22 Apr Testing intumescent coatings is crucial
Dr Jifeng Yuan, General Manager – Fire & Building Products NE/SE Asia at Element Materials Technology, discusses testing processes and their importance to intumescent coatings for structural steelwork.
Passive fire protection measures are a key consideration in every building’s design and ensuring there is adequate protection in place for structural steelwork is an important part of the fire safety strategy. Among a variety of steelwork protection options, intumescent coating is one of the most common and globally accepted measures.
Within the built environment, intumescent coatings often comprise a thin film layered over steelwork as a primer, basecoat and sealer. The basecoat layer is what reacts to a fire, and it expands to many times its normal size to create a greater thermal barrier of protection around the steel. Fire resistance requirements vary but most intumescent coatings can withstand fire for increments of 30, 60, 90, 120 or 180 minutes, depending on the materials, the specification, the design of the building, and the structural requirements of the steelwork.
Coatings can be applied to steelwork on-site or off-site, and installation following the application of the protective coating is generally straightforward. Coatings are a good solution for various shapes and sizes of steel, and they can be applied to achieve an attractive finish if steelwork is to be exposed as part of a building’s design.
Like all fire protection measures, testing intumescent coatings is crucial to determining if they will perform as expected in the event of fire. In the case of structural steelwork, this testing is designed to check that the steelwork will maintain integrity and loadbearing capacity long enough for occupants to safely vacate the building. Ideally, it should be long enough for fire services to arrive and extinguish the fire, therefore preventing building collapse. This not only saves lives but saves significant recovery and rebuilding costs. It is therefore important to invest in well-tested and well-trusted products to save significant potential costs in future.
Tests and standards
As is common with globally accepted products, there are several relevant tests and standards to fire test intumescent coatings, but the most common are BS 476 parts 20, 21 and 22 and EN 13381-8. Engaging with a reputable, accredited fire testing provider and consulting the fifth edition of the UK ASFP Yellow Book and/or European Assessment Document (EAD 350402-00-1106) will determine what testing is most appropriate for each coating product.
BS and EN test packages vary slightly, however the technical principles are all aiming in the same direction. The test program must be designed to adequately demonstrate the ability of the coating to maintain the maximum anticipated structural performance of the steel section and provide sufficient thermal data to cover the anticipated range of section types and sizes. The test program will include loaded sections and unloaded sections, and in many cases, it covers different orientations (horizontal and vertical) and different shapes (I-sections, circular hollow and rectangular hollow sections).
BS and EN test conditions also vary slightly. A typical example is that in the EN test, the furnace temperature is measured and is therefore controlled using plate thermocouples, while in the BS test, it uses Type K thermocouples as specified in EN 60584-1. Other examples include the insulation between the top flange of a loaded beam and floor slabs, different methods of load application, and the choice of concrete slabs.
The determination of the test package and test conditions will therefore vary and depend on the product’s and end market needs. Manufacturers will generally work very closely with the testing provider and certification body from start to finish to ensure a high level of accuracy and detail in the testing delivery.
During the lifetime of the intumescent coating system in service, it may be subjected to a variety of environmental conditions. The ability of the intumescent coating system to withstand the deteriorative effects of water, humidity, UV, and temperature is a measure of its durability. Any deterioration of the intumescent coating system can have an impact on its fire resistance properties.
Therefore, the fire protection system requires testing and assessment when exposed to these environmental factors, and it is particularly important that these products still fulfil their original fire protection role after a lifetime of environmental exposure. Well accepted durability testing standards include examples such as EN 16623 and ISO 12944.
The EN 16623 standard is for reactive coatings for fire protection of metallic substrates. Within its wider scope, it has dedicated sections for examining the compatibility of the reactive coating component with or without primers and topcoats and covers a reactive coating system’s environmental durability in various service and end use conditions. It also establishes a process for assessing levels of compatibility with primers and topcoats and their influence on the reactive coating system’s fire performance. In addition to durability, the standard also provides guidelines for the manufacture, storage, application, maintenance and repair of the reactive coating system and the final inspection of its installation in end use.
ISO 12944 for paints and varnishes specifically looks at the corrosion protection of steel structures by protective paint systems. Steelwork can be vulnerable to corrosion and may exist in environments where this is likely, but a coating can prevent this from occurring, or extend the life of a steel product before corrosion occurs, while also adding fire protection.
Certifying steelwork fire protection
In support of product testing, certification provides both initial and ongoing independent verification of quality assurance. Third-party certification enables a manufacturer of protective coatings to demonstrate consistency in quality from one factory location to another, and consistency in quality from batch to batch and from year to year. A UKAS or similarly accredited product certification process that is performed in accordance with the requirements of ISO/IEC 17065:2012 ensures the highest quality standards.
Certification technical experts provide guidance throughout the process and ensure that all requirements are satisfied. The certification process follows accredited technical schedules and is therefore consistent in all cases, whilst at the same time being individual to the customer and product. It begins with a detailed audit of the factory production control process (FPC) and independent product sampling.
Following initial certification, a schedule of audit fire and durability (where relevant) tests, conducted on material that has been independently sampled, is required to maintain the validity of certification, along with regular factory production control audits. At the end of a certificate’s validity period, revalidation can be provided via a new application to include a full review of the technical file and the on-going review by certification engineers.
Voluntary certification to globally recognised standards, such as the Warringtonfire Certifire scheme, is increasingly being specified by end-users providing the manufacturer with a ‘passport to trade’ and a valuable competitive advantage.
Intumescent coatings provide one of the most efficient methods of protection for steelwork products. They do not alter the structure or structural properties of the steelwork; they can be applied and installed with relative ease; and they can be used on products of varying shapes and sizes. However, using intumescent coatings as part of a building’s passive fire protection specification is just one step in ensuring life safety and business continuity.
Launching new protective steelwork products onto the market can be a complex business, and due to the nature of these life safety products, it’s critical that the best possible advice is sought from the beginning.
An end-to-end solution including independent fire testing, technical assessment, fire certification and fire safety engineering can provide a globally respected mark of quality assurance. It helps to ensure market entry and competitive advantage by selecting the best possible scope of testing and certification, and by providing support and advice throughout.
When lives are at stake, it’s crucial to take all precautions possible to ensure consistent high-quality, and a rigorous steelwork protection testing and certification program can help to achieve that.
For more information about Warringtonfire, Element Materials Technology and intumescent coatings testing, please visit www.warringtonfire.com/landing/structural-steelwork