PSI - Issue 72

Ivan Aranđelović et al. / Procedia Structural Integrity 72 (2025) 354 –361

357

fixed specific fire load is Q i = 0. For liquid fuels, it also can be assumed that fuel amount that can be found in the boiler room is sufficient for no more than 15 minutes of operation and that the boiler efficiency is higher than 50%. Based on the above assumptions, the total specific fire load can be calculated using the following equation:

A P t 

w

Q Q

 

(1)

m

where Q is specific fire load [MJ/m 2 ], Q

m is movable specific fire load [MJ/m

2 ], P is installed boiler heating duty

[MW], t w is total combustion time [s] and A is boiler room area [m

2 ]. Based on the adopted assumptions, the value of

parameter t w can be determined as:

=2∙15∙60=1800s.

(2)

3. Analysis - Purt’s method The fire risk of the structure contents ( R s ) is a coefficient that qualitatively shows the harm to people and equipment. It is calculated using the equation: = ∙ ∙ (3) where H is the harm to people coefficient, D is the harm to property coefficient and F is the smoke effectiveness coefficient. In this case study, H = 1 because there is no expected harm for people, and F = 1 because there is no danger of smoke and corrosive gases. If installed capacity of boiler is larger than 500 kW or boiler room area is larger than 150 m 2 , D = 2 because expensive equipment is installed in the boiler room and because interruption of the boiler operation causes stoppage of the supply of thermal energy to consumers. Hence, R s = 2, which means that installation of fire alarm system, is necessary in the boiler room, except in the case of installation of the automatic fire extinguishing system, which is a technically unacceptable solution due to the large area and height of boiler rooms. Fire risk of the structure construction ( R 0 ) is a coefficient that qualitatively shows the hazard for the building construction and is calculated using the form:     i k W R P C P B L S R        0 0 (4) where P 0 is the structure content fire burden coefficient; C is the structure content combustion coefficient; P k is the structure construction material fire burden coefficient; B is the size and position of the fire sector coefficient; L is the extinguishing start delay coefficient; S is the fire sector width coefficient; W is the structure’s carrier construction fire resistance coefficient; and Ri is the fire risk reduction coefficient. Structure content fire burden coefficient P0 will be determined by Table 1, given in EUROALARM standard. Table 1. Structure content fire burden coefficient ( P 0 ) Movable specific fire load Q m [MJ/m 2 ] Structure content fire burden coefficient P 0 0 ÷ 251 1.0 252 ÷ 502 1.2 503 ÷ 1004 1.4 1005 ÷ 2009 1.6