What are the common methods used for jointing low-voltage PVC wire-armoured cables?
There are several common methods used for jointing low-voltage PVC wire-armoured cables, with one of the most popular methods being the resin joint, also known as the Scotch-cast joint. This method involves several steps to ensure a secure and reliable joint between the cables. What are these steps and how do they contribute to the effectiveness of the joint?
Steps for Making a Resin Joint in Low-Voltage PVC Wire-Armoured Cables
1. Preparation: Before starting the jointing process, it is crucial to prepare the cable ends by ensuring they are clean and free from any dirt, moisture, or contaminants. This step also involves stripping the cable insulation to expose the conductors and removing any outer layers of the armoured sheath.
2. Cleaning: Using a suitable cleaning agent or solvent, the exposed conductors and armoured sheath are cleaned to remove any oxidation or grease. This step helps to improve the conductivity of the joint.
3. Twisting: To create a strong electrical connection between the cables, the corresponding conductors that need to be joined together are twisted. This twisting action ensures a secure bond between the conductors.
4. Insulation and Sealing: A layer of resin-based insulating material, such as Scotchcast compound, is applied around the exposed conductors to provide insulation and seal the joint. This helps to protect the joint from environmental factors and prevent moisture ingress.
5. Armoured Sheath Reinstatement: Once the resin-insulated conductors are in place, the armoured sheath is reinstalled over them. It is essential to ensure that the sheath is properly positioned to maintain the structural integrity of the cable.
6. Outer Wrap: An outer wrap of resin-impregnated tape or a suitable insulating material is applied over the joint area to provide additional protection and reinforcement. This outer wrap enhances the mechanical strength of the joint.
7. Curing: The final step involves allowing the resin to cure according to the manufacturer's instructions. The curing process typically involves a specific period of time for the resin to harden and reach its optimal strength, ensuring the longevity and reliability of the joint.
By following these seven steps of making a resin joint in low-voltage PVC wire-armoured cables, electrical engineers and technicians can create durable and secure connections that meet industry standards and regulations.