Cellulosic and hydrocarbon fire insulation to steel beams and columns and jet fire protection for tubular sections
However, different maximum temperatures are often specified, taking into account the temperature profile and load on the sections. Critical temperatures ranging between 400°C and 620°C are common, with 400°C widely used in the offshore industry.
FireMaster blanket and FireBarrier products provide fire insulation to steel beams and columns to ensure they maintain load-bearing capacity in a fire. Ultimately preventing collapse of the structure they are supporting.
FireMaster blanket is flexible enough so that it can easily be wrapped around the outer profile of I beams, columns and tubular sections.
The blanket can be applied in single or multiple layers, providing insulation which meets a variety of steel critical temperatures, from 150°C upwards.
Tubular sections can be protected against jet fires for fire durations of up to three hours, using FireMaster blanket and microporous insulation.
The thickness of insulation that is required to be applied to steelwork to provide fire protection will depend on a number of factors. These are:
Steelwork is insulated against fire to maintain its temperatures below a specified critical temperature limit to ensure its loadbearing function is maintained. The limit usually commonly applied to supporting structural steel offshore on for example, living quarters is 400°C for a 60 minute period.
This limit is also often applied to process plant equipment. Other temperature limits may be applied depending on the function of the structure. For example support steelwork for emergency shutdown valves is usually limited to a maximum temperature of 200°C for 60 minutes. Secondary steelwork in process areas may have a maximum steel temperature of 550°C specified for 60 minutes.
The section factor relates the surface area of the steel section exposed to fire to the amount of steel in the section cross-sectional area available to absorb heat from the fire. The surface area of the fire-exposed section divided by the cross-sectional area is defined as the ‘section factor’; ‘Hp/A’ or ‘F/A’. Steel sections with large section factors will exhibit faster temperature rise in a fire than those with smaller section factors as the ratio of area receiving heat to the mass of steel available to absorb that heat increases. Section Factors are calculated by dividing the external fire-exposed perimeter of the steel section by its cross sectional area.
Fire testing of structural steelwork fire insulation is designed to relate section factor to insulation thickness for a variety of failure temperatures and this requires a large variety of sections to be fire tested. FireMaster Marine Plus blanket has been fully tested in order to generate the required thickness tables in accordance with Annex E4 of EN 13381-4 fire test procedure for structural steelwork in hydrocarbon fires.
This test standard also requires loaded beams to be fire tested in order to assess the ‘stickability’ of the insulation system as the beam deflects under load with increasing temperature. This is to ensure the insulation system has adequate integrity for use.
In order to assess any impact of the beam deflection on the insulation system, identically insulated reference non-loaded columns of the same section factor are also tested to allow temperature rise data to be compared in loaded and unloaded conditions.
Fire load and duration
The heat flux or temperature to which the steel is exposed will influence the thickness of insulation required for fire insulation. From the fire tests, tables are constructed using multiple linear regression analysis of the fire test data to relate fire exposure time, section factor and critical temperature to insulation thickness.
FireMaster structural steel system fire testing and certification
The FireMaster structural steel system is testing in accordance with EN 13381-4 method using the hydrocarbon fire temperature/time curve specified in EN 1363-2 for protection periods up to 240 minutes and is Type Approved by Lloyds Register. Testing for cellulosic fire protection of structural steelwork has also been carried out in accordance with EN 13381-8 method with Lloyds Register Type Approval for up to 180 minutes.