How should the installation and maintenance of fire-resistant cables be carried out?
Release date:
2022-10-19 14:26
Source:
At Fire-resistant cable During the laying and installation process, measure the insulation of the cable and address any issues promptly. Before and after cable laying, as well as before and after fabricating terminal and intermediate joints, repeatedly measure the cable's insulation resistance and compare the results to ensure high-quality performance at every installation step. Additionally, whether cutting or suspending the cable, allow sufficient time for the cable to sit undisturbed prior to construction—this helps prevent moisture from compromising the magnesium oxide insulation layer.
After installing fire-resistant cable terminations and intermediate joints, immediately perform an insulation test, followed by a second test 24 hours later. If the cables are laid and installed at the termination or intermediate joint without any signs of moisture and with no damage to the protective layer, the insulation resistance value—converted to a 1000-meter length of cable—should remain above 1000 megohms at room temperature. During the actual test, if the megohmmeter pointer points to "C," it indicates that the cable is functioning properly. However, if the insulation resistance drops during the second measurement, the fault location must be identified. Typically, the fault occurs either at the termination or intermediate joint. To pinpoint the issue, you can use a blowtorch flame to heat the lower section of the termination and both ends of the intermediate joint, then re-measure the cable's insulation resistance. After heating for just a few seconds, if the insulation resistance plummets dramatically, it confirms that there’s a problem with the terminal or intermediate joint. In such cases, the faulty termination or joint should be removed, and the cable itself should be reheated with the blowtorch until its insulation quality meets the required standard. If the insulation resistance remains unchanged after reheating, proceed to inspect other terminals or intermediate joints along the circuit until the exact fault location is found, then repair it using the same method described above.
Fire-resistant cables can be installed in two ways: vertical installation and horizontal installation. When installing cables in the same direction, they should be laid one by one from near to far, based on the branching points of the cables, to avoid crossing and ensure an aesthetically pleasing arrangement. During installation, pay close attention to cable handling—never drag or rub the cable continuously along the ground, rough walls, or hard surfaces. Avoid pulling the cable over sharp, rigid objects altogether, and never allow it to come into contact with or be struck by sharp, pointed items. Additionally, welding operations must not directly or indirectly touch or collide with the cable or its circuitry. When making connections, the copper sheath of the fire-resistant cable must be properly grounded. For mineral-insulated cables, the copper sheath itself can serve as the grounding conductor, with one end connected to earth. During construction, mineral-insulated cables can be handled manually. If conditions permit and appropriate lifting tools are available, mechanical handling is also acceptable; however, care must be taken throughout the process to protect the cable and prevent any damage to the fire-resistant cable.
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