Vertical Tray Flame Test and Vertical-Wire Flame Test (VW-1)

Flame

There are many tests used to measure the flame resistance of various copper wire and cable products. Flame Resistance is usually defined as the ability to stop burning once the source of heat is removed.

The following tests are most commonly used in North America.

Vertical Tray Flame Test

UL 1581/IEE 383This test is performed on cables attached to a 1′ wide, 8′ tall vertical metal ladder tray.  A 10″ ribbon burner with an air/propane mixture applies 70,000 BTUs/hour of combustion for 20 minutes, 24″ from the bottom of the cable.  The cable must self-extinguish before the flame reached the top of the tray.

CSA FT-4
This test is a later version of UL 1581 and is more strict.  To pass, the resulting char can’t be greater than about 4.5″ (1.5m).

IEEE 1202
The newest version of UL 1581, this is essentially identical to CSA FT-4.

UL 1685
This is more or less UL 1581 with an added smoke emission requirement.  If it passes, a wire can be given a “Limited Smoke” listing.

ICEA T-29-520
Yet another version of UL1581, the only difference is that the BTU value is 210,000 instead of 70,000 and the cable spacing increases.

Vertical-Wire Flame Test

UL 1581 VW-1
This was the first flame test developed for studying how flames spread on wire and cable.  The test is performed with a 24′ wire and a Tirrill burner.  Two clamps hold the single sample vertically.  The burner is mounted at a 20° angle and applied for 15 seconds, then reapplied four more times each time the wire stops burning.  If the sample doesn’t burn more than 60 seconds after any of these burning sessions, or if less than 25% of the indicator flag burns, or the cotton batting is ignited during the test, the wire passes.  A “tray rated” cable must pass this test as well.

CSA FT-1
The Canadian version of the VW-1 test.

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