In the process of selecting cables, we will see some parameters, such as UL flame retardant rating. As one of the standards, UL flame retardant rating represents different qualities of cables. This article will briefly explain different UL flame retardant ratings.

1、 CSA fire rating

FT1: Vertical combustion test (no requirement for drips)

FT2: Horizontal Combustion Test

FT3: Vertical combustion droplet test (cannot ignite news paper)

FT4: Conduct vertical combustion test in a closed combustion chamber (similar to a closed building) with a thermal energy of 70000 btu/h

FT5: Fire resistance test, usually used for portable cable trays in underground operations

2、 UL fire rating

A: Horizontal fire test

B: VW-1: Vertical fire test, droplets cannot ignite cotton wool.

VW-1SC: Vertical fire test, separate testing of insulated core wire and finished wire.

C：CL2 (VERTICAL TRAY FLAM TEST)：

Perform vertical combustion test in a sealed combustion chamber (similar to UL1581 in a sealed building)

D：CL2R(RISET CABLE)

E：CL2P(PLENUM CABLE)

F: CM (Communication Cabinet) communication line;  G：CMR ；  H：CMP .

The content of UL plastic material 94-V0 (94V0 refers to the so-called flame retardant level, which is divided into 5 levels) 94-V0 will extinguish immediately when the fire leaves and will not spontaneously ignite.

When 94-V1 burns, it will burn for 1 second and then immediately extinguish without spontaneous combustion

When 94-V2 burns, the fire will burn for 2 seconds and then immediately extinguish without self ignition

When 94-V5 burns, the fire will burn for 5 seconds and then immediately extinguish without self ignition

When 94-HB burns, once the fire leaves, it will burn until only carbon remains

3、 Comparison of UL94 plastic flame retardant rating and UL 1581 VW-1 flame retardant rating

There are a total of 12 types in UL94: HB, V-0, V-1, V-2, 5VA, 5VB, VTM-0, VTM-1, VTM-2, HBF, HF-1, HF-2.

The UL94 flammability rating is the most widely used combustible performance standard for plastic materials. It is used to evaluate the ability of materials to extinguish after being ignited. There are multiple evaluation methods based on combustion speed, combustion time, anti droplet ability, and whether droplets burn. Each tested material can obtain many values based on color or thickness. When selecting a material for a product, its UL rating should meet the thickness requirements of the plastic part wall. The UL rating should be reported together with the thickness value, reporting only the UL rating without thickness is not enough.

4、 The flame retardant rating of plastics increases gradually from HB, V-2, V-1, V-0, 5VB to 5VA

HB: The lowest flame retardant rating in UL94 standard. Require a combustion rate of less than 40 millimeters per minute for samples with a thickness of 3 to 13 millimeters; Samples less than 3 millimeters thick,

Burning speed less than 70 millimeters per minute; Or extinguish before the 100mm mark.

V-2: After two 10 second combustion tests on the sample, the residual flame and residual flame will extinguish within 60 seconds. Dripping particles can ignite cotton.

V-1: After conducting two 10 second combustion tests on the sample, the residual flame and residual flame will extinguish within 60 seconds. Dropping particles cannot ignite cotton.

V-0: After conducting two 10 second combustion tests on the sample, the residual flame and residual flame will extinguish within 30 seconds. Dropping particles cannot ignite cotton.

5VB: After conducting five 5-second combustion tests on the sample, the residual flame and residual flame will extinguish within 60 seconds. Dropping particles cannot ignite cotton. For block samples, it is allowed to be burned through

5VA: After conducting five 5-second combustion tests on the sample, the residual flame and residual flame were extinguished within 30 seconds. Dropping particles cannot ignite cotton. It is not allowed to burn through block samples.

5、 The wire burning method in UL1581

1. VW-1: Vertical burning test (UL wire burning rating)

2. FT1: Vertical combustion test;

3. FT2: Horizontal Combustion Test;

4. FT4: Vertical combustion test;

5. FT6: Horizontal burning and smoke testing. The combustion level of FT class is the CSA standard wire combustion level

Among the above levels: VW-1 is at the same level as FT1. FT2 is the easiest to pass and has the lowest level (FT6>FT4>FT1>FT2);

VW-1 is stricter than FT1, both of which burn vertically. The judgment criteria are: 1 Burning marks (kraft paper) cannot be carbonized by more than 25%; 2.5 times of 15 second combustion continuation

The burning time cannot exceed 60 seconds; 3. Burning droplets cannot ignite cotton; VW-1 requires compliance with 1, 2, and 3; FT1 only requires compliance with 1 and 2

6、 For the wire industry

The V-2, V-1, V-0, 5VA, and 5VB of UL 94 assess the materials used in the wires. During testing, standard samples must be developed using separate testing materials and will not be labeled on the wires.

VW-1 VW-2 FT-1 FT-2 assesses the wire itself, and after passing the test, the corresponding grade can be marked on the wire.

The flame retardancy of wires is completely different from that of UL94. For example, an insulation material that can pass through UL94 V-0 may not necessarily pass VW-1;

In addition, UL94 is a flame retardant material for insulation materials, while the flame retardant requirements for wires are generally specified in UL758 62 1581; Different objects;

So the flame retardancy in UL94 such as V-0 V-1 is not the flame retardancy of wires at all; There is no "V-0" printed on the AWM wire.

The VW-1/FT1 and UL94 V0 combustion tests have significant differences in equipment:

1. The height and temperature of the flame are different

2. The methane flow rate used during testing is also different

3. The back pressure of methane is also different

4. The volume of the combustion chamber also varies: VW-1 requires a volume greater than 4 cubic meters, while V0 only requires a volume greater than 0.5 cubic meters

5. The number of burns also varies

6. In the combustion results, V0 requires recording of residual burning time, while VW-1 does not require it

But the test conditions and methods for 5V level combustion and VW-1 combustion in UL94 are similar and relatively close. Reminder: Whether it is VW-1 or UL94 combustion testing equipment, it must refer to ASTM5025 and ASTM5027. UL1581 and UL94 are only testing methods, and the requirements of the testing equipment must be in accordance with ASTM standards.