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Structural Steel Fire Protection

Structural Steel Fire Protection, a key component of high-res building and structure design

In case of a fire in a high-rise building, preserving the stability of the building’s structure is one of the most important aspects of passive fire design. Protecting the structural adequacy of a building enables enough time for the safe evacuation of the building’s occupants, whilst also preventing collapse of the structure. Fire containment and prevention are key components of a building’s structural design.  It is often a requirement for the architect during the design stage of a project to consider building material options and systems that are not just fire resistant but fit within the requirements of the overall aesthetic layout of a building.

What is Structural Steel Fire Protection?

Structural Steel is a durable, noncombustible and fire resistant material widely used in commercial and industrial building construction. 

Steel beams, steel plates, girders, sections, and columns are used extensively in the sector as it is designed to have a good strength/weight ratio.  Structural steel  however can still fall victim to structural failure when temperatures start to rise above 500°C. In general, structural steel loses its yield strength at 550°C and most building fires exceed that temperature at some point.

Fire protection of steel structures is essential and can be achieved using passive steel fire protection systems such as board, paints and sprays.  

The fire protection of steel consists in insulating the steel with a passive fire system that is designed to absorb the heat, providing crucial additional time that the building’s structure is not exposed to a fire source.   Once the structural steel is protected, the system provides essential time during the event of a fire where the steel is prevented from reaching its critical failure temperature.

What are the structural steel fire protection building regulations in Australia?

Australia’s National Construction Code (NCC) guidelines define performance requirements for buildings exposed to fire. All building work (new construction, additions and alterations or change of use of a building) must comply with these requirements to facilitate the safe evacuation of building occupants and minimise the damage to other properties.

NCC Volume One is a performance-based code. Compliance with the NCC is achieved by satisfying the Governing Requirements and the Performance Requirements.

There are 3 ways to comply with these requirements, using a Performance Solution, using a Deemed‐to‐Satisfy Solution or a combination of both.

  • The DTS typically focuses on the assessment of individual elements to ensure that all critical points are met. It also includes compliance to the relevant standards.
  • The Performance Solution allows people to satisfy the requirements through alternative means. Due to a better understanding of real-world fires, this performance-based approach can provide a better fit to actual or near-actual fire scenarios that can be met by a range of acceptable solutions.

More details on the NCC compliance document.

Progressive Materials is the leading supplier in WA of Promat passive fire products and systems that have been tested at nationally accredited laboratories around the world to a variety of standards.  The standards of concern for us here in Australia are AS 1530: Part 4 and AS4100 in relation to structural steel fire protection. 

What are the different types of structural steel fire protection systems?

Promat passive fire protection materials are designed to insulate steel structures from the effect of the high temperatures generated in a case of fire.

They can be divided into 2 types, the reactive materials like intumescent paint and the non-reactive materials (ablative) such as fire rated boards and vermiculite spray.

Fire rated board

Boards are a popular solution for structural steel fire protection as they offer a clean, boxed appearance, are cost effective and can be applied on unpainted steelwork. Strong and durable, boards are ideal for a decorative finish and commonly used for fireproofing steel beams and steel columns.  

Promat boards often only require a single layer of protection for FRL’s up to 2 hours.   The single layer systems save space, install time and critical weight within a building.   

Benefits of using Promat fire rated boards for fire protection of steel:

  • Up to 4 hours FRL
  • Uniform thickness guaranteed
  • No preparation of the steel required
  • Does not require special equipment
  • Easy maintenance
  • Dry trade application, can be installed simultaneously with other trades
  • Can receive any architectural finish

table of 3 PROMATECT boards Fire Resistance Limit specifications

 

Using calcium silicate fire protection boards from Promat such as PROMATECT 250  can be one of the fastest and most cost effective ways of protecting structural steel.  For  Fire Resistance Levels (FRL’s) up to 2 hours only a single layer of board is required in almost all instances.   The range of Promat boards can provide structural steel fire protection up to 240 minutes in line with AS 1530.4.

Below are some progress shots of a maintenance project under construction.   The high quality work and attention to detail is courtesy of Property Fire Maintenance . This project had failure of the original intumescent coating, and is subsequently being repaired with a single layer board system.

