Experimental investigation of the effects of a sidewall and cable arrangement on a horizontal cable tray fire in an open atmosphere

Abstract

The work deals with the influence of a sidewall and cable arrangement on the behavior of a fire involving horizontal cable trays in the framework of fire safety assessments in nuclear installations. The analysis is based on large‐scale fire tests performed in the open atmosphere in the frame of the OECD Nuclear Energy Agency (NEA) PRISME 3 project and on the corresponding simulations applying the FLASHCAT model for predicting the fire heat release rate. The fire configuration consists of five horizontal trays filled with PVC‐insulated power cables. The parameters investigated are the presence or absence of a sidewall and the cable arrangement (loose or tight bundles). The results show that the presence of a sidewall increases the fire HRR in comparison to a scenario without a sidewall. This effect is due to the increase of the flame spread velocity on the lower trays. Regarding cable arrangement, a tight configuration in bundles reduces the fire HRR in comparison to a scenario with a loose arrangement. This result is due to the reduction of the fire heat release rate per unit of area (HRRPUA) as well as the flame spread velocity. The performance of the FLASHCAT model in predicting the effects of the sidewall and the cable arrangement was also assessed on the basis of the fire tests and satisfactory agreements are reported. The presented analysis demonstrates that the fire scenario with horizontal cable trays against a sidewall and with a loose cable arrangement represents a conservative scenario for fire risk assessment. In addition, on the basis of these experiments, the effect of cable arrangement is more substantial than the sidewall effect.

Common OECD/NEA FIRE and PRISME Cable Benchmark Exercise

“…The choice of the CFS-2 test is based on the cable type (PVC insulated cables) and the ventilation renewal rate (15 h -1 ) as close as possible to the real fire event characteristics. The second step (Step 2) consisted of a blind simulation of the CFP-D1 cable fire test [7] performed within the PRISME 3 project. Only the input data on the experimental conditions were accessible to the participants and the CFP-D1 test was planned to be carried out after the due date of the blind simulations.…”

“…), no theory has yet been put forward on how to model all the aspects of the problem, even for simple, open atmosphere conditions. Some approaches in the form of experimental studies [10], [11] and more recently [3], [4], [7] have nevertheless been carried out and an empirical model referred to as FLASH-CAT [11] (short for flame spread over horizontal cable trays) was developed by the NIST for horizontal cable tray fires in open atmosphere. FLASH-CAT is a relatively simple model for predicting the growth and spread of a fire within a vertical stack of horizontal cable trays.…”

“…The CFP-D1 test [7] was selected for the blind simulations of the Benchmark Exercise Step 2_1. The experimental setup of this test is close to that of the CFS-2 test, as illustrated in Fig.…”