BS7609 Guidance Notes - Crimping Cables With Cembre Lugs & Tooling

By Chris Dodds on 9th September, 2014

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BS7609 Guidance Notes - Crimping Cables With Cembre Lugs & Tooling

The BS7609 Code Of Practice For Installing Uninsulated Connectors With Copper Or Aluminium Conductors.

The BS7609 code of practice sets out what is best practice for the installation and inspection of uninsulated compression and mechanical connectors for power cables with copper or aluminium conductors. 

BS7609 Cembre Crimping Lugs Best Practice

What Is Crimping? 

Crimping is the method of attaching the metal terminal around an electrical conductor to give a good electrical connection. Using a correct tool such as a Cembre Cable Crimping Tool and high compression force, the cable lug is effectively bonded to the electrical conductor using very high force. 

6 Simple Steps Showing How Crimping Should Be Done.

  1. Cembre Lugs, Die Sets, Crimping ToolChoose a manufacturer providing crimp tooling, die set and crimp cables lugs matched to work together to give assured crimping performance.
  2. Each crimp lug should be marked with a reference on the barrel or palm - this shows that the cable lug selected is the correct size and type for the conductor. 

  3. Cembre Lug - Strip Insulation BackPrepare the conductor by stripping the insulation back. The strip length should be equal to that of the lug barrel. Take care to avoid damaging the conductor strands - exposed strands should be cleaned to remove any remaining insulation.

  4. BS7609 Cable CrimpingFully insert the conductor into the barrel of the lug - check the cable conductor is fully inserted using the inspection hole provided.

  5. Using the manufacturers instructions, crimp the lug - paying careful attention to the positioning of the crimp die on the barrel of the lug. If multiple compressions are required pay attention to the sequence in which they are made. 

  6. Use the following 6 points to check the completed crimp:

  • Marking on the lug shows it is correct for the conductor type and size.
  • The marking on the cable lug shows the correct die set was used.
  • No insulation is trapped in the barrel.
  • Excess grease is removed from insulation and cable lug.
  • If an inspection hole is provided, the conductor has been fully inserted.
  • It is not over-compressed or under-compressed. Both of these can have a detrimental effect on the performance of the joint.Incorrect compression can cause excessive flash or burrs. If in any doubt, samples should be produced for test purposes.

Cembre Crimping Tool

In addition to the requirements of BS7609 Cembre advises the following :

It is important that the crimped cable installation is not compromised by a poor choice of copper tube lug, or by the use of a ‘mismatched’ crimping system.

  • Cembre supports the Approved Cables Initiative (ACI) Code of Practice to ensure that the conductor used is both third-party approved and appropriately marked.Cembre Lugs
  • The cable lug should have an equal current carrying capacity to that of the conductor. Copper tube lugs designed and manufactured by Cembre achieve maximum electrical conductivity with minimum resistance by the use of high purity, electrolytic copper having a cross sectional area equivalent to that of the conductor.

  • Cembre Crimps

    Beware lugs manufactured from thin wall copper tube as they have the potential to cause elevated temperatures when the conductor is carrying high levels of current.

  • Recommended procedures for conductor preparation and crimping Cembre copper tube lugs, Cembre Copper Lugsincluding number, position and sequence where multiple compressions are required.

  • Cembre copper tube lugs are also fully annealed after pressing to alleviate residual stresses within the palm area and ensure optimum mechanical and electrical performance at the connection interface.

  • Ensure Cembre crimp tooling is certified as calibrated regularly and serviced correctly and all equipment, particularly die sets, is inspected for damage or wear and maintained in good condition.

Crimping Best Practice Requirements

  • Approved cable conductor correctly prepared
  • Conductor strip length = cable lug barrel length
  • Manufacturer and size shown on crimp lug
  • Cable lug and conductor have equal copper content
  • Crimp tool optimises performance of dies
  • Crimp dies matched to tool, lug type and size
  • Correct number, position and quality of crimps
  • Cable lug marked to check correct dies used

Choosing the correct Cembre die set:

  • ALWAYS refer to the Cembre die selection chart. A die selection guide booklet is also included with every new Cembre crimp tool, whether hydraulic or battery crimping tools.

The number and sequences of compressions per cable lug:

  • The number and sequence of compressions shown in the die selection guides are specifically determined for Cembre lugs from the lug type and design, the force applied by Cembre crimp tooling and the bite width of the matched die set.
  • ALWAYS apply the correct number of compressions as per the die selection guide in order to assure the performance of the joint after cable crimping.

  • Apply each compression in the correct sequence to avoid distorting the cable lug.


Which lug and die combination to use when using extra flexible conductors?

