Top drop clamps for overhead cables
When it comes to overhead cable fastening at the local loop’s level, there are many models of drop cable dead-end clamps. Both clamps and spirals for overhead drop applications are engineered to meet specific mechanical, optical and environmental constraints. From raw materials to their design and dimensions, everything is carefully figured out by R&D engineers to provide effective solutions to field challenges. The selection of a suitable newtork equipment to the infrastructure to be deployed represents thus a major challenge for the development of reliable and future-proof FTTH infrastructures. To make sure that the selected product is the most appropriate solution for your network configuration, it is necessary to refer to the technical characteristics of the cable to be deployed, such as: :
- the external diameter of the cable
- the approved minimum bend radius
- the density of the cable sheath
Based on these three criteria, we can precisely determine which is the most suitable technological solution among the following ones, for each type of cable to be installed:
- Conical clamping solutions
- Clamps with a wedge design
- Mandrel clamps
- Helical dead-ends
Short span clamp or helical dead-ends?
To correlate a certain cable to a suitable technology solution for enabling dead-ending of drop cables, it is extremely
important to take a close look at each particular case. Therefore, for the dead-ending of drop cables presenting FRP rods and therefore a stiff construction, an external diameter of 5 to 6 mm for a minimum bend radius of 20 mm and
a HDPE sheath, drop clamps based on conical clamping system are to be preferred. They enable the cable installation without bend radius constraint, while also preserving the functional characteristics of the cable in case of overload.
Moreover, thanks to their compact design, they provide an effective solution for the intensification of networks as they are simple and fast to install. Indeed, a telecom technician takes on average only 4 secondes to install a clamp
with envelopping wedges while the average installation time for a helical dead-ending is of 22 seconds.
For cables presenting a low density sheath or subject to permanent stresses such as aeolian vibrations, it is recommended to use helical deadends. These anchoring solutions made from twisted aluminum alloy wires forming two legs and a loop offer a wider contact surface and therefore, a better cable grip. Thanks to a grit layer applied on their legs, these spirals enable a good cable grip. A pitch without grip is intended for the sag adjustment before the complete cable installation into the device.
What to choose for small diameter cables : wedge or mandrel clamps?
When it comes to small-diameter drop cables, the most appropriate overhead cable fastening solution is the one that copes with all the mechanical stresses to which the cable may be subject to. Thus, for cables with a 4 mm diameter, a bend radius of 15 mm and a construction including FRP rods in the polyethylene outer sheah, wedge clamps are the most suitable solution. Thank to their small FRP rods and their low density outer sheath , these cables offer better bend radius performances. To install the cable into the wedge clamp, cable loop is placed onto the wedge, enabling thus to increase and to re-distribute the contact surface. Thus, this dead-ending device enable a quick and reliable installation. Moreover, 5/35 cable clamps also enable the sag adjustment subsequent to the cable installation into the clamp. Available in 5 versions, including different bail materials and lengths so to meet all mechanical and evironmental constraints, 5/35 clamps are used for simple or double anchoring of round or flat cables, depending on the model.
For drop cables with even more reduced diameters of 3 mm and a minimum bend radius of 10 mm, mandrel clamps for short spans are the most befitting solution. Thanks to their construction without FRP and to their low density outer sheath such as those made from polyurethane, these cables can be reliably self-tighten around the central mandrel over several turns. This enables the distribution of the clamping force over a large surface and protects cable from tensile stress. In addition, the cable sag can be adjusted even after the cable complete installation into devices such as @ or Mini@. Moreover, thanks to an integrated cable tie, cables installed in the mandrel clamp present no risk of slippage induced by æolian vibrations.