A new standard test method for the quantification of fire propagation behavior of electrical cables using Factory Mutual Research Corporation's small-scale flammability apparatus

Abstract

A new specification test standard for cable fire propagation has recently been developed at Factory Mutual Research Corporation (FMRC), using FMRC's 50 kW-scale flammability apparatus. Guidelines for fire protection of grouped cables in non-combustible industrial and commercial occupancies have been formulated. Cables are classified into three groups on the basis of their fire propagation behavior: Group 1 cables: fire propagation beyond the ignition zone is not likely to occur and fire protection is not required; Group 2 cables: fire propagates slowly beyond the igaition zone and fire protection is required in most applications; and Group 3 cables: fire propagates rapidly beyond the ignition zone an d fire protection is always require d. This paper describes the concepts associated with the development of the standard test and fire protection guidelines for cables.

Combustion Characteristics of Materials and Generation of Fire Products

“…On the basis of the discussion above, an emprical parameter termed fire propagation index (FPI) [16,17,28,[42][43][44][45][46] Fig. 36.3).…”

“…Heat release rate from CDG and OC calorimetries in the FPA was originally defined as the "actual heat release rate" until 1986 [9,[12][13][14][15]; thereafter, however, it was changed to "chemical heat release rate" to account for the effects of (1) the chemical structures of the materials and additives; (2) fire ventilation; (3) the two dominant modes of heat release, that is, convective and radiative; and (4) the effects of flame extinguishing and suppressing agents. The FPA is a standard test apparatus for electrical cables [16,17], for wall and ceiling insulation materials, replacing the 7.6 m (25-ft) corner test (as described in section "Fire Propagation" of this chapter) [18], for clean room materials used in the semiconductor industry [19], and for conveyor belts [20].…”

Screening of plenum cables using a small‐scale fire test protocol

“…where t ig is the time to ignition in seconds (determined as the first moment that a flame remains attached for at least 4 s at the same location or over most of the sample surface [5]); ' q 00 e is the external radiant heat flux (kW/m 2 ). The inverse slope of the straight-line in Figure 3 is the thermal response parameter (TRP).…”

“…Figure 5 reveals that cables may be classified as non-propagating with FPI values equal to or less than 7 and propagating when FPI values are equal to or greater than 14. Note that all plenum rated cables (1)(2)(3)(4)(5) are the non-propagating type and their FPI values are equal to or less than 7. This correlation suggests that the FPI measured in the fire propagation apparatus (ASTM E-2058 and NFPA 287) may be used for screening cables for UL-910 tests, which require a large quantity of cables making the test very expensive.…”

Flammability of Polymers

“…In the table, FPI values are from the small-scale tests (ASTM E2058 Apparatus), and visual observations and extent of fire propagation are from the large-scale parallel panel tests for polymers and electrical cables, where data are taken from Refs. [21,22,40,[80][81][82][83][84]. The correlation between small-and large-scale vertical fire propagation data suggests the following:…”