Steel elements should be cleaned in accordance with any applicable standard before erection on site. Once erected the steel may be exposed to the elements for a period of time in which some rust is likely to form on its surface. Generally all steel surfaces to be sprayed should be clean and free from heavy rust, mill scale, oil and grease. Light rust will not affect the stickability of the fire spray.
In order to maximise and retain the cost effectiveness of the spraying system, any services should be installed after spraying is completed. Where existing or new services must be installed before Spraying operations, these should allow for suitable clearance from the surrounding steel work, to enable the proper Vermitex 'AF' thickness to be applied without undue effort.
Where paints with a melting point below 500°C are present Vermitex ‘AF’ may still be applied, however this will depend on the shape and size of the steel element. In some circumstances, reinforcement in accordance with AS 3784.1 (Section 8 - Methods of Mechanical Retention), may have to be employed. Please refer to LAF for further details.
In certain conditions (static elements) Vermitex ‘AF’ is suitable for bridging small gaps up to 75 mm wide. For larger gaps subject to movement or vibration, suitable mechanical reinforcement must be employed to bridge such a gap.
Some building codes do apply ‘stickability’ restrictions to steel members that can be upgraded with standard Fire Spray materials without the aide of mechanical reinforcement. These restrictions relate to the size of the steel member and to materials that have not proven ‘Stickability’ under Fire Test conditions. LAF’s products such as Vermitex have amply demonstrated ‘Stickability’ when subjected to rigorous fire testing, on horizontal steel Plate 700 mm wide. Please refer to LAF for further details.
When structural steel elements form part of are part of a Separating Element of Construction (partition, ceiling, etc) care must be taken to ensure that the Insulation Criteria requirement (mandatory in certain Standards) for Separating Elements of Construction is not impeded. In some cases the thickness of the fire spray may have to be increased to prevent an excessive rise in temperature on the ‘cold face’ of the separating element of construction.
A two (2) hr FRL is required on a partition which abuts the bottom flange of a steel beam. A fire has developed on one side and has been active for 2 hours. The temperature of the structural steel element is now 490° C, well within its critical temperature of 540° C. The corresponding temperature on the ‘cold face’ of the Beam however, (on the surface of the Fire spray furthest away from the fire side) is 385° C. In accordance with AS 1530.4 this temperature would have prescribed failure of the Separating Element of Construction as the Standard allows, at any one point of the Partition, a maximum temperature of 180° C.
As a result of the above any stored combustible materials or cables located in the vicinity of the steel beam could have ignited and thus contributed to the spread of the Fire.