  • Cembre copper tube lugs for extra flexible conductors 35sqmm to 185sqmm have the same cross sectional area of copper as standard Cembre A-M lugs for LV applications, but with a slightly wider inner diameter to more easily accommodate the fine strands.
  • Above 185sqmm it may not be possible to use the correct size standard lug with an extra flexible conductor. For example, say a 240sqmm lug does not fit on a 240sqmm extra flexible conductor, it is acceptable and common practice to use the next larger size of lug, here 300sqmm.

  • The lug MUST however be crimped with the die set appropriate to its size, 300sqmm, since using a 240sqmm die set will distort the cable lug and be detrimental to performance.


Which lug and die combination to use when using compacted conductors? 

  • For low voltage applications use Cembre A-M Copper tube lugs. Matched crimp tooling and hexagonal die sets MUST be used.
  • Always apply the rule that the cross sectional area of the lug should at least equal that of the conductor so, when using compacted conductor it is essential that the correct size lug be used, even if the fit appears ‘loose’ prior to crimping.

  • The apparent ‘loose’ fit is due to the air between conductor strands having been ‘compacted out’ during manufacture, causing a slight reduction in the diameter of the conductor. The resulting gap between conductor and cable lug barrel wall is fully taken up during the crimping process.

  • Do not be tempted to move down a lug size to obtain a tighter fit, as there will then be insufficient copper in the shoulder or palm of the cable lug. As an example, for 185sqmm compacted conductor use A37 lug, ME37-C die set and appropriate Cembre crimping tool.

                   Cembre Hydraulic Crimping & Cutting Tools             Cembre Cordless Hydraulic Battery Crimping & Cutting Tools

T&D are Main UK Stockists for the Cembre range of compression connectors (cable crimp lugs and splices) for all low and high voltage crimping applications of power, control and instrumentation cables with either copper or aluminium conductors.

Cembre copper, aluminium and bimetallic cable lugs and splices are designed for high voltage cable crimping applications including 3.3kV, 6.6kV, 11kV and up to 33kV. Cembre 2A HV cable lugs and splices are made from high purity copper, annealed and tin plated with extended barrels for reliable high voltage electrical connections.

Cembre electrical connectors are the market leading crimping system for reliability, consistency and peace of mind performance - specify Cembre to crimp, splice and terminate your vital high voltage electrical circuits.

Cembre High Voltage Crimp Lugs - Features ...... Cembre High Voltage Cable Lugs

Quality - Cembre high voltage crimp lugs and splices are manufactured from electrolytic copper tube - the copper tube dimensions are designed to obtain the most efficient conductivity and mechanical strength to resist vibration and pull out.

Strength - Cembre high voltage crimp lugs are annealed to guarantee optimum ductility which is an absolute necessity for crimp connectors which must withstand the severe deformation arsing when compressed by hydraulic crimp tools. In electrical installations subject to vibration, crimp terminals must perform a reliable connection - annealing avoids cracking or breaks between the cable lug palm and barrel.

Reliability - Cembre crimp lugs feature an extended barrel design facilitating full insertion of the the copper conductor into the crimp lug - the cable lug barrel length has been designed to allow easy and accurate positioning of the dies during the crimping operation.

Compression Connectors for Connecting & Terminating HV Conductors - Compression (crimp) connectors are an established method of connecting and terminating high voltage cable conductors. To ensure a reliable connection or termination, the following should be observed.

  • Both cable conductor and compression crimp should be cleaned down using cable cleaning wipes
  • The size, shape and metal (copper or aluminium) must be correct for the cable conductor
  • The correct crimp die set should be selected
  • The cable conductor must be fully inserted into the crimp connector
  • The correct compression or crimping sequence must be followed and the full compression pressure applied.

Failure to observe these precautions can result in a compression connector, lug or termination that fails in service.

Cembre Cable Lugs - Tin Plated Industrial Cable Terminations 

Tin plated cable lugs provide superior and extended service in industrial, hazardous and high voltage installations - tin plating is recommended for corrosive atmospheres (offshore, marine, oil, gas, petrochem and water industries). Noxious gases or liquids overtime attack surfaces of copper cable lugs which potentially can cause serious electrical and mechanical performance overtime. Cembre tin-plated cable lugs resist corrosion degradation for stable high voltage cable connections.

For more information Click Here: Cembre Cable Lugs, Crimps & Connectors HV up to 33kV 

Video Playlist: Cembre Cable Lugs, Splices & Crimping Tools LV 11kV 33kV

Cembre Cable Lugs, Splices & Crimping Tools

Category:  Cable Crimping & Cutting Tools

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