The pylons are up,
the power is flowing.

Netze BW relies on all-rounder Unimog in overhead line construction and network maintenance.

Ben Berger often works safely at lofty heights where many others would soon get dizzy. He has to climb pylons or work from a crane cage to check or repair insulators and cables when there are signs that a pylon needs to be replaced due to decay. Since the middle of last year the Netze BW team has been running a U 5023. It transports team leader Jonas Kälberer and his three colleagues rapidly to their work site, retaining its manoeuvrability even in deep mud or on steep slopes.

The team need a good eye and a delicate touch to get close to the pylon when working on such jobs. Once the boards have been laid to reduce the ground pressure, the hydraulic supports mounted on the Unimog ensure stability. Kälberer grabs the remote control to lower the crane mounted behind the cab and position the cage. "The crane's location behind the cab optimises the weight distribution," Kälberer explains.

He directs the crane with its 18 metre jib to exactly the required position. "Up to 50 mm² the cables are relatively easy to handle," Berger comments, after shortly afterwards having detached the spiral binders from the top of the pylon. "Above that, the steel cables become heavy and cumbersome." Colleague Franz Perlinger frees the pylon from its foundation using the excavator. Kälberer has in the meantime detached the cage. He picks up the old pylon by the hook and pulls its easily out of the ground. A few minutes later, it is lying flat. Franz Perlinger harnesses the new pylon, and the next stage of the job follows.

The service team replace around 150 pylons a year. The wooden pylon has to be sunk 2.5 metres into the ground – a precisely regulated depth. Additional stays may be required depending on the ground. Once the pylon has been correctly erected, Ben Berger climbs up to attach the cables. "We are allowed to climb pylons on open land without auxiliary equipment for three months of the year – that's a strict rule of the employer's liability insurance association," he explains. A helmet, crampons and safety cable are of course mandatory.

Mobile even in mud.

The rain is getting heavier, but the job will still be finished on time. A colleague is informed by phone that the cable can be reconnected to the grid. The old, sawn-up pylon and the tools are loaded up and secured. The Unimog ploughs through the muddy ground. "It's a good thing we insisted on tractor tyres, they're well worthwhile," Jonas Kälberer comments. When the rough-profiled 22.5 inch tyres are back on asphalt, he presses a button to increase the tyre pressure again. "The mud is now not an issue for us. That's because the wheels are enclosed, and our Unimog has wading capability to a depth of 80 centimetres." A short time later, one of the secrets of why the Unimog is so popular as an autonomous work machine is revealed: a high-performance voltage converter as a power generator. "It provides 3.6 kilowatts of power, which is enough for all our hand-operated equipment. That means we can also use tools such as an angle grinder, and can even carry out welding if necessary."

The mud is now not an issue for us.

Jonas Kälberer, Team Leader Netze BW

Netze BW relies on a range of different Unimog variants.

While Klevenz's crew are at work with their U 5023, operations manager Hans-Peter Theurer is coordinating a 16.5 tonne U 530. The implement carrier features a drill, but is rarely used for replacing pylons. "We don't replace even 15 a year," Theurer reports. "What we do a lot is work on roof supports, as well as often replacing transformers. That means our Unimog often has to pull an emergency power unit or some other item of auxiliary equipment." Many of the buildings in the surrounding villages do not yet have underground cabling; the power supply is routed via the roofs. "If problems occur, or when upgrades are due, it's up to us. So our main workplace is a cage."

Erecting pylons out of the ground up to overhead cables is also part of the job. It's hard work, because newly installed cables have to be attached to the terminal tower. Jürgen Blöchle and apprentice Janis Klaritsch are working on just such a job. Florian Grupp is at the wheel of the Unimog. The crew pulls aluminium cables with a 300 mm² cross-section into the pylon. It's no job for a weakling because, as Grupp explains, "a metre of cable weighs a kilogram". Working from the cage, they pull the cables one by one up the 18 metre pylon. The three men take eight hours to install all the cables.

"The specification is that the 20 kV cables have to be sunk one metre deep into the ground." To do that, they park the U 530 parallel to the cable route, allowing an adequate safety clearance. The crane has to be deployed far enough to lift the engineers up to the necessary working height in the cage. That's no problem, because the job can carry a tonne even at full extension. Finally, working from the cage, Florian Grupp must position himself properly to secure the cables to the fixture on the top of the pylon.

Once everything is secured, he uses his power screwdriver to fix the cable ends in their terminals. By the late afternoon, the new 20 kV overhead cable section is ready to be connected. The Unimog has done its job with supreme assurance.

Source: Unimog magazine 2/2018
Text: Gerfried Vogt-Möbs
Photos: Henrik Morlock

visible-md and up (hidden-sm and down)
visible-lg and up (hidden-md and down)