Cable Lugs & Crimping Tools Using The Hexagonal Crimp Method

Published 03 Sep 2018

Cable Lugs & Crimping Using The Hexagonal Crimp Method

Cable Lugs & Crimping Using The Hexagonal Crimp Method

uploaded by Chris Dodds - Thorne & Derrick Sales & Marketing Manager

Hexagonal Crimping Of Cables

Thorne & Derrick International, based in the UK, are leading suppliers of cable crimp lugs and associated crimping tools for Low, Medium & High Voltage Cables and Power Systems – this series of articles by Klauke discusses the theory and practise of installing compression type cable lugs and connectors.

Klauke cable lugs and crimping tools are used by Jointers, Linesmen, Panel Builders and Electrical Engineers to install underground cables and overhead line conductors on power, transmission and distribution networks including LV MV & HV systems, 11kV-33kV.

➡ Download 2018 Klauke Cable Lugs catalogue and see the complete range of tools for cutting and crimping cables.

In this Article we cover the following:

  • Hexagonal crimping is suitable for both copper and aluminium conductors
  • A professional hexagonal crimp generally requires use of crimping dies which match sizes of conductors and connecting material
  • The classification of manufacturer specific crimping dies and cable lugs is rather regulated by the cross section of the cable
  • The primary application of standardised hexagonal crimps is with electric utilities within a range from 10kV up to 30kV
  • Depending on the tool narrow or wide cable crimps can be used

Hexagonal crimps for aluminium and copper

In daily practice hexagonal crimping is the most common kind of crimping of cable lugs and cable connectors for medium/high voltage power cables and systems.

The reason is very simple – this type of crimp is suitable for both copper and aluminium conductors. Hexagonal crimps can be found in panel building industries as a manufacturer specific crimp and also as a DIN standard lug crimp for example in utilities (aluminium and copper conductors including 11kV and 33kV power cables).

Technically the hexagonal crimp is characterised by a centrical and constant force effect applied during the crimping operation from all sides and creating a larger contact area.

Hexagonal Crimp Lugs

Hexagonal crimps are suitable for both copper (above) and for aluminium (below)

The individual strands of the conductors are being deformed homogeneously in their entirety without any damage. The results are good electrical properties of these connections.

Mechanical and electrical properties of tubular and DIN compression cable lugs are being defined by the IEC 1238 part 1. It defines the requirements that an electrical connection has to fulfil for a permanent safe operation within intended applications.

Hexagonal Crimp

The cross section of a hexagonal crimp performed with a manufacturer recommended tool shows the uniform positioning of conductors in the cable lug

Apart from mechanical pull out tests also electrical durability tests are included. The field of application of hexagonal crimps comprises the processing of conductors as per:

VDE 0295 Classification

  • Class 1: round solid conductors
  • Class 2: round stranded conductors
  • Class 5: round fine stranded conductors
  • Class 6: round finest stranded conductors
DIN VDE 57295

Conductor types acc. to DIN VDE 57295: round solid, round stranded, fine stranded, compacted

In addition hexagonal crimps per DIN 46235 and DIN 44267 can also be used for processing of non-tension and full tension connections of aluminium cables per DIN 48201 Part 1 of aluminium ropes per DIN EN 50182.

The correct Crimping tool

For processing cable lugs per DIN 46235 crimping dies with die codes per DIN 48083 can be used. This combination enables hexagonal crimps per DIN 46235 and 46267. For hexagonal crimps of standard tubular cable lugs it is suggested to strictly observe manufacturers tool recommendations.

Hexagonal crimps are exposed to high loads. For this reason only high quality tools should be used which in addition feature special functions guaranteeing correct and safe crimps. Battery powered crimping tools of the latest generation give an acoustic warning if the required crimping force has not been reached.

High quality mechanical crimping tools can only be opened when the crimping operation has been completed. Until then an integrated locking device blocks the tool – a totally completed cable crimp is important as the required compression of the crimp material is only reached at the end of the crimp phase.

Preparation For a professional crimp

A professional hexagonal crimp generally requires use of crimping dies which match sizes of conductors and connecting material. That means that cable lugs and connectors need to correspond to the dimensions of the conductor and crimping die.

