lubricant.

Contact lubricant for aluminium connections contain corundum, a sand-like mineral which is characterised by its great strength and high wear and corrosion resistance, even in high temperatures. During the crimping process, the compound causes a kind of abrasive effect, which rubs and destroys the oxide layer. In addition, the lubricant allows better sliding friction between the conductor and the sleeve. A connector seizure is prevented, which in turn leads to the largest possible contact surface. In the case of multi-stranded conductors, the lubricant also spreads between the individual wires during the crimping process and seals them. This prevents the penetration of oxygen and moisture.

Another major advantage is that aluminium crimping joints can withstand greater current loads when coated with the contact lubricant than they can without it. We therefore recommend the basic use of cable lugs and connectors with contact lubricants. This will ensure that you will be safe when using a large number of cable lines.
Step by step: Processing aluminium compression cable lugs and connectors

Aluminium has special properties meaning that precise steps have to be taken for its processing. The ideal steps for obtaining a clean connection are as follows:

  1. Remove the insulation from the aluminium conductor.
  2. Treat the bright finish ends of the conductor, for example, carefully with a knife or a wire brush to roughly remove the oxidisation layer and to produce a clean contact surface. Ensure that when cleaning there are no metal residues left on the conductor, as otherwise this can cause contact corrosion.
  3. Insert the conductor into cable lug or connector up to the full insertion depth of the sleeve. The compound flows out of the sides and creates an exclusion of air, which prevents re-oxidisation.
  4. You can now make the hexagonal or indent crimping using the suitable crimping tool. Single and multi-stranded sector shaped conductors must be rounded with a suitable round press insert prior to crimping.
  5. Finally, remove any excess compound.

Alternative markings are provided on aluminium cable lugs for narrow and wide crimpings. The advantage of the wide variant is that the number of crimpings required is halved. However, note that a suitably strong crimping tool must be used for this.

You can use Klauke pre-rounding dies for sector shaped conductors. Unlike for copper conductors, no sleeve has to be used for multi-stranded sector shaped conductors.