12:6 Bolt joints Bolt joints Users/installers of bolted connectors always have to adhere to, and follow electrical codes and norms in the local region where they are making such installations. The information below is general and hence, should never be seen as an installation instruction. The installation of a terminal with bolt joint for electrical transmission requires special attention. It is important that this is done in a correct manner, as important as the contact crimping at the other end of the terminal as described above. The joint must achieve a sufficiently high clamping force, distributed in a desirable manner and ensure the electrical properties over a very long time under high and varying loads of different characteristics. It is very important to follow the installation instructions. These are based on theoretical calculations, verified tests and experience from field studies. Tightening must be carried out in a controlled manner using torque tools, where the relevant screw is tensioned to the specified torque. The accuracy of the tool is of great importance. The clamping force of a properly tightened screw shall create a contact area large enough to ensure good conductivity, without the risk of overheating. In order for the clamping force to be distributed evenly and create a sufficiently large contact area, hard flat washers must always be used, type BRB HB200 SMS 70, under screw head and nut. See image below. This applies regardless of the hardness of the conductive materials (which are softer than HB200). Otherwise, there is risk of large deformation of the conducting material that reduces the tension, which can increase the risk of inadequate contact area and overheating. Bolt joints. Tension washers The use of different types of locking elements or spring washers often increases the risk of settlement. If a spring washer of type DIN 6796, with a very high clamping force, is positioned and secured between e.g. nut and the hard flat washer, it can provide an increased margin towards excessively high settlement. The diameter of the tension washer should be less than or equal to the flat washer’s, even after tightening fully. Otherwise, the risk of settlement at the outer edge of the flat washer increases where the clamping forces are concentrated. When using spring washers, 1 is sufficient and it is preferably placed on the opposite side of the terminal. Bolt joint with spring washer. Mounting the terminal against the connection rail Max. 2 terminals of the same size on the same screw. Current load should be checked. Preparatory: • Clean contact surfaces from dirt, oxide layers and grease using a steel brush and denatured alcohol. This is especially important for aluminium. Surfaces that are tinned, nickel-plated, silver plated must not be brushed. • Petroleum jelly or contact grease reduces corrosion risk on cleaned surfaces Fastener selection: • Screws and nuts of strength class 8.8. • Greased galvanized screws provide the least dispersion of the pre-tension force. • Choose stainless A4-80 in environments when there is a high risk of corrosion. Recommended tightening torque Thread Steel 8.8 * Steel 8.8 * Steel 8.8 * Steel 10.9 * Steel 10.9 * Steel 10.9 * Stainless * Stainless *Stainless * - Mv Ff p Mv Ff p Mv Ff P M5 5,5 6,6 118,0 8,0 9,2 164,0 5,5 6,2 111,0 M6 9,5 9,2 114,0 13,0 13,0 160,0 9,5 8,6 107,0 M8 23,0 17,0 116,0 32,0 24,0 164,0 22,0 16,0 109,0 M10 45,0 27,0 92,0 64,0 38,0 129,0 45,0 25,5 88,0 M12 78,0 40,0 125,0 110,0 56,0 175,0 76,0 37,0 116,0 M16 200,0 75,0 156,0 280,0 110,0 229,0 185,0 69,0 144,0 Mv = tightening torque (Nm) Ff = pre-tensioning force (kN) p = flat pressure (N/mm²) FZB = electroplated + gloss chromed FZY = electroplated + hard chromed FZM = FZM= mechanically galvanized * (FZB, FZY, FZM) A4/80 Selection of washers: • Always select hard flat washers of the BRB, HB200 type. • The tension washer can normally be excluded. If a tension washer of type DIN 6796 is used, it must be placed between the screw head/nut and the flat washer. It must never be placed directly against an electrical contact surface without a flat washer in between. The flat washer must have an external diameter at least as large as the tension washer. • 1 spring washer is sufficient and it should be placed on the rear of the busbar, between nut and hard flat washer, see diagram. Installation: • The screws must be tightened with torque tools so that tightening is controlled. • Torque wrenches must be calibrated regularly. Oil the screw when installing. Even if the torque is recorded correctly, the pre-tension force depends entirely on the friction. • Tightening torque according to the table above. Accuracy better than ±5%. • The terminal palm and busbar may be of different materials. Al/Al gives a weaker joint. It is important to clean and use contact grease. Tension washer + flat washer can reduce the risk of settlement. Al/Cu gives a higher risk of corrosion and settlement, use contact grease. Cu/Al provides low risk of galvanic corrosion when the rail is made of Al. Cu/CU provides the best joint, good contact and small risk of settlement.
RkJQdWJsaXNoZXIy NTYxNjk=