Test Procedures for Flame Retardancy
Flame Retardancy in a cable describes the ability of the materials to cease burning once the source of heat is removed. Several tests have been formulated to measure this property, with the most common being:
VW-1 (Vertical-Wire) Flame Test (UL 83) (Formerly FR-1)
Very similar to the "All Wires Flame Test" except that after the flame application, the flame is not reapplied after 15 seconds if the sample is still burning, but only when the flame is extinguished. If the sample burns for longer than 60 seconds after any application, this constitutes a failure.
Horizontal Flame Test (UL 44, 83)
A moderate flame test conducted on a horizontal sample in a special enclosure. A Tirrill gas burner with a 1500F flame is applied to the sample for 30 seconds. The flame must not spread more than 2” left or right of the point of application or ignite cotton on the floor of the test chamber by means of burning particles falling from the cable.
All Wires Flame Test (UL 83)
A vertical flame test in an enclosure using a Tirrill gas burner with a 1500 F flame. A paper flag is positioned on the sample, 10 inches above the point at which the flame touches the specimen. The flame is applied for 15 seconds removed for 15 seconds and then re-applied for 15 seconds. The total number of flame applications being 5. The sample shall be considered unsatisfactory if more than 25% of the paper flag is burned away or flaming or glowing particles ignite the cotton base of the enclosure or if after the last application of flame the sample continues to burn for longer than 60 seconds.
Vertical-Tray Flame Test (IEEE 383)
A stringent test which is usually applied to jacketed cables lashed to a vertical metal ladder type tray 8 feet high. The combustion source is a ribbon burner with a flame temperature of 1500F and heat source of 70,000 BTU's per hour. Burn time is 20 minutes. The cable is required to not propagate the flame to the top of the tray, a distance of 6 feet from the point of application.
Vertical-Tray Flame Test (UL 83, UL 1277)
Based upon the IEEE test with minor modifications such as flame temperature 1600 – 1750F.
Vertical-Tray Flame Test (210,000 BTU)
Similar to 70,000 BTU per hour test with the exception of the heat source being increased to 210,000BTU per hour.
CSA has a performance standard C22.2 No. 210.2 for Appliance Wiring Material that has the following ratings:
- FT1 – Vertical Flame Test (similar to "All Wires Flame Test")
- FT2 – Horizontal Flame Test (similar to "Horizontal Flame Test")
- FT3 – Burning Particles Flame Test (similar to "VW-1 Flame Test")
- FT4 – Vertical Flame Test (similar to "UL1685 Vertical Tray Flame Test")