The use of heat shrink technology in installation of low voltage and medium voltage cable joints and terminations is a proven solution and has been in use for decades. It is known that the quality of the tube is critical to successful installation. When everything is in place and installed correctly, the result is mechanically durable, waterproof and meets lifetime requirements.
Accessory kits often include more than one heat shrink tube. The tubes can be semiconducting or insulating. In addition, it may include adhesive or consist of layers with different material properties. The structure and properties of the tube are designed exactly to meet the specific requirements of the accessory kit. This is one of the reasons why Ensto manufactures almost all the tubes needed for its accessory kits.
Quality Management in Own Hands
“The role of heat shrink tube is crucial to the functionality of the entire range of our accessories. High quality must be guaranteed with no exceptions,” says Timo Koivisto, Quality Manager of Ensto.
The actual quality of a heat shrink tube is revealed during installation when tube is heated for shrinking. If installed heat shrink tube doesn't work as it should, it will cost time and money. Getting a replacement product to the site takes time and often the entire assembly needs to be replaced. For this reason heat shrink tubes are an important part of overall quality of the accessory.
“Ten years ago, we decided to take quality control in our own hands. In practice, it meant investing in production lines of tube extrusion and expansion,” says Koivisto. The new production facilities were founded in connection with Ensto's factory and headquarters in Porvoo, which is located on the southern coast of Finland near the capital Helsinki.
First Extruded and Then Expanded
Initial tube is produced by extrusion with three-screwed crosshead, which provides great flexibility in the production process and materials. A wide variety of material recipes are used for different tubes. The key is to use high-quality plastic and rubber granules compounded with additives such as colorants and stabilizers.
The reels of extruded tube are taken to a separate process where the tube is cross-linked, usually through radiation. That creates the tube a “memory” of this original size.
When tube has a memory of it’s original size cross-linked tube reel is transferred to third process and new line for expansion. The tube is heated, expanded in diameter, and rapidly cooled to keep the new expanded size. The idea is, that the tube later will shrink back to its original size when heated at installation,“ says Jukka Räisänen, the maintenance specialist of Ensto's heat shrink production.
In case of heat shrink tubes, the distinguishing factor is high quality. It can only be achieved by running own production lines with a strict quality control.
The whole production line must be reliable, especially the line control software and parameter monitoring. The quality of the extrusion is ensured by measuring parameters like tube diameter, wall thickness and centricity. In expansion, the quality control focuses on wall thickness and ability to shrink to the desired size.
From the Porvoo factory, reels of high-quality heat shrink tube are transported to Ensto factory in Keila, Estonia. There the tubes are cut to suitable lengths to be used in a variety accessory kits delivered to customers around the world.
Investments to Increase Capacity
Customers expect that accessories are easy to install, designed to support flawless installation and have long lifetime. Ensto has developed its components through the years and many of the products represent unique innovations.
In case of heat shrink tubes, the distinguishing factor is high quality. It can only be achieved by running own production lines with a strict quality control.
“Our customers value high the European production and quality. Nordic customers appreciate especially the experience and know-how gained in harsh and demanding environment,” Timo Koivisto points out.
“The decision to start own production also represents our company culture, which focuses on customers. We work every day to provide best possible solutions to their needs.. An important part of that is to make sure that only the highest possible quality leaves the factory,” he says.
In the spring of 2022 the latest investments in heat shrink production were taken in to use. The quality of the company's low and medium-voltage accessories has been noted, and the growth in demand made this rather large investment timely. We believe that our position in the market will continue to strengthen, Koivisto states.