Incorrect Crimping

Incorrect Crimping

Incorrect Crimping

Incorrect Crimping

Correct Crimping

Correct Crimping

Incorrect and correct crimps in comparison: An incorrect crimp (crimping,middle: low force crimping, and usage of incorrect crimping tools can result in an increase in joint resistance and may jeopardise the installation)

An incorrect combination can lead to low compression – excess compression crimps with potentially fatal consequences: Faulty cable crimps and lugs can lead to increased contact resistance with rise of temperatures which in the worst case can cause fire.

Inappropiate Tools

Incorrect or materials processed with in-appropriate tools can cause heavy defects on installations resp. electrical equipment

Poor quality cable lugs

Cable lugs of poor quality and/or processing may cause fire

For this reason manufacturers of branded electrical and cable accessory products such as Klauke recommend for crimping operations their cable lugs and connectors solely use of their own appropriate crimping tools. High quality crimping dies can be recognised by a polished surface with rounded edges.

Crimping dies

Example of a crimping die with polished profile

These crimping dies are precisely manufactured and guarantee a constant and neat deformation of copper or aluminium. Prior to the cable crimping operation the electrical engineer or cable joint must ensure that the conductors need to be brushed to achieve a metallic clean surface and that oxide layers have to be removed from the aluminium cables.

While stripping cable conductors it has to be observed that some are not being damaged and that bared length is more or less identical with insertion length of cable lug or connector. Crimping dies need to be clean and metallic bright. To avoid the incorrect die selection Klauke differentiates in colour, silver stands for aluminium dies and yellow gold for copper die sets.

Crimping die

Left: crimping die for aluminium, silver coloured; right: crimping die for copper (yellow-gold colour)

Tip: Klauke recommends to start crimping operations on cable lugs always from the palm towards the cable. In this case the compressed material can slide towards the cable end which hasn’t been crimped.

Cable Lug Connector

A cable lug or connector always needs to be crimped under consideration of the crimping direction and use of appropriate tools

Manufacturer specific hexagonal crimps

For hexagonal crimping operations we distinguish between two versions:

  • The hexagonal crimp as per DIN 48043 Part 4
  • The manufacturer specific hexagonal crimp

Within the standard copper range the so called manufacturer specific hexagonal crimps are used for cable types as per VDE 0295 class 2.

Hexagonal Crimp Lug

Permissible – manufacturer specific hexagonal crimp

Manufacturers with a reputation for quality such as Klauke offer hexagonal crimping dies for processing standard copper tubular cable lugs as per EN 13600 and approved cable conductor connections as per IEC 1238.

These cable lugs are being used for instance in the construction of electrical control cabinets because of design and smaller dimensions. To accomplish a professional crimp it is of great importance to use high quality tools. Only using such tools guarantee that a sufficient degree of compression is being achieved to insure optimum contact properties.

To achieve an IEC approved connection it is necessary that all components used match each other – this includes cable lug, crimping tool and suitable die set.

This concerns the cable lug and appropriate conductor but also the suitable appropriate crimping die and crimping tool – resulting in a safety engineered system.

The classification of manufacturer specific crimping dies and cable lugs is – other than with DIN standard crimps – not controlled by die codes; it is rather regulated by the cross section of the cable specified in sqmm.

Specific Crimp

Manufacturer specific crimp with indication of cross section

Every manufacturer is responsible for the electrical durability of connections being processed with their products – specified tests have to be provided as evidence.

As a professional and safe hexagonal crimping is dependent from an exact matching of crimping dies and cable lugs Klauke recommends for crimping their cable lugs solely use of their own tools as well. In case of special applications it is advisable to involve the preferably identical manufacturer of both tools and cable lugs.

Brand manufacturers will perform – if required – for the specific application pull out tests (accelerated tests) as per IEC and where applicable also tests of the electrical contact resistance and recommend depending on the results adequate tools and materials.

Hexagonal crimps for aluminium & copper

In particular when it comes to international projects and processing of specific cable types for instance in China or India IEC or customer specific standards can be complied with in terms of safety.

Standardised hexagonal crimping

The primary application of standardized hexagonal crimps is with electric utilities within a range from 10 kV up to 30 kV. The reason is the very homogeneous crimping which produces a consistent electrical field and consequently has a positive impact as to an unwanted field scattering.

Other than with indent crimps hexagonal crimps do not show any mechanical indent of material which in case of electrical field control needs to be balanced with a conductive compound.

