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October 2010 - Vector - Page 58 CONTRACTOR'S TOOLBOX Compression crimping information Termination of compression connectors to an electrical conductor has been used for over 50 years and to date is the dominant connecting technique used. Copper Copper has always been used in electrical connections. Stone Stamcor uses copper of at least 99,9% purity in the terminals and manufactured under stringent quality checks to ensure that dimensional accuracy is maintained. Independent testing of our products is in accordance with IEC 61238-1. Resulting in, high conductivity (only silver is better), good deformation properties and good jointing ability. During manufacturing the terminal is annealed to achieve as good deformation around the conductor as possible when crimping. This gives a crimp connection with low contact resistance and good mechanical characteristics. The most commonly used crimping method for copper is the hexagonal crimp. This shape gives a gentle and mechanically strong crimp with minimal risk of conductor strands being damaged resulting in removing virtually all the air leaving a tight homogeneous mass of connector and conductor with the minimum amount of creepage. Before crimping of a terminal commences a visual inspection of the tool should be performed to check and ensure that it is clean and without defects. The pressure in the hydraulic pump must be checked regularly as per the manufacturer’s specifications. Check that the correct tool and die set combination have been chosen for the terminal and conductor which are to be crimped. One manufacturer's die may not suit another’s connectors, as the dies are designed to give the correct compression and to ensure optimum performance under continuous use. To be certain that a tool has performed the correct compression and the desired deformation is achieved, the crimp result should be measured. These dimensions are available from the manufacturer and are normally measured across the flats (A/F) of the hexagonal faces where the impressions of the press dies are made. The tooling systems are essential for proper installation of a compression connector since connectors and dies are designed as a unit for specific wire sizes. Only the recommended tools and dies should be used to achieve the desired compression ratios. (Available from the manufacturer of the connectors.) Aluminium Stone Stamcor uses aluminium with a purity of at least 99,5% for the manufacture of connectors and cable lugs which has good characteristics such as, low weight, strength in relation to its weight, good conductivity - around 60% of that of copper and easy to work with. Crimping methods for aluminium differs throughout the world – mainly hexagonal and indent. When crimping aluminium it is important to break the layers of insulation oxide as efficiently as possible and a deep indent crimp is the most effective method in achieving this. An oxide inhibiting compound such as Penetrox should always be used when crimping aluminium with any of the techniques, (hex or indent), as it contains evenly suspended particles which penetrates the wire’s (stranded cable) or conductor’s (solid sectorial) surface oxides to establish excellent continuity between the individual strands / conductor and the connector barrel for a low resistance connection maintaining an air tight connection. The deep indenter compresses the cable strands/conductor to form an intimate contact with each other and the connector barrel. The result is an excellent electrical connection with high pull-out strength. Contact Theo Momple, Stone Stamcor, Tel 011 452-1415, [email protected] The most important reason for this is that cold compression provides both simplicity and safety. Stone Stamcor’s compression connectors are designed for reliable and controllable electrical connections. The complete installation is fully inspectable.
