Cable Termination Methods
Let’s understand the two common methods for cable terminations: Heat Shrink and Cold Shrink Cable Terminations.
These methods were developed in the 1960s due to the introduction of rubber and polyethylene insulated cables. Both types use expandable material that is sold in an expanded state. Heat shrink technology uses heat to shrink onto the cable, while cold shrink technology uses the rubber’s natural properties to shrink onto the cable without any external heat. Even though both methods shrink onto the cable, their performance characteristics are quite different.
Let’s go through both the methods
1) Cold Shrink Method
Cold shrink technology involves using pre-stretched rubber sleeves that are placed around the cable junctions or terminations. These sleeves are designed to tightly fit around the cable once the core that keeps them expanded is removed. As the core is taken out, the rubber sleeve naturally contracts or “shrinks” onto the cable, creating a secure, pressure-sealed fit. This method does not require any heat or flame, making it simpler and safer to install, especially in sensitive or hazardous environments.
2) Heat Shrink Method
Heat shrink technology uses sleeves made from materials that shrink when exposed to heat. During installation, these sleeves are slipped over the cable connections and then heated, typically with a heat gun. The heat causes the sleeve to contract tightly around the cable, forming a protective seal. This method requires precise heat application to ensure even shrinking and a good seal, making it slightly more complex and requiring more equipment and safety precautions than cold shrink methods.
In essence, cold shrink is like a rubber band snapping back to its original size once stretched, while heat shrink is like a plastic wrap that tightens around an object when heated. Both methods are used to protect cable joints and ensure electrical integrity, but each has its own advantages and ideal applications.
Let’s understand the difference in detail
Heat shrinkable terminations are tubes that shrink when exposed to heat, usually applied with an electric or gas heat gun. This causes the expanded plastic tubes to shrink to the size of the cable underneath, making installation quick and easy. These kits can be used for XLPE cables in both indoor and outdoor settings, even in extremely hazardous conditions. They provide non-tracking stress control connections for medium to high-voltage cables, and they are resistant to water, UV, erosion, and corrosion.
Cold shrink terminations do not require heat. They are used for medium-high voltage installations where a naked flame or heat source is not safe, such as in areas with flammable gases. During installation, the technician simply removes the supporting cord, which causes the tube to shrink and fit onto the cable. Cold shrink terminations offer excellent insulation and resilienceThey also feature triple air-tight sealing technology to ensure superior air tightness.
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Termination Kits
Let’s understand what the Heat Shrink Cable Termination Kits contain. The kits manufactured at Axis offer reliability and flexibility to meet the demands of cable network operators, suitable for LV & MV Cables. The components are designed to handle extreme weather, outdoor sunlight, and heavily polluted areas, addressing typical partial and surface corona discharge under challenging service conditions. All components are supplied in an expanded state and shrink effectively upon heat application.
Here’s what you’ll find in the kit:
- Anti-tracking Tubes: These tubes are designed to meet outdoor conditions and performance requirements for medium voltage power cable end terminations. They are resistant to splitting, have excellent arc resistance, are flexible, conform to shapes and core bends, and are suitable for both outdoor and indoor applications.
- Stress Control Tubes: These tubes provide electrical stress grading and relief on screen interruptions, avoiding localized stress accumulation that can lead to failures. Made from specially formulated Polyolefin, they offer a good balance between electrical and mechanical properties.
- Lug Sealing Tubes: These tubes protect the interface between the termination lug and the cable core covered with the non-tracking MV tube.
- Lugs: These provide high-performance connections.
- Cleaning Tissue with Solvent: Used to clean the XLPE insulation surface.
- Tinned Copper Braid: Protects conductive wiring from interference and handles large currents and low voltage.
- Stress Control Mastic: Applied on the connector and semi-conducting screen to fill gaps and uneven surfaces.
- Sealing Mastic: A durable, conformable mastic with excellent moisture and environmental seal, used for sealing medium voltage cables and accessories and covering sharp edges.
- PVC Insulation Tape: Thermally compatible tape used to insulate electrical wires and other conductive materials, and for marking joint construction.
- Black Sealing Mastic: Another durable, conformable mastic with excellent moisture and environmental seal for medium voltage cables and accessories and covering sharp edges.
- Rain Sheds: These are designed to provide additional weather protection for outdoor cable terminations, especially in areas prone to heavy rain. Rain sheds help to deflect water and minimize the accumulation of moisture around the cable joints, enhancing the overall insulation properties.
- Breakouts: Used at the branching point of cables, breakouts provide excellent environmental sealing and mechanical protection. They ensure that each cable is individually sealed and protected where multiple cables emerge from a single termination point.
- Cu Binding Wire: This copper binding wire is used to secure and stabilize the cable cores within the termination or joint. It ensures a solid mechanical hold, maintaining the integrity of the installation.
- Emery Paper: Provided to prepare the cable surfaces before applying seals or mastic. Emery paper is used to clean and abrade the insulation, ensuring a clean surface for better adhesion of other components.
- Silicone Grease: Applied to the cables and accessories to enhance the sealing and ease of installation. Silicone grease helps reduce friction during the installation of slip-on parts and improves the moisture resistance of the completed assembly.
- Back-Up Ring: These rings are used to support and reinforce the cable ends within the termination kit. They provide structural integrity to the installation, preventing the deformation of the sealing elements under thermal or mechanical stress.
- GI Binding Wire: Galvanized Iron (GI) binding wire is used for grounding and mechanical securing purposes. It offers robust corrosion resistance and is essential for ensuring a secure and durable grounding connection.
- Jubilee Clamp: A versatile and adjustable clamp used to secure components within the termination kit. It provides an effective way to ensure that all parts remain tightly fitted and positioned correctly throughout the operational life of the cable termination.
These components ensure the termination kit can withstand harsh conditions and maintain reliable performance.
Heat Shrink VS Cold Shrink
Cold shrink and heat shrink techniques each offer their advantages and disadvantages. Cold shrink, being easier and quicker to install, is ideal for installations in tight spaces or challenging conditions. Heat shrink provides a more secure seal and suits applications that require greater mechanical strength. Here are some recommended points by our expert:
- In the case of Application: Depending on your application’s specific needs, choose between cold shrink and heat shrink. Go for cold shrink if quick and easy installation is a priority. If you need maximum protection and durability, heat shrink might be the better choice.
- Consider Environmental Factors: Assess the environmental conditions of the installation site. Heat shrink will perform better over extreme heat, while cold shrink could be preferable in environments with temperature fluctuations or extreme cold.
- Installation Tip: Cold shrink tends to be more user-friendly for beginners due to its simpler installation process. For those experienced in using heat shrink, some extra steps are never a problem.
Conclusion
The specific requirements of the project ultimately determine the choice between heat shrink and cold shrink. By evaluating factors such as ease of installation, environmental conditions, expertise, and cost, you can make an informed decision that ensures the success of your cable sealing and protection needs.
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