Writer： admin Time：2021-04-12 08:49 Browse：℃
Ensuring your power cord meets fire prevention requirements for a device is a safety measure you cannot ignore. In a previous blog discussing teat procedures, we mentioned multiple tests that power cords must undergo before being approved by safety agencies. To refresh your memory, some of the tests we talked about were:
This post will cover another important test: flame rating, or flame resistance.
Fire safety is a huge concern when working with electrical wires, cables, and cords. For power cords and cables to meet Underwriters Laboratories (UL) standards, they must undergo multiple flame tests. Flame resistance rating tests for custom cables and cords involve using a flame to test how long a sample piece burns or smokes. To pass each test, the cord sample must self-extinguish within a specified time.
We’ll break down three flame resistance rating tests to help you understand how they’re performed, along with the criteria for passing each test.
The FT2 horizontal flame test for flexible cords includes a series of cycles. During each cycle, a burner flame burns a horizontal sample for 15 seconds, then is turned off for another 15 seconds. Alternatively, the flame will burn until the sample stops smoking before 15 seconds have passed and must not go beyond 100mm from end to end. This process is repeated 5 times. To pass the FT2 horizontal flame test, no burning particles can fall from the cable while it’s burning.
The FT1 vertical flame test is performed similarly to the horizontal flame test, except the flame is held at a vertical angle. In this flame-resistance rating test, the sample must endure five, 15-second burning repetitions. You will know your sample passed the FT1 vertical test when it doesn’t smoke longer than 60 seconds and when no more than 25% of the paper indicator is burnt.
UL VW-1 vertical wire flame tests are only performed on finished cable and the internal insulated single conductors. The purpose of this flame resistance rating test is to screen out flammable wires.
In this test, a wire sample is mounted with a paper indicator placed above and below the sample. A Bunsen burner is applied to the cord for 15 seconds and then removed. The flame is then reapplied and repeated in the same procedure as the above tests. To pass this flame resistance rating test, the sample must not burn for more than one minute or burn more than 25% of the paper indicator. Another requirement is that the cotton at the burner base must not catch flame during the test.