The low voltage network designed for electricity distribution implies to realize tap connections, junctions, connections… As many operations which require a conductor protection especially from the external environment. Without a protection of the cable from bad weather, from humidity… we could notice the following phenomenon :
- Lines disruption,Escalation of lines losses,
- Electrical risk for fitters and lines,
- Degradation of the quality of electrical connections…
In this context, a major concern of manufacturers and fitters is the guarantee of watertight networks and equipment avoiding water penetration into connections and cables. This way a specific material is necessary with shrinking properties.
Two technologies coexist and yet with the same vocation: create or recreate watertightness. We can find on one hand the heat-shrinkable technology and on the other hand the cold shrinkable one. Each one of these technologies is more or less used in different part of the world according to installation customs, desired use…
Two shrinkable technologies on the market
The heat shrinkable technology is realized from synthetic material reacting to heat. This way, by applying a significant heat on the product, this one will retract. During this operation, the product follows and adapts to the shapes of the body inside. Thanks to this material, watertightness is ensured again.
The implementation of this technology is made thanks to a heat source which activate the product, we think for example to a blow torch to realize this function. Fitters must use a tool difficult to carry and which can be dangerous either for works on the soil or in height especially when a gas pipe is close to the working area. This complexity during the installation encourages the use of cold shrinkable technology, which doesn’t require specific tools.
Unlike heat shrinkable equipment, cold shrinkable products do not require implementation tools. Products, made of synthetic material, are kept prestressed by a tough stake, which when removed, enables the product to reach its shrinking size and this way to compress around one or several conductors… The product fits perfectly with the body of the equipment to insulate, protect or watertight.
A wide range of products
If we consider products present on the market, we can find :
- Tube : we call them sleeve for small lengths and sheath for high ones. There are also split sleeves used especially for the maintenance of overhead lines.
- Cap : also known as end cap, it enables to protect cable end as a movable sealing end cap would do it.
- End : also known as cable sealing end, E4R or E2R, it is used to separate cable’s conductors.
Their shape and conception material varies according to the installation with cold or heat technology but the function remains the same. According to practices on the field, installation constraints, budget, fitters would prefer one technology or the other.
Benefits and disadvantages of cold and heat shrinking
Each one of these technologies gets some benefits and inconveniences. If the heat shrinkable one remains competitive and gives many options regarding models and types, it remains more difficult to implement in terms of time, handling… The cold shrinkable technology offers this asset of an easy installation but is more expensive and generates more waste.
Some use cases
As mentioned above in this article, shrinkable equipment can be required for many uses. Right after; find some examples of installation cases where this kind of equipment can be required.
In many countries, very urbanized cities are equipped from an underground electrical network and not an overhead one. Issues in terms of aestheticism but also congestion are at the origin of this choice. The area of this network is not very extended but we can observe many branching because of the dense population. Many connections, tap connections must be realized requiring accessories like connectors, sleeves which are implemented on the cable. In this case, it is necessary to use equipment which guarantees a perfect sealing like heat shrinkable sheaths designed to adapt after shrinking to the shape of connection accessories.
Sub-surface junctions EJAS
In suburban and rural areas, the issue of the electrical network is not the same. Areas are more extended and distances to reach are longer. That’s why, the network is made of overhead lines. These lines get many advantages: they are less expensive than underground ones and the maintenance is easier to achieve. When both networks (underground and overhead) must be connected together, some specific junctions are required especially for that use: EJAS. Under this designation we generally find a group of products: three phase sleeves, one neutral sleeve, a 4 outlets end and four sheaths.
Thanks to sheaths and to the 4 outlets end, the junction is safe against water and dust infiltration. Generally, sheaths are used on sleeves in order to create a watertight junction.
When an insulation piercing connector doesn’t work anymore, this one will be removed from overhead lines. This removal will let appear holes realized in the insulation during the piercing. In order to reform the watertightness, the use of split sleeve is recommended. Split sleeves are only available for heat-shrinkable process because they allow to turn around the cable without dismantling the existing network.
Similarly, when a cable or its core is damaged, it is important to watertight the cable insulation to secure the network and avoid potential water infiltrations.
Both technologies lend themselves to uses in overhead or underground environment. The choice of one or the other depends on different criteria either they are technical or economical.