Progressive Materials provided section factor calculations to ensure that only a single layer of PROMATECT 250 board was required to meet the 120/-/- FRL to the steel work.   We were also able to deliver the product to site on the same day it was ordered, due to our large local stockholding of Promat products.

 

PROMATECT 250 board is supplied in a range of thicknesses  for varying fire resistance levels.   The range of thicknesses includes

  • 15mm (most commonly used for 60 minute FRL’s)
  • 25mm (most commonly used for 90 minute FRL’s)
  • 30mm (most commonly used for 120 minute FRL’s)

The sizes above are just to be used as a guide only.  Based on the individual section factor of each beam or column, thicknesses may vary from the sizes listed above.   The full range of PROMATECT 250 is kept in stock in Wangara, and can be supplied the same day as an order.

Vermiculite and Cementitious coatings for steel

Spray coating is an ideal solution for complex steel shapes and details such as bolts and connections. It can be applied quickly however it is not suitable for aesthetic purposes. 

Promat Fire Sprays are supplied as powder that produces a pumpable mixture when mixed with water. There are different types of fireproof coating for steel and the selection of the right product will be based on the environment, substrate and type of protection required.

Benefits of using vermiculite spray for fire protection of steel structure:

CAFCO® 300 is the most cost effective vermiculite spray product on the market.

It is a lightweight coating that provides very efficient fire resistance with minimal thickness to structural steel.

  • Structural Steel Protection of up to 240 minutes
  • Economical. Produces high yield with low density
  • Can be used in conjunction with accelerators for faster curing time and efficient density
  • Can be applied directly on bare steel
  • Compatible with most primers if required
  • Low material cost, efficient thicknesses.
  • 0% ozone depleting raw materials.
  • Produces a monolithic coating
  • Direct spray application

 

Intumescent paint

Thin film intumescent paint generally has three components in relation to application: a primer, the intumescent layers and a sealer coat. The intumescent layers are the part that reacts in a fire.  At approximately 200 degrees celsius a chemical reaction takes place causing the product to expand and form an insulating layer which slows the temperature of the steel rising to a critical level. 

It is a good solution to achieve attractive surface finishes and is typically used to easily cover complex shapes. Intumescent coating and fire paint can be applied directly to the contour of primed I and H section columns, angles, channels, beams and hollow sections to provide fire protection for up to 120 minutes depending on the product and environment.

Coatings can be applied either on or off-site, however if off-site, the connection plates and bolts are still required to be protected once the steel is erected on site.

Benefits of using intumescent paint for fire rated columns and steel structure:
Cafco® SPRAYFILM WB3 is a water based intumescent coating consisting of polyvinyl acetate resins and fillers for the fire protection of structural steel. It is preferably spray applied with airless paint equipment for speed and quality of finish. Brush and roller application is also possible.

  • Single pack water-based intumescent paint
  • Structural Steel Protection of up to 120 minutes
  • Compatible with commonly used primers
  • Compatible with many topcoats to provide durability for various usage category, from internal to external application
  • Produce a thin and seamless finish
  • Can be applied using brush, roller and also airless spray
  • For both open and hollow sections
  • Application onto galvanised steel is possible
  • Quick application and easy cleanup
  • Fast drying time

FAQ

What is the most cost effective way of protecting structural steel?

A: When large amounts of steel work are requiring fire protection, Cafco 300 Vermiculite Spray is often the most cost effective

Can I fix window frames or door frames to protected structural steel?

A: It depends on what product is used to protect the steel from fire.   PROMATECT 250 Board from Promat can take fixings through the board back into the steel for windows, doors and any other items that are required to be fixed back into the steel. 

Does intumescent paint finish like powder coated steel?

A:  No. An experienced applicator can get a high quality finish using intumescent, however.  The product is a protective coating and its primary function is to provide fire protection

How much clearance do I need to provide from structural steel coated with intumescent?

A: We recommend a minimum of 50mm from all coated faces of the steel.  When intumescent reacts to fire, the protective coating can expand up to 50 x its original thickness, and needs to be unimpeded in this zone to form an insulating charing mass.


19 Oct 2020