Experimental evaluation of the efficiency of application of intumescent flame retardant coatings for electric wires and cables under simultaneous fire and current load impact

Introduction. In order to preserve the operability of wires and cables in fire conditions, intumescent flame retardant coatings are used, the effectiveness of their application in the case of real fire mode has not been investigated.

Aims and purposes. The purpose of the article is to evaluate experimentally the effectiveness of the use of intumescent flame retardant coatings for electrical wires and cables under simultaneous exposure to fire and current load.

In order to achieve this purpose, experimental tests on wires and cables of different brands, treated with intumescent water dispersion fire-protective paint “Ogneza-VD-K”. At the same time, the influence of heated ambient temperature on electrical parameters of wires and cables, such as resistivity, inductance and capacitance, was assessed.

Methods. Experimental study of heating in a muffle furnace of wire and cable samples treated with intumescent water-dispersion fire-retardant paint. Analysis of the obtained results.

Results and their discussion. The dependences of resistivity, inductance and capacitance of common electrical cables on ambient air temperature are obtained.

It was found that for all considered cables, the short circuit occurred at ambient temperatures in the range of 180–230 °C increasing the fireproofing coating to dimensions that protect the cable from external thermal impact. In this case, the phases and amplitudes of the input electrical signal can change significantly before a short circuit occurs.

It has been found that the swelling of fire retardant paint under fire conditions in a muffle furnace occurs at 400 °C and not at 200 °C as in the case of standard tests.

It is shown that the dynamics of temperature change inside the muffle furnace approached the temperature regime of a real fire in the room of the MCPU (Main circulation pump units) section of the Leningrad NPP (containment) of the reactor building and in the cable room of the 3rd safety channel of the safety building.

Conclusions. Working capacity of electric wires and cables treated with flame retardant should be determined in real fire conditions in the premises where these wires and cables are used.

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