DIN Standardised Hexagonal Crimp

Mainly for electric utilities: DIN standardised hexagonal crimp

Copper cable lugs as per DIN 46235 and copper connectors as per DIN 46267 part 1 can be crimped with crimping dies as per DIN 48083 T4.

For aluminium cable lugs as per DIN 46329 and compression connectors as per DIN 46267 part 2 and other aluminium connectors and cable lugs with appropriate tube dimensions as well hexagonal crimping dies as per DIN 48083 part 4 can be used.

Hexagonal profiles as per DIN comply with the dimensional specifications of DIN cable lugs and are standardized within given tolerances.

However, there are no specs given as to the crimp width which is either 5mm for copper or 7mm for aluminium. Identification marks on DIN cable lugs give important notes as to manufacturer, dimensions and design of cable lugs, which indicates the crimping tool resp. crimping die as necessity for crimping operations conforming to standards.

This inscription is found behind the manufacturer code.

For instance KL18 stands for

  • KL: manufacturers code (in this case Klauke)
  • 18: tool resp. die code

For a professional completion of a standardised crimp the tool code is decisive: The tool code of crimping die used has to conform with the tool code of the cable lug.

Imprinted Tool Code 18

The imprinted tool code “18” on the cable lug (above) gives information on the crimping die to be used. The completed crimp (below) with imprint “18” on the cable lug proves that the correct crimping die was used

The die code is engraved mirror-inverted on the crimp surface of the crimping die and once crimping operation has been completed it is visible on the cable lug.

Tool codes correspond approx. with the tube dimensions of the cable lugs. For copper die codes range from 5 up to 58; this corresponds to cross sections from 6sqmm up to 1000sqm. In the same way hexagonal crimping dies for aluminium and appropriate tube dimensions of these cable lugs and connectors are standardised.

Tool Code

Tool code on the cable lug and imprinted code verify a correct crimp

Wide or narrow crimps

Depending on the tool narrow or wide crimps can be used. On a cable lug of 50sqmm cross section for instance one has the alter-native to do two narrow crimps or one wide crimp.

Narrow & Wide Crimp

Narrow crimp (above) and wide crimp (below)

Tools with a crimping force of up to 6t (60kN) are suitable solely for narrow hexagonal crimps of 5mm width on copper. Tools with a crimping force of more than 12t (120kN) are suitable for wide crimps according to manufacturers instruction.

Usually the electrician prefers narrow crimps as tools are lower in weight and easier to handle. For cable assembly, however, wide crimps are preferred as they reduce the number of crimps required and consequently save time.

For standard tubular cable lugs mostly narrow crimps are being used. Mechanical and battery powered tools – lower in weight – and up to 60kN are being applied.

A special feature is with aluminium cable lugs: To compensate the lower conductivity of aluminium compared with copper the narrow crimp in this case is 7mm.

Also important: The DIN standard does not prescribe a specific crimp width either for copper or for aluminium.

This information is given by the manufacturer by means of wide and narrow markings on DIN compression cable lugs. It should be observed that cable lugs resp. connectors and tools including crimping dies come from one single source, e.g. a brand manufacturer.

Crimp marking

Crimp marking indicate to narrow resp. wide crimping

Indent crimps

Old, but proved and tested: indent crimping constitutes the oldest type of crimping operations in electrical installations. In panel and control cabinet construction even today it is a widely used method of crimping copper – as classical indent crimp and “W” indent crimp.

Further Reading

Review other Blogs in this series of articles about Cable Lugs, Crimping Cables & Tools:

Cable Lugs – Crimping Applications & Standards

Copper Cable Lugs For Special Applications

Indent Crimping Of Cables – Benefits & Limitations

Cable Lugs & Crimps – Hexagonal v Indent Methods of Crimping

DIN Standard – Crimping & Compressing Aluminium Cable Lugs & Connectors

Copper & Aluminium – Crimping CU-AL Cables

Electrically Driven Crimping Tools For High Volume Applications

 

LV MV HV Cable Accessories & Substation Electrical Equipment

Thorne & Derrick are Specialist Distributors of leading manufacturers of Cable Accessories, Jointing & Installation Equipment.

LV MV HV cable accessories used to joint, terminate, connect, cleat and gland power cables to air and gas insulated substations, transformers, switchgear and overhead line networks.

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