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Fire protection

Fire protection according to DIN EN 45545-2:2013-08

DIN EN 45545-2:2013-08, which emerged from the technical specification DIN CEN/TS 45545-2:2009-07 and has been ratified since March 2013 and converted to national law, specifies the “Requirements on fire behavior of materials and components”.

To qualify plastics for certain operating and design classes of rail vehicles, the standard describes testing methods for determining hazard levels (HL) based on different requirement sets (R). In this case, HL 3 corresponds to the highest requirements.

The following tests are performed in order to qualify the plastics for electrotechnical applications:

  • Oxygen index according to DIN EN ISO 4589-2
  • Development of smoke gas in accordance with EN ISO 5659-2 (25 kW/m²)
  • Toxicity of smoke gas NF X70-100-2 (600°C)
  • Glow-wire test according to IEC 60695‑2‑11
  • Vertical small flames test according to EN 60695-11-10

The un-reinforced polyamides used for Phoenix Contact terminal blocks with flammability rating UL 94 V0 meet the most stringent requirement of HL3 in accordance with the tests described in the requirement sets R22, R23, R24, R25, and R26.

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Behavior in fire according to DIN 5510-2

In section, DIN 5510-2 “Preventive fire protection in railway vehicles – Fire behavior and fire side effects of materials and parts” requires the insulating materials that fix the energized parts in their position and are not tightly molded must meet the requirement V0 according to DIN EN 60695-11-10, which is comparable with UL 94. As an alternative, an oxygen index OI ≥30% according to DIN EN ISO 4589-2 is required for areas that are not accessible to passengers.

Both requirements are met by the un-reinforced polyamides used for Phoenix Contact terminal blocks with flammability rating UL 94 V0.

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Behavior in fire according to NF F 16‑101/NF F 16-102

NF F 16-101 describes the behavior in fire of plastics on the basis of two indices (I and F). The following tests are being run:

  • Glow-wire test (NF EN 60695-2-10 and  NF EN 60695-2-11)
  • Oxygen index (NF EN ISO 4589-2)
  • Smoke gas toxicity (NF X 70-100)
  • Smoke gas opacity (NF X 10-702)

Index I is determined from the results of the glow-wire test
and the oxygen index, using the table. Here, I0 is the best classification and I4
the worst.

  • I0 - oxygen index 70% - glow wire 960°C, no flame formation
  • I1 - oxygen index 45% - glow wire 960°C, no flame formation
  • I2 - oxygen index 32% - glow wire 960°C, no flame formation
  • I3 - oxygen index 28% - glow wire 850°C, no flame formation
  • I4 - oxygen index 20% - glow wire 850°C, flame extinguishes quickly


The F index is based on the measurement of smoke gas opacity and smoke gas toxicity. The following concentrations in mg/m³ for the smoke gas toxicity are considered critical:

  • Carbon monoxide (CO) 1750
  • Carbon dioxide (CO2) 90,000
  • Hydrochloric acid (HCl) 150
  • Hydrobromic acid (HBr) 170
  • Hydrocyanic acid (HCN) 55
  • Hydrofluoric acid (HF) 17
  • Sulfur dioxide (SO2) 260

Using the test results, a smoke index is documented and can be assigned to classes F0 – F5 depending on the value. F0 corresponds to the best classification here and F5 the worst. The terminal blocks from Phoenix Contact attain the classification I2/F2.

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Surface inflammability according to ASTM E 162 (NFPA 130)

Surface inflammability test  

Surface inflammability test

To evaluate the surface inflammability of plastics, a “flame spread index” is devised according to ASTM E 162 to provide information on flame propagation under given test conditions.

For this purpose, a sample (152 x 457 x 25.4 mm) is irradiated with a heat source (815 °C) at an angle of 30° and ignited with a naked flame at the top end. During the 15-minute duration of the test, the time in which the flame front reaches two measuring points that are 76 mm apart is determined. The product of this flame propagation time and a calculated heat development factor yields the flame spread index.

In the American railroad sector, the maximum limit value is 35. In this test, the drip behavior of the plastic is evaluated. The terminal blocks from Phoenix Contact achieve a flame spread index of 5, drip without burning, and are therefore well below the maximum permitted values of the Federal Railroad Administration (FRA) of the US Department of Transportation.

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Development of smoke gas according to ASTM E 662 (NFPA 130)

Smoke generation ASTM E 662  

Smoke generation according to ASTM E 662

The standard ASTM E 662 specifies a procedure for evaluating the specific optic density of the smoke during an open fire or a smoldering fire. For this purpose, the percentage of light transmitted in relation to the burning chamber volume is observed.

A sample (76 x 76 x 25 mm) is placed in a smoke density chamber as defined by the NBS (National Bureau of Standards). The test object is irradiated with a heat of 2.5 W/cm². The following processes are then simulated for 20 minutes:

  • Burning with a naked flame
  • Smoldering fire, avoidance of a naked flame.

There are special limit values for the optical smoke density of both processes that are recorded after 1.5 and 4 minutes:

  • Specific optical smoke density (Ds1.5) – limit value 100
  • Specific optical smoke density (Ds4) – limit value 200
  • Maximum smoke density (Dm) during the 20 minutes

The polyamides used for Phoenix Contact terminal blocks fulfill all the requirements of the Federal Railroad Administration (FRA) of the US Department of Transportation in accordance with ASTM E 662.

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Smoke gas toxicity SMP 800 C

SMP 800 C describes the maximum permissible values of poisonous smoke gases when a plastic is burned. In comparison with BSS 7239 (Boeing standard), this standard specifies more precise measuring methods for the qualitative and quantitative determination of toxic smoke gases that result when a test object is completely burned. For this purpose, 6 liter of smoke gas is removed from the NBS chamber during the ASTM E 662 test between the 4th and 19th minute and fed to the analysis.

SMP 800 C limit values of toxic smoke gases in ppm:

  • Carbon monoxide (CO) 3,500
  • Carbon dioxide (CO2) 90,000
  • Nitrogen oxides (NOX) 100
  • Sulfur dioxide (SO2) 100
  • Hydrochloric acid (HCl) 500
  • Hydrobromic acid (HBr) 100
  • Hydrofluoric acid (HF) 100
  • Hydrocyanic acid (HCN) 100

The polyamides used by Phoenix Contact are many times below the critical concentrations.

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Halogen-free flame protection

Halogens are, among other things, the chemical elements fluorine, chlorine, bromine, and iodine. One
property of halogen compounds, particularly those containing bromine, relates to the reduction in the degree of inflammability when used in plastics. In the event of fire, poisonous corrosive smoke gases are formed, which can also lead to secondary damages.

For this reason, Phoenix Contact does not use any flame protection systems which contain halogens or other additives. Polyamide, polycarbonate, polycarbonate/acrylonitrile butadiene styrene (PC/ABS) and polyolefines feature halogen-free flame protection systems.

Terminal blocks from the CLIPLINE complete system are made of polyamide 6.6 (PA 6.6) with the fire protection classification UL 94 V0. According to state-of-the-art technology, these polyamides are used halogen-free, with melamine cyanurate as flame protection agent.

Phoenix Contact terminal blocks are therefore, without exception, entirely free of halogens.

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