Fire Protection

Intumescent coating systems, formulated to expand at increased temperatures, are designed to maintain the steel’s stability in the event of a fire.

Intumescent coating systems, formulated to expand at increased temperatures, are designed to maintain the steel’s stability in the event of a fire.

Intumescents offer aesthetics, safety

The new generation of waterborne intumescent coatings for structural steel can address green building needs and speed up on-site and in-shop applications, writes RONNIE PESKENS, global product manager fire protection at PPG Protective and Marine Coatings.

March 2020

The use of exposed steelwork, both internally and externally, has grown rapidly over the last 20 years as architects have implemented modern design principles with a strong focus on aesthetics. Structural steel is no longer hidden behind walls and ceilings but has become a part of everyday life.

Open office plans feature circular columns and air-conditioning systems which run through cellular beams. Sports arenas make extensive use of curved trusses in roof assemblies, which are considered an architectural feature. In summary, exposed steelwork is used to create an identity to a building and to a business.

These changes in building design have had a knock-on effect to the process of passive fire protection (PFP).  Traditional PFP systems, including cementitious spray and fire-resistant boards, have seen increasing levels of competition from intumescent coatings. Cementitious sprays, although considered a cost-effective solution, are usually applied in very high thicknesses.

When a fire strikes, the char must keep the steel fully encapsulated and not crack.

When a fire strikes, the char must keep the steel fully encapsulated and not crack.

This adds substantial weight to the structure and may even require the use of thicker steel. The risk of corrosion underneath the cement and the difficulty of repairing subsequent damage, have been a source of major concern in recent years. Moreover, these kinds of sprays deliver very rough finish standards, which are often not acceptable to designers.

The installation of boards, on the other hand, is a high cost process, which requires specialist skilled labour. Even though boards provide a highly efficient thermal barrier, the lack of pre-fabricated shapes for complex structures limits their use to standard beams and columns.

Intumescent coatings are designed to expand at high temperatures, from a very thin, lightweight film into a thick foam-like layer that forms an insulation char to protect the steel. They offer an aesthetically-pleasing, single solution for both corrosion and fire protection.

The steelwork is typically treated with an anti-corrosive primer before application of the fire-retardant paint in-shop or on-site. Intumescents can be applied to nearly every shape and size of steel and can be customised with a variety of colour topcoats.

Traditional intumescent coatings, first introduced in the 1990s, use solvent-based, acrylic technology. These coatings are easy to apply with standard airless spray equipment, allow high film builds and offer relatively fast drying and recoat times. Typical fire ratings range from 15 to 120 minutes. As buildings often consist of modules with a number of different fire ratings, this usually requires a multi-product solution.

Intense competition and technological limitations have resulted in specialised products to address fire ratings above 60 minutes and from 60 to 120 minutes but such multi-product offers can be challenging in both shop and site applications since there is a risk they are mistaken for one another.

PPG Steelguard ... compatible with a wide range of PPG primers and topcoats.

PPG Steelguard ... compatible with a wide range of PPG primers and topcoats.

In recent years, there is clear trend towards adopting green building schemes such as Leed (Leadership in Energy and Environmental Design) and Breeam (Building Research Establishment Environmental Assessment Method), a key component of which is indoor air quality (IAQ) of building materials. This not only includes volatile organic compounds (VOCs) in the can, prior to application, but also the release of residual solvents and other emissions after installation is completed. 

The use of waterborne intumescent coatings has been steadily growing over the last few years and these systems are especially suitable for on-site application, as well as maintenance and repair. They contain little to no VOCs, have low odour, and are easy to apply with spray, as well as brush and roller in locations where spraying is not allowed.

This is especially important in industries where fast return-to-service and high levels of safety are required, such as airport terminals. In-shop application companies are now investing in ventilation and air-conditioning equipment to accommodate application of waterborne materials as well. This is may open new opportunities for the industry.

Technology is improving, giving rise to a new generation of waterborne intumescent coatings. Advancements in resin synthesis and formulation have led to a new generation of products.

For instance, PPG Protective and Marine Coatings’ flagship waterborne intumescent is PPG Steelguard 651 which is free of phenol ethoxylates and formaldehyde and does not contain any halogenated fire retardants or boron-containing compounds. This is not only beneficial during the application process, as it also improves indoor air quality and provides lower smoke toxicity than traditional systems.

As a result of extensive research into the intumescent char mechanism, PPG Steelguard 651 offers competitive thicknesses across the full spectrum of fire ratings, from 15 to 120 minutes. This includes three-sided and four-sided I-beam and columns, circular hollow sections and cellular beams.

Dry film thicknesses have been improved dramatically compared to both solvent-based and previous waterborne generations. Fire ratings up to 30 minutes now start from only 193 microns. Steelguard 651 has been tested and certified in accordance with EN1338-8, BS476, various international standards, and carries the CE mark.

In addition to these improvements in product properties and performance, architects are now also taking fire engineering into consideration during the design stage. This usually includes optimisation of the steelwork design related to the location and load-bearing capacity of the elements, as well the fire rating requirement. This approach can generate significant savings on the total applied cost of the fire protection materials.

PPG engineers are available globally to provide expertise in fire protection and advice on the relevant industry standards and fire ratings. The company has the engineering capability to support clients in the early stages of development, guiding them through the specification process and providing support through to project completion and beyond.  

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