Corridors of power
As renewable energies are expanded, it is essential that the extra-high voltage grid is adapted to changing generation and consumption structures. HFI-welded steel pipes from Mannesmann Line Pipe can contribute significantly to protecting this critical infrastructure.
The growing electrification of technologies and processes makes the electricity grid the key lifeline for industry, commerce, government and private households. Extensive infrastructure measures, and particularly in the extra-high voltage grid, are necessary for efficient electricity distribution. In this context, underground power cables are becoming increasingly important.
Well-equipped for all eventualities
Protection for underground cables is highly critical when they cross rivers, roads or railway lines. But this also applies to the confined spaces of inner-city areas, where numerous cables and pipes are already installed and new ones are to be added. This is where HFI-welded steel pipes offer secure and lasting protection.
Cable conduits made of steel
Steel offers a large number of benefits over other materials:
Mechanical strength
- Steel conduits are highly resistant to pressure and impact and can withstand high tensile forces during trenchless installation.
Huge diversity
- External coatings such as PE, PP, fibre cement or GRP increase resistance to a wide variety of ground conditions and stresses. In addition, steel tubes can be integrated into a cathodic corrosion protection system (CCPS) to enable the condition of the infrastructure to be assessed automatically.
Electromagnetic compatibility (EMC)
- Steel conduits reduce electromagnetic fields around the cable, thereby minimising potential interference from neighbouring infrastructure.
The ESM push-in welding socket with an internal bevel at the pipe end ensures damage-free cable pulling. The pipe is welded with a simple fillet weld. The system is also suitable for trenchless applications.
The ZSM joint manufactured by Carl Hamm enables positive-fit final assembly without the need for tools or welding on site. The connection is gas-tight, detachable and designed for high tensile forces.
Suitable for any application
HFI-welded steel conduits are suitable for all established installation methods and, in particular, for such trenchless techniques as HDD (horizontal directional drilling). The joining technology is a key aspect of durable and safe underground installation. In addition to external cable protection, it is also essential that the cables themselves are pulled in without damage. Mannesmann Line Pipe offers three product variants to suit the application.
ESM push-in welded socket
This joining technique is familiar from water pipe installation and the laying of pressurised cable conduits in urban areas, and has been further developed for use on cable conduits. The internal bevel at the pipe end protects the cable insulation during pulling. The pipe is welded with a simple fillet weld, which is also suitable for trenchless applications.
Pipe end with weld bevel
For applications requiring high tensile forces or where pulling has to be performed without socket joints, the pipe ends are supplied with a prepared weld bevel. The nominal bevel angle is 30°±5°, and the web height is 1.6 mm ±0.8 mm. To prevent damage to the cable, the weld root inside the pipe must be ground flat.
Tension-resistant push-in socket (ZSM)
The ZSM joint from manufacturer Carl Hamm is ideal for job sites without welding facilities or with tight deadlines. With this system, the sleeve and spigot end are welded on at the factory and the weld root is ground down. Final assembly with a positive fit is carried out using shear element chains, without the need for additional tools or welding work on site. The connection is gas-tight, detachable and designed for high tensile forces.
Tried and tested in use at Munich's utilities company
Stadtwerke München Infrastruktur (SWM), Munich's utilities company, operates an approximately 400 km long 110 kV pressurised gas cable network as a higher-order electricity distribution network, which is to be gradually replaced by VPE high-voltage cables and significantly expanded. The reason for the expansion is the load forecasts in connection with the energy, heating and mobility transition. Safety considerations in particular have prompted SWM to continue laying its 110 kV cables in steel conduits that can be operated at a pressure of 2 bar for remote monitoring. Around 50 km of steel conduits with ESM push-in welded sockets in DN150 and DN200 have now been used. Conduits are supplied on demand with a black interior finish and a 2 mm thick HDPE exterior coating.
HFI-welded steel pipes from Mannesmann Line Pipe were used in the construction of the 110 kV distribution grid for Stadtwerke München Infrastruktur, including installation beneath the A95 motorway.
Technical data
Diameters: 114.3 mm to 610.0 mm
Wall thicknesses: 5-12 mm
Lengths: up to 16 m
Manufacturing standard: EN 10217-1 or -3
Grades: P235TR1 – P355NH
Further details and the technical publication 'Kabelschutzrohre aus Stahl für die Städte der Zukunft’ (in German only) are available for download on our website
https://www.mannesmann-innovations.com/en/innovations/cable-conduits