Cable pulling example

The following calculation example from Brugg Cables is an extract from their public document titled 'Manual for Transportation and Cable Laying Maintenance', published 2016. The calculation example is found on pages 12ff.

This example validates our cable pulling module and has been added to our test cases, ensuring that cable pulling calculations won't unexpectedly and unnoticeably change.

Cable selection

In the Cable tab of the cable pulling module the cable is selected, which in the example is of type XKDT 1x240/35 mm2, 20/12 kV. Cableizer does display all relevant cable properties, which closely correspond to the values in the Brugg Cables manual (Cable weight m_tot per m of 3.36 kg, cable diameter D_e of 41 mm, minimum bending radius r_mbp of 615 mm, permissible pull force F_ppc of 9600 N). Please be aware that Cableizer outputs all forces in [daN] (10 N = 1 daN). In addition it is shown if the cable is a single-core or a multi-core cable, and whether or not it is armoured (for armoured cables, it is possible to select pull on the armour in the cable editor as an alternative to pull on the conductor).

Once the cable has been selected, it is time to select the number of cables that are pulled in together, which in this case is 3. Brugg Cables does not mention whether or not the cables are bound together (triplex), but from their admissible pull force which is 28800 N and thus thrice the permissible pull force of a single cable, it is concluded that the cables are assumed to be bound together. For three unbound cables the total permissible pull force is normally assumed to be only twice the permissible pull force of a single cable, as the two cables on the bottom will take all the force (the cable laying on top is not exposed to any friction). If the automatically calculated limit is not suitable, it can be manually entered (e.g. if the pull is made with woven mesh pulling grips). The admissible sidewall pressure has been selected as 10'000 N/m in accordance with the Brugg Cables manual. Both the permissible pull force and sidewall pressure limit values are optional. However, they should not be omitted as the program will clearly indicate if those limits are exceeded along your cable route.

Conduit selection

In the Conduit tab of the cable pulling module a PE conduit with an inner diameter of 120 mm is selected in accordance with the Brugg Cables manual.

The conduit ratio CR_pull, the conduit fill CF_pull, and the conduit clearance CC_pull all show that the conduit dimensions are suitable for the intended cable pull. The conduit jamming ratio CJ_pull is not displayed since the three cables are bound together (triplex) and there is no risk for jamming. Please notice that the conduit preview is up to scale and helps to avoid possible input errors.

Brugg Cables calculates without weight correction factor f_wc and sidewall pressure factor f_rad, and so they have not been applied to our calculation. Please consult with your supplier whether or not to apply these factors to your calculations.

Route editor

In the Routing tab of the cable pulling module the example route is composed of sections and bends. Please notice that the length of the cable route is slightly different between Cableizer and the Brugg Cables example due to the way the bends are handled. We have also focused on the alternative with an elevation of 20 m within the last section.

Our two- and three-dimensional preview help you to verify that the input is correct.

The friction coefficient μ_dyn is 0.15 all along the route (Cableizer does allow optional individual inputs for every section or bend). And since the reel is powered, there is no cable reel force.

The approximate results show a good agreement with the Brugg Cables manual, which states a maximum pulling force F_pull of 10'215 N and a maximum sidewall pressure F_rad of 1'858 N/m. The difference in the sidewall bearing pressure is due to the fact that Cableizer is calculating with the inside bending radius of the conduit, while Brugg Cables is considering the radius of the centerline of the bend r_arc (which is also used as input in Cableizer). The results also show that it is beneficial to opt for a pull in the forward directions if possible, which has both lower pulling forces and sidewall bearing pressures than a pull in the backward direction.

Forward direction pulling forces

In the Forward direction and Backward direction tabs of the cable pulling module, the pull force curves and radial force curves can be calculate and displayed. As shown below, the forward pull force curve does correspond to the curve from the Brugg Cables manual.

Special feature: Pull a cable over a longer route

It is now possible to set a cable length that is shorter than the cable route and get corresponding pull force and sidewall bearing pressure curves. The software calculates sequentially the pull force and sidewall bearing pressure of the cable being pulled over the whole route in steps of 10 cm. This leads to rising and falling values as the cable enters and leaves bends, slopes and cable pushers. The output provides the highest pulling force and sidewall pressure the cable experiences during the pull.

This feature has been added on customer request. Please let us know if you have any proposals for improvements or clarifications.

Cableizer - The Online Cable Optimizer

Model power cables and calculate current rating, magnetic fields, electrical parameters, short-circuit currents, pulling forces... Experience the full potential of our browser-based simulation platform cableizer.com! Our 14-day free trial includes full access to all the simulation features of Cableizer.