The promise for exceptionally high productivity without losing on cable quality may raise eyebrows. Yet, several customers have made the leap of faith towards rapid crosslinking.
The promise for exceptionally high productivity without sacrificing cable quality is subject to be questioned. Yet, several customers have made the leap of faith. The reports about Maillefer Round Curing (MRC) in high voltage cable manufacturing have convinced them. They are committed to MRC and have come to rely on the most advanced and groundbreaking curing technology as an essential part of their VCV lines.
MRC technology allows the quality production of cables without giving up on line speed. Here, the key to high productivity is to focus first on tight roundness control via rapid crosslinking rather than on insulation cooling. By reconsidering the parameter priorities, the line’s optimum speed is not compromised.
Challenges to overcome
The insulation process of high voltage submarine cables is, in many ways, a very complicated process. It requires balancing between many limiting factors such as, production length, production time and production speed. Higher speeds are of course beneficial to reach longer lengths in shorter time.
Production speed, on the other hand, is limited by cable core geometry, curing power and extruder performance. With typical technology, cable core ovality starts to increase dramatically when increasing speed and the related curing power. Technological innovations brought by MRC remove these challenges. Thanks to a special heat impulse the curing process begins by forming a crosslinked layer on the outside of the core. This initial crosslinked layer keeps the cable core round during phases of expansion and shrinking that follow, specifically throughout the curing and cooling parts of the CV line.
Thanks to MRC technology, it is now possible to also increase curing power of the CV tube without any issues. In other words, the curing process starts very efficiently and also increases the total curing power without negative side effects. More curing power naturally leads to higher production speeds. Typical speeds for a standard VCV line and a VCV line with MRC are shown in figure 1. Customer reports show record speeds of 1.55 m/min for a 220 kV 400 mm2 copper conductor cable core.
Exceptional results and roundness
High speed alone is nothing without exceptional quality as well. MRC technology provides the best results in terms of cable core ovality. Typically, achieving perfection with thick insulation layers and small conductor is quite demanding. With MRC technology it is possible to produce cores with 0.995 roundness, routinely, at record speeds.
MRC as an upgrade
Just as our new VCV lines benefit from MRC so can existing Maillefer VCV lines, thanks to our upgrade package. In this case, the first curing section is swapped out with a new MRC section. The compatible unit is made of a special high temperature resistant steel structure.
Once in place, it is then integrated into the existing line control. An upgrade of the NCC application* is included. The automated NCC calculator is easy to use. All existing NCC recipes are available as is, without change. NCC optimization guarantees maximum effectiveness for MRC and minimal risk for degrading outer semicon. The downtime duration for an MRC upgrade is typically two weeks.
Solve the future problems already today
Sustainability, continuous demand for increased productivity and insulation material savings are increasingly hot topics topics in cable industry. With an MRC technology, available new or as an upgrade to your existing VCV line, your production is ready to face the future challenges. Take the leap towards better productivity and increased cable roundness with less insulation material consumption.
Roger Möller